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MG MGF Technical - Height 35.5. Tyres uneven wear
|My F height is 35,5 to the wheels arch which I understand to be borderline acceptable - 36.5 looks too high-, however I have noticed some uneven wear on the inner part of the front tyres. What would be the possible camber, caster and toe correction to avoid that wear?|
|Brian, the answer is toe. |
In the first instance, get the tracking checked, you may find that you have more toe-out than you expect, and simply correcting to standard setting will sort this out.
However, there are other settings to try:
Two best tried options are:
0 degrees front toe - as used on TF. Works well, will avoid excess tyre wear
0 degrees 5 minutes toe in (per wheel) - gives much improved stability on motorways, and makes the front of the car feel more chuckable in corners.
More on this here: http://www.mgf.ultimatemg.com/group2/suspension/tracking.htm
|My car is set to 34,5 -no lowering knuckles- and tyres wear has been avoided correcting toe and tracking. However ride is somewhat rough.|
|It will be: when you lower to that level, hydragas pressure is under 280 psi (it should be around 400 psi). The net result is that the spring rates drop - in other words the suspension gets softer. That may sound odd in view of your experience, but in fact the reason why your suspension feels so rough is because the spring rates are now so soft, and the suspension has so little travel, the suspension spends much of its time compressing up against the bump stops. |
This gives the bad ride quality you are experiencing.
Without doubt, getting the hydragas pressure up to where it should be will dramatically improve ride and handling. But as Brian says, a ride height of 368mm looks wrong. Knuckles are certainly the way forward. And if you go for that level of modification, then replacement dampers are a good idea too (but these can be done at a later date).
All the usual mg specialists can help out with getting your suspension sorted. Mine was done by Techspeed 5 years ago (been delighted with the results!), but if you are interested in adjustable dampers, then Mike Satur and B&G are both worth dropping a line.
|Rob, If I remember well the recommended height for the the hydra system to be pumped was 36.8 +- 1. So 35.5 does not look that bad and probably is well within the standard limits.|
|Mike, yours is, but A. Mouldon's is definitely not (345mm)|
|Just to get the record straight here, the standard MGF ride height dimension should be 368mm +/- 10mm from the front wheels centre vertically up to wheel arch.|
|Don't forget the temperature correction from 17C Pete ;o)|
|You're right Rob, just that everybody here was using unknown units (inches?)and measuring from the ground. What tyre pressure and what tyres, what wheel diameter - all too complicated.|
|Mine has been running at 34 cm for a year now and looking great. No lowering kcnuks and no uneven wear as that was corrected. Only worry is eventual damage to the hydra units if that could happen. But fine so far.|
|Sorry. And riding is not at all harsh compared to TF.|
|It is somewhat intriguing but I pumped my F to 36,5cm about in September -very cold wheater then- and at present both front wheels stands at about 34cm -with temp reaching 36°C-. I have not noticed any hydra fluid on the floor so wonder were is it going.|
|Sometimes setting the height of hydragas suspension is something of an artform - it is very easy for the suspension to overshoot or undershoot the desired ride height - even if, once set when you've finnished, at the desired height. Hence the "rule of thirds" when pumping/ releasing pressure from the suspension. |
I suspect that what's happened here Mike is that the suspension has equilibrated and settled at the lower than anticipated ride height. So long as one corner of the car is not obviously lower than the others (which can indicate hydragas sphere failure) there really isn't anything to worry about.
This thread was discussed between 14/12/2005 and 19/12/2005
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