gregybn Posted April 14, 2011 Share Posted April 14, 2011 SPEEDOMETER ERROR...??? ok... this is a serious issue. lots of riders saying... "i can go this fast" - "i cruise at this speed" - "this is my top speed" - well, i finally got my new tank bag last week... and today - finally put the garmin colorado 300 gps right in front of my eyes i took a short ride today with the gps... what a surprise! seems the cbr speedo is approximately 10% high vs. the gps speedo sez 100 - gps sez 91 speedo sez 80 - gps sez 73 speedo sez 115 - gps sez 104 speedo sez 60 - gps sez 54 ok, ok... numbers did fluctuate a bit... hard to hold a steady speed on thai back roads... watching the speedo with one eye, the gps with the other... don't forget the cows and dogs with another eye and the kids and chickens with another eye (how many eyes do i have...???) regardless... i'm seeing anywhere from 9% - 11% difference --- let's just round off to 10% for convenience sake. so who are we gonna trust here fellow riders --- mr. honda's digital speedo - or mr. garmin's satellite gps knowing full well - on every bike i've ever owned (many)... some speedo error is always there - maybe more - maybe less... so --- this begs the question... what are the REAL cruising + top speeds for the cbr250? at this point... i'm inclined to believe lower than riders are spouting for their "digital display" hey - don't get me wrong... it's still PDQ for a quarter-liter bike... and handles real nice - straights or curves... i still love this bike... it's a keeper but --- but we should take a few grains of salt with the speed figures being reported? any other riders with actual speedo vs. gps data... --- please report in. let's get some sense of reality here. Link to comment Share on other sites More sharing options...
dave_boo Posted April 14, 2011 Share Posted April 14, 2011 Kawasaki Ninja 250R measures ~8% slower (i.e. 92 when going ~100) with a Garmin Zumo 550....on stock tyres. Haven't really measured it since I replaced the IRC with Pirellis though. However, according to my chart the Ninja should do 100 in fifth at 8550 RPM with the old tyres; the new ones raise the RPM to 8600. I.E., the speedo drift with the is probably close to 3% with the new tyres (drift with old tyres - 5% difference between old and new tyre's RPM at same speed). Or put another way the tach was reading 7800 RPM with the old tyres (versus the 8550 that the engine needs to be at to actually reach 100 km/h) and the new tyres should make the tach read at 8350 when the speedo hits 100. That 2mm less diameter that the new tyres have spun over 163 399 times (the revs my tyre makes in 100 km) is quite a distance; they have to make up 327 m over that 100 km. Link to comment Share on other sites More sharing options...
gregybn Posted April 14, 2011 Share Posted April 14, 2011 btw... good points dave... tire size and inflation will make some difference... other-than-stock tires, wear patterns, with less/more kms, inflation psi --- sure - go figure my data were based on... running stock tires... less than 4000km... standard pressures - about 28psi. still - aren't arguably most riders reporting their recent speeds... on low-km, stock tires, at normal pressures maybe let's wait for more data points... Link to comment Share on other sites More sharing options...
dave_boo Posted April 14, 2011 Share Posted April 14, 2011 Not to be pedantic, but tyre pressure + rider weight need to be considered. At 28 psi the bike (at 360 lbs) will have ~6,43 in2 of tyre touching the ground. Add in a rider weighing 172 lbs and you have ~9,5 in2 touching the ground. On the other hand a rider weighing 200 lbs will have ~10in2 touching the ground at the same pressure. Moving up to 29.5 psi the lighter rider will have ~9,0 in2 versus the heavier rider's 9,5 in2. Basically for the heavy rider each 1,5 psi increase takes away 0,5 in2of contact space. Or going from the 28 psi to 32 means that you lose 1,3 in2 or 13%. This is obvious not a direct corelation between sidewall height since, for instance on the CBR's 140 width, it requires a patch 3,6 in. by 2,8 in. for the stock pressure and 3,6 in. by 2,4 in. for 32 psi. Using the CBR's stock tyre again, a decrease of contact patch by 0,4 in. on the 32 psi pressure requres a similar 14% increase in sidewall height. 86% of 140/70 means your sidewall is going to measure 112 mm versus the stock 98. Which means that in fifth the CBR will be going 5050 rpm versus the 5250 that it does with tyres inflated to 28 psi. Or put plainly ~4% difference. Obviuosly less tyre contact area means more sidewall height which means greater distance traveled per revolution. Link to comment Share on other sites More sharing options...
gregybn Posted April 15, 2011 Share Posted April 15, 2011 (edited) Not to be pedantic, but tyre pressure + rider weight need to be considered. At 28 psi the bike (at 360 lbs) will have ~6,43 in2 of tyre touching the ground. Add in a rider weighing 172 lbs and you have ~9,5 in2 touching the ground. On the other hand a rider weighing 200 lbs will have ~10in2 touching the ground at the same pressure. Moving up to 29.5 psi the lighter rider will have ~9,0 in2 versus the heavier rider's 9,5 in2. Basically for the heavy rider each 1,5 psi increase takes away 0,5 in2of contact space. Or going from the 28 psi to 32 means that you lose 1,3 in2 or 13%. This is obvious not a direct corelation between sidewall height since, for instance on the CBR's 140 width, it requires a patch 3,6 in. by 2,8 in. for the stock pressure and 3,6 in. by 2,4 in. for 32 psi. Using the CBR's stock tyre again, a decrease of contact patch by 0,4 in. on the 32 psi pressure requres a similar 14% increase in sidewall height. 86% of 140/70 means your sidewall is going to measure 112 mm versus the stock 98. Which means that in fifth the CBR will be going 5050 rpm versus the 5250 that it does with tyres inflated to 28 psi. Or put plainly ~4% difference. Obviuosly less tyre contact area means more sidewall height which means greater distance traveled per revolution. great stuff dave... i, for one, appreciate your pedanticism and detailed calculations btw... the 10% error i mentioned above... (stock tires, low wear, normal pressures) then also must have a factor for my 2-up riding... total rider weight for me + missus = about 260lb = 115kg this will thus increase the contact patch + decrease the sidewall height... which leads to a smaller wheel diameter - than a smaller single rider thus, for one wheel revolution... we are going a (uncalculated) slightly smaller distance on the road... which will translate into a comparable decrease in indicated speed over ground which will thus translate into a higher discrepancy between mr. speedo and mr. gps so - for my next trip... i'll take a solo ride and increase the tire pressures to max... thus have a lesser contact patch and increased sidewall height... which should give me a slightly longer distance for one wheel revolution... which should translate into a lower percentile difference between my gps and speedo but, will i really be going any faster (objectively)... realizing it takes less rpm's to turn a bigger wheel - the same distance then --- at some arbitrary engine rpm...? actually - according to the speedo's read-out i'll be going slower... (at that same arbitrary engine rpm, of course...) but i'll have a few more rpm's to wring out of the engine... thus can potentially reach higher speeds all interesting stuff... great mental exercise - to clear my brain after too much scotch last nite maybe i'll hazard a guess that 2-up as i initially described... which gave a 10% error... might be halved (i.e., 5%) by a single rider (proviso - optimized tire pressure and wear) even then... once riders start changing from stock tires... and thus subtly changing tire profiles, sidewall heights and diameters... any individual differences, for individual riders, on individual machines... will be arguably show different speedo results with more~less difference to "actual" speed. now everyone buy a gps and go test these theories out we'll wait for your reports... but remember to keep (at least) one eye on the road while the other eyes are watching the speedo and gps chok dee... dave_boo... if i have erred in my above suppositions and prognostications... please, i stand to be corrected... and will also drink more scotch before attempting any further analysis Edited April 15, 2011 by gregybn Link to comment Share on other sites More sharing options...
BigBikeBKK Posted April 15, 2011 Share Posted April 15, 2011 Tony changed his tune in the years because he outgrew his ninja it happens. I might not like the guy much but it will happen to others too who drive the cbr 250 for a long time. For me it probably wont happen as i wont be doing to much real touring on it and mostly city fun. Just getting deeper in the city then before. I feel safer on this bike then i do on the nouvo in faster traffic. The Ninjette was the smallest bike I've ever owned. I bought it shortly after I moved to Thailand in 2008 when it was the only domestically produced 250cc bike available in the Kingdom. I shed a few tears leaving by CBR600F2 behind in Japan but was told it would be more trouble and expense than it was worth to try and ship it to Thailand and get it road legal. I looked at imported big bikes and was shocked by the prices so decided to go for the 250R because is was cheap as chips and fully legal. Wicked fun little bike as long as you kept her in the power band. She was a dog two-up and going up hills and trying to keep up with bigger bikes on the fast roads though. I can only imagine that the CBR 250 must be even worse... Thank goodness Kawasaki came out with their 650cc ER6n, Ninja 650R (aka ER6f) and Versys. Business has been good so I treated myself to the K5. Ride On! T Link to comment Share on other sites More sharing options...
BigBikeBKK Posted April 15, 2011 Share Posted April 15, 2011 In 1983 kawasaki produced a parallel twin 250 producing 26bhp and what was it called? Wait for it! It was called a "Ninja." We may have to accept the name on those lowly 250's and maybe the bigger ones should be called big ninja or boss ninja or something. And at that time the Ninja 900 had 115 BHP. Current model Ninja 250R outputs 25-27 RWHP. Even assuming a 15% drivetrain loss (because manufacturers are pretty notorious about their HP claims), that's only an increase of 5 hp maximum and a minimum of 2 3/4 hp over nearly 30 years. Meanwhile the top of the line Ninja went up ~23 BHP. As I pointed out ages ago; everybody knows about the CBR250RR and compares the new CBR 250R to that. Makes a great story; Honda built a 45 hp 250cc bike 15-25 years ago. The new CBR only puts out some 55% of the power...ergo it's an anemic thumper. On the other hand Kawasaki put out a Ninja ZX-2R that also had 45 hp. Meaning that the 2008+ model Ninjas only make ~60% of the power. Furthermore they take 48% more time on the 0-96 km/h, and have 77% of top speed. Guess that means the Ninja 250R is an anemic little twin? I mean it would have to be if the anemic little thumper of a CBR beats it in everything but possibly top end, right? I'd never heard of the ZX-2R before you mentioned it recently Dave. Sounds like a brilliant little screamer. Was that bike ever sold in the US? Link to comment Share on other sites More sharing options...
BigBikeBKK Posted April 15, 2011 Share Posted April 15, 2011 (edited) Honda's pushing stateside... Yikes... yet another ad aimed at noobs... " the perfect entry-level bike for motorcycle enthusiasts who are either new to riding or have little experience with motorcycles." Honestly, I don't think the bike's THAT bad. They should really push it's fuel efficiency in their ads. With fuel prices on the rise it's a nice little fuel efficient commuter. Edited April 15, 2011 by BigBikeBKK Link to comment Share on other sites More sharing options...
dave_boo Posted April 15, 2011 Share Posted April 15, 2011 And at that time the Ninja 900 had 115 BHP. Current model Ninja 250R outputs 25-27 RWHP. Even assuming a 15% drivetrain loss (because manufacturers are pretty notorious about their HP claims), that's only an increase of 5 hp maximum and a minimum of 2 3/4 hp over nearly 30 years. Meanwhile the top of the line Ninja went up ~23 BHP. As I pointed out ages ago; everybody knows about the CBR250RR and compares the new CBR 250R to that. Makes a great story; Honda built a 45 hp 250cc bike 15-25 years ago. The new CBR only puts out some 55% of the power...ergo it's an anemic thumper. On the other hand Kawasaki put out a Ninja ZX-2R that also had 45 hp. Meaning that the 2008+ model Ninjas only make ~60% of the power. Furthermore they take 48% more time on the 0-96 km/h, and have 77% of top speed. Guess that means the Ninja 250R is an anemic little twin? I mean it would have to be if the anemic little thumper of a CBR beats it in everything but possibly top end, right? I'd never heard of the ZX-2R before you mentioned it recently Dave. Sounds like a brilliant little screamer. Was that bike ever sold in the US? Just like the CBR 250RR, the old Versys, the first run of the XR-1200, the Super Tenere, the Transalp, etc. no it wasn't... Link to comment Share on other sites More sharing options...
BigBikeBKK Posted April 15, 2011 Share Posted April 15, 2011 And at that time the Ninja 900 had 115 BHP. Current model Ninja 250R outputs 25-27 RWHP. Even assuming a 15% drivetrain loss (because manufacturers are pretty notorious about their HP claims), that's only an increase of 5 hp maximum and a minimum of 2 3/4 hp over nearly 30 years. Meanwhile the top of the line Ninja went up ~23 BHP. As I pointed out ages ago; everybody knows about the CBR250RR and compares the new CBR 250R to that. Makes a great story; Honda built a 45 hp 250cc bike 15-25 years ago. The new CBR only puts out some 55% of the power...ergo it's an anemic thumper. On the other hand Kawasaki put out a Ninja ZX-2R that also had 45 hp. Meaning that the 2008+ model Ninjas only make ~60% of the power. Furthermore they take 48% more time on the 0-96 km/h, and have 77% of top speed. Guess that means the Ninja 250R is an anemic little twin? I mean it would have to be if the anemic little thumper of a CBR beats it in everything but possibly top end, right? I'd never heard of the ZX-2R before you mentioned it recently Dave. Sounds like a brilliant little screamer. Was that bike ever sold in the US? Just like the CBR 250RR, the old Versys, the first run of the XR-1200, the Super Tenere, the Transalp, etc. no it wasn't... Well, I moved to Japan in '97 so to be honest haven't really kept up on what's been available in the States in recent years, but I think we can agree that there are very few models under 600cc sold in the US. But I rode a lot in Japan and saw many CBR250RR's but never saw a ZX-2R. I think you need to do some fact checking- Kawasaki has been selling the Versys in the US since 2007 and the Honda Transalp has been sold in the US as far back as 1989 (XL600V)... The CBR250RR and Kawasaki ZX-2R were never sold in the US. Link to comment Share on other sites More sharing options...
dave_boo Posted April 15, 2011 Share Posted April 15, 2011 Not to be pedantic, but tyre pressure + rider weight need to be considered. At 28 psi the bike (at 360 lbs) will have ~6,43 in2 of tyre touching the ground. Add in a rider weighing 172 lbs and you have ~9,5 in2 touching the ground. On the other hand a rider weighing 200 lbs will have ~10in2 touching the ground at the same pressure. Moving up to 29.5 psi the lighter rider will have ~9,0 in2 versus the heavier rider's 9,5 in2. Basically for the heavy rider each 1,5 psi increase takes away 0,5 in2of contact space. Or going from the 28 psi to 32 means that you lose 1,3 in2 or 13%. This is obvious not a direct corelation between sidewall height since, for instance on the CBR's 140 width, it requires a patch 3,6 in. by 2,8 in. for the stock pressure and 3,6 in. by 2,4 in. for 32 psi. Using the CBR's stock tyre again, a decrease of contact patch by 0,4 in. on the 32 psi pressure requres a similar 14% increase in sidewall height. 86% of 140/70 means your sidewall is going to measure 112 mm versus the stock 98. Which means that in fifth the CBR will be going 5050 rpm versus the 5250 that it does with tyres inflated to 28 psi. Or put plainly ~4% difference. Obviuosly less tyre contact area means more sidewall height which means greater distance traveled per revolution. great stuff dave... i, for one, appreciate your pedanticism and detailed calculations btw... the 10% error i mentioned above... (stock tires, low wear, normal pressures) then also must have a factor for my 2-up riding... total rider weight for me + missus = about 260lb = 115kg this will thus increase the contact patch + decrease the sidewall height... which leads to a smaller wheel diameter - than a smaller single rider thus, for one wheel revolution... we are going a (uncalculated) slightly smaller distance on the road... which will translate into a comparable decrease in indicated speed over ground which will thus translate into a higher discrepancy between mr. speedo and mr. gps so - for my next trip... i'll take a solo ride and increase the tire pressures to max... thus have a lesser contact patch and increased sidewall height... which should give me a slightly longer distance for one wheel revolution... which should translate into a lower percentile difference between my gps and speedo but, will i really be going any faster (objectively)... realizing it takes less rpm's to turn a bigger wheel - the same distance then --- at some arbitrary engine rpm...? actually - according to the speedo's read-out i'll be going slower... (at that same arbitrary engine rpm, of course...) but i'll have a few more rpm's to wring out of the engine... thus can potentially reach higher speeds all interesting stuff... great mental exercise - to clear my brain after too much scotch last nite maybe i'll hazard a guess that 2-up as i initially described... which gave a 10% error... might be halved (i.e., 5%) by a single rider (proviso - optimized tire pressure and wear) even then... once riders start changing from stock tires... and thus subtly changing tire profiles, sidewall heights and diameters... any individual differences, for individual riders, on individual machines... will be arguably show different speedo results with more~less difference to "actual" speed. now everyone buy a gps and go test these theories out we'll wait for your reports... but remember to keep (at least) one eye on the road while the other eyes are watching the speedo and gps chok dee... dave_boo... if i have erred in my above suppositions and prognostications... please, i stand to be corrected... and will also drink more scotch before attempting any further analysis The point of my post was that since, unlike the Ducati (to a lesser extent) mentioned earlier or cagers, there is a pretty big disconnect between RPM and speed on motorcycles for two reasons. Number one being the percentage the rider is of the bike. In a nutshell different weights affect the sidewall height at different RPMS. This is a problem since the speedo is driven off the front wheel on most bikes. Also different seating positions place different percentages of weight over the front tyre affecting sidewall height also. Going back to the speedo being driven off the front wheel; turning, front tyre slippage, etc throws off the numbers. Link to comment Share on other sites More sharing options...
dave_boo Posted April 15, 2011 Share Posted April 15, 2011 Well, I moved to Japan in '97 so to be honest haven't really kept up on what's been available in the States in recent years, but I think we can agree that there are very few models under 600cc sold in the US. But I rode a lot in Japan and saw many CBR250RR's but never saw a ZX-2R. I think you need to do some fact checking- Kawasaki has been selling the Versys in the US since 2007 and the Honda Transalp has been sold in the US as far back as 1989 (XL600V)... The CBR250RR and Kawasaki ZX-2R were never sold in the US. I put the Versys in the wrong space; however it doesn't change the fact that all of the bikes I listed (and reading the post again listed quite poorly--I'm not an English teacher) had first runs where the bikes were released outside of the US...and those are the ones that I remembered off the top of my head. Link to comment Share on other sites More sharing options...
Just1Voice Posted April 15, 2011 Share Posted April 15, 2011 Dave, JUST out of curiosity, how much "margin of error" would there be with someone such as myself at 172cm and 64kg? Any "guestimates"?? hahaha Link to comment Share on other sites More sharing options...
BigBikeBKK Posted April 15, 2011 Share Posted April 15, 2011 Not to be pedantic, but tyre pressure + rider weight need to be considered. At 28 psi the bike (at 360 lbs) will have ~6,43 in2 of tyre touching the ground. Add in a rider weighing 172 lbs and you have ~9,5 in2 touching the ground. On the other hand a rider weighing 200 lbs will have ~10in2 touching the ground at the same pressure. Moving up to 29.5 psi the lighter rider will have ~9,0 in2 versus the heavier rider's 9,5 in2. Basically for the heavy rider each 1,5 psi increase takes away 0,5 in2of contact space. Or going from the 28 psi to 32 means that you lose 1,3 in2 or 13%. This is obvious not a direct corelation between sidewall height since, for instance on the CBR's 140 width, it requires a patch 3,6 in. by 2,8 in. for the stock pressure and 3,6 in. by 2,4 in. for 32 psi. Using the CBR's stock tyre again, a decrease of contact patch by 0,4 in. on the 32 psi pressure requres a similar 14% increase in sidewall height. 86% of 140/70 means your sidewall is going to measure 112 mm versus the stock 98. Which means that in fifth the CBR will be going 5050 rpm versus the 5250 that it does with tyres inflated to 28 psi. Or put plainly ~4% difference. Obviuosly less tyre contact area means more sidewall height which means greater distance traveled per revolution. great stuff dave... i, for one, appreciate your pedanticism and detailed calculations btw... the 10% error i mentioned above... (stock tires, low wear, normal pressures) then also must have a factor for my 2-up riding... total rider weight for me + missus = about 260lb = 115kg this will thus increase the contact patch + decrease the sidewall height... which leads to a smaller wheel diameter - than a smaller single rider thus, for one wheel revolution... we are going a (uncalculated) slightly smaller distance on the road... which will translate into a comparable decrease in indicated speed over ground which will thus translate into a higher discrepancy between mr. speedo and mr. gps so - for my next trip... i'll take a solo ride and increase the tire pressures to max... thus have a lesser contact patch and increased sidewall height... which should give me a slightly longer distance for one wheel revolution... which should translate into a lower percentile difference between my gps and speedo but, will i really be going any faster (objectively)... realizing it takes less rpm's to turn a bigger wheel - the same distance then --- at some arbitrary engine rpm...? actually - according to the speedo's read-out i'll be going slower... (at that same arbitrary engine rpm, of course...) but i'll have a few more rpm's to wring out of the engine... thus can potentially reach higher speeds all interesting stuff... great mental exercise - to clear my brain after too much scotch last nite maybe i'll hazard a guess that 2-up as i initially described... which gave a 10% error... might be halved (i.e., 5%) by a single rider (proviso - optimized tire pressure and wear) even then... once riders start changing from stock tires... and thus subtly changing tire profiles, sidewall heights and diameters... any individual differences, for individual riders, on individual machines... will be arguably show different speedo results with more~less difference to "actual" speed. now everyone buy a gps and go test these theories out we'll wait for your reports... but remember to keep (at least) one eye on the road while the other eyes are watching the speedo and gps chok dee... dave_boo... if i have erred in my above suppositions and prognostications... please, i stand to be corrected... and will also drink more scotch before attempting any further analysis The point of my post was that since, unlike the Ducati (to a lesser extent) mentioned earlier or cagers, there is a pretty big disconnect between RPM and speed on motorcycles for two reasons. Number one being the percentage the rider is of the bike. In a nutshell different weights affect the sidewall height at different RPMS. This is a problem since the speedo is driven off the front wheel on most bikes. Also different seating positions place different percentages of weight over the front tyre affecting sidewall height also. Going back to the speedo being driven off the front wheel; turning, front tyre slippage, etc throws off the numbers. Very few bikes measure speed at the front wheel anymore. Most modern bikes measure speed at the crank or sprocket. Link to comment Share on other sites More sharing options...
gregybn Posted April 15, 2011 Share Posted April 15, 2011 'BigBikeBKK' --- Very few bikes measure speed at the front wheel anymore. Most modern bikes measure speed at the crank or sprocket. certainly - the sensor is on the drive-shaft these days... this still begs the question... revolutions of the drive-shaft is still directly related to revolutions of the wheels... which is then translated to diameter of the wheel... which must eventually translate to speed over ground. and remember... those digital speedos contain various inherent inaccuracies... but how and why --- this is what we still seek to understand. Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter. Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits. so then, we must understand this following point as well... it seems that manufacturers build in certain biases... based on int'l regs. to wit... In many countries (Thailand too?) the legislated error in speedometer readings is ultimately governed by the United Nations Economic Commission for Europe (UNECE) Regulation 39 which covers those aspects of vehicle type approval which relate to speedometers. The main purpose of the UNECE regulations is to facilitate trade in motor vehicles by agreeing uniform type approval standards rather than requiring a vehicle model to undergo different approval processes in each country in which it is to be sold.European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers are similar to the UNECE regulation in that they specify that: The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h. The UNECE regulation relaxes the requirements for vehicles mass produced following type approval. At Conformity of Production Audits the upper limit on indicated speed is increased to... ...110 percent plus 8 km/h for two (...) wheeled vehicles which have a maximum speed above 50 km/h an assumption here... since the cbr's many of us are riding are manufactured in thailand - BUT will also be exported internationally - we might reasonably state that the above regs are de-facto. so if i understand all this stuff correctly... my cbr already has a built-in bias to any accurate speed shown on the speedo... ...by at most --- 110% + 8kmh this can also be influenced by "Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size." so if we also take into account - an easily done gps comparison... wherein we understand stuff like this... Garmin's specifications quote 0.1mph accuracy but due to signal degradation problems noted above, perhaps 0.5mph accuracy in typical (motorcycle) applications would be what you can count on.--- It certainly appears that the GPS receiver can be relied upon to measure +/- 1 MPH and is certainly more reliable than the speedo --- The GPS is accurate for the determination of speed over ground (about 10 times more accurate than a car odometer) when moving at relatively constant speed in straight lines... Absolute error increases slightly at higher speeds but in percentage terms is less. so, fellow riders - let's get down to the nitty gritty here... if i may conclude... #1 - based on industry standards - you are NEVER going as fast as you think you are #2 - and if you really want to get an accurate speed - you CAN rely on gps technology i am ready, willing to be proven wrong in these "assumptions" thanks once again, to the bottle of scotch that greatly assisted me through this tedious research chok dee Link to comment Share on other sites More sharing options...
dave_boo Posted April 15, 2011 Share Posted April 15, 2011 Dave, JUST out of curiosity, how much "margin of error" would there be with someone such as myself at 172cm and 64kg? Any "guestimates"?? hahaha Less than I at 174 and 100 kg.... But give me more information and I'll guesstimate... Link to comment Share on other sites More sharing options...
dave_boo Posted April 15, 2011 Share Posted April 15, 2011 certainly - the sensor is on the drive-shaft these days... this still begs the question... revolutions of the drive-shaft is still directly related to revolutions of the wheels... which is then translated to diameter of the wheel... which must eventually translate to speed over ground. and remember... those digital speedos contain various inherent inaccuracies... but how and why --- this is what we still seek to understand. Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter. Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits. so then, we must understand this following point as well... it seems that manufacturers build in certain biases... based on int'l regs. to wit... In many countries (Thailand too?) the legislated error in speedometer readings is ultimately governed by the United Nations Economic Commission for Europe (UNECE) Regulation 39 which covers those aspects of vehicle type approval which relate to speedometers. The main purpose of the UNECE regulations is to facilitate trade in motor vehicles by agreeing uniform type approval standards rather than requiring a vehicle model to undergo different approval processes in each country in which it is to be sold.European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers are similar to the UNECE regulation in that they specify that: The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h. The UNECE regulation relaxes the requirements for vehicles mass produced following type approval. At Conformity of Production Audits the upper limit on indicated speed is increased to... ...110 percent plus 8 km/h for two (...) wheeled vehicles which have a maximum speed above 50 km/h an assumption here... since the cbr's many of us are riding are manufactured in thailand - BUT will also be exported internationally - we might reasonably state that the above regs are de-facto. so if i understand all this stuff correctly... my cbr already has a built-in bias to any accurate speed shown on the speedo... ...by at most --- 110% + 8kmh this can also be influenced by "Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size." so if we also take into account - an easily done gps comparison... wherein we understand stuff like this... Garmin's specifications quote 0.1mph accuracy but due to signal degradation problems noted above, perhaps 0.5mph accuracy in typical (motorcycle) applications would be what you can count on.--- It certainly appears that the GPS receiver can be relied upon to measure +/- 1 MPH and is certainly more reliable than the speedo --- The GPS is accurate for the determination of speed over ground (about 10 times more accurate than a car odometer) when moving at relatively constant speed in straight lines... Absolute error increases slightly at higher speeds but in percentage terms is less. so, fellow riders - let's get down to the nitty gritty here... if i may conclude... #1 - based on industry standards - you are NEVER going as fast as you think you are #2 - and if you really want to get an accurate speed - you CAN rely on gps technology i am ready, willing to be proven wrong in these "assumptions" thanks once again, to the bottle of scotch that greatly assisted me through this tedious research chok dee Conclusion #1 is correct. Conclusion #2 is also correct with the caveat that a steady speed is needed for a bit of time. A GPS obviously is not going to respond as quickly as a speedo cable would, however it's good for setting your speed when cruising or determining your overall top speed. Some necessary points though; a speedo ran off the transmission will still have errors introduced by different sized rear tyre, sprockets, etc. Obviously doing the math and using a speedo healer or new gear (assuming it's analouge) is still necessary. I've never heard of a speedo being off by 18%; seems like most all are between 8-10. Link to comment Share on other sites More sharing options...
Just1Voice Posted April 15, 2011 Share Posted April 15, 2011 (edited) Dave, JUST out of curiosity, how much "margin of error" would there be with someone such as myself at 172cm and 64kg? Any "guestimates"?? hahaha Less than I at 174 and 100 kg.... But give me more information and I'll guesstimate... Ok, I'm 172cm & 64kg, and let's say I'm maintaining a speed of 120kph, according to the speedometer, over a distance of say 5 kilometers on a flat road. Any "guestimates" as to what my actual speed would be? Oh, the bike is strictly stock, which means IRC originals. Edited April 15, 2011 by Just1Voice Link to comment Share on other sites More sharing options...
edwinchester Posted April 16, 2011 Share Posted April 16, 2011 Your actual speed as compared to that indicated has nothing to do with your height or weight. Believe me, your body , no matter how tall, short lightweight or obese will not affect the gearing of your bike. 120 indicated is probably a genuine 110......ish. Link to comment Share on other sites More sharing options...
Dakling Posted April 16, 2011 Share Posted April 16, 2011 (edited) If you change radius of front wheel/tire combo it will throw the speedo out of whack. Give a cop some cash to bring a radar gun and clock you to see your real speed. Granted the gun must be calibrated properly too. Just be sure he doesn't hit you with a ticket after the test. I wonder if odometers are out as much, never really thought about it before but I wonder if they are calibrated better. Edited April 16, 2011 by Dakling Link to comment Share on other sites More sharing options...
Hili Posted April 16, 2011 Share Posted April 16, 2011 Nearly all black. Thanks to SumetCycle for the black fairing parts! One thing to notice is that the side pieces are not gloss black, its plain matt plastic same like the piece under the seat. But i like Rims will follow..... Link to comment Share on other sites More sharing options...
hehehoho Posted April 16, 2011 Share Posted April 16, 2011 Thanks. A nicer looking ride all in black. But something does need to be done to the CBR's silver rims. How much for the set inc. installation? Link to comment Share on other sites More sharing options...
Hili Posted April 16, 2011 Share Posted April 16, 2011 Thanks. A nicer looking ride all in black. But something does need to be done to the CBR's silver rims. How much for the set inc. installation? Its around 3000 you can message SumetCycle for the exact price. Installation i did by myself take some time but its not that hard. Sure, like i said the rims will go black next week, i will anodize them. More resistant than paint. Link to comment Share on other sites More sharing options...
jackjones Posted April 16, 2011 Share Posted April 16, 2011 (edited) Apparently MCN from the UK are at a testing ground at this moment trying out the CBR against the Ninja. They are trying them out on a two mile straight to see how they compare and if either of them can reach 100 mph. The results should be out soon. The comments in the MCN forum under the article were quite funny and one guy said he would buy the Kawasaki, even if it only did 40mph, because the Honda was so ugly!! and another guy asked if they had got the Honda's wheels from a 1980's parts bin. ( cheeky blighters ) Edited April 16, 2011 by jackjones Link to comment Share on other sites More sharing options...
taichiplanet Posted April 16, 2011 Share Posted April 16, 2011 (edited) I think it is just the paint scheme that lets down the CBR250. I've been playing around with wheel colours on the gray bike and almost any colour is better than the silver they painted the wheels; including pink! Or maybe i have bad colour sense!! Photochopped a gray bike to have full gray (rather than gray and silver), black wheels, smoked screen, chopped the tail and reduced the size of the indicators. IMO it looks much nicer! And a little wilder just for fun! Edited April 16, 2011 by taichiplanet Link to comment Share on other sites More sharing options...
jackjones Posted April 16, 2011 Share Posted April 16, 2011 They look good to me in whatever colour but I am still waiting for someone to paint theirs in Castrol Honda colours. Link to comment Share on other sites More sharing options...
visions Posted April 16, 2011 Share Posted April 16, 2011 (edited) <BR>I think it is just the paint scheme that lets down the CBR250. I've been playing around with wheel colours on the gray bike and almost any colour is better than the silver they painted the wheels; including pink! Or maybe i have bad colour sense!! <IMG class=bbc_emoticon alt= src="http://static.thaivisa.com/forum/public/style_emoticons/default/smile.gif"> <BR><BR>Photochopped a gray bike to have full gray (rather than gray and silver), black wheels, smoked screen, chopped the tail and reduced the size of the indicators. IMO it looks much nicer! <BR><BR><BR><BR><BR>In Australia the black bike IS black, no silver at all. But with gloss and matt black breaks it up enuf to look great.<BR>Also have the Tri Colour which a lot of people like (aka the 150)<BR>The 3rd colour is the red, same as in thailand.<BR><BR>Re the wheel colour of the 2 tone grey/silver bike, I think Black Chrome could look ok with rim tapes in red or whatever. (The black chrome is a spray paint that is virtualy indistinguishable with real chrome)<BR><BR>In the USA the bike sells for $3999...........in Australia (The Aus $ is stronger than US$) it sells for $6300 (200,420 baht) Aussi Govt is making a good whack eh!! Edited April 17, 2011 by visions Link to comment Share on other sites More sharing options...
visions Posted April 17, 2011 Share Posted April 17, 2011 The price here, being so high.....what I am seriously considering.....................is an exteemly good example of the CBR250RR. at a considerable saving in cost. Low Ks (and from what i can see is genuine) New fairings so looks a modern bike................but with a 45hp 4 in line engine........the performance cannot be matched by the new CBR There is a very big selection of the old CBR250RR in Australia Link to comment Share on other sites More sharing options...
BigBikeBKK Posted April 17, 2011 Share Posted April 17, 2011 (edited) The price here, being so high.....what I am seriously considering.....................is an exteemly good example of the CBR250RR. at a considerable saving in cost. Low Ks (and from what i can see is genuine) New fairings so looks a modern bike................but with a 45hp 4 in line engine........the performance cannot be matched by the new CBR There is a very big selection of the old CBR250RR in Australia Sweet! Now THAT is a CBR worth getting excited about! Ride On! T Edited April 17, 2011 by BigBikeBKK Link to comment Share on other sites More sharing options...
katabeachbum Posted April 17, 2011 Share Posted April 17, 2011 The price here, being so high.....what I am seriously considering.....................is an exteemly good example of the CBR250RR. at a considerable saving in cost. Low Ks (and from what i can see is genuine) New fairings so looks a modern bike................but with a 45hp 4 in line engine........the performance cannot be matched by the new CBR There is a very big selection of the old CBR250RR in Australia Sweet! Now THAT is a CBR worth getting excited about! Ride On! T a CBR 250 deserving the R :jap: Link to comment Share on other sites More sharing options...
.png.3b3332cc2256ad0edbc2fe9404feeef0.png)
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now