proportioning valve. Need more rear braking power

[Suburban_Tyler]

I have a 1990 R1500 2wd Suburban. The rear brakes need more power to them. I tried tightening the shoes and bleeding the brakes. When I have a trailer hooked on it gets down right scary trying to stop. Thats with about 1,500lbs behind the Suburban and not a whole lot of tongue weight. If the windows are down I get hear the tires starting to slip. I can literally get better rear brake power if I push the parking brake down. Is the a different proportioning valve I can get that would do better as far as getting more power to the rear brakes. Normal driving it stops fine. Always has a good pedal. If I have to make sudden stops you can count on one or both of the front tires locking up depending on the surface.

[hatzie]

The standard disc drum brakes are biased by the master cylinder and combination valve to around 70% disc and 30% drum.

It sounds like the trailer brakes aren't working. I ran an 18' Brewer landscape trailer, carrying 3 commercial mowers or loads of loam and mulch, without adjusting the bias on the tow vehicles. They stopped fine till the trailer brakes dropped out. It was a scary ride when the trailer brakes were getting dodgy.

[Suburban_Tyler]

Originally Posted by hatzie

The standard disc drum brakes are biased by the master cylinder and combination valve to around 70% disc and 30% drum.

It sounds like the trailer brakes aren't working. I ran an 18' Brewer landscape trailer, carrying 3 commercial mowers or loads of loam and mulch, without adjusting the bias on the tow vehicles. They stopped fine till the trailer brakes dropped out. It was a scary ride when the trailer brakes were getting dodgy.

Trailer doesn't have brakes. It's just a 10' trailer with a lawn mower on it, but it sure makes a huge difference in stopping. I just need more braking power to the rear. As messed up as it sounds, setting the parking brake makes a huge difference. 2 winters ago if it wasn't for me setting the parking brake going down a hill I would have slid into a house. Very little brake pressure the front just locked and picked up speed as it slid. A little brake pressure from the parking brake helped get things under control.

[v30crewcab]

have made sure the rear shoes are not installed backwards? there is a front and rear shoe. the rear one has more lining than the front one. that will do what you are saying.

[Suburban_Tyler]

Originally Posted by v30crewcab

have made sure the rear shoes are not installed backwards? there is a front and rear shoe. the rear one has more lining than the front one. that will do what you are saying.

I think they're correct but I don't know for sure. It's definitely worth checking.

[kelsfine69]

I have the same problem with my 87 1/2 ton...in the winter the front brakes lock up on snow and ice and if you throw it in neutral it stops alot better. I think they are all like that from what i have seen but i want to try a master cylinder myself....

[hatzie]

It's worthwhile to add brakes to a 10' trailer especially if you're having issues stopping. Assuming you're running 13"-15" 5on4.5" or 5on5" wheels... You can replace the hubs with 10" Dexter type electric brakes for around $350-$375 in parts including the weld-on axle flanges, controller, and breakaway kit.
Nothern Tool 10" drum trailer brake kit $230
Weld-on Axle Flanges
Breakaway kits are required under most states vehicle codes. They cost around $50. Get one with a charge circuit and don't use Scotchloks to wire it in unless you like re-wiring every spring.
Breakaway Kits
Controllers are around $50 as well.

I've been down this road with the smaller landscape trailers. You'll never get the stopping power you want by re-biasing the truck brakes. When/if you upgrade to a bigger trailer... The trailer brakes will follow the trailer and make it easier to sell. As a bonus the truck will already be wired for the brakes on the bigger trailer.

State DOT Police are getting much more aggressive with individuals towing trailers than they were in years past. If you're running without trailer brakes on heavy loads (you're unable to slow it down on a hill... that means you have a heavy load) they will catch you. DOT fines are astronomical. $400 in brakes is way cheaper than a $2000 fine.

That being said...

1 How did you set the adjusters when you adjusted the shoes against the drums? I usually spin em up till they lock the wheel and back off till it spins free again. I take a spin and re-adjust twice to make sure all the slack is out of the springs and cables.

2 Are the automatic adjusters hooked up properly, free spinning, and lubed with high temp grease like Sil-Glyde?

3 Do you set the parking brake at least twice daily to take up the slack in the adjusters?

[Mrknowitall]

Originally Posted by hatzie

The standard disc drum brakes are biased by the master cylinder and combination valve to around 70% disc and 30% drum.

It sounds like the trailer brakes aren't working. I ran an 18' Brewer landscape trailer, carrying 3 commercial mowers or loads of loam and mulch, without adjusting the bias on the tow vehicles. They stopped fine till the trailer brakes dropped out. It was a scary ride when the trailer brakes were getting dodgy.

Originally Posted by hatzie

It's worthwhile to add brakes to a 10' trailer especially if you're having issues stopping. Assuming you're running 13"-15" 5on4.5" or 5on5" wheels... You can replace the hubs with 10" Dexter type electric brakes for around $350-$375 in parts including the weld-on axle flanges, controller, and breakaway kit.
Nothern Tool 10" drum trailer brake kit $230
Weld-on Axle Flanges
Breakaway kits are required under most states vehicle codes. They cost around $50. Get one with a charge circuit and don't use Scotchloks to wire it in unless you like re-wiring every spring.
Breakaway Kits
Controllers are around $50 as well.

I've been down this road with the smaller landscape trailers. You'll never get the stopping power you want by re-biasing the truck brakes. When/if you upgrade to a bigger trailer... The trailer brakes will follow the trailer and make it easier to sell. As a bonus the truck will already be wired for the brakes on the bigger trailer.

State DOT Police are getting much more aggressive with individuals towing trailers than they were in years past. If you're running without trailer brakes on heavy loads (you're unable to slow it down on a hill... that means you have a heavy load) they will catch you. DOT fines are astronomical. $400 in brakes is way cheaper than a $2000 fine.

That being said...

1 How did you set the adjusters when you adjusted the shoes against the drums? I usually spin em up till they lock the wheel and back off till it spins free again. I take a spin and re-adjust twice to make sure all the slack is out of the springs and cables.

2 Are the automatic adjusters hooked up properly, free spinning, and lubed with high temp grease like Sil-Glyde?

3 Do you set the parking brake at least twice daily to take up the slack in the adjusters?

he knows what hes saying!!!

Id leave the porp valve alone!
anything @ or over 500lbs tongue weight is REQUIRED to have brakes....

if shes a 1/2t heres some ref pics i had saved for such an occasion








annndddd hahahahahahaha

[Krwright]

I had the same issue. My case was the rubber line in the rear. The braking in the rear was never right. I changed the master, proportioning valve, wheel cylinders, drums and shoes with no improvement. Then after about a year i lost everything in the rear. I took the hard lines off and stood on the pedal and not a drop of fluid would pass through. Put a new rubber line on and couldn't ask for better braking.
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[hatzie]

Originally Posted by Mrknowitall

annndddd hahahahahahaha

Looks like it was on one of my father's rigs...
Never could get him to do maintenance till it was really broken.

[Mrknowitall]

Originally Posted by hatzie

Looks like it was on one of my father's rigs...
Never could get him to do maintenance till it was really broken.

Isnt that awful!? Found in archives lol
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[Suburban_Tyler]

Originally Posted by hatzie

It's worthwhile to add brakes to a 10' trailer especially if you're having issues stopping. Assuming you're running 13"-15" 5on4.5" or 5on5" wheels... You can replace the hubs with 10" Dexter type electric brakes for around $350-$375 in parts including the weld-on axle flanges, controller, and breakaway kit.
Nothern Tool 10" drum trailer brake kit $230
Weld-on Axle Flanges
Breakaway kits are required under most states vehicle codes. They cost around $50. Get one with a charge circuit and don't use Scotchloks to wire it in unless you like re-wiring every spring.
Breakaway Kits
Controllers are around $50 as well.

I've been down this road with the smaller landscape trailers. You'll never get the stopping power you want by re-biasing the truck brakes. When/if you upgrade to a bigger trailer... The trailer brakes will follow the trailer and make it easier to sell. As a bonus the truck will already be wired for the brakes on the bigger trailer.

State DOT Police are getting much more aggressive with individuals towing trailers than they were in years past. If you're running without trailer brakes on heavy loads (you're unable to slow it down on a hill... that means you have a heavy load) they will catch you. DOT fines are astronomical. $400 in brakes is way cheaper than a $2000 fine.

That being said...

1 How did you set the adjusters when you adjusted the shoes against the drums? I usually spin em up till they lock the wheel and back off till it spins free again. I take a spin and re-adjust twice to make sure all the slack is out of the springs and cables.

2 Are the automatic adjusters hooked up properly, free spinning, and lubed with high temp grease like Sil-Glyde?

3 Do you set the parking brake at least twice daily to take up the slack in the adjusters?

It's funny that you mentioned adding brakes to the trailer and thats actually a great idea but I don't feel it will resolve my problem. I have a set of brakes for a trailer laying around. I don't have an issue putting them on there. I actually run a 15' wheel with a 225/75-15 tire. I just brought up the issue cause with 1500lbs extra of weight behind it, it doesn't stop unless I stop like a train. If I have an emergency situation I think a little extra would help. I'm not arguing the fact trailer brakes would help either. I have 3rd row seating in it. If I had 7 200lbs guys with a cooler in the back I would kinda be in the same situation but some of the weight would be distributed more to the front.

I set the adjusters fairly tight. I tighten them to where it has a light drag on the drum. I do actually set the parking brake more than twice a day. Its a habit to set it every time I put it in park.

[hatzie]

Originally Posted by Suburban_Tyler

It's funny that you mentioned adding brakes to the trailer and thats actually a great idea but I don't feel it will resolve my problem. I have a set of brakes for a trailer laying around. I don't have an issue putting them on there. I actually run a 15' wheel with a 225/75-15 tire. I just brought up the issue cause with 1500lbs extra of weight behind it, it doesn't stop unless I stop like a train. If I have an emergency situation I think a little extra would help. I'm not arguing the fact trailer brakes would help either. I have 3rd row seating in it. If I had 7 200lbs guys with a cooler in the back I would kinda be in the same situation but some of the weight would be distributed more to the front.

I set the adjusters fairly tight. I tighten them to where it has a light drag on the drum. I do actually set the parking brake more than twice a day. Its a habit to set it every time I put it in park.

You could check the flexible axle line like Krwright suggested. The flexible frame to axle line can decay internally. I've had them lock up front calipers. It's possible to have dry rotted lines block fluid flow too.
Fill the Master Cylinder and open the bleeders to see if you get fluid flow via gravity.

[Suburban_Tyler]

Originally Posted by hatzie

You could check the flexible axle line like Krwright suggested. The flexible frame to axle line can decay internally. I've had them lock up front calipers. It's possible to have dry rotted lines block fluid flow too.
Fill the Master Cylinder and open the bleeders to see if you get fluid flow via gravity.

I will check that.

[Suburban_Tyler]

Well it has been a while but I finally got the chance to change that brake hose that goes from the frame to the axle. Just from normal braking I can feel the brakes applying themselves with less effort from the pedal. Hard stops seem to be better as well. Before I could hear the front tires starting to squall on a moderate to hard stop without locking them up. Now I'm guessing the rear grabs hard enough to transfer so weight to the front and pushes down a little harder on the front tires along with assisting the front in stopping cause it stops a lot faster. Thank you for the advice guys.

[INSIDIOUS '86]

You can also upgrade to a3/4 ton braking system wider front rotors and a dual diaphragm booster and bigger wider brakes on the back
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