Uneven tyre wear, geometry,bushes, spacers problem..?

[Zico]

I could do with some expert opinions on my wheel + tyre setup.

The car is a Pug 106 GTI which I use as a runabout/weekend fun toy. Its now on throttle bodies, been cammed, remapped, had some light headwork, a closer ratio gearbox, adjustable dampers all round, some chassis strenghtening and much improved breathing at inlet and exhaust, it goes very well indeed now but it really needed some improvement in the grip department and a big brake upgrade was an absolute neccesity
I had the option of buying some 15" lightweight Rally style OZ racing magnesiums which have an ET40 offset, at a great price which was too good to pass up, it meant I could fit the Brembo 4-pots, bigger 283mm discs and braided hoses which I'd had lying around, due to the extra inch in wheel diameter allowing the necesary clearance for the rotors.

So basically I've went from 185/55 R14 to 195/45 R15 which has a very similar rolling circumferance, however the ET40 ? offset on the OZ Mags meant I've had to fit bolt on 20mm spacers (which the wheels in turn bolt onto) and it works out at 10mm over the original offset iirc.


The extra grip, reduced sidewall flex and of course the stonking brakes have certainly made it a very different car to drive.. obviously far more grip and outright pace at the expense of some driving enjoyment in the handling dept... simply not as adjustable on/beyond the limits of grip.

The problem is that Im getting uneven wear (on the insides) on both tyres and more recently an increasing level of understeer, also the tyres hop/judder (tracking?) a bit when reversing on full lock.. now the lower arm bushes are visably kinda ok-ish... if a bit past their sell-by date. So just a few quick questions...

1. Are the spacers most likely to be the root of my problem... or is the offset difference minimal enough to get away with it..?

2. Maybe just a case of having the tracking done to remove some excessive toe-out ?

3. Or does this sound to you to be more of a worn bushes problem ?



I've been poorly (in my opinion) advised by someone who reckons he knows what he's talking about.. to push the top mounts/chassis legs out by 10mm using the adjustable strut brace to compensate for the slightly increased negative camber !... I certainly dont want to go down this road but would really appreciate some advice on what I should be looking at doing to get this problem sorted the correct way..


Many thanks.

[johnny99]

Before you do anything, check the alignment and wear of any bush's or joints. The wheel change will not change camber. You have been poorly advised.

John

[terence]

As above! It does sound more like a tracking problem though,you would need to be running a huge amount of negative to take out the inside edges of your tyres.

[GORDON STREETER]

You may wear the inside of the tyre out with too much neg camber driving on the road, as no way can you drive as fast as on a race track (regardless of what people think or say). I have run as much as 4 deg neg and still take the outside edge off regardless of what the tracking is.

[phoenix]

Hit any pot-holes recently? Sounds like toe out to me, which might be down to worn something, but more likely due to a knock bending something like a steering arm, a TCA or even a suspension mounting point/bracket.

[Zico]

Thanks for the pointers/info chaps..

Originally Posted by phoenix

Hit any pot-holes recently? Sounds like toe out to me, which might be down to worn something, but more likely due to a knock bending something like a steering arm, a TCA or even a suspension mounting point/bracket.

Yeah, the B-road up to my girlfriends has got into a really bad way in the last few months, you pick your lines to avoid them..

Might just go ahead and replace the lower arms, track rod ends and ARB drop-links in a one-er.

Thanks again..

[thebear]

A `mild' toe adjustment might also be in order. FWD cars require `toe out' as part of their standard settiing (the rears are set to toe-in). Have the shop set the the maximum specified `toe in' (possibly "0"). This can add some oversteer so take care when the road is damp.

[Notso Swift]

Actually Bear, a lot of road FWD cars do still spec the front to toe in, but toe out is what you want Toe out will not help your wear on the inside though.
YOu say slightly increased Neg camber... what from?
Have you adjusted more in, what sore of Neg are we taling about any more than about -1 will be a lot on the road and you will wear in insides just because you spend so much time going in a straight line. On the track we spend so little time going in a straight line and we are happy to sacrfice wear for lateral grip, but our tyre life is measured in heat cycles not on '000 of miles

[Zico]

Originally Posted by Notso Swift

Actually Bear, a lot of road FWD cars do still spec the front to toe in, but toe out is what you want Toe out will not help your wear on the inside though.
YOu say slightly increased Neg camber... what from?
Have you adjusted more in, what sore of Neg are we taling about any more than about -1 will be a lot on the road and you will wear in insides just because you spend so much time going in a straight line. On the track we spend so little time going in a straight line and we are happy to sacrfice wear for lateral grip, but our tyre life is measured in heat cycles not on '000 of miles

I was told that the spacers +10 offset was giving me neg camber by the guy who thought he knew what he was talking about (used to race mini's... allegedly ) but when I really think about it.. its not the case atall, I just have a very slightly wider track and tyre and maybe more stress/wear on the T/r ends because of this.

The 106 GTI has a very well balanced chassis with fantastic turn in and healthy amount of progressive lift-off oversteer as standard.. think of a slightly softer sprung 205 GTI with slightly longer suspension travel.
I noticed a few clunks today from the steering or maybe ARB drop-links..
Once I've replaced the lower arm bushes, T/R ends and ARB drop-links, I think I'll probably go for the factory settings again.

Thanks to all for your very helpful replies..

[Notso Swift]

I thik evrey one pretty much agrees that you should not listen to that guy who "knows what he is talking about"
You could be introducing (or more acurately accentuating) a bump steer issue, but 10 mm is not that much. Besides, youhaven't said it is bucking and weaving, quite the opposite. you say it feels good.
with camber for a road car I would keep to 0.5 to 1.0 neg, 2 mm toe out, and as much castor as you can get (assume you have power steer)

[Zico]

Originally Posted by Notso Swift

You could be introducing (or more acurately accentuating) a bump steer issue, but 10 mm is not that much. Besides, you haven't said it is bucking and weaving, quite the opposite. you say it feels good.
with camber for a road car I would keep to 0.5 to 1.0 neg, 2 mm toe out, and as much castor as you can get (assume you have power steer)

Thanks, Notso Swift, that really is very helpfull, yes there is a slight bump steer issue with the dampers set on comfort mode.. it does snatch at cambers, and 'buck & weave' as you say.. but when you go up a damper click all round its barely noticable for some reason and no longer an issue.

What a fantastic forum, great advice, thanks again..