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Slick tyres after Blyton
unijacko67 - 14/4/14 at 10:53 PM

Just took my tyres off the car tonight after Blyton ppc day to find out that the o/s front and rear have worn quite badly, but on the inside edge for about an inch. Is this normal.

I only had 13 psi in them cold and they are avon's so might not have been hard enough.

Live rear axle so can't be too much camber and almost exactly the same front & rear.

Any ideas. I did stay out on them for a while, but just seemed a bit odd.

ali f27 - 14/4/14 at 10:57 PM

have you 4 wheel aligned it can be quite a long way out we have just done race car and were surprised how far out it was

unijacko67 - 14/4/14 at 11:05 PM

Yeah wheelbase is to within a mm and the rear axle centre is centred with the front. I made a jig that bolts onto the rear hubs and goes the length of the wheelbase, then measured the distance to the front hubs ect so I think that is very accurate.

I'm no expert like, but a bit of a fart with all that stuff. lol

laptoprob - 15/4/14 at 07:26 AM

quote:
Originally posted by unijacko67
Just took my tyres off the car tonight after Blyton ppc day to find out that the o/s front and rear have worn quite badly, but on the inside edge for about an inch. Is this normal.

I only had 13 psi in them cold and they are avon's so might not have been hard enough.

Live rear axle so can't be too much camber and almost exactly the same front & rear.

Any ideas. I did stay out on them for a while, but just seemed a bit odd.


Its quite normal for them to wear badly on those two at Blyton mate. I have/had the same issues on my 888's many times but for them to wear that badly on the inside only i would say your camber is too extreme and needs to be dialled out a touch.

ali f27 - 15/4/14 at 07:27 AM

Ask about you never know might just be blyton local garage has all the gear when we built the car we made everything adjustable and the laser gear was a doddle to use mark did kames sprint at the weekend and said it was way better have you corner weighted it could be your weight i imagine yor car is very light just some ideas

unijacko67 - 15/4/14 at 09:09 AM

quote:
I would say your camber is too extreme and needs to be dialled out a touch.


Yeah thats what I thought, but no camber on the rear as it's live axle and the front tyre is almost identical in wear.

Pictures taken from rear of the car with the wheels stacked in the same position as they came off.

Obviously they picked up a bit of debris on the way back to the pits.







CNHSS1 - 15/4/14 at 02:23 PM

my two penneth

most of it looks like tread migration, which generally means you are getting them hot enough by generating enough load, so that's a good thing!
it looks to me as if the shoulder is thin on rubber where it meets the sidewall. Often this is due to too low a pressure (come back to that in a mo) causing the tread surface to buckle and form wave instead of the normal slightly crowned profile.

problem is, that unless you know exactly the construction and compound of the slick, then the pressure may be fine but the construction too soft. If you speak to Avon or any other race tyre supplier, they will often have a number of cionstructions even for the same size tyre. Some will be stiffer wall, or different bias to the plys to suit whichever single seater series they were aimed at. Often any tyre aimed at a downforce category will be much stiffer in the sidewall than say a non-wings formula. The issue then becomes that the same size tyre, in a different construction, will react completely differently to the same pressure.
some of the stiffer sidewall slicks will look perfectly ok with 2-3psi in them on a single seater!! (leaky split rims...).

id suggest a little more pressure to ensure the tread doesn't buckle, and see if that improves the wear pattern. If it does you may need to tweak the dampers a little to get the car handling as you want it. Alos well worth checking each tyre after a number of laps with a temp gun on all three areas, inner centre and outer tread, to get an idea of how the tyres working. Slicks are quite sensitive to camber and toe, and temperature of course, so once too hot they disintegrate pretty quickly, so you should need a few laps on circuit compound slicks to switch them on, if they are perfect out of the pits, they will likely melt after 3-4 hard laps!

do you know the source of the tyres? (and I don't mean Freds Tyre Shop lol), the series they came from?

whats the weight of the car on each axle?

unijacko67 - 15/4/14 at 03:15 PM

Thanks ss1,

I got the tyres from BMTR and told them it was for track use on a 750kg car. Each wheel will have around 450lbs on them with driver and more at Blyton as I had passengers all day.

I've just shown them to a sprint chap and he has said almost exactly the same thing as you regarding under inflation so I think I need a bit more psi in them. He sugested around 22 psi and check when back to the pit's.

I also probably did a few too many laps in one go.

Thanks for your help.