davedipster

I'm running coilovers on a newage sti and the rates are 5 front and 4 rear.

I know that the std sti suspension rides very close to bump stops, so is running 6mm before the bump stop using coilovers an issue on the front of an sti?

This is a fast family car not a trackday special.

suspension experts?

cheers
Dave

davedipster

Done some more accurate measurements and It was running 6mm right front and 10mm left front from a rather stiff bump stop.
Anyone running BC BR coilovers on a newage sti with 5/4 springs will be this close, or closer with passengers! not much bump travel at all almost on the bumpstops.
Fitting some 6Kg springs tomorrow that will according to my math give me an extra 14mm travel.

Last thing you want is to sit on the bumpstops all the time,the right front bumpstop looks rather tired, so the car must of been sitting on that alot!


davedipster

mejpickles

Hi davedipster

I have just ordered (in a group buy) some BC coilovers for my 05 Sti type UK
With the 5/4 springs.

did you fit them yourself ?
could you post a pick of them?.

davedipster

Here are the pics...

1st one shows the full strut travel unloaded 120mm - 40mm(bumpstop) = 80mm.

[IMG][/IMG]

Now this is what happens when it's on the car, 70mm of travel is taken up by the weight of the car leaving only 10mm bump travel (the offside front is only 6mm)



I'm changing my 5/4 springs to 6/4, this will add 14mm of travel.

The rears are not an issue, 15-18mm bump travel left on 4Kg/mm springs.

The sti is some 75Kg heavier than an wrx, due to the gearbox mostly, I'm guessing this is some of the reason why it's so close to the bumpstops at the front. In fact 75Kg on a 5Kg/mm spring = 15mm compression, so a wrx would be 15mm+10mm=25mm away from the stops, much better than 10mm!


dipster

DuncanG

Its good to see someone getting to grips with the basics of suspension setup.
It will tend to make the ride feel harsh. The sti is often critised for that.

That 'hard' bumpstop is made from polyurethane foam and will, with sufficient force, compress to about 1/3 of its free length. So the bump travel will be more than you think.

Remember that 75kg is shared by both sides, so that's 7.5mm of a change not 15.

These BC coilovers have separate spring pre-load and height adjustments and that makes it easy to alter bump travel without changing spring rates (or ride height). Increase the spring preload by 10mm and the bump travel will also increase by 10mm while the droop travel reduces by 10mm - simple. However be aware that any spring only has so much travel capability before it becomes coil-bound and you really don't want that - make sure the bumpstop will be fully compressed before the spring goes coil-bound.

120mm total travel is not a lot so its important to do what you are doing and that is to optimise the use of that travel between bump and droop. Too little droop will make it skittish; too little bump and you will be riding the bumpstops, get a harsh ride, and lose grip.

All the dyno plots I've seen for BCs show they use very little bump damping and rely mainly on rebound damping. That means you will be working the springs and bumpstops hard on any real road. So the increase in front spring rate could be helpful for bump control.

davedipster

I have just fitted 6Kg springs to the front, lets see how it goes now.
Thanks for the info.

dipster

davedipster

First impressions are great, put 6Kg 200mm springs on the front and left the 4Kg 220mm springs on the back. I have preloaded the springs by 5mm and now due to the greater spring rate I have 25mm before hitting the front bumpstops.
On the rough roads around here the front is certainly not bottoming out like it was, much better.

Got the alignment done by superstyres in Maldon, top chaps!


dipster