ACB10 - scrubbing and geometry

[Asterix]

Can't find standard geometry settings (toe, camber, castor) for ACB10's - can someone point me in the right direction?

And I wish I'd seen the following advice on the Avon website before the Croft trackday on the 9th. Don't have time to do anything about it before Croft sprint next monday. Obviously some of the multi-lap stuff can't apply to sprinting, but does it apply to first use? Should I "find the time"?

QUOTE

User Advice

For most purposes, racing tyres will benefit from an appropriate 'Scrubbing in' procedure. This provides the best combination of performance and longevity under race conditions.

There are several difficulties that arise when using racing tyres if they are not scrubbed in prior to use. The most common is "Cold Graining", where the layer of the tread compound in contact with the track, fails in shear with the layer below. The result is a very visible low frequency, high amplitude rippling effect. This is more common with new tyres particularly when used in wet, damp or greasy conditions.

Avon Tyres Motorsport recommends that a standard scrubbing in procedure be used whenever possible (conditions and regulations allowing). This consists of subjecting the tyres through one gentle heat cycle, gradually loading them up whilst avoiding drifting the car. This should take about three to four laps of a circuit where the lap time is in the region of 60 to 100 seconds. The last lap should only be about 80% race speed. If possible, scrub in at least one new set of tyres during free practice, and put these aside for the race. In this way you will know that they have been balanced correctly, and have no slow punctures etc. Getting this done early is important as the qualifying session may become wet or be red flagged, which could force the use of new tyres in a race.

When regulations or circumstances do not allow the above procedure to be carried out, then the following should be borne in mind: -

   *

     Graining of the loaded front tyre can be avoided if it is ensured that they are fully up to temperature before pushing hard.

   *

     It is relatively easy to generate temperature in the driving tyres as they are transmitting power most of the time. The front tyres, however, will need to be given more time and be loaded up progressively before they will be 'In' fully. It should be noted that it is the loading of tyres that introduces the significant heat, not sliding or wheelspinning.

   *

     For qualifying, the best results have been shown to have been achieved when the front and rear tyre temperatures are the same when measured at the base of the tread. If pushed too early, the rear will come in before the front causing understeer, and taken to the extreme, cold graining as detailed above.

   *

     It is quite possible to get the rear tyres to go off before the front tyres come in, which will lead to a car that is never balanced, making set-up and qualifying very difficult.

Thus to get the best from a set of scrubbed tyres, look after the rear tyres by not using full power out of corners, and instead work the front tyres progressively without inducing large amounts of understeer. When the fronts are fully up to temperature, go for a time (really hooked up lap). Push hard for 2 to 3 laps, and then back off the pace for a lap to allow the tyres to recover, and to get some clear track. Repeat this procedure for the best results.

It should be noted that there is always going to be a slight performance peak from new tyres, but it will only be possible to take advantage of this if the car is balanced on its tyres. A correctly scrubbed in set of tyres will always give more consistent performance over its lifetime than a set that has been used hard from new, even if it hasn't grained.

[conibear]

IME, toe out 1/2 degree at front, 1/2 degree toe in at rear but depends on width of front track.

Camber front about 1.5 degrees and 0.6-0.8 at rear.

Castor less as possible, can you adjust yours then?

Tyres pressures dependant on compound and scrubbing is a waste of money    

[Asterix]

IME, toe out 1/2 degree at front, 1/2 degree toe in at rear but depends on width of front track.

Camber front about 1.5 degrees and 0.6-0.8 at rear.

Castor less as possible, can you adjust yours then?

Tyres pressures dependant on compound and scrubbing is a waste of money    

cheers. Re. castor, the answer is "no, I'm just stupid"  

re. scrubbing...Avon seem to be referring to  a running in process, are you talking about "buffing"?

Compound is A24.

[conibear]

scrubbing buffing, just give them stick in your 1st practice run, they are crossplys so 1 lap and they should have got rid of all the ****y oil based adhesive crap.

A24 is medium to hard I think, so pump them up a bit and see how they change when you finish a run

[Asterix]

cheers.

A24 is the softest ACB10, i believe.

[conibear]

cheers.

A24 is the softest ACB10, i believe.

Oh, in that case they shouldn't need to much air to start with then

[Asterix]

cheers.

A24 is the softest ACB10, i believe.

Oh, in that case they shouldn't need to much air to start with then

ta

Atmospheric pressure it is then    

[Scottish Bloke]

ACB10's should be run with NO camber in my experience.

[salexander]

A24 is the softest compound.  Camber settings are usually kept very low, no more than 1/4 degree.  There are lots of variables on any given day so you need to experiment a bit and check temperatures across the width of the tyre and check pressure gain after the run, typically aim for around 20psi when hot.

The procedure quoted by Avon is fine for racing but pretty meaningless when you are talking about a 2-lap sprint

[Terry Everall]

I ran ACB 10s on Busa with 0.5 deg front camber and zero on rear. Tyre pressure at 16 to 17psi

worked for me

[conibear]

So then, how can a 2 lap sprint, differ enough from a 10 lap race, enough so to require different suspension settings on a similar constructed tyre  and can someone please explain how a tyre that requires NO or VERY LOW camber, work to its design when you load up the suspension

 

[gp350se]

Better bring snow tyre's for monday looking at the forcast.

[Scottish Bloke]

So then, how can a 2 lap sprint, differ enough from a 10 lap race, enough so to require different suspension settings on a similar constructed tyre  and can someone please explain how a tyre that requires NO or VERY LOW camber, work to its design when you load up the suspension

 

Hasn't done me any harm, but what do I know  

I run them practicaly 0' camber, 17 psi and no toe. Works for me. FYI, car is a Vx redtop 500kg bla bla bla

each to there own I suppose........

Coat

[zoso]

So then, how can a 2 lap sprint, differ enough from a 10 lap race, enough so to require different suspension settings on a similar constructed tyre  and can someone please explain how a tyre that requires NO or VERY LOW camber, work to its design when you load up the suspension

 

Because tyres work differently at different temperatures...2 laps is not going to get them as warm as 10.

Remember the difference between static and dynamic camber.  Suspension systems will add camber to the tyre through the movement, by changing the static you are altering the dynamic.

[custardtart]

So then, how can a 2 lap sprint, differ enough from a 10 lap race, enough so to require different suspension settings on a similar constructed tyre  and can someone please explain how a tyre that requires NO or VERY LOW camber, work to its design when you load up the suspension

 

Because tyres work differently at different temperatures...2 laps is not going to get them as warm as 10.

Remember the difference between static and dynamic camber.  Suspension systems will add camber to the tyre through the movement, by changing the static you are altering the dynamic.

that's all good stuff but i see the point that why would you have different settings for a sprint over a race, does a slightly colder tyre really need a totally differnt suspension set up? I'd have thought they'd be the same with possibly slightly different tyre pressures that's all.

i'm doing my first sprint this year after a few yeas of circuit racing and I'll be using acb10's instead of Yoko A048's so i'm interested in this discussion.

For what it's worth, I'll be happy to feedback any differences noted as I'm planning on doing a bit of testing with the acb's prior to my 1st sprint.

What might be useful is if anyone has any temperature readings from acb10's taken after 2 laps, i suspect they are up to working temp after 1 lap and the second lap is at more or less optimal temp, the AO48's are upt to temp after 1 lap and they are not as soft as the acb's.