Rear Suspension

[2052006 10]

I currently have SBC phase 1 suspension which basically consists of Bilstein Struts and approx -25mm springs on the front and a standard 205 beam lowered to match. All is in good order and virtually every suspension component has been replaced/refurbished.

 

I am not convinced that it is agile as it should be though. Particularly in slow/tighter corners it seems to want to "understeer" more than I think it should ie. comparing it with other cars. It is hard to describe and also hard to determine exactly, as the steering does weight up much more than other cars which I think is normal on 205s. It is fine in faster, more open corners, it is just in slower corners where it doesn't seem to "pivot" round them effortlessly as some cars do - if that makes sense.

 

So I'm thinking of upgrading to SBC phase 2 spec (or similar) which I think has 20mm bars and 23mm arb. My question is what exactly do stiffer bars/arb achieve? How will it make the car feel and are there any negative effects. My thoughts are that it will "help" the back end round, making it seem more agile in slow/tight corners. Am I on the right lines here?

 

Also I know the SBC kit includes a negative camber kit on the rear. What does this achieve? More stability?

 

 

Thanks!

 

Pete

[Rippthrough 98]

First step is to check the tracking, too much toe in can cause exactly what you just described.

[Baz 421]

Above, and what tyres are you running?

[2052006 10]

Tracking was done in August and I think it has been like this since.

 

I thought it could be my tyres which were old F1s which needed changing. So now it's got new 912s on it. On the back are some P6000s in OK condition - could it be these?!

 

Also, I have considered the fact that it's got a heavy gti6 engine up front. However, it acted similarly with the alloy block before - at the time I thought it was just because I needed new tyres. New tyres have improved the grip on the front, but I still feel it's not as agile like I say.

.

So what about bigger bars/arb - is this what I need - assuming my tracking's ok (it certainly doesn't pull one way or the other in a straight line anyway)?

[James_R 3]

The extra nose weight won't help, nor will the power wanting to make it more understeery, I'f try a bigger rear ARB first that would be the cheapest solution to try, but generally lowering a 205 without adding some stiffness in the rear will do this. Anthony should be able to help I'd imagine.

[2052006 10]

What size is a standard 205 arb then?

 

Also, with the extra weight over the front, would this mean the rear needs to be stiffer than it other wise would?

[RossD 44]

19mm rear

17mm front

Edited November 16, 2009 by RossD

[McDude 33]

I have the SBC Phase II and it is absolutely awesome, but it won't help the front end at all because the front end remains no different from phase I.

 

I would agree that sometimes turn in on the tighter bends isn't great, but usually a bit of braking effort helps load up the front and it steers in just fine. As others have said, get your tracking checked.

 

The Phase II will give an extremely well planted rear with a much more progressive break away under LOOS - it makes the car sublime on B-roads and very grippy on trackdays.

[James_R 3]

The extra 20something kilo's on the front (6 engine)

 

As ross said, 19mm is the std rear anti roll bar, 22 is a nice step up without it going too mad.

[Baz 421]

I have the SBC Phase II and it is absolutely awesome, but it won't help the front end at all because the front end remains no different from phase I.

 

Yes it will, because by upgrading the rear you can help the front.

[brumster 135 1 Cars]

Not a fan of running different-pattern/compound tyres front and rear but I'm not up on those tyres you mention, so I couldn't really comment.... but in basic terms, a stiffened front end and softer, more compliant rear end will make the car errr towards a more understeery nature. The front should be quite quick but ultimately if you want the car to spin on a dime you need to make the rear 'tighter'...

 

Assuming the front geometry is good and the front bushes in the arms are okay, tightening up the rear to bring it inline with the front (assuming the lowering has also included firmer springs?) would be a sensible approach. I'm in a similar boat myself, need to uprate my rear ARB after putting the thicker 309 ARB on the front.

[2052006 10]

Yes it will, because by upgrading the rear you can help the front.

 

Yes, this is was what I was hoping, from what I have read anyway.

 

I take it then, that a bigger rear arb, rather than bigger torsion bars, has a bigger effect on turn in and handling in corners?

 

McDude, can you remember the spec of your SBC bars and arb?

[James_R 3]

Upgrading the ARB is the cheaper option to attaining an effective higher spring rate on turn in over bars, the cost difference is £150 vs £300 for torsion bars as a pair see PUG_309's group buy topic for an idea.

[Batfink 201]

the difference is the antirollbar makes your rear suspension more dependant, while the torsion bars keep things independant..

This will have a different effect on handling though both can get the car to oversteer more.