What does this tyre wear tell me? (first track day)

[rotorwings]

After my first day ever on track my front two tyres have wear as shown below in the images.
There seems to be a build-up of rubber on the inner 1/3 of the tyre surface.

My guess is that this might indicate that I am running too little camber?

Any tyre wear detectives out there care to comment?

[url]

|http://thumbsnap.com/f4x3JT41[/url]

[jeffw]

That shows your tyres have got hot enough to pick up discarded rubber on the track. this is quite normal. It will clean off on its own on the road or you can use a heat gun and scrapper to do it yourself.

[DCL]

Yes, that looks normal to me. There's no serious wear on either edge so I think your camber is OK. The fact that the rubber has accumulated in the center area suggests IMHO that maybe your hot tyre pressures may have been a bit high.

[fergus]

A cheap probe type tyre pyrometer is your friend here. Insert it in each 1/3 section of the tyre about 3-5mm under the surface to get your temps. This makes it easier to define whether you have a pressure or geometry issue.

Simply setting "X degrees negative camber" on your car may be sub optimal for *your* driving style and pace or the track, so may give less grip than a setup which the tyre temps suggest is using more of the tyre section more evenly than a really aggressive setup.

Looking at the surface of the tyre alone can mask some problems as you can get hot/cold tear which can suggest issues which would require a different course of treatment...

[ForzaGilles]

DCL said:

Yes, that looks normal to me. There's no serious wear on either edge so I think your camber is OK. The fact that the rubber has accumulated in the center area suggests IMHO that maybe your hot tyre pressures may have been a bit high.

+1

[rotorwings]

DCL said:

Yes, that looks normal to me. There's no serious wear on either edge so I think your camber is OK. The fact that the rubber has accumulated in the center area suggests IMHO that maybe your hot tyre pressures may have been a bit high.

Thanks, that's some good info. I had a feeling that the pressure might have been too high. I was running 22.5psi cold on the front and back. Based on what I have read, I think 20psi cold might be better? At least on the front...

If I lower the pressure, am I likely to need to run more camber?

[Dr Slotter]

My first thought on seeing the pictures was "normal, but a bit too much pressure". I would aim for 21 hot and then tweak from there. I wouldn't muck about with the geometry just yet.

[Shropcat]

If the rubber accumulates towards one side of the tyres it can also just mean that your have done more RH (or LH) cornering.

[fergus]

Shropcat said:

If the rubber accumulates towards one side of the tyres it can also just mean that your have done more RH (or LH) cornering.

most of the rubber in the picture is pickup rather than relating to the surface of the carcass itself.

[DCL]

rotorwings said:

Thanks, that's some good info. I had a feeling that the pressure might have been too high. I was running 22.5psi cold on the front and back. Based on what I have read, I think 20psi cold might be better? At least on the front...

If I lower the pressure, am I likely to need to run more camber?

As you lower the pressure, more of the tyre will come in contact with the track and the rubber will work further across. There will always be some rubber picked up, but it tends to happen more if 'surface' temperature is high, and that's often due to the tyre sliding more (ie a lot of under-steer on the front). As the tyre begins to work properly, and balance is achieved, it will reduce.

For track work I'd start at 18 psi cold and then lower it to balance the car. You may find it's goes as low as 15 psi cold on the front. At those pressures you will need more camber as the tyre will move more, but I wouldn't change until there's evidence that the outer edge is having a hard time. The ZZR likes about 2.5 degrees on track, but as said, the best amount depends on many things including how you drive it, and the nature of the track. Nothing beats time spent testing these things.

Edited by DCL on Wednesday 6th July 15:17

[rotorwings]

Thanks for all the great advice. I'll start with a drop in tyre pressures and then reassess.

[Amris]

DCL said:

rotorwings said:

Thanks, that's some good info. I had a feeling that the pressure might have been too high. I was running 22.5psi cold on the front and back. Based on what I have read, I think 20psi cold might be better? At least on the front...

If I lower the pressure, am I likely to need to run more camber?

As you lower the pressure, more of the tyre will come in contact with the track and the rubber will work further across. There will always be some rubber picked up, but it tends to happen more if 'surface' temperature is high, and that's often due to the tyre sliding more (ie a lot of under-steer on the front). As the tyre begins to work properly, and balance is achieved, it will reduce.

For track work I'd start at 18 psi cold and then lower it to balance the car. You may find it's goes as low as 15 psi cold on the front. At those pressures you will need more camber as the tyre will move more, but I wouldn't change until there's evidence that the outer edge is having a hard time. The ZZR likes about 2.5 degrees on track, but as said, the best amount depends on many things including how you drive it, and the nature of the track. Nothing beats time spent testing these things.

Edited by DCL on Wednesday 6th July 15:17

I had a really interesting conversation with Andy at PGM regarding tyre pressure on my recent visit there. He suggested running the ZZR at 23/24 degrees (hot) on track, and the ZZS's at 27/28. This differed from track to track but they found this to be the best compromise of performance over degradation. Similarly in the wet he advised putting the pressures right up into the 30's. Took me completely by surprise as you only ever hear most people reporting 18-20 degrees.

[bcr5784]

Amris said:

I had a really interesting conversation with Andy at PGM regarding tyre pressure on my recent visit there. He suggested running the ZZR at 23/24 degrees (hot) on track, and the ZZS's at 27/28. This differed from track to track but they found this to be the best compromise of performance over degradation. Similarly in the wet he advised putting the pressures right up into the 30's. Took me completely by surprise as you only ever hear most people reporting 18-20 degrees.

I must admit I've always been surprized how little variation in tyre pressures are used in cars on the track. In karting there are big variations track to track and wet, dry and damp. The only thing I can think of is that kart races are very short and you therefore want to get heat into the tyres quickly - but not cook the tyres by the end of the race.