Wheel Alignment Question, Car Feeling More Skittish

[hardsteppa]

no worries. It was well over a year when I did mine and can't recall how much it needed to be lengthened but we are talking 1 or 2mm, it's a very small adjustment. Don't know if you've played around with your on alignments much but once you're in the range of where you want to be it comes down to very small adjustments indeed. Eg - front tie rods/rack ends, 1/2 a turn of these gives a couple of mm toe change (sorry not near my notes to say exactly) and I end up making adjustments like 1/8th of a turn to get it feeling 'just right'. Anyway what I'm getting at is, if you work out the percentage of how much it needs to be lengthened and you look at it and go, it's almost exactly the bloody same, it probably won't be once you get it on the car and it's doing it's job.

You can make a bump-steer gauge for around $100, main cost of that is the micrometer which is handy for all sorts of other measurements anyway and good to have if you've not got already.

[Dale FZ1]

http://www.sau.com.au/forums/topic/445063-r33-gtst-track-build/?p=7522364

This shows how you can sort bump steer issues yourself. Total cost of bits and pieces maybe $150 including a Chinese hydraulic bottle jack. Assuming you already have a set of chassis stands and trolley jack plus a level concrete floor to work on.

It just depends how motivated you are to learn and have a go, vs finding a suspension specialist that knows how to sort these issues without charging ridiculous money.

BTW, the relationship between the camber arm and traction arm might not be as per the suggestions above. If you want to stand the tyre more upright (good idea, target about 0.5 to 0.75 neg) then do that first.

For the bump steer, think about what the wheel has been doing at this point to achieve the bad handling. Wheel goes up, and starts pointing (toeing) out. That means the traction arm is too long. You should look at shortening the traction arm. Comments about small adjustments making a big difference are true. It's not something you should do by eye because there's no way of knowing what geometry you've actually achieved. If the arms aren't installed yet, do a measurement from centre to centre and match them to stock.

Then acquire all the low tech but reliable bits to stringline and adjust to your heart's content.

[GTSBoy]

Bump steer doesn't have to be toe out.

[Dale FZ1]

No it doesn't.

But it's toe out that brings about the lack of rear end stability that's the issue under discussion.

If it's toeing in under bump, then it should generally stay reasonably composed.

None of it is rocket science, and much easier to understand if explained simply. With basic equipment it can be corrected with fairly minor adjustment.

[V28VX37]

Thanks for your post Dale that's a pretty nifty setup you've got there, it's good to know that DIY alignment is possible if one is keen enough!

I just chucked in the adjustable traction rods, luckily I had done the Whiteline eccentric bushing kit previously so the nuts weren't crazy seized.

Here's how the camber arms measure (bolt-to-bolt roughly at the middle):

• LH: OEM 309mm vs. adjustable currently at 314mm
• RH: OEM 310mm vs. adjustable currently at 314mm

So there's about +5mm per side to correct for negative camber that'd otherwise creep in with this amount of drop. That's about +1.6% compared to OEM length.

Here's the traction rod measurements:

• LH: OEM 210mm vs. new adjustable set to 212mm
• RH: OEM 211mm vs. new adjustable set to 213mm

+1.6% on 210mm is approximate +3.4mm but I decided to play it safe and only do +2mm for now. The suspension shop can work out a better setting

I'll be interesting getting the whole dynamic geometry right with three separate points of adjustment (traction rod, camber arm, HICAS eliminator arm)...

Based on a quick drive the car does feel better, more stable around bumpy corners. Good stuff.

[V28VX37]

...

Based on a quick drive the car does feel better, more stable around bumpy corners. Good stuff.

Quick update on this just in case anyone else is having bump steer issues.

I was putting stiffer springs on my BC BR coilovers last week and noticed that one of the rears had a slight leak, rear right to be precise, which is where the bump steer issue was most evident.

I replaced the insert (shock) last night and lo and behold, the bump steer is good as gone! I compared the old shock to the new by hand and there was very little damping in the old one. So essentially the rear corner has been hanging pretty much by the spring only, no wonder it felt all vague and jittery...

Also for context I had previously replaced my left rear shock last year as it got super squeaky; I probably should have been more suspicious of the RH one now. The left side lasted just under 20,000kms and the right about 30,000. I'm not sure if it's the sedan or these coilovers specifically but the rears seem to wear out quicker than the fronts.

Lessons learned:

• Always check the most obvious things first
• Change things in pairs where you can

[V28VX37]

Traction Tyres in Rowville.

x111111111ty.

Have read that Tyrepower North Melbourne are also good.

That'd satisfy the "inner Melbourne" part of your post

Thanks for the tip Greg, I took the car to Tyrepower North Melbourne today. Great service and aligned exactly to the specs I wanted, at about half the cost compared to the previous place I used to go to. Thumbs up!