^ pretty much it, there is a listing on bprojects ebay, they are anodised purple.

ok cheers guys, had a rough idea but now its a bit clearer, so some kind of spacer between the bottom of the strut and the steering arm lengthens the strut and changes the angle of the control arms and tie rods ends thus reducing bump steer?

the spacers sandwich between the balljoint and the strut, so the wheel height is unaffected, but the control arm is moved downward. That means at lowered suspension heights, the control arm once again has a little downward angle as it moves out to the outside (wheras if you lower em enough, it will be dead level, or even an upward angle. This pretty much avoids the 'unloading' under lateral force issue that can crop up.

The second thing mentioned was bump steer spacers, which are related but not necessarily the same thing (it depends on where the steering knuckle attaches to the ball joint or the strut. Basically the deal is this - you need the tie rods (the thing between the steering knuckle and the drag link) to be as close as possible to the lower control arm in length and in angle. That way when the suspension compresses, they move 'together' and there is no change in the steering angle. If they are different, then you might have 'ideal' toe in at ride height, but go over a bump, or as the suspension compresses on the outside of a turn those angles and lengths are different, so it changes the steering angle with suspension travel. This is known as bump steer. And on some cars it is shocking, and often gets worse as you lower them (especially if the control arm passes 'horizontal' at a different range of suspension compression than the tie-rod). On some of the worse affected cars that are then worsened through lowering, go over a bump and it's enough to make the car veer strongly in one direction (with about as much force/rate as if you had switched lanes on a freeway at 100km/h)

A body mopars aren't too crash hot for it, especially once they are lowered. There are a few rack and pinion conversions for them. One of the early ones, by a complete dirt bag was so bad you'd think he was trying to kill his customers. He didn't even know what bump steer was but sold that kit (and it made it even worse than worse case scenario with std steering and massively lowered ride height).

Anyway one of the tricks, to counter this, is to space the outer tie-rod end (the pivot point) for hte steering knuckle lower down. usually this corrects things (seems most of the design issues tend to 'need' correction in the same direction, even though it's possible to require either if the design is bad enough.

Anyway, so one 'kit' lowers the control arm (and some of them lower the tie rod end too, if the location of them is both shifted by that single spacer plate) and the bump steer kit either has special tie rod ends where the tapered pin is there, but there's an extra inch of straight pin then the ball joint/socket joint - spacing that pivot point lower by an inch (or so) compared to standard tie rod ends. Of course this puts more stress on the pin, more change it can have issues (1 inch isn't so bad). On some early porsches the amount it has to be shifted is massive, and they have long spacer bolts, but then they weld another support beam to the stub axle and the tie rod is swapped for a rose joint and is 'suspended' between the centre of the longer bin - supported at both ends.

Whilst I knew about bump steer correction before, the only reason I know aout the porsche stuff is I tried to find some good links with pics to help explain it, as I know the written text sometimes just struggles where a picture can help a lot.

http://www.pelicanparts.com/catalog/s ... /POR_911M_SUSprf_pg32.htm

http://forums.pelicanparts.com/porsch ... ade-bump-steer-kit-3.html

Since I mentioned the angles and lengths of the tie rods and the control arms (for strut cars at least, it's a little different for dual wishbone cars depending on how high or low the steering knuckle is) let's say we 'got it perfect' Great. but we need more neg camber, and can't get any more from teh strut top adjustment. We 'might' be tempted to redrill the lower control arm bolt, so it is relocated 1cm further outboard in the crossmember. This will definitely work, but to get it back to proper 'toe-in' we have to adjust the tie-rods out by 1cm (assuming they have the adjustment left) problem is now the tie rod is 1cm longer than the control arm, and as the suspension travels, the angles and lengths don't change in unison. Hello bump steer. On a well developed track car, there'll be very little total suspension travel, maybe 1-2 inches tops (for most scenarios) Anyway - point being they can 'get away' with a bit more, because the much reduced total travel means that the bump steer won't be too severe.

but that same amount of bump steer per inch of travel (for want of better terms) on a streeter - even one with stiffer springs, will see twice as much suspension movement (let alone one with std springs, which can be bottomed out pretty easily in my experience) it's a big deal and it makes the car very unpredictable an unstable entering and during mid corner.

Obviously the 'way to go' if you had the above scenario would be to lengthen the control arm by 1cm (or whatever amount) and adjust the tie rod out by a similar amt, and then it'll have roughly hte same bump steer (or lack of it) that it started with. Obviously lengthening the control arm isn't easy or cheap, but it might help demonstrate the context a bit better.

There was a thread on performance forums years back about a guy who had a quad bike (one of the new chinese bikes that are now flooding the market, with 'mixed' quality control. Anyhoo, it seems the tie-rods could be mounted different ways, probably a straight pin not a tapered one. Anyhoo, the guy posted pics of the front suspension (sadly originals aren't there any more). I managed to find a slightly edited pic, and then 'unedited' it as best I could, then did 2 new edits to it. Bump steer can be an issue with as little as 1-2mm of steering change through suspension travel. No kidding, this bike probably had 2-3 inches of bump steer - and it's obvious why.







Now obviously on 99% of cars out there it'll never be within coo-ee of being that bad, but it illustrates the point, and how it can be addressed. So if you have 'some' bump steer in a factory car, and the tie-rod and control arm lengths can be made similar, then getting them on the same angle *usually by relocating/altering the tie-rod end or it's attachment point, then it can sort it.

In some instances, you just can't get the angles/lengths the same, and you have to essentially relocate the tie rod end to find the lesser of two evils - find the angle that causes the least amount of steer angle change over the range of suspension travel the car will actually experience.

ahh im running 13x7s on the front. yeah ill give you a buzz tomorrow some time and we can organise a time for me to come round and have a look. cheers rob ;)
um from what i can gather bump steer spacers effectivly lengthen your strut to change the control arms angle to a more steep angle, if that makes sence. haha
ebay :)

sorry to hijack your thread and forgive my ignorance but how do bumpsteer spacers work and where do i get some?

Ah,good to hear Nathan,what rim width have you on the front now?This may still be an issue even with 185's.I need to have a look at it and may be able to give you a few ideas.One of the biggest gains i have employed in all the leaf spring Dattos i have used has been to alter rear roll steer movements whilst keeping a soft spring rate on the rear.Give me a ring if you want.
Cheers
Rob

oh and to add, its not understeering as bad as i first thought, went for a mountain run yesterday and it was holding on pretty ok, but the issue is still there, id rather more oversteer than understeer

thats alot of information jmac thanks. haha bert! i got new tyres! they are 185/60s all round. not running 155 65s any more haha.
so really what your saying jmac, is possibly suit a spring to the shocker rate and possibly bump steer spacers to keep the control arms at a good angle?
and no, i have an open diff

Do you have a locked diff?

Not being a smartrrrs but how did you lower it and still have stock springs? And just how far is it lowered?

If the springs have been cut, that increases their rate but it also drops the suspension height, so for any given corner the total suspension compression (as in where it ends up, not the amount of travel from it's relatively lower starting position) will be lower than with std springs/ride height.

This is important, as it means you'll get to teh point that the lower control arm passes vertical and the outside edge of the control arm is 'higher' and the inner control arm bush bolt pivot point is lower.

I'm totally murdering the physics here but basically this combination can actually allow forces to 'unload' the outside front, instead of helpful weight transfer/downforce (evne though the car can 'roll over' the tyre itself can unload.).

It's a little bit like leaf springs if you use lowering blocks to the point the axle line is too high, then it will lose traction off the line under hard acceleration easier.

So, what I'm getting at here is that although this might sound totally backward, if you have soft springs and a lower ride height, then it could be so low it is unloading hte suspension, and one of the ways you can actually combat it is with slightly stiffer springs, or a slightly higher (but possibly still less than brand new factory spec) ride height.

You might also find that the shock damping rate on bump is too high now, and teh wheel is having trouble staying on the road in a corner with any minor undulations in the road. Worse still, if the shocks are too stiff, but the springs too soft, it will keep breaking loose as it can't ride the bumps well, but then won't have the spring rate to help push and get the downforce onto the wheel when weight transfer does take place during cornering (weight transfer not necessarily body roll).

If the control arms aren't on those bad angles,and the shockers are too stiff on bump (or a combo of that and the springs being too soft) then yes, less front bar or adding/increasing rear bar stiffness would be the go.

You can also try dialling in some toe-out. It's a no-no on street driven cars as it'll chew out the inside edge of the tread (esp with some neg camber in the mix too) but it will noticeably improve turn in and mid corner (and even to some extent corner exit) stability. It might make it a little more likely want to pull to one side or the other under very heavy brakes too.

As far as your camber settings go, they seem pretty good, certainly nothing there that would cause understeer - they'd be in a good range to help prevent it.

Last but not least - tyre pressures. I have nfi what tyres you are running, but if they are taller sidewall, or just average tyres in general, you can often get some decent turn in (with radial street tyres) and overall cornering predictability/stability from increasing the tyre pressures, up to as much as 40psi (but make no mistake, you_WILL definitely wear out the centre of the contact patch a hell of a long time before the tyres would otherwise have lasted for with more modest inflation pressures. Certainly experiment right up into the high 30s or above if you don't mind that trade off.