Tire Rack: "Shaving can increase tire life" (?)

True, some very soft R compound tires will "chunk" around the outside edge at full depth which can lead to a very short tire life.

 

Tires with tall and squirmy tread generate excessive heat. The excessive heat causes the tire to chunk and turn into garbage. By shaving the tire the tire does not heat excessively and so doesn't chunk.

 

Yup. I used to have TireRack heat cycle and shave tires for my race car with great results.

 

shaved is always better. duh

 

With DOT race rubber I've done it both ways. I'm too dumb to notice a difference and what is 6/32 or 8/32 shaved to 4/32" anyway? I can't feel that or see that in longer life. So I shave my tires to 4/32 by tracking them...drive them to the cords and then get new ones. One advantage to some compounds of race rubber like Toyo RA1's/R888 for example is that keeping them full tread (not shaved) is a huge advantage if you are buying tires in the 4th quarter and it happens to rain at your trackday. Oh...I have my own tire mounting machine so if I want more life I'll flip some tires that can be flipped and I'll get more life that way than shaving them.

 

BAM!!

In all seriousness Ian, think of what Kimi's rain tires did in Malaysia. That's what can happen to R compounds, although not that quickly.

 

I think this is spot on. And track rubber tends to have a life dictated by heat cycles, not tread depth. If less tread leads to reduced heat cycling, the tire actually lasts longer than full tread.

 

Well longer life and better performance are party-line with heat cycling and shaving, but this statement above I don't buy. A heat cycle is one warmup and one cool down and the count of cycles is not effected by whether a tire is shaved or not. Although the speed of a tire is heat cycle dependent. If you managed a full tread tire i.e. don't chunk it and compare the ultimate life vs. a shaved tire that now is down 50% of its tread depth before your first lap, that total life time many not be so different. A typical dot tire is 8/32 shaved to 4/32. Lets say you buy 2 sets of tires one shaved one not. If say you wear 2/32 (twice the wear) on an unshaved tire/heat cycle= 4 cycles bore you see the cords Vs. wear 1/32 on shaved tire/cycle = 4cycles before you see the cords You now will be buying 2 new sets of tires at the same time.

Overheating a tire is not managing a tire and it is slow. Chunking is not a property of an unshaved tire but a result of bad tire management.

A shaved tire is faster supposedly because of tire squirm of full tread blocks but to be honest how many here are good enough or consistent enough or even ever collected data to see this difference? There is a bigger difference between different dot tire brands and compounds than shaving would ever get you.

To the OP...do you use a "probe" pyrometer in the hotpits and have you collected data? If you have not done that then there is more you can do in this area to preserve and manage tire life before you get into the minor benefits and additional costs (Tire rack charges for this) shaving and preheatcycling will give you.

 

His statement is true. The life of the tire depends more on the heat cycles because the properties of the rubber changes as heat is introduced into it (the rubber becomes harder and has less grip). We have discovered this on the Toyo R888s we run on our BMW World Challenge Touring Cars. The tires are good and consistent up to 5-6 heat cycles. After this the tire is drastically slower than before and causes the handling of the car to feel like it is way off. At this point we sell the tires off as take offs at a steep discount. The tires are then great for DE guys who want to have fun on them. From there they get about another 20-25 cycles before they show cords.

As for full-tread vs shaved tires. The shaved tires are going to faster and will last as long as the full tread tires. The shaved tire will be at a minimum 1-2 seconds a lap faster than the full tread tire. This can be repeated with most drivers. Tire management on a modern day Ferrari weighing 3200lbs or more with drivers on full tread tires is a very hard thing to do when you are driving the car on the track. It can be done but the car will be lapping slower than it could with shaved tires. The tires even at a moderate pace will see excessive squirm and heat build up with the full treads. I don't have data numbers to back this up but my own experience driving lots of different cars with this type of tire on it. Every time I have driven a car on track with full tread tires I put excessive heat in the tires to get a fast lap time because they are sliding around more. So fast lap times throw with a full tread tire throw tire management out the window. The only way to use tire management then is to be in an endurance race where you are running 13 Hours straight and have a set lap time that you want the car to turn every lap.

 

A treaded tire (especially a treaded street tire) at any given cornering load automatically creates a higher slip angle due to the additional squirm in the tread. This creates two poor qualities:

First, the additional squirm generates more heat with no gain in cornering grip. As the tire temperature climbs the tread will overheat and get greasy. Grip then goes down. Continue to run the tire hard and it will continue to get greasier as temps continue to go up. Soon there after the tread starts flying off in big chunks, usually starting from the outer sidewalls.

Second the additional slip angle caused by the squirm slows the tire's response to directional changes. The car feels "mushy and lazy" to steering inputs compared to a shaved tire.

Don't confuse slip angle with sliding as many do. Simple illustration is performed with a new pencil. Hold it upright with the eraser against the paper. Press the eraser against the paper while slowly twisting the pencil back and forth in your fingers. You'll find you can twist the pencil quite a few degrees in either direction without the tip of the eraser itself moving against the paper. The harder you press the eraser into the paper the more angle you can generate before the eraser slips. This is slip angle. Now cut half of the eraser off the top and repeat the test with the same amount of force pressing into the paper. You'll find you can't twist the pencil as far before the eraser slips. Total grip of the eraser is the same in each case but the slip angle decreased.

 

That's one of the best descriptions I've seen of SA.