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Mazda RX8 rear sways side to side at speed


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Hi All, thank you in anticipation, my RX8 fitted with Nissan SR20, Greddy TD06 Turbo Engine, also fitted with LPG tank in the boot on the shelf as far forward as possible, as well as lowered suspension, 265*35*18 Handkook Ventus V2 Concept high performance tyres rear, 245 front. On reaching speeds of around 170 kilometers per hour, the rear end sways side to side from center.

Other wise the cornering is very good. Running tyre pressures front 32, rear 30 psi cold.

Would a lip spoiler or other help solve this problem, or any other suggestions.

The car overall I am more than happy with, getting 9.5 kilometers a liter on a long run, excellent oil pressure, no need to top up between oil changes.   

Thank you.

Regards Tom

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Possibly a spoiler that is properly designed....

 

When I had my Lexus sports car at about 110-115 miles per hour you could feel the car squat down & hug the road even tighter....

 

The only thing I could attribute this to was the spoiler.....

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I would take it to a  " Cockpit " outlet and get 4 wheel  alignment computerized analysis done first and then take it from there.

The only time l had trouble you describe was when l had wire-spoked-rims.

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25 minutes ago, Ace of Pop said:


Wasn't that when U had the Raleigh Bycycle.?.?
 

How funny my prize procession bicycle when a young lad was was a Raleigh one. :laugh:

 

The MG-BGT l had was bought with wire rims and every year the spokes had be checked & trued,  l found a mug who swapped them for his mag ones.  :biggrin:

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Once again amazed at the stuff I read here.   I hope to heck you aren't driving 170 on my part of the country.   

 

Are you NUTS??????  

 

Hard enough to drive with all the normal lunatics with zero driving education or experience in Thailand.  It's a wonder you're still alive.  

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First check up - get a suspension specialist to check all rear suspension parts. Then progressively check any other areas that affect handling, tyres wheels etc. (this should be done by a suspension specialist hopefully).

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1 hour ago, TGIR said:

Once again amazed at the stuff I read here.   I hope to heck you aren't driving 170 on my part of the country.   

 

Are you NUTS??????  

 

Hard enough to drive with all the normal lunatics with zero driving education or experience in Thailand.  It's a wonder you're still alive.  

Before start making assumptions and accusations, are you aware of that there are several racetracks and drag-strips in Thailand?

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13 minutes ago, goloeilmanz said:

Before start making assumptions and accusations, are you aware of that there are several racetracks and drag-strips in Thailand?

Do you really think he was driving on a race track or drag strip? :whistling:

 

Plenty of expertise around those areas and would probably solve his problems.

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How funny my prize procession bicycle when a young lad was was a Raleigh one. :laugh:
 
The MG-BGT l had was bought with wire rims and every year the spokes had be checked & trued,  l found a mug who swapped them for his mag ones.  :biggrin:

Lol, I had exactly the same experience in a wire wheeled mg-bgt.... passengers screaming in the back


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It can be difficult to diagnose these types of problems over the internet. I do not have any experience with RX8s but in my opinion, it could be worn suspension, incorrectly installed parts, alignment issues, bad tyres, shocks, rear sway bar or an incorrectly installed aerodynamic aid. If any one of these is out of spec it will most likely have an influence on the other components.

 

As other have suggested, I would start having someone competent check that the suspension in all four corners is in good order and replace any worn components.  Then I would suggest finding out the alignment specs for your year of car and have it checked at a decent alignment shop.  This may be difficult as you mentioned that you have had the car lowered. Was it done with proven parts and an experienced installer? Or by Somchai and Son with an Oxy Acetylene torch, two big hammers and a grin on their faces?

 

Are you running the original body work or has it been modified?

 

Do you still have the original wheels and tyres? If so after checking the suspension and alignment it may be worthwhile to put the original rear wheels on to see what difference there is.

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Funny. This sounds like me after I got a 175mph superbike.

 

I took it back to the dealer to complain that if I put my feet on the back pegs and went over 130mph it started to shimmy. 

 

They told me very politely to piss off because they could not legally recreate the issue.

 

From then on I kept my feet on the front pegs...

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Now I am out of the nanny state I can admit to having broken the speed limit in the uk a little bit.

 

BMW 335i (3.0 litre twin turbo) 0300 Sunday morning, clear skies, clear road M25 A2 intersection and not a sniff of the pigs. Up the slipway on to the M25 and off we went

 

Took her up to 140 mph ( capped at 155) and all she did was hunker down and suck the living shit out of the road. My pants filled at that speed so I backed off but what a rush!

 

never done it since......

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The old LGBTI, yep over 90 mph it would snake a little, maybe it was worried about what was coming up behind.

RX8 with a Toyota engine up front and a LPG tank in the tiny boot, you need more than a spoiler for that. Suspension/chassis can't cope with different weights. I'd do what the other guys say, keep the speed down and get a real expert, or scrap it.

Happy motoring.

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7 hours ago, The Dark Lord said:

Now I am out of the nanny state I can admit to having broken the speed limit in the uk a little bit.

 

BMW 335i (3.0 litre twin turbo) 0300 Sunday morning, clear skies, clear road M25 A2 intersection and not a sniff of the pigs. Up the slipway on to the M25 and off we went

 

Took her up to 140 mph ( capped at 155) and all she did was hunker down and suck the living shit out of the road. My pants filled at that speed so I backed off but what a rush!

 

never done it since......

I had the coupe, very quick car with paddle shift. 140 was easy, and solid. It was quicker then the M3 of the time when it came out.

Lots of empty road where I used to live. Good fun pissing off the Audi TDIs etc.

The only thing I didn't like was all the bloody moaning warning lights and beeps etc.

:thumbsup:

 

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When you say sway, do you mean a gentle oscillation ? It may be as simple as adjusting tire pressures. Caster, camber, spring rates can all play a part. Is the suspension on the car now able to adjust the instant centre ?

 

Some guidelines here - https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=58

 

Here all the parameters of suspension tuning are to be found ... http://www.motoiq.com/MagazineArticles/ID/2804/The-Ultimate-Guide-to-Suspension-and-Handling-Its-All-in-the-Geometry-Part-One-The-Roll-Center.aspx

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On 7/1/2017 at 5:23 PM, TGIR said:

Once again amazed at the stuff I read here.   I hope to heck you aren't driving 170 on my part of the country.   

 

Are you NUTS??????  

 

Hard enough to drive with all the normal lunatics with zero driving education or experience in Thailand.  It's a wonder you're still alive.  

Lolz funny how all the 'likes' for someone who cracked 170km/h. The challenge is to find a decent stretch of road where you can crack 170mph. 170 is do-able just about anywhere... On Kaset-Nawamin road in Bangkok I used to do 1km to a U-turn then return 1/2km the other side... that 1km was quick, 1st gear hitting 130km/h in maybe 4 seconds, then second and third gear before getting on the brakes... the other side, 1/2km just 1st and 2nd gear.

 

What's wrong with getting up a bit of speed when you have some clear tarmac in front of you?

Edited by ben2talk
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3 hours ago, George FmplesdaCosteedback said:

The old LGBTI, yep over 90 mph it would snake a little, maybe it was worried about what was coming up behind.

RX8 with a Toyota engine up front and a LPG tank in the tiny boot, you need more than a spoiler for that. Suspension/chassis can't cope with different weights. I'd do what the other guys say, keep the speed down and get a real expert, or scrap it.

Happy motoring.

"...scrap it" before you crap it! :smile:

 

Just a little poetic licence and humour here.

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Lolz funny how all the 'likes' for someone who cracked 170km/h. The challenge is to find a decent stretch of road where you can crack 170mph. 170 is do-able just about anywhere... On Kaset-Nawamin road in Bangkok I used to do 1km to a U-turn then return 1/2km the other side... that 1km was quick, 1st gear hitting 130km/h in maybe 4 seconds, then second and third gear before getting on the brakes... the other side, 1/2km just 1st and 2nd gear.
 
What's wrong with getting up a bit of speed when you have some clear tarmac in front of you?

Nuffin,there are many deserted stretches of fine roads in Thailand.In the NE there are Motorways that were built by Chavalit a B57 could land on it without disturbing the Stall holders in lane1..yes they are in 1!!!Hi Ways round Sukhothai are, often near empty at times, the classic is the stretch to Krabi , I often stick on 200 , lucky if you can spot more than 10 vehicles in an a early morn run . I drive to conditions not Dictates..Limits to Thais are Targets to hit.. get out a bit, Thailand ain't just Soi6..?[emoji207]


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3 hours ago, Ace of Pop said:

Hi Ways round Sukhothai are, often near empty at times,

Very true & very safe multi lanes both ways too,  very open views way ahead & also clear views of both off sides of the road.

 

Your always get the health & safety brigade on TV along with spell & grammar checkers.  :laugh:

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On 7/1/2017 at 7:07 PM, goloeilmanz said:

Before start making assumptions and accusations, are you aware of that there are several racetracks and drag-strips in Thailand?

Nope, not aware of any but the drag strip between Petchaburi and Bangkok......my guess is old Tom isn't running on anyone's track but his own.   

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How did you manage to get passengers in the back of an MG BGT? Were they leprechauns? I can barely get a couple of bags of shopping on the rear seats on mine.

It was open top, I was 17 and it was my first go in a proper car (all my previous experience limited to 2 1960's Nuffield tractors and an old Land Rover).... can't blame them for screaming


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2 hours ago, lemonjelly said:


It was open top, I was 17 and it was my first go in a proper car (all my previous experience limited to 2 1960's Nuffield tractors and an old Land Rover).... can't blame them for screaming


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What do you mean "open top"? The MG GT was a hard top, it might have had a sun roof.

198ccb1b19b8ed29543c7479b38ea864.jpg

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On 7/2/2017 at 2:30 AM, Barty said:

How did you manage to get passengers in the back of an MG BGT? Were they leprechauns? I can barely get a couple of bags of shopping on the rear seats on mine.

I had the same as giddyup's posted picture,  use to sway at high speed so l got the spoke wheels trued up every year.

l've crammed as as many as 3 average sized adult people in what was an actual back seat in the hard-top MGB-GT, my 2 kids sat there in comfort.  :thumbsup:

 

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Hi Guys, thank you for all your comments and suggestions, will try them out and see if I can improve things, have lowered the rear  tyre pressures by 3/ 4lbs cold, this has made some improvement. All four wheels were aligned at a shop recommended  by a shop in Bangkok who sets up cars for racing, no problems.

Think next thing is buy and fit a spoiler recommended by  Mazda.

Thank you, All.

Tom 

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