Rear suspension arms for slight bump steer on a daily driver

[Sibbers]

I've had a good old go at this one, but I just can't pin it.

I've got an S15 which is lowered by 35mm or so. Not much. Wheels are 9" wide an ET25, but no spacers. Subframe bushes have been replaced with whiteline polys and suspension arm bushes appear to be ok (as well as you can tell from looking and wobbling things)...

Car drives brilliantly with the exception being on hard cornering the rear feels like like its toeing out a bit on the side being compressed... I've had the car aligned, although it probably needs doing again - however the symptom was there both before and after so I wondered if anyone here knew what it might be?

Alignment was roughly the same as the whiteline sport spec due to camber limit.

Any ideas?

[sparky_s13]

Strap a go pro to the rear quarter to watch the wheel movement.

Take it you have stock traction arms? These play a part in bump steer.

[Sibbers]

Yep stock traction arms. They are suspect number 1 - I can move them with my hand (roll forward and backward) but not in/out/up/down so just want to make sure I don't waste money.

Any further confirmation (I don't have a go pro) and advice about which arms to get (ie: non rose jointed?) or can I get away with just bushes despite nto being able to adjust length..?

[Sibbers]

Had a read of this and becoming more confident that what I need is traction arms, and I think the bushes are ok - does anyone have any input on how to work out length? Pretty sure that the guys with hunter alignment gear don't touch these and wouldn't be able to assess the correct length unless the car was actually compressing in the same way it occurs on the road.

Or am I being dense? (probability high)

[Clarkey]

Not sure how it would affect a car lowered only 35mm on stock arms, but mine had awful bump steer in the back with 50 odd mm lowering and camber arm lengthened for ~1.2deg. I read this http://www.nissanroadracing.com/showthread.php?t=1652 and figured that traction links sat in the shed should probably go on.
Lengthened them over stock by the same amount as the camber arms had been, the car became much better behaved. As you can see from the graphs it's important to tune this right to avoid toe out under compression. I don't see why you couldn't analyse this properly using a hunter machine, just unhook the shock and take readings throughout the stroke. Probably take a bit of time mind.

[Sibbers]

Actually that's a really good idea seeing as the rear shock is so easily removed. not so sure my local hunter bods would go for it though, they're more slaves to the machine than geometry experts. Good link, thanks. Makes me slightly more sure that toeing out is what I'm feeling - perhaps i feel it more despite only being 35mm lowered (guessing) because my suspension compresses more with 4kg springs.

Other guides seems to just say make it a little bit longer. I like that. very specific. Seems like some people just weld in a few mm's extension to the arm they already have.

[sparky_s13]

For the sake of a few quid I would rather buy the adjustable ones than potch about cutting and welding them which would render them useless if you changed your set up again etc.

Still need to buy some myself.

[Sibbers]

Agreed. Just having trouble finding bushed ones sold in this country. That said, DW site has a guide saying "this is a bit complex, we recommend extended by 10mm for most applications" (paraphrasing slightly!)

[immy21]

Dw sell them, as do apex performance.

[zeppelin101]

Apex sell bushed ones. Driftworks arms are all rose joints.

[immy21]

I might be wrong but I'm sure DW sold bushed Hardrace arms last time I was looking to buy some.

[Sibbers]

Cheers lads, guess these are the ones then although maybe not the best price.

http://www.hardrace.co.uk/apex-rear-...bber-bush.html