Slip and slide brakes

[MM3846]

Upgraded to D90 fronts, and I disabled ABS since it tried to kill me twice last week... Probably messed up the sensors putting in new swivel pins. Anyway, it rained today and my brakes are locking up insanely quickly on the road. Tires are year old Cooper AT3s, 245/75 in size. No problems on dry pavement, and almost every car I've owned hasn't had ABS.

Am I the only one? I'm going to throw my buddy's scanner on my ABS to see what's up as soon as I can get over to his shop to try and salvage my ABS functionality, but I don't see that happening since getting that to works seems like a fools errand from what I've read.

 

[p m]

With 110 brake calipers in the front (same pistons as 90), I was able to lock up the front tires (265/75s) on dry pavement for the first time ever. So I suspect this effect would be much more pronounced with smaller tires and on wet pavement.

Probably that brake proportioning valve could use some tweaking.

 

[Tugela]

I have D110 calipers up front on my D1, rolling 235/75/16 tires (unusual size, but I like them), disabled ABS (pulled fuse), and I have not had a problem locking up. And I live in Seattle where it rains 400 days a year. Maybe it's my driving style? I tend to go slow, keep long following distances, and brake gently.

I also suspect my braking would improve with adjustment of the proportioning valve. I don't even know if that is something that can be adjusted, and if it can I don't know how to.

My front brakes create lots more dust than the rears, but that could also be a function of the pad model. I think they are Mintex.

 

[MM3846]

I definitely do drive semi-aggresssvely compared to most, but I'd say I'm actually more conservative than most drivers here. Maybe it's because my rear brakes aren't up to snuff? The calipers and pads are new, but the rotors are toast. I've never heard of any factory proportioning valve being adjustable, and the fronts should be locking up first anyway. Seems like it really isn't a "problem" so much as an annoyance. Crazy to think these brakes are smaller and the Disco lighter than a lot of newer trucks... I wonder how a something like a LR4 would brake without ABS.

 

[cdansan]

I have 110 calipers in front, ABS physically removed and adjustable proportioning valve from Summit.
No issues with locking up front or rear tires, been running like this for about 2 years.

 

[robertf]

how are 110 fronts different from 90? I'm talking 300tdi era brakes. I thought they were the same

The 110 rears are on and bled. No complaints about pedal travel, but I've been working on other stuff and haven't driven that vehicle more than 10 miles since the conversion.

my other truck with just 90 fronts does lock up on occasion, but it always stops where I expect it to.

 

[Tugela]

how are 110 fronts different from 90?

D110 and D90 front brake setups are mostly identical, the two differences being:

1. D90 calipers have a spacer, making them wider, which then requires/allows use of
2. vented rotors

D110 calipers lack the spacer and can therefore use solid Disco rotors. This was a selling point for me choosing D110 over D90 calipers, as I had just installed new rotors. Plus I'd read cautionary tales of other guys annoyed at how gunked up their vented rotors got with mud.

cdansan: how did you calibrate your adjustable proportioning valve? Trial and error until you got the performance you liked, or is there another method? What were the settings you used? More force sent to rear brakes to balance out increased stopping power of the fronts?

 

[MM3846]

cdansan: how did you calibrate your adjustable proportioning valve? Trial and error until you got the performance you liked, or is there another method? What were the settings you used? More force sent to rear brakes to balance out increased stopping power of the fronts?

That's what I did on my Jeep. Long stretch of empty road, trial and error until I found a good balance. Of course after I upgraded the brakes again I couldn't get the front to lock before the rears. I entertained putting a limiting valve on but ended up getting rid of the truck.

 

[cdansan]

I guess I have 90 calipers as I have vented front rotors.
The proportioning valve had intructions that basically said start at 50% of the adjuster travel and adjust out for more rear brakes and in for less.
I think that I have found a comfortable setup, it feels like the rears are working and there is less front end dive when you get on the brakes.
I have started to actually get significant wear in the rear pads. Whereas before I would change the front pads twice for every rear set.

 

[robertf]

you know those adjustable things aren't really proportioning valves, just regulator valves for the rear. It won't decrease pressure to the one side if the other has a fault.

 

[MM3846]

you know those adjustable things aren't really proportioning valves, just regulator valves for the rear. It won't decrease pressure to the one side if the other has a fault.

I used one of these, which actually was a real proportioning valve

What you're talking about (I think) is one of these, which is pretty much just a regulating/limiting valve

But yea, they aren't going to replace a smart, modern and working ABS proportioning valve.

 

[Buddy]

This proportioning valve talk has me wondering. What's the best way to test if your proportioning valve is working?

My brakes work adequately enough on the road and in high range at least for the limited amount my DI spends on it. However, since upgrading to the 4.75 gearing I've been having issues coming to a complete stop on steep hills off road. It does ok on flat ground but if I'm coming down a steep hill it will slow down to a crawl but then I'll have to step on the pedal with both feet for the last little bit to actually stop the truck. I finally started putting the truck in neutral if I have to stop on a steep downhill and that seems to work well enough. But it's a pain to always have to remember to put it in neutral.

I ordered a set of 110 front calipers which I hope will help. But I'm also wondering if I'm just not getting good pressure to both the front and rear because of a bad proportioning valve.

 

[fishEH]

I pretty much had the same issue on my 98, Tobias. The rear brakes never seem to work well on any of my trucks. I feel like the original stock proportioning valves on these trucks are probably crapped up. My 95 came with an adjustable one from Summit and seemed to work well.

 

[MM3846]

This proportioning valve talk has me wondering. What's the best way to test if your proportioning valve is working?

My brakes work adequately enough on the road and in high range at least for the limited amount my DI spends on it. However, since upgrading to the 4.75 gearing I've been having issues coming to a complete stop on steep hills off road. It does ok on flat ground but if I'm coming down a steep hill it will slow down to a crawl but then I'll have to step on the pedal with both feet for the last little bit to actually stop the truck. I finally started putting the truck in neutral if I have to stop on a steep downhill and that seems to work well enough. But it's a pain to always have to remember to put it in neutral.

I ordered a set of 110 front calipers which I hope will help. But I'm also wondering if I'm just not getting good pressure to both the front and rear because of a bad proportioning valve.

Going downhill in low is hard on the brakes. I think you'll be ok with the 110 calipers. You really don't want the rears to do much in that situation anyway, if they have too much power you'll swap ends and that is a real code brown scenario.