ACB-10 break in

[JamesA]

OK, the ACB-10s are here, how important is the break in procedure to tyre life and traction? The instruction I have are: "Race tyres should be broken in carefully by bringing the tyres up to temperature gradually over the first 15 minutes. The last lap should be as fast as reasonable. Then stop, take the weight off the tyres if parked on concrete and let the tyres cool."

I have the ACB-10s for track and autocross use, is the above a good precedure or even necessary?

For track use what do you think is the best tyre pressure when up to temperature?

[Peter Carmichael]

It is a good procedure. The official version from Avon last time I looked said to let the tyres rest for 24 hours after this first heat cycle. The tread compound cross links a lot of bonds during this process. It is very important that you don't slide the tyres around until the cross-linking has fully formed as the tread compound will "cold-grain" which basically means it will tear microscopically. You should use all possible measures in an attempt to get temperature into the tyres without sliding them, especially the fronts.

 

21 psi hot.

[yankeedoodoo]

How do you like those for autocross? I'm using CR500's and think I need something wider & stickier. Also, how do ACB 10's stand up wear wise?

[Mike Biddle]

Yankeedoodoo, I use them for autocross, and they are excellent, I have 37 trophies to prove it!

 

They don't last long, around 3,000 miles is probably the best you'll get depending on weight of right foot!.

 

They come in lots of different grades too, including some very sticky ones designed for short events like sprints etc where fast warm up is important. Not road legal though.

 

I guess you would be in B modified? So tyre choice should be free.

 

 

[fireblade]

From the Avon web site...

 

If you can follow this procedure, you have more self-control than I do :-)

 

John Latham

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Use of Racing Tyres

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.

 

Cooper-Avon Racing Tyres recommend 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.

[robmar]

ok can someone explain to me what loading of the tyres means

 

"It should be noted that it is the loading of tyres that introduces the significant heat, not sliding or wheelspinning. "

 

rob

[Dave M]

"loading"

 

I understand it to mean hard acceleration (without wheelspin) followed by hard braking (without lock up) rather than weaving all over the place. I got this from one of Carrol Smith's books. I cylce though this sequence to warm up my ACB10s for our super sprints (1/2 lap warmup - flying start - 3 timed laps)

 

Could be wrong though

 

Dave