I've been trying to figure out what would be the effect on braking if a car with ABS had to do take emergency evasive action and in doing so completely deflated the front tyre (i.e. it became free to rotate on the rim)
What would be the effect on steering when an emergency brake application was made and the ABS came into action
Regards TIA
if it locked that brake would be released until the rim started to turn again, same as normal
Do you mean:
1) in effect only one front brake would be working Or 2) do all the brakes release Or 3) if the brakes are split diagonally the opposite side rear would also releaseI can imagine that if it is
1) then the car would swerve rather violently 2) the braking is drastically reduced 3) a combination of 1 & 2 but not so markedly
each wheel is braked individually, yes you might get some swerving , but you would in any case even if not braking and yes there will be some reduction in overall braking efficiency, but again there will be with a flat tyre in all circumstances.
What scenario do you want to occur? Best bet to test it is to hire a track and try it out. My local Stock car track is available quite cheaply, tarmac oval 1/4 mile, excellent for testing, running in etc.
The scenario is onewhich happened to me some years ago ... I came over the brow of a blind summit (rather too fast with hindsight) and found to my horror a car travelling towards me straddling the white line. I swerved t the nearside and my front nearside tyre was knocked off the rim. Fortunately the oncoming car also swerved and there was no collision. However my car became almost uncontrollable - frantic opposite lock had little or no effect ... Things happened so fast that I cannot remember exactly what the sequence of events was after that but I do know I came to rest a long way from where I intended. I've no wish to repeat it even on a track
For the tyre to come off it must have been very flat. Once a car starts sliding it can be very difficult to work out what you need to do to correct it and a flat tyre compounds the problem. Once tyres are sliding sideways there is nothing that the abs can do to correct the situation, indeed it is foreseeable that the abs may even think you are stationary (while sliding sideways !!) The cure is (usually) to release everything (foot pedal wise) and steer toward the way you want to travel, unless you are going backwards in which case just hope for the best. However, you are best to learn all this on a stock car track for that one fateful day that you need it on the road. A skid pan session can be very helpful too.
I'm interested in this in the context of tubeless tyres coming off rims not designed for them, e.g. most cars of the 50s and 60s.
What type of vehicle was it, and do you recall whether it had "humped" rims?
Given the fun one can have trying to unseat tyre beads with damn great pneumatic spades, it's always seemed unlikely to me that the sort of forces that can be generated in even a violent manoeuvre would be enough to shift an inflated tyre. BICBW, in which case an awful lot of Morris Minors, MG Midgets, MGBs, and pre-1965 Rolls-Royces (and many others) perhaps ought to have new tubed tyres fitted.
I assumed it wasn't merely a violent swerve that knocked the tyre off the rim, but impact with a low kerb (low enough that it didn't just mash the wheel against the kerb too).
It was as you described " impact with a low kerb (low enough that it didn't just mash the wheel against the kerb too" except that it was a verge comprising clay and grass with a vertical edge and slightly higher than the tyre wall. The tyres (and wheels) were in very good condition and correcly inflated - But the tyre bead was completly free from the alloy rim Incidentally the car was a Honda Accord 2.0 Exec (2000 on a V plate)
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