Quote:
Originally Posted by lazyluka
If you down shift at high revs without rev matching, your rear wheels lock up momentarily. As Sport-Tech mentioned the guy didn't rev match.
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Not to be pedantic, but the wheels don't really lock up--quite the opposite in fact. Consider the downshift sequence:
-------------------------------------------------pre-clutch shaft rpm --- post-clutch shaft rpm
1. 3rd gear engaged: ------------------------------- 3000 --------------- 3000
2. clutch in, shift to 2nd, no throttle change ------- 5000 --------------- 3000
Now when you let the clutch out quickly the engine will suddenly accelerate the driveshaft harshly since the pre-clutch (engine-side) shaft is spinning 2000 rpm faster than the post-clutch shaft, thus causing the rear wheels to lose a bit of traction as they are suddenly accelerated and so they chirp, they don't lock up. It's the same process (at a less dramatic level) that happens when you dump the clutch at 4000 rpm from a standing start and lay rubber.