Tyre Wear

[No Crust Racing]

Hi Guys,

I've got a question regarding my tyre wear up front.

Car is S13 with Coilovers running Bridgestone Potenza Semis.

After the last track day I noticed the inside edge of the fronts had taken a noticable beating, I did around 160k's at Winton.

I'm running -2.5 deg camber up front with toe set to 0 (from what I recall, can't find last alignment settings camber I'm certain though) and -1.5 in the rear.

The reason I'm querying my camber setting is that I have two conflicting bits of info. On one hand I'm thinking that I'm running too much camber for my vehicle speeds and not getting the tyre contact patch evened out under cornering (it's only a CA with minor mods). On the other hand I had Luke Youldon (he was my driver trainer on the last track day I did) tell me that I need a bit MORE camber to stop the car wanting to understeer in higher speed corners (like the double apex left hand sweeper at winton). He said it was that or that my semi slicks were almost gone (which is highly likely as I bought them second hand to learn on).

I can throw up some pics if necessary but it's pretty straight forward, the inside edge of both fronts is clearly more worn than the outside edge.

My gut feeling tells me a bit less camber would be better. I have adjustable camber tops on these coilovers but I know that changing my camber settings will throw out my toe also and I'm not sure which way to adjust or by how much.

Thoughts appreciated

[Marlin]

What hot tyre pressure do you run, and what tyre?

[No Crust Racing]

About 32-33psi and they're Bridgestone Potenza 540's or something (not an RE55's - of that I'm sure).

They measure 235/45/17's

Edited November 29, 2009 by ActionDan

[Marlin]

Hmmm, well, your camber spec and toe is the same as mine in the front and I certainly don't wear the inner section.

Is it super duper stiff, like rock hard coil overs? The car not rolling over on the tyre is the only reason I can see.....

[No Crust Racing]

Standard sway bar, front shocks are only running 6 "clicks" up from the softest setting out of a possible 32 steps, so close to softest, they're only 8kg springs too.

Reckon I'm just not carrying enough corner speed? My car is not that quick, mild mods on a CA doesn't give big power.

[phunky_monkey]

Camber is not excessive Dan, I was running more than that and never had issues wearing the inside of the tyre.

If you're not getting the outright cornering grip that is usually generated by the old semi-slicks then, as Ben has said, maybe the car isn't rolling over enough with the stiff springs you're running.

[Russman]

Don't worry about it man

Buy a heat gun and next time you go to winton get a reading of the outside, middle and inside of the tyre and adjust the camber to suit. Try to get even temp across the tyre and that's the best camber setting you can have for that track.

Problem is if you're tight like me. Don't wanna pay $100 for a heat gun

To me a 'understeer-less' car is more important that tyre wear.

Could also be caused by braking wear

[No Crust Racing]

Hey Dane

Yeah dunno, I didn't think 8kg was "that" stiff and I've got the shocks pretty soft. I might knock'em back further for the Fun Day coming up, see if it makes much of a difference.

[No Crust Racing]

Russ,

Dude look at my car, I'm ALL about budget racing

True, no understeer is win, and the semi's were dirt cheap as they were second hand but if I can get more out of them (I'm already flipping them on the rims etc) then that would be great.

I'm more interested in improving my handling by having the right settings and I'm concerned my tyre wear shows that I'm running the wrong setup for my car speed/skill/track etc

[phunky_monkey]

Hey Dane

Yeah dunno, I didn't think 8kg was "that" stiff and I've got the shocks pretty soft. I might knock'em back further for the Fun Day coming up, see if it makes much of a difference.

You're right Dan, they're not that stiff but if the tyre you're using is that old (RE540's haven't been around for a long time now) then they're probably sliding a little instead of biting down into the tarmac and rolling the car onto the correct contact patch. If the spring was softer it may actually roll it over with less grip from the tyre.

Having said that though I wouldn't go changing the springs or anything, I'd say it's the tyres letting you down mate. That's my theory anyway!

[No Crust Racing]

Well they are old and they are very second hand so the heat cycles have probably hardened the compound a bit.

Clarify something for me, if I wind the camber out a bit, say back to -2 deg, that will give me a touch more toe out than it has now yes?

[No Crust Racing]

Furthermore, I spoke to DMS about it (here in Albury/Wodonga) and Jamie reckons the car needs less Castor (from memory it's running about +5.5) as this increases load on the tyre shoulder during cornering. He said he'd start there and then look at tyre pressures (which are currently around 32-33 hot) given the alignment fgures being as I have claimed.

He noted that -2.5 was sfa camber and that it should not be wearing the edge hard.

Edited November 30, 2009 by ActionDan

[djr81]

A few things:

1. Find a photo of your car cornering & then look at the outside wheel/tyre. That will tell you what is going on as much as anything.

2. You wont learn anything running on second hand tyres.

3. 2.5 degrees camber is not much nor for that matter is 5.5 degrees castor. The effect of 5.5 degrees castor is not great when you have a quarter a turn of lock on the car.

4. What are your front toe setings?

5. 8kg is stiff.

6. Everyone you speak to will have a theory. Most of them will be wrong. Mine included.

[No Crust Racing]

A few things:

1. Find a photo of your car cornering & then look at the outside wheel/tyre. That will tell you what is going on as much as anything.

2. You wont learn anything running on second hand tyres.

3. 2.5 degrees camber is not much nor for that matter is 5.5 degrees castor. The effect of 5.5 degrees castor is not great when you have a quarter a turn of lock on the car.

4. What are your front toe setings?

5. 8kg is stiff.

6. Everyone you speak to will have a theory. Most of them will be wrong. Mine included.

1. I don;t have any with the new rims/tyres and suspension settings, I might after this next track day.

2. Disagree, learned that even second hand semi's shit all over brand spanking new "WAN -LI" which came on the car, of course this was not a surprise. What I really learned is that My GT-R with it's Dunlop Direzza's would have a hard time out cornering my S13 with these super cheap/stuffed semi's. Ergo, I will be buying new semi's when these die rather than good street tyres.

3. Agreed - I'm simply exploring theories, bottom line is the tyres are wearing. I'd like to know why so I can minimise this.

4. As I understand it, 0.

5. On the softest damper setting they "feel" no different to a car with stock shocks on lowered springs. 8kg, by comparison to what a lot of other track cars are running (only based on what I read of other people's setups) seems soft by comparison. Perhaps this is a "perspective" thing.

6. lol agreed and thanks for your input, much appreciatd

7. Lists rule.

[djr81]

1. I don;t have any with the new rims/tyres and suspension settings, I might after this next track day.

2. Disagree, learned that even second hand semi's shit all over brand spanking new "WAN -LI" which came on the car, of course this was not a surprise. What I really learned is that My GT-R with it's Dunlop Direzza's would have a hard time out cornering my S13 with these super cheap/stuffed semi's. Ergo, I will be buying new semi's when these die rather than good street tyres.

3. Agreed - I'm simply exploring theories, bottom line is the tyres are wearing. I'd like to know why so I can minimise this.

4. As I understand it, 0.

5. On the softest damper setting they "feel" no different to a car with stock shocks on lowered springs. 8kg, by comparison to what a lot of other track cars are running (only based on what I read of other people's setups) seems soft by comparison. Perhaps this is a "perspective" thing.

6. lol agreed and thanks for your input, much appreciatd

7. Lists rule.

Please don't confuse damper settings with spring settings. The spring will define how much roll you have in mid corner (along with sway bars etc). The damper won't. Adjustable shocks aren't worth a pinch of sh!t unless you pay huge money to Penske's etc.

I am not advocating buying shit Chinese rubber. I am simply stating that with second hand tyres you are inheriting the previous owners wear patterns & then superimposing your own. Which is less than usefull. For what it is worth the inside of my tyres wear too. Mostly on the rear as it is wheelspin that kills them. Are the fronts you have fron the back end of someone elses car?

[No Crust Racing]

Please don't confuse damper settings with spring settings. The spring will define how much roll you have in mid corner (along with sway bars etc). The damper won't. Adjustable shocks aren't worth a pinch of sh!t unless you pay huge money to Penske's etc.

I am not advocating buying shit Chinese rubber. I am simply stating that with second hand tyres you are inheriting the previous owners wear patterns & then superimposing your own. Which is less than usefull. For what it is worth the inside of my tyres wear too. Mostly on the rear as it is wheelspin that kills them. Are the fronts you have fron the back end of someone elses car?

Noted regarding damper/spring differentiation. Sway bars are stock, spring isn't "that" firm so it should roll enough to get a decent contact patch if that's where you're heading?

Agreed re second hand tyres, even still, these are considerably better than what it was running. An improvement is an improvement regardless of the margin. These gained me lap time for a very good rate and while I'm learning (very green with track driving) I'm not stressed about flat spotting them or ruining them, as they were dirt cheap. So dirt cheap + made a very notable improvement = win?

These tyres came with even wear, it was only AFTER my first track day on them that the wear changed considerably. I have no which end of the car they originally came from before I got them.

[phunky_monkey]

Well they are old and they are very second hand so the heat cycles have probably hardened the compound a bit.

Clarify something for me, if I wind the camber out a bit, say back to -2 deg, that will give me a touch more toe out than it has now yes?

You'll be adjusting them independently Dan, so you can wind it back half a degree and keep toe at 0 from what I'm aware.

Here are my settings, which are a fair bit more aggressive than they used to be:

Camber F

-5 degrees

Camber R

-2 degrees

Toe F

0

Tow R

+2mm

Castor

7.5 (max without hitting anything)

I've only used them for one lap so I can't tell you what it's like yet, but interesting to see multiple suspension places different opinions on what works.

[No Crust Racing]

Oh I know they adjust independently what I mean isthat whenyou adjust camber it means the toe settings change at the same time, which is fine so long as you have enough adjustment to bring it back to where you want it.

That being said, I was just trying to confirm in which direction toe changed when backing off the camber.

[Russman]

Castor should not change with more or less camber. Correct me if I'm wrong people.

Dane. +2mm rear = drift?

[No Crust Racing]

sorry Russ I must not have explained myself well.

What Jamie was saying is that more caster = mroe neg camber through cornering = more load on the tyre shoulder, more heat, more wear etc.