Speedometer Error

[gregybn]

wrong thread - go to cbr250...

admin - please delete

[dave_boo]

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.

[Garry]

Another reason I like my Ducati. Speedo signals are taken from the back wheel and not froma sensor in the gearbox, where clutch slip, changed gearing have major inputs on the sensors signals. The only issue apart from built in error, would be wheel spin, which reads instantly on the dash. I intend to GPS my Ducati one day and see what amount of error is built into it.

edit: I meant to add, for those who are interested in having as accurate a reading as possible, then check out this website: http://www.healtech-electronics.com/ and their Speedo-Healer

[PaulD]

Something very odd: My Lifan 250 V-twin has an accurate speedo - measured between 40 to 100 so far. Garmin gps. All stock, tyres inflated to company specs. (Because I drive a little auto-scooter in town, and a car, I've not run the Lifan faster with the gps on board.) I've seen it now - complete honesty in a speedometer, and built in Thailand!

Every other bike I've ridden here in Thailand is more concerned about "face" than honesty.

[Richard-BKK]

Something very odd: My Lifan 250 V-twin has an accurate speedo - measured between 40 to 100 so far. Garmin gps. All stock, tyres inflated to company specs. (Because I drive a little auto-scooter in town, and a car, I've not run the Lifan faster with the gps on board.) I've seen it now - complete honesty in a speedometer, and built in Thailand!

Every other bike I've ridden here in Thailand is more concerned about "face" than honesty.

Lifan is a Chinese company, and the Thai build Lifan LF250-B is also sold in China. Selling a motorcycle in China which shows an incorrect speed at 100km/h is in China not allowed. Some Chinese motorcycles have at lower speeds an inaccuracy...

(Motorcycles in China cannot go faster than 100km/h, break the rule and you get in serious problems)

[Loz]

like the 180kmh limiters put on some bikes in japan?

My old Gixer 750 J went off the clock at 180kph. Had to put a bicycle digi speedo on it.

FWIW - those bike speedos are bloody good! and have a full trip computer as well as being removable!

[Garry]

like the 180kmh limiters put on some bikes in japan?

My old Gixer 750 J went off the clock at 180kph. Had to put a bicycle digi speedo on it.

FWIW - those bike speedos are bloody good! and have a full trip computer as well as being removable!

Cateye make some nice bike computers. I used one on my mountain bike for years in the middle east. I'm curious, where did you place the pickup sensor on your 750? disc brake bolt area & caliper mount?

[gregybn]

like the 180kmh limiters put on some bikes in japan?

My old Gixer 750 J went off the clock at 180kph. Had to put a bicycle digi speedo on it.

FWIW - those bike speedos are bloody good! and have a full trip computer as well as being removable!

Cateye make some nice bike computers. I used one on my mountain bike for years in the middle east. I'm curious, where did you place the pickup sensor on your 750? disc brake bolt area & caliper mount?

interesting concept...

i've used cateyes on my various mtn and road bikes for years...

maybe i'll try one on my cbr250

be advised... for accuracy

chalk a line on the pavement and measure your wheel diameter to the closest 0.5cm...

one rotation - from valve to valve (vertical position)

you can program this into the cateye for an "actual" diameter...

accuracy is pretty dam_n good

but - even better...

have someone else measure as you sit on the bike...

so the load (contact patch) on the tire will be reflected in an more accurate diameter.

chok dee

[Garry]

like the 180kmh limiters put on some bikes in japan?

My old Gixer 750 J went off the clock at 180kph. Had to put a bicycle digi speedo on it.

FWIW - those bike speedos are bloody good! and have a full trip computer as well as being removable!

Cateye make some nice bike computers. I used one on my mountain bike for years in the middle east. I'm curious, where did you place the pickup sensor on your 750? disc brake bolt area & caliper mount?

interesting concept...

i've used cateyes on my various mtn and road bikes for years...

maybe i'll try one on my cbr250

be advised... for accuracy

chalk a line on the pavement and measure your wheel diameter to the closest 0.5cm...

one rotation - from valve to valve (vertical position)

you can program this into the cateye for an "actual" diameter...

accuracy is pretty dam_n good

but - even better...

have someone else measure as you sit on the bike...

so the load (contact patch) on the tire will be reflected in an more accurate diameter.

chok dee

You're trying to convert the converted on how to set up a Cateye computer. Agree on the accuracy though.