i found this on the r6 board i go too.. i saw it a few months ago (either here or there) & thought it would be good to post because of recent tire questions.....
This letter was posted by Erik Astrup on a news group not long ago, it is a letter sent to him from a guy at Dunlop Race Tire Service...
Steve is well known in the racing world, and you've likely seen him in the
background shots in the winner circle. Steve is really hard to miss!
Anyway, Steve is President of Race Tire Service and is "Da Man"
for Dunlop on the East coast. He used to be out in the West coast
which is where I first met him at AFM races. Good guy.
Anyway, here's Steve's input -
Here is something you can post with regards to DOT racing tires on the
Erik Astrup has asked me to post regarding running DOT racing tires on the
First thing I must mention that I work exclusively with Dunlop product and
can only speak about product that I have first hand knowledge and
SAFETY. There is not a safety issue in running DOT racing tires on the
street. By SAFETY, I mean the tire will not have a failure or come apart
from normal aggressive street use. Excluding road hazard. (Falling down
on oil, gravel or excessive throttle is not a tire failure)
DIFFERENCE: The biggest difference in the racing tire and the street tire
is in the construction. Street tires have JLB construction and race tires
have a Cut Breaker or Cut Belt construction.
JLB is when the main tread belt (the ply just underneath the tread rubber)
has all of it plies running in the same direction. All the fibres are in
the same direction, pointing the way the tire rotates.
Cut Breaker construction is when there is 2 belts, both have the plies
running at an angle to the rotation.
Take one hand and hold it in front of you, point your finger to the
ceiling and keep you fingers side by side. This is what direction the
fibres run on a JLB breaker. Now take both hands with the fingers side by
side, lay one set of fingers on top of the other set at a 45 degree
angle. This is what a Cut Breaker looks like. (a picture is worth 1000
words, wish I had a picture to describe it better).
Whether you understanding the direction of the plies or not, the basic
difference in feel and performance is that the JLB construction is very
good for stability over bumps and feedback on odd surfaces. It also give a
much more smooth ride. This is better for a street ride and over the
things that one runs over when riding in street conditions.
The Cut Breaker is better at overall side grip. The basic word here is
SIDE GRIP. Cut Breakers give much more side grip and a bit of a stiffer
TEMPERATURES: What does tire temperature have to do with performance? Lets
first understand an old falsehood "Race tires won't stick till you warm
them up" this is untrue and is a falsehood. Here are the facts. If you
took a race tire and a street tire and ran them side by side, the race
tire would provide more grip than the street tire in every temperature
range. So if both tires are at 60F the race tire works better. If both at
160F, the race tire still works better. Now will a cold race tire work as
well as a hot street tire? I don't know, it would depend upon the
tires. (But I am sure that someone did this and fell down, then started
the rumor. ) The big difference comes in the cold verses hot
performance. A race tire get much better when hot. A street tire gets a
little bit better when hot.
WARM UP TIME: Dunlops generally come in, in 1 lap (the warm up lap). A
street tire gets a little bit better when hot, but not as much as a race
tire. The harder one rides the quicker and hotter the tire gets. These
are basics datums. The rider has to gain experience with tires and how
they work by riding on them many times. There are not hard numbers to
describe degrees of traction for every increase in temperature. Experience
is the key here.
Why would you use a RACE TIRE for the STREET?
Plus points - More grip.
Minus points - Harsher over bumps, less feedback, cost more, tend to wear
Why would you use a STREET TIRE for the STREET?
Plus points - sufficient grip, smooth ride, more stable over bumps, last
longer, cost less
Minus points - Don't look as cool as my friend with race tires.
If you are riding on the street and really need a race tire, you should
not be riding on the street.
Street tires give very good grip, enough to have a very fun time in the
canyons. A street tire on the track will run about 1.5 seconds slower than
a race tire. Compared to 15 seconds slower for the average street rider
that goes to the track, it is easy to see that experience and practice
makes a much bigger difference than just tire choice.
Ride and have fun.
Steve Brubaker, President, Race Tire Service Inc.
Dunlop Motorcycle Roadrace Tire Distributor Eastern US
Order 800-772-TIRE, Tech Info 615-641-2234, Fax 615-641-8959