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Old 09-18-2019, 01:41 PM
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Caliper Position-- Front or Back?

I just got a kit to convert my 8" Ford rear end from drum to disk brake. The way the instructions say to install it puts the caliper at about 1 o'clock or at about 11 o'clock in front or back. Both of these positions will hit the inner fenderwell with the arm for the Ebrake on the back of the caliper during compression of the suspension. I'm not cutting the inner fenderwell. But by flipping a bracket 180* I can mount the calipers at about the 4 o'clock position. Not exactly according to directions, but then I don't think I ever bought anything for a hotrod that didn't need at least some modification to make work! I realize that this puts the bleeder not at the top of the caliper, so I will have to take the caliper off to bleed it, but other than that does the position of the caliper makes a difference? For instance, my C5 Corvette has the front brakes mounted on the rear just below center. The rear brakes are mounted on the front just above center. I'm thinking those GM engineers had a reason as to where they placed the calipers. I'm thinking with the caliper on the front the wheel wants to trip over the caliper. With the caliper on the rear the wheel wants to run under the caliper. I'm sure this must figure into the engineering somewhere. Anybody got any insight?

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Old 09-18-2019, 02:35 PM
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Makes No difference in performance but the bleeder eally needs to be up. Or if you have too you can drill a new hole for the bleeder.
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Old 09-18-2019, 05:45 PM
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Quote:
Originally Posted by jaw22w View Post
I just got a kit to convert my 8" Ford rear end from drum to disk brake. The way the instructions say to install it puts the caliper at about 1 o'clock or at about 11 o'clock in front or back. Both of these positions will hit the inner fenderwell with the arm for the Ebrake on the back of the caliper during compression of the suspension. I'm not cutting the inner fenderwell. But by flipping a bracket 180* I can mount the calipers at about the 4 o'clock position. Not exactly according to directions, but then I don't think I ever bought anything for a hotrod that didn't need at least some modification to make work! I realize that this puts the bleeder not at the top of the caliper, so I will have to take the caliper off to bleed it, but other than that does the position of the caliper makes a difference? For instance, my C5 Corvette has the front brakes mounted on the rear just below center. The rear brakes are mounted on the front just above center. I'm thinking those GM engineers had a reason as to where they placed the calipers. I'm thinking with the caliper on the front the wheel wants to trip over the caliper. With the caliper on the rear the wheel wants to run under the caliper. I'm sure this must figure into the engineering somewhere. Anybody got any insight?
Our minds work alike. I asked Phoenix area Super Comp builder Tom Yancer about one of his latest cars. He had the calipers on the rear of the wheels and I asked if that wouldn't tend to unload the tire when the brakes were applied, as opposed to mounting them on the front of the wheel and planting the tire when the brakes were applied. He said he never thought about it much and wasn't concerned with it. Maybe I'm full of beans.
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Old 09-18-2019, 06:56 PM
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Quote:
Originally Posted by techinspector1 View Post
Our minds work alike. I asked Phoenix area Super Comp builder Tom Yancer about one of his latest cars. He had the calipers on the rear of the wheels and I asked if that wouldn't tend to unload the tire when the brakes were applied, as opposed to mounting them on the front of the wheel and planting the tire when the brakes were applied. He said he never thought about it much and wasn't concerned with it. Maybe I'm full of beans.
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Our minds work alike. I asked Phoenix area Super Comp builder Tom Yancer about one of his latest cars. He had the calipers on the rear of the wheels and I asked if that wouldn't tend to unload the tire when the brakes were applied, as opposed to mounting them on the front of the wheel and planting the tire when the brakes were applied. He said he never thought about it much and wasn't concerned with it. Maybe I'm full of beans.
Doesnít matter cause itís a rotational force.
Iíve run the both ways and never ever felt a difference.
We put the fronts at 10pm for the added shock clearance. We put them at 2pm on the back for the added weight distribution.
I have put the brakes on a bracket (floated) that has a rod that goes forward to the chassis to use the brakes to load the chassis and keep the rear up in the air on corner entry in our dirt cars.

The brakes will aid in the downward pinion movement if the bushing allow but itís not enough any driver can feel.
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Old 09-18-2019, 08:10 PM
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I prefer mounting rear calipers, more to the front 9, 10 11 o'clock

The Clocking usually depends on the E-brake arm on the caliper and the direction of the cable
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Old 09-19-2019, 01:15 AM
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You can mount them anywhere they dont interfer with suspension or linkage.

I ran them at 7 o clock before. Cantilever air ride with coil over shocks that ended up almost inside the rim. I wanted to maximize my side to side damping so I put the shocks behind the axle.

Just used a old rotor to bleed them then slid the caliper and pads from the old rotor to the new.

Generally I like 10 because that allows for linkage and bags in the future.
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Old 09-23-2019, 12:05 PM
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I'm like techinspector1. There is a force in play here, just as techinspector1 said. I'm sure I have read something about the effect of position somewhere, but I have had them all over the place on different cars and never could tell the difference. Anyway, the installation of the rear disks is complete. I have mounted the calipers at about 4 o'clock. Getting them bled out was a pain. I had never messed with Ebrake calipers before. I finally discovered that the Ebrake arm was installed 1 flat off on the shaft. Wouldn't keep the puck tight enough to have pedal on the first shot. Fixed that and they bled right out. The kit worked, but I had to drill, cut, grind, and weld before it was over. I had to make rotor sized spacers for the calipers for bleeding them off the mount, but it worked fine. I also had to completely remove the proportioning valve from the rear system to get enough fluid back there.
Now the results. I have the best brakes I have ever had in my 1926 T coupe. Even the proportioning seems good after some hard gravel stops, which I thought might be a problem after removing the PV.
The problem is the pedal now takes more stroke. Actually seems kind of excessive. But they work good once you get the pedal down far enough. I am attributing this to the fact that the calipers need more fluid movement than the old wheel cylinder did. This is a corvette type MC (didn't change MC, supposed to be good for either) with a 1" bore. I'm thinking to go to a 1-1/8" bore MC to move that extra fluid. Pedal ratio is 6:1. The pedal moves 3" with hard pedal pressure, where the brakes would be locking up. There is no pump up, so all air is out.
Am I thinking right in going to the 1-1/8" bore MC? I think that should shorten the stroke. What should that do for the "feel"?
Like I said, the brakes are working good, I'm just fine tuning.
Oh yeah, these are manual, no power brakes.
Thanks for any input.
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Old 09-23-2019, 12:56 PM
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The bigger MC will move more fluid but reduce the "feel" somewhat.
You can try, if it's possible, to change the ratio but I don't think you'll like it.
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Old 09-23-2019, 01:26 PM
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Congrats !
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Old 09-23-2019, 03:05 PM
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Quote:
Originally Posted by cerial View Post
You can mount them anywhere they dont interfer with suspension or linkage.

I ran them at 7 o clock before. Cantilever air ride with coil over shocks that ended up almost inside the rim. I wanted to maximize my side to side damping so I put the shocks behind the axle.

Just used a old rotor to bleed them then slid the caliper and pads from the old rotor to the new.

Generally I like 10 because that allows for linkage and bags in the future.
Quote:
Originally Posted by johnsongrass1 View Post
The bigger MC will move more fluid but reduce the "feel" somewhat.
You can try, if it's possible, to change the ratio but I don't think you'll like it.
Yeah, I don't want to change the pedal ratio. IIRC 6:1 is the recommended ratio for manual brakes. Less for power brakes, I think I need the long pedal especially for 4 wheel manual disks.
Correct me if I'm wrong. All else being the same with only a change from 1" bore to 1-1/8" bore, wouldn't pedal pressure increase to achieve the same clamping pressure at the caliper?
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Old 09-23-2019, 03:42 PM
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That is correct.
Pedal will move less so less pressure at the caliper for the same foot effort.
I don't think it's gonna matter much to ya though. You also have the option to try a different pad compound and see if you like that. A pad with more grip will negate the extra pedal effort.

Decreasing pedal travel reduces feel by giving you less distance from initial pad engagement to wheel lock up. Having less "graduations" per say is what reduces the feel. Picture only 1" of travel to lock up vrs 7" inches and you might imagine this. However, having too many, mean you have to use your whole ankle/foot, perhaps the knee and leg to lock up. The leg and knee are not as good at fine motor controls as just the ankle so in performance theory, adjusting things so that the brakes lock up at the end of the drivers ankle travel is what you want. You also have to adjust the pedal height not only from the all the down, but also from the floor to the ball of the driver foot to be comfortable. Although I suppose its all subjective because while I like my foot resting on the pedal just below the ball of my foot, leg and ankle at 90', and 6 or 7" of travel, but I have had other professional drivers that prefer it differently such as the toes or arch on the pedal. I also tend to use the brakes more than most so that could be part of it. That's probably more info than you were really asking for but it gives you something to think about. I'd guess that a 1 1/8 bore MC is gonna get you were you want be.
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Old 09-23-2019, 06:22 PM
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My pedal hits right at the ball of my foot right where I like it because I built it that way. The 3" movement is within ankle range, it just feels kinda' long because it is longer than before. The car has 21K on it now. I just got used to it. I'm thinking it is probably worth giving the 1-1/8" MC a try. Thanks guys.
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