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18 Jun 2010, 13:42 (Ref:2714312) | #1 | ||
Racer
Join Date: May 2002
Posts: 153
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Subaru WRX breaking rear traction
Just wondering if anyone else wants to lend weight to this theory.
The other weekend a driver I was servicing for ended his rally with the WRX in the trees. A fast right 2 corner, nose in and everything seeming fine when all of a sudden the rear seemed to lose traction with the usual result of running wide, touching the trees and game over. Nothing much thought about it, driver is compotent driver, though perhaps not as familar with a 4WD as some (most of his dirt racing being FWD, mostly tarmac with the 4WD) and was pushing hard, so easy to ignore. Just watched some coverage on the national championship over here and another driver who ended in the trees, seemed to have the same explanation for his excursion into the trees. This time a tighter right hand, though still fairly quick. Same unexpected break away in the rear end. This in a completely different part of the country on a vary different rally. Just wondering if perhaps we're missing something that the rest of the rally world is already aware of ? I know one of the local manufacturers teams used to rewind the electronic centre diff for a stronger engagement. Not sure if both teams were running the same suspension ? Maybe nothing, but thought I'd ask |
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Happiness is seeing the race ....... in your rear view mirror |
18 Jun 2010, 19:11 (Ref:2714450) | #2 | |
Veteran
Join Date: Dec 2003
Posts: 6,885
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I think it's more a vehicle dynamics issue than anything mechanical.
A couple of things: 1. The driver was simply going too fast for the corner and exceeded the grip limit of the tires. 2. The driver lifted off the gas suddenly causing throttle off oversteer, weight shifted to the front, the rear tires get light and the car starts to rotate. In rally this can be facilitated by the camber of the road or changes in grip on the road surface. 3. The driver was too hard on the throttle causing throttle on oversteer. When you accelerate weight shifts over the rear tires and too much power along with the curvature of the road can cause the rear tires to break grip and the rear of the car starts to rotate. 4. The drivers eyes were focused on the outside of the corner rather than on the road. Hands and feet follow the eyes. 2WD and 4WD have some differences but it doesn't change the fact weight transfer happens in a vehicle and whatever tires that were on the car are only going to have a certain limit of grip. |
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18 Jun 2010, 20:47 (Ref:2714485) | #3 | ||
Race Official
Veteran
Join Date: Mar 2003
Posts: 10,351
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I'd agree - driver error is the most likely cause, too much speed carried into the corner (followed by a mid corner lift) or too soon on the throttle coming out of the corner seem likely.
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18 Jun 2010, 21:51 (Ref:2714513) | #4 | ||
Veteran
Join Date: Jan 2008
Posts: 3,768
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I have heard of some Subaru drivers complaining (or rather being a little unsure) of the DCCD when left in "Auto" mode. Not sure whether rally cars run with this switched on though - or if your car even has it!
As has been said though, I suspect its more likely a dynamic issue rather then a mechanical one. |
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