anti-lock brake system: effect of changing wheel/tire sizes
anti-lock brake system: effect of changing wheel/tire sizes
(OP)
I'm looking for the reasoning behind the recommendation that tire OD should not be increased beyond 15% above stock on ABS equipped trucks. Right now I'm only interested in the effect of tire OD on the ABS system. I'm not interested in the stability problems of "Monster Trucks".
If I understand the technology, the idea is to modulate the hydraulic pressure to the brake caliper of any wheel that is exhibiting signs of slip (slowing down relative to the other wheels). I understand that using larger OD tires will require a commensurate increase in hydraulic pressure at the caliper in order to obtain the same braking effect. However, the effect that tire size would have on the modulation is unclear to me.
If I visualize a "DC" pressure with an "AC" component superimposed as the hydraulic pressure on the caliper during ABS operation is the "AC" modulation amplitude proportional to the "DC" level? Is this how varying vehicle loads are accomodated?
Regards,
Gunnar
If I understand the technology, the idea is to modulate the hydraulic pressure to the brake caliper of any wheel that is exhibiting signs of slip (slowing down relative to the other wheels). I understand that using larger OD tires will require a commensurate increase in hydraulic pressure at the caliper in order to obtain the same braking effect. However, the effect that tire size would have on the modulation is unclear to me.
If I visualize a "DC" pressure with an "AC" component superimposed as the hydraulic pressure on the caliper during ABS operation is the "AC" modulation amplitude proportional to the "DC" level? Is this how varying vehicle loads are accomodated?
Regards,
Gunnar
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RE: anti-lock brake system: effect of changing wheel/tire sizes
By changing the tyre OD you will mess this sort of calibration up.
Your point about the extra efforts is good as well, the system will always seem to be underperforming, which may flag error messages (the change in angualr velocity of the wheel per change in brake line pressure will be doubly different from the original installation).
To fit an OD 15% greater you will almost certainly have to lift the vehicle up - this alone will have a huge effect on your braking perofrmance (and you guessed - it will make it worse).
Having said all that, there is a margin for error, if you were off-roading with the thing I'd try it. On-road your insurance company may have an opinion.
"If I visualize a "DC" pressure with an "AC" component superimposed as the hydraulic pressure on the caliper during ABS operation is the "AC" modulation amplitude proportional to the "DC" level?"
Yes, pretty much
" Is this how varying vehicle loads are accomodated? "
It sounds sensible, as most vehicles don't have laod sensors any more.
Cheers
Greg Locock
RE: anti-lock brake system: effect of changing wheel/tire sizes
Regards
pat