Legends and Dwarf Race Cars - Camber Cutting Asphalt Tires
Leary Racing Products – 1-303-922-4227
Why camber cut tires?
This cutting technique is to add camber to the tire and increase the amount of tread coming in contact with the track surface during cornering. This is done by shaving rubber off the tread at a specific angle, thus increasing camber angle. Importantly, camber cutting tires also reduce tread flex during cornering, which improves tire stability (track contact) and improves the grip of the tire on an asphalt surface. One additional benefit of cutting tires is that it reduces tread chipping or tearing, which is very common on uncut Legends tires. On asphalt, new camber cut tires are always faster than old, non cambered cut tires.
Adjustments to cars with camber cut tires: To optimize the use of camber cut tires, small adjusts to tire pressures; camber angle and toe out may need to be made. Use a needle type parameter (not an infrared surface parameter) to record tire temps. The objective is to get the tires edge (closet to the inside of the race track) 5-10 degrees hotter than the outside edges of the tire.
Pros of pre-mounting tires prior to cutting
It is always the best practice to camber cut tires on the rims they will be raced on. Rims must be straight and in good condition before mounting tires and shaving. Once a tire is cut on a rim, you want to try to keep it mounted on the same rim for the duration of the tires life. If a rim is damaged and needs to be replaced, it is recommended that the tire be cut again to “true it” after mounting the tire on the new rim. Most tire cutters have a set of rims they can use for mounting/cutting purposes, but it is always best to use the rims that you will be racing on.
Tire circumferences and Stagger
Since 2003, BF Goodrich has standardized tires diameters extremely well. This standardization, however, makes it very difficult to establish much rear tire stagger (which helps to get the car to turn left.) Tire cutting providers do an excellent job at “matching” tires to gain small differences in diameter and small amounts of stagger, typically only 1/8 to ½ differences from left to right.
Tread depths (NOTE: Tires can be cut to your specifications. Tell Mike what to want!)
New tires from the factory come with an established tire tread depth of 10/32. Tires that have a depth of 2/32 have “hit the wear bar” indicator and are now considered to be illegal (by Legends rules). We recommend a tire depth of 4/32.
Leary Racing tire cutting provider offers three, cambered depth cuts:
· Lowest depth of 5/32 to 6/32 – This is a “normal” camber cut tire with an average tire life of 10-12 races. (Requires break-in sessions)
· Lowest depth of 4/32 to 5/32 – This is an “aggressive” camber cut tire with an average tire life of 4-7 races. Rated as “fast”
· Lowest depth of 3/32 to 4/32– This is camber cut tire which is typical used for a national event with an average tire life of only 1-2 races. Rated as “very fast”.
Proper break-in procedure – heat cycles
A tire break-in period is essential. The more tread that is on a new Legends tire, the more heat cycles are required to break in a tire.
The follow break-in guidelines are based on the lowest tread depth measurement of a new tire:
· Lowest depth of 5/32-6/32 – Typically 1 – 10 lap sessions at 60-80% throttle application with a full cool down time (tire cool to the touch) followed by another 10 lap session at 80-90% throttle application with a full cool down time.
· Lowest depth of 4/32 – Typically 1 – 10 lap sessions at 60-80% throttle application with a full cool down time (tire cool to the touch) followed by a 5-7 lap session at 80-90% throttle application with a full cool down time. .
· Lowest depth of 3/32 – Typically 1 – 10 lap sessions at 80-90% throttle application with a full cool down time (tire cool to the touch).
Durometer (Hardness) Readings
Good tire cutters will perform a durometer (hardness) test on each tire they cut. On average, new tire will have a durometer reading of 56-58 (at 70 degrees.) Tires will harden as they go through heat cycles, increasing the durometer reading. Performance of a tire decreases significantly after a slight point increase in the durometer reading: e.g. (58 to 64).
Cutting procedure
It takes approximately 2 ½-3 hours to properly mount and cut camber into 4 new Legends tires and dismount tires. Right side tires require a different cambered angle cut than left side tires. Typically, both right side and left side tires require 12-14 passes of the razor sharp, cutting blade.
Technical questions:
If you have any technical questions regarding the camber cutting process, you are welcome to contact Gary Cagle, Ph.D. at 223-5460 (leave a detailed message if he does not answer).
Primary reasons to camber cut tires:
To reduce tread block squirm
To minimize tire tearing, chipping or chucking of outside edge
To slightly increase contact patch
To slightly reduce rotating mass