L-body SLH brake upgrage problem.
So a bunch of years back I did the full SLH brake upgrade on my Shelby Charger ( Caravan calipers, Daytona rear vented disc, Daytona 4 wheel disc prop valve, and D150 master cylinder. I also replaced all the rubber lines with the stainless ones from FWD.
From day one I've always had a harder than normal peddle feel. It stops well but I have to really push on the peddle to do so, It's almost as tho I had little or no vacuum assist. ( like manual brakes )
Move a few years later and not driving the car until late last summer because of life. I decided to replace the booster and when I pulled the old one I noticed there was a piece broken that could affect it's function, so I thought I fixed the problem... which it did but only by maybe 20% less brake peddle pressure.
Last week I drove a friends Shelby Charger with mostly stock brakes aside from shadow caliper and his brakes work well and his peddle feel is much more what I would expect to have.
Anyone run into the problem and if so what was done to fix it?
Just thinking out loud, could it be the master cylinder causing the issue? These cars have rather small boosters and maybe it could not be proving enough assist to push the large piston in D150 master? I've been thinking about trying a 24mm master out of a daytona...
Re: L-body SLH brake upgrage problem.
Yes. IMO, the D150 MC is too big. I would switch up to a 24mm MC out of a big brake car. I also don't like the vented disks in the rear. They're heavier than the 10.5" non-vented units, and in my experience, they cause the car to lock up the rear when wet or cold out.
If I had to do it again, I would do a swap to later model knuckles and either modify them for the L body strut, or run Rbryant's coilovers. Then I would get some 11" calipers and brackets for the front. In the rear I would either stick with the stock drums, or upgrade to the 10.5" solid rears. I think that's the ideal combination for 99% of hard driving people.
Re: L-body SLH brake upgrage problem.
I never had issue with my stock GLH master cylinder and minivan calipers and 10 inch rear disc.
Re: L-body SLH brake upgrage problem.
Quote:
Originally Posted by
cordes
and in my experience, they cause the car to lock up the rear when wet or cold out.
Huh, I have never had this problem with my setup.
Quote:
Originally Posted by
cordes
If I had to do it again, I would do a swap to later model knuckles and either modify them for the L body strut, or run Rbryant's coilovers.
I do have a set of 91+ knuckles that I do plan on using eventually, and I would love to buy that coil over setup one day, the plan is to autox the car one day
Quote:
Originally Posted by
tryingbe
I never had issue with my stock GLH master cylinder and minivan calipers and 10 inch rear disc.
I went over the SLH write up again and it suggests replacing the rear brake line also, which I never did... did you do yours? and which prop valve did you use? I didn't realize ( should have known better ) there were so many different ones.
Re: L-body SLH brake upgrage problem.
I should note that when I had that brake setup on an Omni, I had DOT legal slicks on the car all the way around.
Check out the prop. valve table that Rich posted a while back. I'll see if I can find it for you, but either way, I think the stock L body prop valve had the lowest pressure going to the rear. That's the way I would go.
Re: L-body SLH brake upgrage problem.
Quote:
Originally Posted by
cordes
I should note that when I had that brake setup on an Omni, I had DOT legal slicks on the car all the way around.
That could have something to do with it, I had been running 200 treadwear tires that are fairly sticky that I recently took off and no issues with rear lock up also. The only time I've had any lockup in the rear was when I was heading into a corner a lot hot and was heavy braking and had the back come a little loose, which made me pucker up. LOL
Quote:
Originally Posted by
cordes
I think the stock L body prop valve had the lowest pressure going to the rear.
I feel like when I was doing the research on the swap I think I read something saying that rear disc brake setups require different pressure bias than drum brakes, so that's why I would have swapped out the prop valve from the car the rear setup came from, which could be totally wrong. Definitely going look into which one I have and do some wrecker diving and find a few of the different options. Thinking out loud again, but I'm really starting to think its more about the valve than the MC
Re: L-body SLH brake upgrage problem.
I highly doubt that the prop valve will make that much of a difference. The D150 MC was just a bad suggestion from the get go IMO. It's too much MC, and once you go to the 24mm unit you'll have much more pedal modulation than previously experienced. I have 11" brakes with the stock drums on the rear of my NYer and the braking is terrific, if a little light in the rear on rare occasion. This is with the stock prop valve, but with the 24mm MC. I have the full 11" setup on my CSX and that brakes well, but with too much rear bias on occasion. My Lancer has the same setup as the NYer, but I don't experience the same braking in the rear as it's heavier in the back of the car.
I think the biggest factor in tuning the rear brakes is the weight over the back of the car. When Reeves went to a tubular trailing arm, he had to make some modifications to his brakes because the car would lock up the rears under any conditions. The weight removed made a huge difference.
Re: L-body SLH brake upgrage problem.
Yeah that make sense. Ok so I really need to swap out this MC and get where it needs to be, then see where its at as far as bias then. Thanks!
Re: L-body SLH brake upgrage problem.
Quote:
Originally Posted by
motorhead153
I went over the SLH write up again and it suggests replacing the rear brake line also, which I never did... did you do yours? and which prop valve did you use? I didn't realize ( should have known better ) there were so many different ones.
I used whatever valve that came on the donor car *90 Dynasty*
There was no need to replace any lines, but I replaced all flex hose with the braid steel hose.
Re: L-body SLH brake upgrage problem.
I have done the D150 master on 2 cars, one with 11" front/10" rear discs, and one with complete factory 11" vented disc setup, and I don't like the heavy pedal pressure needed to get good braking either. I'm going to go back to a 24mm on my Turbo GTC.
Re: L-body SLH brake upgrage problem.
I have the same brake setup on the GLH Turbo that my brother owns now. Caravan front 60mm KH calipers, 11" vented rears. I used the prop valve and 24mm master cylinder from the '91 Lebaron GTC I got the rear brake setup from. The booster is stock GLH Turbo. The pedal is stiff without a whole lot of modulation, but I like it. I also used DOT 4 fluid and Raybestos Super Stop pads in the front and Raybestos PG Plus pads in the rear. I used reman calipers with stainless steel pistons.
I would also say that the rear brakes can lock up a little prematurely, especially when cold or wet out. Not too bad, but I have to keep it my mind when pushing the car hard.
Re: L-body SLH brake upgrage problem.
Got around to swapping out the master cylinder for the 24mm one today and WOW what a difference! So much better, With the same force I would use before to stop hard is about the same force I would use to lock them up! Thanks for the input everyone!
Re: L-body SLH brake upgrage problem.
Glad to hear it made such a big difference.
Re: L-body SLH brake upgrage problem.
Quote:
Originally Posted by
motorhead153
Got around to swapping out the master cylinder for the 24mm one today and WOW what a difference! So much better, With the same force I would use before to stop hard is about the same force I would use to lock them up! Thanks for the input everyone!
Thanks for the feedback, I have a 24mm master here that i have been wanting to put on due to the same issue you describe with the D150 master. Guess I need to get to it, the D150 has to go
