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Leading or trailing caliper: Any difference?
- Thread starter Asm109
- Start date
husky drvr
Platinum Level Sponsor
This article by Marlan Davis at "Hot Rod" magazine should help.
Barry
Diamond Level Sponsor
As applied to typical road vehicles, "friction brakes" are mechanical devices that convert kinetic energy to thermal (aka, heat) energy and then waste the thermal energy to the atmosphere. A LOT of energy is involved. A single stop of a 4,000 lb. vehicle from 60 MPH results in enough heat energy to boil a half gallon of 70°F. water at sea level.
The position of a disc brake caliper will affect the transfer of heat energy from the caliper / pads / rotor to the atmosphere (OTBE, more air flow = quicker heat "dissipation"), exposure to dirt / water / rocks, brake line / bleeder location, etc., but the process of using friction to convert kinetic energy to heat energy is what it is.
It has traditionally been held that moving the heavy pieces (calipers, pads, mounting brackets, etc.) toward the center of the vehicle (front calipers behind the spindles and rear calipers ahead of the rear axle) reduces the polar moment of inertia which is advantageous for vehicles which need to turn quickly (e.g.; "sports cars"). Moving the heavy pieces away from the center of the vehicle increases the polar moment of inertia and makes the vehicle more difficult to turn (aka, more stable) which could be advantageous for drag racing, land speed racing, etc. In a Series Alpine (or Tiger), there is usually something in the way of something else so putting the calipers in the "best" location may be difficult or impossible.
Pick your poison and take a drink.
The position of a disc brake caliper will affect the transfer of heat energy from the caliper / pads / rotor to the atmosphere (OTBE, more air flow = quicker heat "dissipation"), exposure to dirt / water / rocks, brake line / bleeder location, etc., but the process of using friction to convert kinetic energy to heat energy is what it is.
It has traditionally been held that moving the heavy pieces (calipers, pads, mounting brackets, etc.) toward the center of the vehicle (front calipers behind the spindles and rear calipers ahead of the rear axle) reduces the polar moment of inertia which is advantageous for vehicles which need to turn quickly (e.g.; "sports cars"). Moving the heavy pieces away from the center of the vehicle increases the polar moment of inertia and makes the vehicle more difficult to turn (aka, more stable) which could be advantageous for drag racing, land speed racing, etc. In a Series Alpine (or Tiger), there is usually something in the way of something else so putting the calipers in the "best" location may be difficult or impossible.
Pick your poison and take a drink.
Last edited:
Aladin Sane
Diamond Level Sponsor
When I added rear disc brakes to my project, I put them behind the axle. Right or wrong.
Barry
Diamond Level Sponsor
That is where DanR's Saturn caliper kit is designed to be mounted and is what I would have done. I can't imagine that the Saturn calipers weigh enough for front or back to matter.
husky drvr
Platinum Level Sponsor
A-S,
Just a question A-S, if you had tried to mount the calipers on the forward side, how would you have implemented the operation of the parking brake?
Not all design considerations have "performance" as the top priority. Make something fit and operate safely and reliably is the top, usually.
Just remember, "Good enough is the worst enemy of great."
Have a good day,
Aladin Sane
Diamond Level Sponsor
I didn't use the alpine parking brake rods. I used modern flexible cables that would have allowed installation in any location around the axle. I used a modified version of Dan's conversion kit. These are installed on a Dana axle, hence the need for some modifications.
Aladin Sane
Diamond Level Sponsor
I think the answer is "it does not make a meaningful difference".
Aladin Sane
Diamond Level Sponsor
In a quick non scientific survey of the parking lot at my office, all the rear calipers were behind the axle. The fronts were a mix of some in front and some behind.
Leading and trailing were part of the language of the old days and drum brakes. Not so sure there is need for that terminology in the modern world of disk brakes. Especially in the world of mounting X brakes on Y axle in Z car.
For me the process looked like this Find a caliper that seems to have braking capacity that is appropriate with the car and axle location (front/rear). Find a rotor that will mount on the axle and is compatible with the caliper. Figure out a way to mount the caliper on the axle.
The location of the caliper is usually determined by where it is possible to mount the caliper in relation to such things as location of the rotor, car frame, springs, exhaust pipe, brake lines and parking brake. Always keep in mind that when mounting any non stock item on an Alpine, you are operating in a world of a quarter inches.
Bill