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Tarmac Rally, Suspension Suggestions


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#16 rally1380

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Posted 25 March 2017 - 09:15 AM

using polybush on the back and standard bushes on the front.

That sounds the wrong way round - the rubber should be on the back so there is a little more compliance under braking

Agreed. Under braking the tiebar is pulled back as the body tries to move forward. So harder bush on the outside lessens the altering in geometry.... In theory.

Edited by rally1380, 25 March 2017 - 09:34 AM.


#17 tiger99

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Posted 25 March 2017 - 01:13 PM

Yes! If you use two poly bushes I suspect that you will have a fatigue fracture of the tie rod or the mounting on the subframe sooner, rather than later, as poly will not let the joint flex enough to cope with full suspension travel. The braking force is usually much greater than the tractive force so the harder bush on the front hives less overall castor change.



#18 Cooperman

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Posted 25 March 2017 - 06:06 PM

I always use standard tie-bar bushes and change them often.

 

The tie-bar 'ears' must be strengthened with a triangular piece of 4 mm thick steel welded to the 'ear' and the sub-frame web. It's obvious how to do it when you look at it.

 

On a rally car the suspension needs to be a bit compliant and not 'tight' as it would be on a track car. Too many people set rally suspension too hard and find the car won't hold the road or handle as they like. The suspension needs to 'work' on rallies and the Mini especially so. The available suspension travel is small to start with, so raising the ride height slightly and fitting compliant suspension parts does help. When one of the staff reporters from Mini Magazine drove my 'S' several years ago he remarked at how relatively soft the suspension seemed compared to some Minis he had driven. I use standard OE spec rubber cone springs rather than the competition ones as the initial rate is a bit lower and I find this works well. 






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