disc brake conversion need advise

[tlape4965]

I have a 1990 GMC Suburban that I'm doing a disc conversion on and I need help with the proportioning valve issue. Most of what I have seen on here are earlier models. What can I do to get the braking right? I can't find any proportioning valves that seem right. I would go with an adjustable one if I knew how to hook it up. The stock one on my truck seems to be two individual valves. Thanks for any help.

 

[herkdriver007]

I did the disc swap on mine, OEM pro-valve and no issues so far. IMO, use what you've got then after driving it, determine if you need the adjustable setup.

 

[cuervo]

My 91 braking suffers a bunch after the disc brake swap; wish I would not have done it.

 

[imiceman44]

I have a 1990 GMC Suburban that I'm doing a disc conversion on and I need help with the proportioning valve issue. Most of what I have seen on here are earlier models. What can I do to get the braking right? I can't find any proportioning valves that seem right. I would go with an adjustable one if I knew how to hook it up. The stock one on my truck seems to be two individual valves. Thanks for any help.

Sure this is a 90?
it looks like a 70 with the PV on the booster?
Or does this truck have the rear anti lock brake?

 

[tlape4965]

Sure this is a 90?
it looks like a 70 with the PV on the booster?
Or does this truck have the rear anti lock brake?

No it's a '90. There is two valves back to back.

 

[dremu]

Sure this is a 90?
it looks like a 70 with the PV on the booster?
Or does this truck have the rear anti lock brake?

Bing bing bing. 1990-91 R/V's have the RWABS, that's the black box to the right in the picture.

-- A

 

[tlape4965]

Bing bing bing. 1990-91 R/V's have the RWABS, that's the black box to the right in the picture.

-- A

That was my next question. There is a 4 pin plug coming from that black box (RWABS) going to the back of the proportioning valve. Since I'm changing to a disc to disc PV and there is no spot for the plug, what is the plug for and what is the result running with out it?

 

[dremu]

That was my next question. There is a 4 pin plug coming from that black box (RWABS) going to the back of the proportioning valve. Since I'm changing to a disc to disc PV and there is no spot for the plug, what is the plug for and what is the result running with out it?

The result is that your brakes will work just fine. The RWABS is famous for being cantankerous and many folsk, myself included, just unplug the damn thing when it fails.

-- A

 

[tlape4965]

The result is that your brakes will work just fine. The RWABS is famous for being cantankerous and many folsk, myself included, just unplug the damn thing when it fails.

-- A

Thanks man. Relieves a lot of issues.

 

[tlape4965]

disc brake conversion need advise (Fixed)

For anyone who hates the performance of their brakes after converting to disc. I was in the same boat. I ordered from Jegs part # 631303 proportioning valve, installed and it works great.

 

[British Slave]

Go to Summit and buy a Wilwood adjustable valve. Part number 260-8419

 

[cuervo]

For anyone who hates the performance of their brakes after converting to disc. I was in the same boat. I ordered from Jegs part # 631303 proportioning valve, installed and it works great.

I'm not sure this would fix my complete issues with the disc break conversion. The other issue is the ebrake doesn't hold at all. If you adjust them to the point it will hold the truck they are so tight they over heat while driving.

 

[sweetk30]

all front fluid is just tee'd in the stock valve.

rear is adjusted/biased to rear to limit pressure.

remove stock and install a tee fitting for the front and blead.

rear adjustable valve inplace of stock and blead.

road test and set to were you like it and be done.

i did my first truck this way and perfect for years.

and if low pedal but good brakes like 1/2 ton master get a bigger master for more fluid volume from a 1 ton and get your pedal back.

 

[CGT80]

I'm not sure this would fix my complete issues with the disc break conversion. The other issue is the e brake doesn't hold at all. If you adjust them to the point it will hold the truck they are so tight they over heat while driving.

I had that problem with the Eldorado calipers on my 79 c20 with a 14bff. I recently took the caddy calipers off and installed calipers from the front of a 4x4 3/4 ton pickup. They work much better than the caddy calipers, but I don't have an e brake now. The e-brake sucked anyway do no loss there. I don't get inspected for an e brake, just smog testing.

 

[cybrfire]

I'm not sure this would fix my complete issues with the disc break conversion. The other issue is the ebrake doesn't hold at all. If you adjust them to the point it will hold the truck they are so tight they over heat while driving.

Sounds like maybe a longer arm on the caliper might help your situtation.

 

[bp71k5]

I'm not sure this would fix my complete issues with the disc break conversion. The other issue is the ebrake doesn't hold at all. If you adjust them to the point it will hold the truck they are so tight they over heat while driving.

You're only supposed to tighten them enough that the e-brake arm doesn't rotate. You might just have too much slop in the cable near the pedal. It took me a while, but I was able to get mine working pretty good.

 

[cuervo]

You're only supposed to tighten them enough that the e-brake arm doesn't rotate. You might just have too much slop in the cable near the pedal. It took me a while, but I was able to get mine working pretty good.

I don't understand what you are trying to say here. I take a stab at it.

- set the ebrake
- adjust the nut on the cable until the arms are as far rotated to the on position
- release ebrake

??

 

[bp71k5]

I don't understand what you are trying to say here. I take a stab at it.

- set the ebrake
- adjust the nut on the cable until the arms are as far rotated to the on position
- release ebrake

??

No. Hook everything up so the spring is keeping the e-brake arm fully disengaged. Then tighten up the screw on the cable to take up any slack in the cable, but not let the e-brake arm rotate at all. That's it.

If after doing that, the brake doesn't hold, drive it down the street, stop and engage then release the e-brake. Then drive more and repeat the same process a few times. This process will force the calipers to self adjust.

Then if it's still not tight you can try adjusting the cable again to see if it loosened up during use at all, but the e-brake lever should be against it's stop when it's disengaged.

If after all that the thing still doesn't work, it means you have too much slack in the cable upstream of the e-brake. This could be from a cable sheathing stop moving and allowing the sheathing to shift when you use the e-brake. It could be a damaged cable mount as well. I had a weird intermediate cable system that had some pre-bent parts in it that I had to do the process of using and releasing the e-brake a bunch of times to unbend those parts of the cable and then adjust out the slack again.

Anyway, sorry for the long post. Good luck with it.

 

[cuervo]

No. Hook everything up so the spring is keeping the e-brake arm fully disengaged. Then tighten up the screw on the cable to take up any slack in the cable, but not let the e-brake arm rotate at all. That's it.

If after doing that, the brake doesn't hold, drive it down the street, stop and engage then release the e-brake. Then drive more and repeat the same process a few times. This process will force the calipers to self adjust.

Then if it's still not tight you can try adjusting the cable again to see if it loosened up during use at all, but the e-brake lever should be against it's stop when it's disengaged.


If after all that the thing still doesn't work, it means you have too much slack in the cable upstream of the e-brake. This could be from a cable sheathing stop moving and allowing the sheathing to shift when you use the e-brake. It could be a damaged cable mount as well. I had a weird intermediate cable system that had some pre-bent parts in it that I had to do the process of using and releasing the e-brake a bunch of times to unbend those parts of the cable and then adjust out the slack again.

Anyway, sorry for the long post. Good luck with it.

Ok, yeah when doing it that way it is never tight enough to hold the truck. I'm pretty sure the TSM caddie calipers do not self adjust.

 

[bp71k5]

Ok, yeah when doing it that way it is never tight enough to hold the truck. I'm pretty sure the TSM caddie calipers do not self adjust.

I have the tsm calipers and they self adjust over here. I do see people move or make new cable holder brackets that aren't strong enough to hold the cable. When you are pressing the e-brake pedal, the cable sheathing cannot be allowed to move even a little bit or that just translates into slack and reduces the movement of the caliper lever. Any chance you moved or modified any of that?