New brake kits

[gunnibronco]

@gunnibronco - if you're running the regular Chevy disc brake calipers (JB6) now w/o an e-brake, I'm presuming you'd not need any on your replacements? If that's true, don't waste your time with the "Eldorado" disc brake calipers you guys have been discussing. Just get a set of the non-e-brake "metric" calipers and use those instead. Simpler, cheaper, and easier to hook up/bleed.

Todd Z.

@toddz69 I don't need the e-brake. My Atlas4 prevents me from running e-brake cables in any easy way. So I added a line lock to my rear brakes for an e-brake.

I ran across those calipers at one time but couldn't find an answer if they fit my caliper brackets. In fact I assumed they would not. Do you have a year/make/model I can cross reference? I've been reading for the last few weeks on this subject and I can't remember.

Thanks

 

[LittleBeefy]

i agree with Todd. Get those metric GM calipers if you can. I’ve never used the Caddy calipers but I know people who have and they are not happy with them at all.

 

[gunnibronco]

i agree with Todd. Get those metric GM calipers if you can. I’ve never used the Caddy calipers but I know people who have and they are not happy with them at all.

I've heard the complaints about the p-brake, but since I wasn't going to use them I didn't worry. But they are expensive so I'm happy to look at other options.

I didn't know they were difficult to bleed, so that's another strike for the Eldo calipers.

Looks like 1985 Monte Carlo is a cross reference. For some reason I came up with info that they had a smaller pin spread than the Eldo/JB6/JB7 calipers.

 

[Yeller]

Have you considered using a MC out of a 1980's Chevy 1 ton (e.g. RAYBESTOS MC39435)? That would keep the lines on the same side as your current MC, but you would have to use an adapter for the different outlet size. It has an integrated reservoir because it's cast so it would be smaller for hood clearance. It's a 1 5/16" bore, which would then allow you to switch back to the El Dorado rears.

Something like that would cost $50-$60 including adapters. The investment would really be in the time it takes to reinstall the Caddy rears, and bleeding everything to see if it works.

Im running the same master and rear calipers and rotors with stock 80’s GM 1 ton single piston (3-1/2”) calipers and rotors and have the same complaint of too much rear bias. Brake pedal travel is good, 9” C3 corvette booster, normal EB angle bracket and linkage. The pedal effort is good but the rear bias is too much. Running the typical bias valve to balance the system, have it backed out as far as it will go. Would love to go to a 2.25” metric caliper but the rotor is too thick and haven’t located anything thin enough for 8 lug

Front axle is a GM 60 with the original brakes and the rear is a 14b with k2500 front rotors and calipers. Happy with the feel and performance but would like better bias.

 

[gunnibronco]

I've reconfirmed what I remember reading. The Metric calipers have a 5.46" pin spacing, the Eldo/JB6/JB7 have a 7.05" pin spacing.

I'm also finding that the Metric caliper won't work with the thickness of the rotor I have. There is a Pirate4x4 thread lists a couple 13" rotors that are thinner, but the height is more than the rotor I'm already using. This would also put my rotors further inboard of my tire sidewall and therefore more exposed to being damaged by rocks.

So to make the Metric calipers work, I'm looking at new calipers, pads, rotors and removing my caliper brackets and fabing new ones myself.

I know the Eldo calipers are more expensive, but I can re-use my pads, rotors and brackets, so they end up being the cheaper option. Also a lot less work to install. I'm leaning back to using the Eldo caliper. The only downside that I know of is the e-brake and I'm not using that. What else makes them harder to install/bleed/etc?

 

[gunnibronco]

Im running the same master and rear calipers and rotors with stock 80’s GM 1 ton single piston (3-1/2”) calipers and rotors and have the same complaint of too much rear bias. Brake pedal travel is good, 9” C3 corvette booster, normal EB angle bracket and linkage. The pedal effort is good but the rear bias is too much. Running the typical bias valve to balance the system, have it backed out as far as it will go. Would love to go to a 2.25” metric caliper but the rotor is too thick and haven’t located anything thin enough for 8 lug

Front axle is a GM 60 with the original brakes and the rear is a 14b with k2500 front rotors and calipers. Happy with the feel and performance but would like better bias.

@Yeller Are you running the 3.5" JB7 calipers in the rear? I'm running the smaller 2.945 JB6 (1/2 ton) calipers in the back. The Eldo calipers are 2.5", so I'm hoping they will help pull the bias forward.

This thread lists 2 rotors that are 8x6.5, but thinner that they say can be used with the Metric calipers. But they are 13" vs 12.5" and have taller "hat" height, leaving them more inboard of the tire. So the caliper hanger bracket would have to be completely revamped. I don't see the advantage over just swapping to the 2.5" Eldo caliper unless there is something I'm missing.

https://www.pirate4x4.com/threads/i-found-an-8-lug-rotor-for-gm-metric-calipers.1112645/

Edit- the hub hole is also smaller and might not fit over the hub. (4.84" or 4.63" vs 5.01") So I don't see how these can easily work.

 

[Yeller]

@gunnibronco no the rear are the JB6. The huge fronts are what necessitated the 1-5/16 master to keep the pedal from slapping the floor. We’re both suffering the same dilemma with very similar equipment other than the bore of the master cylinder.

I ran this set up for a while with a stock 1” master that was manual with no booster. Loved the pedal effort, it was light and easy to modulate, but the travel was way not acceptable, I could push the pedal to the floor easily with my hand. Which coincidentally is when the front tires locked up and the stopping power was spectacular, but the rear still locked up first.

I’ve been running this axle combination since 2001 and have dug into it several times but haven’t found a rotor and caliper combination that I felt fit well enough to make the jump to metric calipers. I’ve seen so many issues with the caddy calipers I have always dismissed them.

 

[toddz69]

So, a

I've reconfirmed what I remember reading. The Metric calipers have a 5.46" pin spacing, the Eldo/JB6/JB7 have a 7.05" pin spacing.

I'm also finding that the Metric caliper won't work with the thickness of the rotor I have. There is a Pirate4x4 thread lists a couple 13" rotors that are thinner, but the height is more than the rotor I'm already using. This would also put my rotors further inboard of my tire sidewall and therefore more exposed to being damaged by rocks.

So to make the Metric calipers work, I'm looking at new calipers, pads, rotors and removing my caliper brackets and fabing new ones myself.

I know the Eldo calipers are more expensive, but I can re-use my pads, rotors and brackets, so they end up being the cheaper option. Also a lot less work to install. I'm leaning back to using the Eldo caliper. The only downside that I know of is the e-brake and I'm not using that. What else makes them harder to install/bleed/etc?

We need to clarify here - I realize that you're talking about keeping your existing bracketry and trying the "large" Eldorado calipers in them instead of the current JB6's. The large Eldorado calipers came on 76-78 cars and have 2.5" pistons. So yes, that's a way to get a smaller piston caliper that fits in your current bracketry.

What I think @LittleBeefy ,and I know I, were recommending was the smaller metric calipers (5.46" pin spacing) as an alternative to what we *thought* you were referring to when you kept mentioning the "Eldo" calipers, which are the smaller 79-85 Eldorado calipers, which are what people are referring to about 99% of the time when they use that lingo to describe a caliper. Most people don't know of the 76-78 variety and until recently they were not reproduced so they were not common.

Now that I know what you're referring to, I can understand that you don't want to do a total reinvestment in your rear brake system just to try something..... I'll let @LittleBeefy or others comment on whether using the 76-78 Eldorado calipers ($$) would be worth it from a slightly smaller piston perspective.

Todd Z.

 

[gunnibronco]

So, a

We need to clarify here - I realize that you're talking about keeping your existing bracketry and trying the "large" Eldorado calipers in them instead of the current JB6's. The large Eldorado calipers came on 76-78 cars and have 2.5" pistons. So yes, that's a way to get a smaller piston caliper that fits in your current bracketry.

What I think @LittleBeefy ,and I know I, were recommending was the smaller metric calipers (5.46" pin spacing) as an alternative to what we *thought* you were referring to when you kept mentioning the "Eldo" calipers, which are the smaller 79-85 Eldorado calipers, which are what people are referring to about 99% of the time when they use that lingo to describe a caliper. Most people don't know of the 76-78 variety and until recently they were not reproduced so they were not common.

Now that I know what you're referring to, I can understand that you don't want to do a total reinvestment in your rear brake system just to try something..... I'll let @LittleBeefy or others comment on whether using the 76-78 Eldorado calipers ($$) would be worth it from a slightly smaller piston perspective.

Todd Z.

Ok, I see. I was looking at the 2.5" Eldo caliper. I've seen the 2" Eldo caliper as well, but didn't consider it because it was a more difficult swap. I'm new to these 1 ton brake swaps, and I was using info from Lugnut4x4 pages and Rock Auto to do my research.

The reason I was really thinking about the 2.5" Eldo caliper is that is puts my rear/front caliper surface area ratio in a similar place as a couple factory set ups I've seen. 08 Super Duty is .64, 96 Explorer is .61. Currently I'm at .8914, but with the large Eldo calipers I'd be at .643. From reading this thread I realize there is a lot more at play, but at least I'm coming closer to where factory engineered systems fall. I was just playing with numbers in a spread sheet to see where my system deviated from factory systems. I wasn't taking swept area and distance from center of the axle into account, just some basics.

 

[ksagis]

Ergo, your too-large MC is robbing your front calipers of potential force.

I need to think about this some more, but why would the same logic not apply to rear calipers as well, such that bias is not affected? Maybe due to proportioning valve?

I erroneously assumed that the larger bore pistons would require at least the same if not more fluid to reach the rotor. I was wrong (I guess modern caliper pistons don’t need to travel as far as 45 year old ones do). I had very little pedal travel AKA a “super stiff” pedal. I just switched to a 1.125” MC. My pedal now travels further but I am getting more brake torque up front as a result.

This was my working theory as well that bigger pistons need more fluid, seems to be basic physics to me.

That said, I’ve read the piston seals are the mechanism that results in pad clearance after releasing brakes, is it possible the parts you just installed have less retraction and therefore need less volume? I’ve been tempted at times to use feeler gauges to try to characterize this theory.

 

[gunnibronco]

I need to think about this some more, but why would the same logic not apply to rear calipers as well, such that bias is not affected? Maybe due to proportioning valve?

I hope I'm not speaking out of turn here. I'm no engineer but I've been thinking and reading about my bias problem for over a month now.

I didn't take his advice to mean a smaller MC will fix the bias. I could think it through and if the MC is pushing equal fluid to a larger front caliper and a smaller rear, the rears will move further/have more force than the fronts. But that won't change with a smaller MC. I suppose that is what the proportioning valve could correct for, but my system is just too far out of balance for the proportioning valve to compensate for.

In fact he said in a post later to reduce the size of my rear calipers first. I'm sure this will pull my bias forward. I've known this but was looking for a work around because I think further reducing my caliper size will end up with a pedal that is super stiff and possibly undriveable. I like a touchy/stiff pedal, but I'm already on the borderline of acceptable. There is obviously some benefit to being able to feather the brakes. If they are either full on or full off, that's not a great situation. His suggestion is to see if the truck is still drivable after swapping calipers, then switch masters. I just need to suck it up and accept I oversized my MC and rear calipers and change both probably.

When I was running my 79 F150 axles with factory calipers front and drums rear, my bias was to the rear as well. I fixed it by going to the larger T-bird caliper. I don't have a larger front caliper option on my 96 F-350 brakes, so my only option is to reduce the size/effectiveness of my rear calipers. Fortunately the Eldorado caliper will do that by reducing the sufrace area about 30%.

Ultimately, I think my bias issue is that my rear calipers and rotors are too close in size to my fronts (too close for the proportioning valve to overcome). My rear caliper surface area is 89% the size of my fronts, on similarly sized rotors (12.5" rears and 12.95" fronts). I ran the numbers for a couple other vehicles for comparison and those trucks are about 64% rear/front. They are also running smaller rotors in the rear, so the rears are far less effective, proportionally, than mine. I've read that rears are only about 25% of braking (I can't remember and may be wrong) and I'm running something like 55% front and 45% rears, very roughly.

 

[toddz69]

Ultimately, I think my bias issue is that my rear calipers and rotors are too close in size to my fronts (too close for the proportioning valve to overcome). My rear caliper surface area is 89% the size of my fronts, on similarly sized rotors (12.5" rears and 12.95" fronts). I ran the numbers for a couple other vehicles for comparison and those trucks are about 64% rear/front. They are also running smaller rotors in the rear, so the rears are far less effective, proportionally, than mine. I've read that rears are only about 25% of braking (I can't remember and may be wrong) and I'm running something like 55% front and 45% rears, very roughly.

I think this is exactly your issue. I had the same problem years ago when I was running the Lincoln Mark V rear discs, which resulted in a rear caliper with a piston size larger than the fronts!(albeit on a slightly smaller rotor). No amount of proportioning valve work was going to pull that one into spec.

Todd Z.

 

[Yeller]

I hope I'm not speaking out of turn here. I'm no engineer but I've been thinking and reading about my bias problem for over a month now.

I didn't take his advice to mean a smaller MC will fix the bias. I could think it through and if the MC is pushing equal fluid to a larger front caliper and a smaller rear, the rears will move further/have more force than the fronts. But that won't change with a smaller MC. I suppose that is what the proportioning valve could correct for, but my system is just too far out of balance for the proportioning valve to compensate for.

In fact he said in a post later to reduce the size of my rear calipers first. I'm sure this will pull my bias forward. I've known this but was looking for a work around because I think further reducing my caliper size will end up with a pedal that is super stiff and possibly undriveable. I like a touchy/stiff pedal, but I'm already on the borderline of acceptable. There is obviously some benefit to being able to feather the brakes. If they are either full on or full off, that's not a great situation. His suggestion is to see if the truck is still drivable after swapping calipers, then switch masters. I just need to suck it up and accept I oversized my MC and rear calipers and change both probably.

When I was running my 79 F150 axles with factory calipers front and drums rear, my bias was to the rear as well. I fixed it by going to the larger T-bird caliper. I don't have a larger front caliper option on my 96 F-350 brakes, so my only option is to reduce the size/effectiveness of my rear calipers. Fortunately the Eldorado caliper will do that by reducing the sufrace area about 30%.

Ultimately, I think my bias issue is that my rear calipers and rotors are too close in size to my fronts (too close for the proportioning valve to overcome). My rear caliper surface area is 89% the size of my fronts, on similarly sized rotors (12.5" rears and 12.95" fronts). I ran the numbers for a couple other vehicles for comparison and those trucks are about 64% rear/front. They are also running smaller rotors in the rear, so the rears are far less effective, proportionally, than mine. I've read that rears are only about 25% of braking (I can't remember and may be wrong) and I'm running something like 55% front and 45% rears, very roughly.

You are correct. When I had this very axle and brake combination in a suburban it was fantastic, typically the rear axle weighed 1500# more than the front, swap that where the front out weighs the rear now there is a bias problem.

The theory about the rears activating first is correct and an import part of vehicle handling dynamics. It helps keep the rear pointed rear, which is good. But too much of a good thing and it locks, then it demands to not be in the rear any longer and insists on a move to the front lol.

 

[ksagis]

I think maybe short wheelbase Broncos with a much higher percent of weight over front tires also plays in

@gunnibronco, I think your idea of finding crappy friction, long wearing pads rear pads is a totally valid workaround (at least cheap and easy). Seems to me that friction is functionally equivalent to piston area to a first order.

I’d give it a try, maybe go to an autoparts store while you’re on travel and look at the codes to identify a D or E for backs and G for fronts. Going with a D for back is effectively reducing your piston area by roughly 50 percent over G in in front.

For 30 bucks and not having to bleed and mess with rest of system, seems like a easy thing to try.

 

[gunnibronco]

I think maybe short wheelbase Broncos with a much higher percent of weight over front tires also plays in

@gunnibronco, I think your idea of finding crappy friction, long wearing pads rear pads is a totally valid workaround (at least cheap and easy). Seems to me that friction is functionally equivalent to piston area to a first order.

I’d give it a try, maybe go to an autoparts store while you’re on travel and look at the codes to identify a D or E for backs and G for fronts. Going with a D for back is effectively reducing your piston area by roughly 50 percent over G in in front.

For 30 bucks and not having to bleed and mess with rest of system, seems like a easy thing to try.

There is something different with the Broncos than other vehicles that makes this rotor and caliper not work well. The JB6 calipers are used as a very common rear disk brake conversion for a lot of axles. The guy from Lugnut4x4 just about turned inside out when I told him the rear calipers were too big and I wanted to change to smaller calipers. I was surprised by his reaction. But he also didn't know the measurement of his Eldo caliper piston, he advertises them as "almost identical in size as the JB6 calipers" but they clearly are not. He struck me as more of a fabricator who's read enough to offer kits and parts that work most of the time, but doesn't have any real brake expertise.

I knew the rear calipers were possibly too big all along. Like I said my first plan for my axles was a semi-float rear axle with the Explorer brakes which use a single 2" piston, on an unvented 11.2" rotor. So jumping to a 3" caliper on a 12.5" rotor was a huge jump. I really do think that's the best answer, which unfortunately will probably force me to swap master cylinders.

I was looking at pads before I read about the friction material ratings and found there was a cheap organic pad sold by Oreilly's. It's the only organic pad I could find. From what I've read organic has the "worst" brake performance of the typical materials. I'm curious what it's rating is. I might check, they are in stock at my local store. I did read a thread here where someone tried that and it didn't really work enough to stop the lock up. It might even be this thread and it might have been Yeller actually. I'll keep that in my back pocket if swapping to the Eldo caliper doesn't work.

I've already ordered new calipers and the suggested MC & fittings. I have a pretty decent brake bleeding system down and an extra quart of DOT3 so it's not such a big deal to make these changes. It will probably be after the Super Cel in Carson City, but I'll post up and let everyone know how things worked out. Part of me just wants to swap everything at once and get it over with, but I'm also curious about the effect of just swapping one thing at a time. Doing the MC will involve modifying my adapter/clocking ring for the hboost and adjusting the hboost push rod so it involves a fair amount of work.

 

[1sicbronconut]

Something new to throw in the mix It's a Jeep application but hoping a 9" might be in the works from someone in the industry. https://brennans-garage.com/products/electric-emergency-brake-eebrake-rear-bracket-kit-41-75-jeep

 

[LittleBeefy]

I need to think about this some more, but why would the same logic not apply to rear calipers as well, such that bias is not affected? Maybe due to proportioning valve?



This was my working theory as well that bigger pistons need more fluid, seems to be basic physics to me.

That said, I’ve read the piston seals are the mechanism that results in pad clearance after releasing brakes, is it possible the parts you just installed have less retraction and therefore need less volume? I’ve been tempted at times to use feeler gauges to try to characterize this theory.

The math applies to the rear calipers at the same time. But those already lock up prematurely in @gunnibronco 's case, so it's not like the additional force can lock them up more. A smaller MC will not change the ratio so it's the front brakes that are being robbed of stopping power by the too-large MC.

You are correct that the piston seals are what retracts the caliper pistons. I went from 7.52sqin of surface area on the T-bird calipers to 7.65sqin SA on the Huge Brakes calipers. At a minimum, I would have expected the 1.25" MC to work about the same in both cases, but it doesn't. I had to go down to 1.125" to get equivalent pedal travel to what I had before. If you put a gun to my head and demanded an explanation, he only things that I can think of is that the shape and dimensions (or the material) of the seal is different and the T-bird inner seal deforms more during brake application than the Huge Brakes seal, meaning that when the pressure is released the T-bird piston is retracting farther. I have disassembled and reassembled both calipers previously, but I did not measure the dimensions of the seals or the groove in the caliper wall. My recollection is that the T-bird seal was "taller" than the Huge Brakes seal, but I can't be certain about that, or even what I had for lunch for 3 days ago.

 

[LittleBeefy]

Ok, I see. I was looking at the 2.5" Eldo caliper. I've seen the 2" Eldo caliper as well, but didn't consider it because it was a more difficult swap. I'm new to these 1 ton brake swaps, and I was using info from Lugnut4x4 pages and Rock Auto to do my research.

The reason I was really thinking about the 2.5" Eldo caliper is that is puts my rear/front caliper surface area ratio in a similar place as a couple factory set ups I've seen. 08 Super Duty is .64, 96 Explorer is .61. Currently I'm at .8914, but with the large Eldo calipers I'd be at .643. From reading this thread I realize there is a lot more at play, but at least I'm coming closer to where factory engineered systems fall. I was just playing with numbers in a spread sheet to see where my system deviated from factory systems. I wasn't taking swept area and distance from center of the axle into account, just some basics.

I'm going to start by saying that I don't have any experience with either of these El Dorado Calipers. I don't know the intricacies or complexities involved with the installation or operation. The main complaint that I had heard about the smaller, more common calipers is that keeping the parking brake adjusted is problematic. I am not in a position to comment on them or fitment.

For bias, I am only concerned with RWD sports cars and classic SUVs/Trucks, but my goal is 65% front, 35% rear in those applications. That is just my opinion. I'm not considering trucks like the Super Duty that would use a 50/50 bias for extreme loads and such.

I'm attaching a table show you my math @gunnibronco so you can get a better idea of the impact of different options.
Assumption alert: I don't know the actual center of force on any of these calipers so I assumed the top of the piston is aligned to the edge of the rotor and the center of force is the center of the piston(s). I used an "average" rating for the coefficient of friction (Mu) on the pads by lettering (i.e. FF pads are .4, not .35-.45) since you won't ever know the actual Mu. I used 550PSI to calculate the ultimate brake torque for comparison, even though brake torque changes with pressure, but that doesn't matter because brake pressure doesn't impact bias.

Here is a comparison of your current brakes vs the large Eldo brakes (assuming you are using the very common FF pads):

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (FF pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.4​

3345​

1499​

Current rears (FF pads)

12.50​

2.935​

1​

6.77​

4.7825​

550​

3721​

0.4​

2977​

1186​

44.2%​

55.8%​

Eldo rears (FF pads)

12.50​

2.5​

1​

4.91​

5​

550​

2700​

0.4​

2160​

900​

37.5%​

62.5%​

I like the bias you get with the Eldo rears. But, if you went with a EE rating in the back on those, here is what you are looking at:

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (FF pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.4​

3345​

1499​

Eldo rears (EE pads)

12.50​

2.5​

1​

4.91​

5​

550​

2700​

0.3​

1620​

675​

31.1%​

68.9%​

If you kept your current calipers and screwed with your pad combo a little (FF front, EE rear), you could expect to get something like this:

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (FF pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.4​

3345​

1499​

Current rears (EE pads)

12.50​

2.935​

1​

6.77​

4.7825​

550​

3721​

0.3​

2233​

890​

37.3%​

62.7%​

If you kept your current calipers and REALLY screwed with your pads (GG front, DD rear), it would look more like this:

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (GG pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.5​

4181​

1873​

Current rears (DD pads)

12.50​

2.935​

1​

6.77​

4.7825​

550​

3721​

0.2​

1488​

593​

24.0%​

76.0%​

To your original question about just screwing with pads to change your bias, you can see that it would work. Of course, YMMV because you don't know what the actual Mu is on any given pad, just a range, and there is a big difference between .26 and .34 even though they are both EE. and a .34 EE would operate very close to a .36 FF (for example).

 

[gunnibronco]

I'm going to start by saying that I don't have any experience with either of these El Dorado Calipers. I don't know the intricacies or complexities involved with the installation or operation. The main complaint that I had heard about the smaller, more common calipers is that keeping the parking brake adjusted is problematic. I am not in a position to comment on them or fitment.

For bias, I am only concerned with RWD sports cars and classic SUVs/Trucks, but my goal is 65% front, 35% rear in those applications. That is just my opinion. I'm not considering trucks like the Super Duty that would use a 50/50 bias for extreme loads and such.

I'm attaching a table show you my math @gunnibronco so you can get a better idea of the impact of different options.
Assumption alert: I don't know the actual center of force on any of these calipers so I assumed the top of the piston is aligned to the edge of the rotor and the center of force is the center of the piston(s). I used an "average" rating for the coefficient of friction (Mu) on the pads by lettering (i.e. FF pads are .4, not .35-.45) since you won't ever know the actual Mu. I used 550PSI to calculate the ultimate brake torque for comparison, even though brake torque changes with pressure, but that doesn't matter because brake pressure doesn't impact bias.

Here is a comparison of your current brakes vs the large Eldo brakes (assuming you are using the very common FF pads):

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (FF pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.4​

3345​

1499​

Current rears (FF pads)

12.50​

2.935​

1​

6.77​

4.7825​

550​

3721​

0.4​

2977​

1186​

44.2%​

55.8%​

Eldo rears (FF pads)

12.50​

2.5​

1​

4.91​

5​

550​

2700​

0.4​

2160​

900​

37.5%​

62.5%​

I like the bias you get with the Eldo rears. But, if you went with a EE rating in the back on those, here is what you are looking at:

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (FF pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.4​

3345​

1499​

Eldo rears (EE pads)

12.50​

2.5​

1​

4.91​

5​

550​

2700​

0.3​

1620​

675​

31.1%​

68.9%​

If you kept your current calipers and screwed with your pad combo a little (FF front, EE rear), you could expect to get something like this:

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (FF pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.4​

3345​

1499​

Current rears (EE pads)

12.50​

2.935​

1​

6.77​

4.7825​

550​

3721​

0.3​

2233​

890​

37.3%​

62.7%​

If you kept your current calipers and REALLY screwed with your pads (GG front, DD rear), it would look more like this:

Brakes

Rotor Size

Piston Size

Piston Count

Piston SA

Piston CoF Distance

Caliper PSI

Clamping Force

mu

Braking Force

Braking Torque (lb*ft)

Bias Rear

Bias Front

Fronts (GG pads)

12.95​

2.2​

2​

7.60​

5.3765​

550​

4181​

0.5​

4181​

1873​

Current rears (DD pads)

12.50​

2.935​

1​

6.77​

4.7825​

550​

3721​

0.2​

1488​

593​

24.0%​

76.0%​

To your original question about just screwing with pads to change your bias, you can see that it would work. Of course, YMMV because you don't know what the actual Mu is on any given pad, just a range, and there is a big difference between .26 and .34 even though they are both EE. and a .34 EE would operate very close to a .36 FF (for example).

Thanks, that's awesome info. How would a proportioning valve work into the equation? I'm guessing your numbers are max without a prop valve and I could turn down from there.

I'm going to move forward with swapping to the Eldo rears and change the rear pads only if I can't get a good feeling bias. I'll swap in the MC if the pedal feel doesn't work.

You have been very helpful, I appreciate the insight!

 

[Yeller]

Reading all of this makes me really question why I have such an issue with bias. Just using surface area as a tool and everything else being equal the rears are 29% smaller. The front calipers are massive 3.4" single piston with a surface area of 9.35" and the rears are 29% smaller at 6.77. makes me wonder if I have some higher coefficient pads in the rear and some crappy ones in the front. Would explain a lot. but either way the pistons still need to be smaller