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Very weird tire wear after fitting Brembo calipers



  ff ph2
Hi all
Car in question is a fairly stock 172 ph2, running on sportslines and koni shocks, used for fast road only.
Used to have an almost perfect tire wear pattern, all of the tire width would wear pretty much the same, and tires lasted very long.
Since fitting Brembo calipers (PMS kit) and 18mm spacers, the outer side of the tires started wearing really fast for no apparent reason.
The pictures show missing rubber on this area - notice the middle isn't even close to the wear indicators, and the shoulders aren't worn (near the sidewall arrow).

I'm running the same amount of camber I did before, about -1.25 which is the sweet spot for me, also as you can see, the shoulder doesn't wear at all so it's not a camber issue.
I've had the alignment adjusted at 2 different places, tried toe in for once than out, no effect on the wear pattern. Camber and caster measured -1.25/3 at both places, again it's the same alignment I've had before.
Tried PS3, AD08R, 595RS-PRO, same pattern with all.

No play in any of the suspension parts, all of which are fairly new, and the same happens both left and right.
My driving didn't change, I don't corner on the limit or to the point of tire screech.
Tried over/under inflating tires without much effect - most of the the time I start with 33-34psi cold at the front, so can get to 40psi hot - whereas the wear pattern allegedly shows underinflation.

The only thought I've had, is after noticing the wear pattern was similar on old tires which I've used after changing track rods and driving with bad alignment, Is perhaps I'm getting excessive toe in under hard braking, as I brake harder than I used to before.

IMG_20200523_091102.jpgIMG_20200523_091157.jpgIMG_20200523_091218.jpgIMG_20200523_091219.jpg
 
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Ant1

ClioSport Club Member
Out of interest did you have the alignment checked before or after fitting the spacers?
 
  ff ph2
Many times before, and a few after.
A good point raised by a friend - the 18mm spacer reduced wheel rate substantially, I could definitely feel a noticeable difference after fitting it.
So it might have worsened body roll which caused that?
 

ZachB

ClioSport Club Member
  182
You still running arch liners and are they intact? So no rubbing (onto bumper bracket)?

18mm with 172 ph2 wheels arnt too wide. People run all sorts of ET, wider than your setup with this not being a problem to theirs
 
  ff ph2
No arch liners,
How do I know if I'm hitting the bumper brackets?
There's a bit of a running noise sometimes on slight understeer, I can't tell if that's normal tire noise or rubbing.
 

Smartie93

ClioSport Club Member
  182
I thought you said you did not drive to the limit? 😉

Your spacers will increase the dynamic toe changes you see under acceleration and braking, but I wouldn't have thought it would be that significant.
 

ZachB

ClioSport Club Member
  182
Yeah with more positive scrub radius and a tyre with a more square profile like that, that outer edge is really close to the bumper bracket and might be taking chunks out of the tyre.
 

ZachB

ClioSport Club Member
  182
WIth my asts (500lb fronts) It doesnt rub with ad08rs, but I had 195/50/16 a048s which would, you could hear the tread scraping the bracket like running a stick along a metal fence.
 
  ff ph2
Hmm interesting,
Checked the bumper brackets which were covered with layers of caked on dirt, no chance it was touching, bent them anyways as far as possible.


I thought you said you did not drive to the limit? 😉

Your spacers will increase the dynamic toe changes you see under acceleration and braking, but I wouldn't have thought it would be that significant.
Are you sure spacers would affect that?
The wheel hub angle is the same as the wheel angle, so why would spacers change this?
It can explain the problem to a degree, although I'm running a narrow non-sport subframe, so not far from stock with the spacers.
 

Smartie93

ClioSport Club Member
  182
Hmm interesting,
Checked the bumper brackets which were covered with layers of caked on dirt, no chance it was touching, bent them anyways as far as possible.



Are you sure spacers would affect that?
The wheel hub angle is the same as the wheel angle, so why would spacers change this?
It can explain the problem to a degree, although I'm running a narrow non-sport subframe, so not far from stock with the spacers.

Dynamic toe changes are not static toe. It is part of the suspension's compliance characteristics. These are changes in wheel position under load, controlled by how the various components in your suspension bend etc.

You will typically gain toe out and lose caster when braking, and subsequently gain toe in when accelerating. There is typically no effect on caster when accelerating as the longitudinal forces are applied at the wheel centre through the drive shaft.

The spacers effectively increase the lever arm your tyres have to compress the bushes, so you get more movement for the same force. An 18mm change in wheel offset is fairly significant but not outside the realms of what people run here.

What suspension components are new? Because the Clio has a fairly unique set up that actually uses the anti roll bar bushes to aid in longitudinal stiffness, hence its bushed and not drop linked. So worn arb bushes will result in more dynamic toe change.
 
  ff ph2
oh I see, that makes sense, thanks for the explanation.
Are we sure braking will cause toe out?
As that will make the inside wear, which isn't the problem :(
Wishbones/bearings/springs/shock/mounts/arb bushes/steering rack rods etc all new.. Always wondered about the front arb setup btw, disconnecting it makes the steering so much lighter and disconnected.

@ZachB Yeah that's obvious, but after seeing the brackets there's no chance it was rubbing.

I know that classic tire pressure wear chart would say I'm running underinflated, but as mentioned I'm overinflated when hot.
Any chance lowering the pressure to say 28psi cold, would actually be the solution, as that would allow better spread of load across the tread?
 
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ZachB

ClioSport Club Member
  182
Idk. Increased positive scrub with not enough camber causes the outside to plow with camber change and not enough roll stiffness. Could be all wrong.
 

Smartie93

ClioSport Club Member
  182
I was just explaining what dynamic toe is as it is influenced by your spacers but I don't think it would cause the issue you're seeing.

If you've only changed the spacers and calipers between now and perfect tyre wear, is it possible to run without the spacers? Or are they there for clearance?
 
  ff ph2
No chance of running brembos on ph2 172 5 spoke alloys without spacers
More camber might solve this, but doesn't suit fast road use from my experience - Massive impact on braking distance and too much oversteer that leaves no room for errors at high speeds...
 

ZachB

ClioSport Club Member
  182
Oversteer? My setup with 2.6deg and 630lb rear springs has understeer tendency.. If you like how it drives then youll just have to sacrfrice the tyres :unsure:
 


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