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MG MGF Technical - Impression of undulation in mg tf

Hi, i have a probleme with my 2004 MG TF (xpower springs), i have change tyres recently for DUNLOP SP SPORT 9000 and if i drive at more than 135/140 KM/H i have an impression of undulation float and my direction are very sensitive...help me pleased !

Thx a lot

jérémy
bugman23

Owning an MGF means I can't really suggest anything from experience, but I would suggest that you have a play with the tyre pressures.

What pressures are you running right now?
Rob Bell

1.8 at front (195/45 R16) and 2.5 at rear (215/40 ZR16)
bugman23

I agree with Rob - the pressures you quote are correct for the Goodyear F1 GSD2, which has a very soft sidewall and needs high pressure. The Dunlop tyre won't need 2.5bar at the rear, I'd guess 2bar would be better. The front could probably be reduced a fraction, try 1.6bar.
Mike Hankin

OK i tried 2 bar at Rear and 1.6 at front tomorow...i hope its the solution...if you have an another council :)...
bugman23

How to know the right pressure quote according to the desing of tires ?

2.5 at rear with Toyo T1R is correct ?
François

Toyos seem to 'like' being at the same pressures as the Goodyears - but I am not sure about the Dunlops. What I would suggest is some experimentation - both upward and downward from the existing pressures, and see how you go.

Hopefully you will alight upon the ideal tyre pressure/ ride/ handling compromise fairly quickly.
Rob Bell

Another option would be to contact the manufacturer of the tyre to see what they recommend. The biggest factor is the axle weight, the MGF's weight (1050kgs approx) is distributed approx 45:55 (Rob will correct me if I'm wrong...), from these figures a manufacturer should be able to calculate an optimum pressure for a particular design of tyre.
Mike Hankin

At that kind of speed (Around 100mph)I would think its like the old 'F' problem of the front end going light and feeling "Twitcy" due to front end lift....

I, like most people with Fs cured this to a degree with the fitting of a front splitter (Trophy)....

I have found that my new TF160 tends to do the same at M-Way speeds, but have yet to see suitable (tested) splitter for the TF!!......
Mark.L

Mark, did you see the pictures on DC's website showing a TF with a KH splitter? Apparently it works as well on the TF as it does on the MGF.

Can't recall the URL right now - but I am sure a quick search of the archives should reveal the answer :o)
Rob Bell

PS Mike - you're spot on with the weight distribution ;o) LOL
Rob Bell

In the DUNLOP website 1.9 for front and 2.5 for rear...
bugman23

>>Mark, did you see the pictures on DC's website showing a TF with a KH splitter? Apparently it works as well on the TF as it does on the MGF.<<

http://www.csmgf.co.uk/darkside/spoilers/TF_Splitter.jpg
David Clelland

I run my Dunlop SP9000's at 1.9 (28 PSI) front and rear (recomended by Techspeed) so thats worth a try to.
Steve White

Steve - I spotted on your Avatar on another site that you've changed the wheels on your car again - back to Silver TF 11-spokes?
Rob Bell

Bugman

I have TOYO T1-S on 16" wheels on TF135. I thought the suspension had become a bit bouncy after 2 years. I am now trying the tyres at 28 psi front & rear (sorry not sure what bar). I have felt no change in handling or road holding but an improved ride - my wife can now read while I drive.

John Ponting

Thx a lot :)

I have put 2bar at rear and its OK :) very good modification after this !!

Thx a lot for all :)
bugman23

nice one - glad you got the problem sorted :o)
Rob Bell

Manufacturers recommendations not necessarily the best then... ;o)
Mike Hankin

Techspeed recommended 28psi F & R, manual says 28 F & 36 R. Changed to 28 F & R and it feels lots better.
Timmeh

I also went with Techspeed's recommendation of 28psi on each corner - much improved ride and handling. I wondered if MPG might suffer as a consequence but I haven't noticed any change.

Bob
R Thompson

This thread was discussed between 12/06/2006 and 14/06/2006

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