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Discussion Starter · #1 ·
I am in the process of installing rear disc brakes on the 9" rear in my '26 T coupe. The brackets I have for caliper mounting can be installed with the caliper in any position around the clock. I am wondering what effect the caliper mounting position has on braking.
My wife's Buick has the calipers mounted on the front of the wheel, front and rear.
My C5 Corvette has the calipers mounted on the rear of the wheel on the front end, and the front of the wheel on the rear end.
Comparing these two it appears there is no effect with caliper mount position (CMP).
My thoughts:
If the caliper is on the front, upon brake application (with car in motion) the wheel would want to roll over the caliper, if there were no suspension components holding the rear end in place. Similarly, if the caliper is mounted on the rear of the wheel, upon braking the wheel would want to roll under the caliper. Either way there are forces applied to to the chassis through the suspension components. Suspension geometry would affect how these forces are handled. It seems to me that if the caliper is on the front, brake application would raise the tire off the road, loosing traction and conversely, if the caliper is on the rear, it would push the tire into the road, gaining traction. I'm saying there is an effect with CMP. It may be small, but I think it is there.
I'm willing to bet that the Corvette engineers had it right over the Buick engineers. I'm thinking that caliper placement was involved in the front to rear brake bias engineer's calculations. My front calipers are mounted on the rear. I think I will mount the rear calipers at the front of the wheel to match the Corvette.
You guys have any thoughts on the subject?
 

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Caliper position makes a difference in extreme (racing) use, not on the street.
Good thing about being able to clock the caliper any position is you can fit them where there is space, or where it looks nicer (or hidden)
 

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I may be mis-using terms but the caliper just creates a moment force on the spindle c/l, becoming torque...the effect is a simple thing, it doesn't matter where around the clock it's does it from and caliper positioning is usually just a matter of packaging such as if a tie rod goes in front then the caliper goes in back, etc. If it happened that the rotor was mounted to the spindle but the caliper was mounted to the chassis, with suspension movement in between the two, then effects such as you are considering would be a factor.

No question it's good to think about stuff like that, if just for an exercise.
 

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I am wondering what effect the caliper mounting position has on braking.
It has exactly zero effect. Caliper mounting on production cars is primarily driven by clearance to suspension components, easiest assembly line integration, and (a distant third) ease of maintenance. Where you grab the rotor from a clocking standpoint has no impact on braking whatsoever, at least not that you can measure. Ask yourself, does the clocking of the torque wrench handle relative to the bolt change how much torque is applied?
 

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It has exactly zero effect. Caliper mounting on production cars is primarily driven by clearance to suspension components, easiest assembly line integration, and (a distant third) ease of maintenance. Where you grab the rotor from a clocking standpoint has no impact on braking whatsoever, at least not that you can measure. Ask yourself, does the clocking of the torque wrench handle relative to the bolt change how much torque is applied?
Came here to say this. I put 3/4 ton truck knuckles and brakes (front steer) on a 66 Bonneville (rear steer). In order to get the steering to function I just swapped knuckles left and right so the steering arms were in the right spot.

The brakes work on a rotational force. It doesn't matter where they are around the circumference of the rotor, as long as the bleeder screw is at the top.
 

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Came here to say this. I put 3/4 ton truck knuckles and brakes (front steer) on a 66 Bonneville (rear steer). In order to get the steering to function I just swapped knuckles left and right so the steering arms were in the right spot.
Did that work? Typically due to Ackermann angle requirement, front-steer knuckles with the tie-rod pivot being outboard of the ball joints can't go straight to a rear-steer ap which needs the tie-rod pivots to be inboard, unless the steering arms are bolt-in and can be changed to be appropriate. Also caliper mounts may be made stronger in the normally-forward position, but that's something else.
 

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Caliper location makes no difference when mounted solidly, clamped or welded to the axle tube. I won’t get into calipers mounted to bearing they rotate around the axle.
just make sure the hole in the bore is at the upper most position. That doesn’t always, be should be, unlike with the bleeder screw.
I’ve seen them drilled at a angle as such the through hole in the bore was at 1oclock, that allowed a pocket or air to be trapped that was quite the pain in the a…to get out. It’s worth the check.
 

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Discussion Starter · #13 ·
Well, none of you guys has managed to convince me that the rotational force put into the chassis's suspension has no effect. Every force has an equal and opposite reaction to that force. That force is being put into the chassis through the suspension links or components. It does not just disappear.
I know I am hard headed and difficult to convince.
As johnsongrass1 alludes to, I have seen calipers mounted floating on the axle with a link to the chassis. Then those forces can be applied to the chassis without affecting the rear end.
I'm just not convinced that CMP has no effect.
As far as the bleeder must be at the top, this is not true either. Every sprint car I ever owned had the left front caliper mounted so you had to take the caliper off, insert a spacer to mock the rotor, hold the bleeder at the top and bleed away. The brakes work as normal with the bleeder at the bottom. Yes, it makes it a pain to bleed, but still works as normal.
 

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Came here to say this. I put 3/4 ton truck knuckles and brakes (front steer) on a 66 Bonneville (rear steer). In order to get the steering to function I just swapped knuckles left and right so the steering arms were in the right spot.
Sorry, but that's a REALLY bad idea. Wrong Ackerman angles as noted, bump steer out the whazoo, and likely a mismatch in the ball joint stud taper angles that causes overloading on those studs.
 

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Then you'll have to convince yourself with more analysis, or not, the force is normally directed by the designer into slowing the car and not moving the chassis around unless it's intentional such as with anti-dive geometry where control arm pivot angles are not in line with moment and do affect suspension movement, in that case causing a lifting effect.
 

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Well, none of you guys has managed to convince me that the rotational force put into the chassis's suspension has no effect. Every force has an equal and opposite reaction to that force. That force is being put into the chassis through the suspension links or components. It does not just disappear.
I know I am hard headed and difficult to convince.
As johnsongrass1 alludes to, I have seen calipers mounted floating on the axle with a link to the chassis. Then those forces can be applied to the chassis without affecting the rear end.
I'm just not convinced that CMP has no effect.
As far as the bleeder must be at the top, this is not true either. Every sprint car I ever owned had the left front caliper mounted so you had to take the caliper off, insert a spacer to mock the rotor, hold the bleeder at the top and bleed away. The brakes work as normal with the bleeder at the bottom. Yes, it makes it a pain to bleed, but still works as normal.
You answered your own question. Braking forces are tramitted into the suspension links when clamped or welded.
That is for sure true.
What your missing is the forces are the same at 12, 1, 2, 3 o’clock or any positions when mounted at the end of the axles.
It’s a different story when floated on the axle, mounted on the pinion, or mounted on the driveshaft but that’s not the question you were asking.
Lastly, calipers will work the same, bleeders at any XYZ position. However, you already know it requires removal to bleed, a pain in the but to have to do every time as most guys here are working on axle mounted brakes on street rods, not sprint cars or other race cars where braking forces are tailored for a specific handing purpose. Now if to debate what can be done on a race car, or how someone might adapt that style brake system to their street car. we can do that and I have lots of experience backed up by data acquisition of on track testing.
 

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Sorry, but that's a REALLY bad idea. Wrong Ackerman angles as noted, bump steer out the whazoo, and likely a mismatch in the ball joint stud taper angles that causes overloading on those studs.
First of all, you all are jumping to conclusions and also assuming I'm an idiot. I very carefully selected those knuckles BECAUSE of their geometry. The ackerman angles are within 1 percent of the stock Bonneville (actually improved for this application). Bump steer isn't perfect, but it's been in use for 6 out of the last 15 years this way.

The ball tie rod ends were easy. Remove bonneville ends and install truck ends. I could have also easily used the correct 2-1 reamer and re-tapered the holes in the truck spindles the the 1.5-1 bonneville tie rod ends.

The spindles were flipped to keep the steering arms on the correct side of the knuckle. I didn't switch front/rear. The truck was a front steer and the bonny was rear steer. So I swapped the spindles side to side so the arms were in the correct orientation for the Bonny steering gear.
 

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You answered your own question. Braking forces are tramitted into the suspension links when clamped or welded.
That is for sure true.
What your missing is the forces are the same at 12, 1, 2, 3 o’clock or any positions when mounted at the end of the axles.
It’s a different story when floated on the axle, mounted on the pinion, or mounted on the driveshaft but that’s not the question you were asking.
Lastly, calipers will work the same, bleeders at any XYZ position. However, you already know it requires removal to bleed, a pain in the but to have to do every time as most guys here are working on axle mounted brakes on street rods, not sprint cars or other race cars where braking forces are tailored for a specific handing purpose. Now if to debate what can be done on a race car, or how someone might adapt that style brake system to their street car. we can do that and I have lots of experience backed up by data acquisition of on track testing.
Agree. It doesn't matter where the forces occur on the moment/radius. Just like when you're torqueing a lug nut, it doesn't matter where the wrench is positioned on the clock, the torque is the same as seen by the lug.
 

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Did that work? Typically due to Ackermann angle requirement, front-steer knuckles with the tie-rod pivot being outboard of the ball joints can't go straight to a rear-steer ap which needs the tie-rod pivots to be inboard, unless the steering arms are bolt-in and can be changed to be appropriate. Also caliper mounts may be made stronger in the normally-forward position, but that's something else.
I think you're misinterpreting what I did. The truck donor was front steer. The Bonneville is rear steer. I didn't convert the bonneville to front steer, I swapped spindles so that it remained rear steer. I specifically chose those knuckles because the steering arm spits out within millimeters of the factory bonneville tie rod end location. Ackerman improved by about 1/2 degree. The inside tire now tracks within 1/2 degree of the radius of the turn whereas it was 1 degree shy on the inside tire before. Not that ackerman is a huge deal. Plenty of high performance vehicles have reverse ackerman like most Winston Cup cars and they certainly don't have troubles buzzing around a track at 200 mph.

Chevy trucks (at least this donor) has slight reverse ackerman. It would have a lot of reverse ackerman if it weren't for the angle used on the tie rod ends By pushing the center and drag forward, they don't need to have the steering arm on the knuckle be outside the ball joint plane. The arm on the knuckle kicks IN just like a typical rear steer vehicle.
 
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