|
|
Post by gazman on Apr 1, 2009 22:47:58 GMT 12
I'm a fan who is really enjoying the emergence of Sprintcars throughout the country - especially Te Marua (thanks for promoting it Mr Halcrow)......I have a huge respect for drivers of all classes but the sprinter drivers just amaze me...... Can someone with a bit of technical experience explain what the story is with the tyre valves that the sprinters run. I heard the announcer explaining it one night but couldnt understand the concept of how they work and what it achieves.... Something to do with altering the pressure at a certain point during the race...... Also is it something that most drivers use or just a few....  Also - while talking about tyres....just how long do those right rear big boys last |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 2, 2009 5:30:21 GMT 12
Hi Gary
Hers some information I poached, researched from the net..
While racing you may see that your rear tire stagger may tend to change in an unfavorable manner (while using bleeders). It may seem to be unpredictable and uncontrollable. With careful bleeder valve Set Point Management, one can effectively minimize size control problems.
Main Reason Tires May Change Size
A common problem is to see the LR tire grow while the RR tire shrinks. This tendency occurs because the RR tire runs hotter than the LR tire, causing more air pressure gain, causing the RR bleeder to relieve more pressure (volume) than the LR bleeder.
Bias ply tires will change size when the air pressure changes. The higher the pressure, the bigger the tire. As a rule of thumb, the size change is linear with air pressure. A 10 psi change will either make the tire 1" bigger or 1" smaller (circumference). Each PSI is worth a .1" change in size.
Realize the use of Bleeder Valves limits the air pressure gain, but does not keep the pressure from lowering if the tire is allowed to cool. This is typically what happens during a caution period. This is when many will notice trouble with their race car handling. Why? There is no system to replace the lost air pressure.
Bleeder Valve Recommendations:
Use Bleeder Valves to REDUCE the air pressure buildup, not eliminate it:
Bleeders should not be used to maintain a constant air pressure. You must always set the bleeder higher than the starting cold air pressure. If your tires cool (caution period), the inflation pressure will be reduced by the amount of pressure the bleeder valve bled off. It is normal to see 7-8 psi of RR buildup (without bleeders). If the bleeders kept the RR tire at a constant pressure hot (no buildup), your car will lose .7 to .8" of stagger if the tires are given time to cool. This is not due to RR tire shrinkage, this is due to LOW AIR PRESSURE. You may be compromising driver safety.
|
|
|
|
Post by GavS on Apr 2, 2009 18:41:40 GMT 12
our tyres can go up 1-2 psi without bleeders, depending on the track and how slick it goes, but we generaly will only use bleeders in long features
how long does a tyre last,
at the recent NZ sprintcars in palmy, we started a feature with 2 brand spanking new tires, and the end of the race they were done. nothing left to race on
|
|
|
|
Post by gazman on Apr 3, 2009 15:09:37 GMT 12
So basically its a system that blleeds off a few psi when the tyre gets to a certain temp... And obviously the skill of the driver and crew comes into play in order to guess when and by how much ... As yous reply says Phill , if the caution period comes into play for a length of time after the tyre pressure has dropped then its going to cause a few handling issues when the race starts again.... Do super saloons use these bleeders.. |
|
