13.6 Inch 2019 Silverado rotor conversion

[Wildblue19]

I know what RWAL is, but Schurkey's post implied to me that 92-95 differed from 88-91. After a cursory glance at your link, I don't see how that's so if it is.

From the link, it appears the difference is only by year for 92-95 suburban vs the 88-up full size PU. However, this is only one data point I found on the subject and there may be some system difference not discussed.

 

[Supercharged111]

From the link, it appears the difference is only by year for 92-95 suburban vs the 88-up full size PU. However, this is only one data point I found on the subject and there may be some system difference not discussed.

I swear I saw a weird one-off 94ish SUV ABS so was hoping the link would give me a little closure on that one. The SUVs took longer to transition to the 400 body back then, so likely the reason for their ABS lag now that I'm thinking about it.

 

[Schurkey]

There were (at least) two main differences in the RWAL units--cast iron body (87--89?) and the aluminum body ('90?--'91). The iron body unit had it's own bleeder screw, which made things easier.

I thought 92--'94 C/K got EBC4 4-wheel / 3 channel ABS.

'95--99(?) C/K got EBC310 4-wheel / 3-channel ABS.

Perhaps I'm wrong.

My source is the ABS bleeding procedure .pdf

 

[arrg]

I know what RWAL is, but Schurkey's post implied to me that 92-95 differed from 88-91. After a cursory glance at your link, I don't see how that's so if it is.

88-91 Standard Cab C/K1500 pickups came standard with JN3 brakes (11.57x1.0 disc/single diaphragm booster). Yes, there was a JN1 manual brake option, but we're talking power brakes here. JN5 brakes (11.57x1.25 disc/dual diaphragm booster) were standard on the extended cab trucks. The RWAL hydraulic unit changed between 90-91 models but still functions the same. Starting in 92, all C/K1500 gas models came standard with JB5 (option code changed) brakes (11.57x1.25 disc/dual diaphragm booster). 92 was the first year of the GMT400 SUV's. They got 4WAL, but as far as I know, the pickups didn't get 4WAL until 95.

 

[Wildblue19]

Thanks for the information and interest on the topic everyone. This front braking modification was step one of getting rid of the pretty inadequate factory braking system. The next steps I am considering are a rear swap with discs and a HB setup.

@Schurkey, I've read several of your posts on other's brake system questions, and would like to discuss with you on the topic of matching a HB/MC/prop valve system to work with the Ram calipers and disc rears. I can expand on the numbers I've run, but here is my process on getting a ballpark for the correct MC diameter. I'd like your input on this, as well as your thoughts on importance on the differences between different generations of HB and proportioning for optimal engagement.

Data on Braking Systems by Vehicle ( Source: Rock Auto )
I chose these vehicles based on the parts I intend to use, but more data points on factory systems would aid this discussion.

1) 14-18 1500 Silverado (thinking about using this generation rear axle for the discs, 9.76" ring gear and locking diff)
- Front Caliper: 2x51mm
- Rear Caliper: 1x 51mm
- MC Bore: 32.5mm
2) 05 Ram 1500 (Front caliper donor vehicle)
- Front Caliper: 2x54mm
- Rear Caliper: 1x 54mm
- MC Bore: 33.27mm
3) 99-06 1500 Chevy w/HB
- Front Caliper: 2x57mm
- Rear Caliper: 1x 51mm
- MC Bore: 37mm

Braking System Ratios (Total piston area per side / MC area)
1) 14-18: 6128mm^2 / 830mm^2 = 7.4
2) 05 Ram: 6870mm^2 / 869mm^2 = 7.9
3) 99-06: 7145mm^2 / 1075mm^2 = 6.65
AVG: 7.31

Custom Setup Desired MC
(Calculating desired MC area based on avg system ratio and custom setup of 05 Ram front and 14-18 rear calipers on my K1500)

Total Area with 2x54mm front and 1x 51mm rear = 6622mm^2
6622 / 7.31 = 905.88
905.88 / pi = 288.35
sqrt(288.35) = 16.98
16.98*2 = diameter = 34mm

Input and comments welcome from all, thanks.

 

[Schurkey]

The math seems reasonable. Can you get a master cylinder with a 34mm bore?

First Guess: You're limited to what's readily available, which may/may not be the desired size.
Second Guess: If you're close...good enough. The big deal is to not have a master cylinder bore so large that you have a hard time stopping if the booster fails; while not having a small master cylinder that requires too much pedal stroke. There's a decent range of "good enough" in between the extremes.

I'd be curious to see what size calipers and rear discs are on the vehicle you've grabbed the front calipers/rotors from.

Brake balance is more than just getting the master cylinder/wheel cylinder ratios close. You've also got the leverage ratio front/rear based on rotor diameter (really, caliper mounting radius) and the force ratios front/rear based on piston area. One goal is to assure that the front brakes lock before the rear brakes. Put another way, you do not want the rear brakes to lock before the fronts. ABS helps with this, but better to use the ABS as "fine-tuning". The brake geometry doing the bulk of the "balancing" work, the proportioning valve and brake-pad friction coefficient tuned to make best use of the geometry, and the ABS taking over only when the rest of the system gets into trouble.

 

[arrg]

The 03-06 GMT 800 SUV's w/ Hydroboost run a 34mm master cylinder.

 

[arrg]

Also, this website is useful to see how making changes to your brake system affects your overall brake torque. https://www.tceperformanceproducts.com/bias-calculator/

 

[Wildblue19]

The math seems reasonable. Can you get a master cylinder with a 34mm bore?

First Guess: You're limited to what's readily available, which may/may not be the desired size.
Second Guess: If you're close...good enough. The big deal is to not have a master cylinder bore so large that you have a hard time stopping if the booster fails; while not having a small master cylinder that requires too much pedal stroke. There's a decent range of "good enough" in between the extremes.

I'd be curious to see what size calipers and rear discs are on the vehicle you've grabbed the front calipers/rotors from.

Brake balance is more than just getting the master cylinder/wheel cylinder ratios close. You've also got the leverage ratio front/rear based on rotor diameter (really, caliper mounting radius) and the force ratios front/rear based on piston area. One goal is to assure that the front brakes lock before the rear brakes. Put another way, you do not want the rear brakes to lock before the fronts. ABS helps with this, but better to use the ABS as "fine-tuning". The brake geometry doing the bulk of the "balancing" work, the proportioning valve and brake-pad friction coefficient tuned to make best use of the geometry, and the ABS taking over only when the rest of the system gets into t

The 03-06 GMT 800 SUV's w/ Hydroboost run a 34mm master cylinder.

Thanks, that plus the calculator you sent will help me build a compatible system.

 

[JimmyTejas]

Getting closer. Waiting on wheels to bolt everything up.

You must be registered for see images attach

You must be registered for see images attach

Have you managed to find a way to make the 19+ front calipers work with GMT400 knuckle? I’ve got an 89 C1500 that I’d love to do the upgrade on.