Technical Bulletin – SC-006
October 4, 2007

Rear Wheel Nut Modification

In an effort to keep the wheel nuts tight during our last race of the season at Phoenix C&R would like to offer a service where the wheel nuts will be modified to include a new primary locking device.  This design should be credited to Chris Santucci who ran this idea last year.  The problem we saw at Louden can be attributed to the lower ambient temperature when the wheel nut is torqued in the pits verses the elevated temperature when the driver is braking for the turns.  Loudon and Phoenix have the most braking force of any tracks we go where we brake hard due to the higher entry speed and therefore will have more brake heat.  The wheel comes loose because the brake heat travels from the rotor through the bell through the axle and moves the nut away from the wheel, the wheel is the last piece to get hot.  The reason only a few people have the problem is because we are close to the limit of failure and so it is due to the law of averages if it happens to you or not.  If you have a problem with your wheel gun, don’t hold your finger on the trigger long enough, don’t have the wheel seated exactly right, etc. then the wheel nut will come loose.  This is the same situation we had last year with the front wheel.  Since the change to steel hubs this problem has gone away.  Changing the rear axle to steel is much more expensive and more likely not obtainable in time for next year and certainly not for the Phoenix race. 

Also we cannot afford to have this problem again in front of our sponsors and NASCAR.  If we modify all the wheel nuts for this last race and have zero problems then we can enter 2008 knowing we have a sound economical solution.

In Phoenix we potentially will experience the same problem as this is an evening race schedule.  Therefore we could have the same problem that we saw last year with the front wheels coming loose but now with the rears.

The wheel retention device should be retained as a complete failsafe mechanism and this will need modifying as shown below.  As with all ideas like this in racing there are no guarantees but it’s our best shot in the time available.

All wheel nuts and rear wheel lock caps (there is no need to disassemble the pin from the cap) should be returned to C&R no later than Monday October 8 for modification.  These parts will be available for pickup on Monday October 22, 2007.

If in doubt please contact Bruce Ashmore
Shop: 317-293-4100
Cell: 317-496-9909