PSA to rear disc brake conversions

[rideexileex]

ALL...

I'm seeing a flux of people and mentions of converting to rear disc brakes, but I'm not hearing much about anyone changing the rest of the brake system, particularly the master cylinder or lack of adding a proportioning valve...

Of course this depends on the particular rear setup, but at least add a proportioning valve inline! I added a Wilwood to mine, and with it full open, the rear discs easily locked up before the fronts (Tundra's). Dangerous! It took quite a reduction before the fronts would again lock before the rears.

I just don't want this to go un-checked.

/Rant

 

[Rockdawg84]

ALL...

I'm seeing a flux of people and mentions of converting to rear disc brakes, but I'm not hearing much about anyone changing the rest of the brake system, particularly the master cylinder or lack of adding a proportioning valve...

Of course this depends on the particular rear setup, but at least add a proportioning valve inline! I added a Wilwood to mine, and with it full open, the rear discs easily locked up before the fronts (Tundra's). Dangerous! It took quite a reduction before the fronts would again lock before the rears.

I just don't want this to go un-checked.

/Rant

Just curious is your ABS not working? if it is nothing should be locking up, and it doesn't matter if you have rear disc's or not. I have rear disc obviously since I pretty much started this trend (here anyway). But I never had any lockup front or rear until my rear abs was disabled when I went to the Front Range off Road full float rear set up. Now I have fixed the ABS and it is functioning and I can no longer lock up front or rear. Not bashing just looking for clarification.

 

[DaMonkey]

I think OP is exactly right. Brakes should be tuned on their own. Not a great idea to have ABS manage you through normal driving conditions. Prop valve should not be considered an option.

I applaud the effort that goes into this conversion, but after doing custom rear discs in the past on other cars, I’m not going to do it if there is no meaningful performance increase for that amount of effort. Tundra brakes up front, sure. But really has anyone overheated and glazed their rears in these trucks? Maybe I’m wrong, maybe guys in the mountain highways, but I think the stock brakes are fine for me (and I usually want to tweak everything).

Someone was looking for a Cnc source for brackets in here. I’ve used a guy called scarebird who makes and sells custom brackets to fit rear discs for different appplications. I’m sure he would be happy to oblige and keep them in stock, he sells for very fair prices. He also knows his conversions, and prop valve is just part of what should be done.

 

[Rockdawg84]

I think OP is exactly right. Brakes should be tuned on their own. Not a great idea to have ABS manage you through normal driving conditions. Prop valve should not be considered an option.

I applaud the effort that goes into this conversion, but after doing custom rear discs in the past on other cars, I’m not going to do it if there is no meaningful performance increase for that amount of effort. Tundra brakes up front, sure. But really has anyone overheated and glazed their rears in these trucks? Maybe I’m wrong, maybe guys in the mountain highways, but I think the stock brakes are fine for me (and I usually want to tweak everything).

I don't disagree that ABS isn't intended to manage every day out of balance brake systems. I ran a year with no ABS in the rear and the only time I ever had the rear lock up was in pretty heavy rain, we don't get snow in Tucson. So balance is very important and the use of a proportioning valve is a great part of the process. I have said many times that the rear brakes of a 3rd gen work great when functioning properly but the rear disc do give an upgrade in stopping power but it is a lot of work and unless you really need the extra stopping power it is not worth it. I just really enjoy the discussion and was in no way trying to bash or disrespect [MENTION=83356]rideexileex[/MENTION].

Just another thought I have had is that 4 wheel ABS systems are designed to work at much higher stopping (clamping) power than older systems that simply relied on balance. So not having a functioning ABS system actually decreases the stopping ability of our 4Runners. I am happy to have figured out how to have ABS on my rear axle once again.
:cheers:

 

[absalom]

Am I the only one with relatively stout stock brakes? Even on ultra steep descents here in Colorado I have zero issues, as long as I gear down.

 

[WeakSauz]

Am I the only one with relatively stout stock brakes? Even on ultra steep descents here in Colorado I have zero issues, as long as I gear down.

+1... I mean... I get the novelty of rear discs on a vehicle that didn't come with them. But these trucks are underpowered slugs. The rear drums have served many of us 300k+miles of abuse

I guess if you were to swap in a 1UZ or LSX, something severely upgraded may be nice. But a stock-ish or even TRD blown 4runner... naaahh, I'll stick with my trusty drums that highly paid Toyota engineers settled on

 

[sleepydad]

I think OP is exactly right. Brakes should be tuned on their own. Not a great idea to have ABS manage you through normal driving conditions. Prop valve should not be considered an option.

I applaud the effort that goes into this conversion, but after doing custom rear discs in the past on other cars, I’m not going to do it if there is no meaningful performance increase for that amount of effort. Tundra brakes up front, sure. But really has anyone overheated and glazed their rears in these trucks? Maybe I’m wrong, maybe guys in the mountain highways, but I think the stock brakes are fine for me (and I usually want to tweak everything).

Someone was looking for a Cnc source for brackets in here. I’ve used a guy called scarebird who makes and sells custom brackets to fit rear discs for different appplications. I’m sure he would be happy to oblige and keep them in stock, he sells for very fair prices. He also knows his conversions, and prop valve is just part of what should be done.

I had somebody work the autocad file for me... I need to go pick it up today if it's ready.

I will post an update when I get the brake bracket cad file back. I'm planning of giving the cad file away, I really have no desire to make brackets and sell them.

the only reason I'm going to do this is because I'm converting my second 4runner to disc as well and I figured if I was going to the trouble maybe others could use the design as well.

I'm also now 99% sure I can make a modified ford mustang ebrake bracket that will allow the stock T4R cable to just connect and work without having to mess with custom cables. once I get that part done I will share that cad file out as well.

 

[rideexileex]

Just curious is your ABS not working? if it is nothing should be locking up, and it doesn't matter if you have rear disc's or not. I have rear disc obviously since I pretty much started this trend (here anyway). But I never had any lockup front or rear until my rear abs was disabled when I went to the Front Range off Road full float rear set up. Now I have fixed the ABS and it is functioning and I can no longer lock up front or rear. Not bashing just looking for clarification.

Rockdawg - after far too many poor experiences with the ABS system while living in WA, MT, and CO, I finally decided to get rid of it entirely... ALL new brake lines from the master cylinder to the respective corners.

I ended up with the rear discs as a byproduct of switching over to the 4th gen axle, which I have been very happy with since!

 

[gamefreakgc]

+1... I mean... I get the novelty of rear discs on a vehicle that didn't come with them. But these trucks are underpowered slugs. The rear drums have served many of us 300k+miles of abuse

I guess if you were to swap in a 1UZ or LSX, something severely upgraded may be nice. But a stock-ish or even TRD blown 4runner... naaahh, I'll stick with my trusty drums that highly paid Toyota engineers settled on

Even I still have the drums with over 300 HP at the crank. I did the Tundra big brake upgrade up front though. I've done some stops from 100+ MPH and the rear drums are fine. A good set of highway rated tires goes a long way though, more rubber touching the road. I think those with braking issues also have aggressive tread mud tires that are not known to be good at stopping, especially in rain.

 

[sleepydad]

I just don't want this to go un-checked.

Not bashing just looking for clarification.

I think OP is exactly right. Brakes should be tuned on their own. Not a great idea to have ABS manage you through normal driving conditions. Prop valve should not be considered an option.

Am I the only one with relatively stout stock brakes? Even on ultra steep descents here in Colorado I have zero issues, as long as I gear down.

+1... I mean...

here are the files I just got....

https://drive.google.com/file/d/1ekTgb1_JhQlQNKo2O8-NqMJYfCiM8YoL/view?usp=sharing

https://drive.google.com/file/d/1YMj2e3m908evN1TsLt_EGYxVS9ADLu3H/view?usp=sharing

<a href="https://imgur.com/c529YmA"><img src="https://i.imgur.com/c529YmA.png" title="source: imgur.com" /></a>
<a href="https://imgur.com/5IfL1Yl"><img src="https://i.imgur.com/5IfL1Yll.png" title="source: imgur.com" /></a>

please note: I have not had these run yet... they show my custom hand grinding and probably need to be edited a bit. if somebody beats me too it? I would like to find a place to run these.

 

[Rockdawg84]

here are the files I just got....

https://drive.google.com/file/d/1ekTgb1_JhQlQNKo2O8-NqMJYfCiM8YoL/view?usp=sharing

https://drive.google.com/file/d/1YMj2e3m908evN1TsLt_EGYxVS9ADLu3H/view?usp=sharing

<a href="https://imgur.com/c529YmA"><img src="https://i.imgur.com/c529YmA.png" title="source: imgur.com" /></a>
<a href="https://imgur.com/5IfL1Yl"><img src="https://i.imgur.com/5IfL1Yll.png" title="source: imgur.com" /></a>

please note: I have not had these run yet... they show my custom hand grinding and probably need to be edited a bit. if somebody beats me too it? I would like to find a place to run these.

Nicely done! I may have to cut a set of these and see how they do. I love the way this forum works together to figure stuff out.

 

[rideexileex]

Guys, respectfully, this isn't a thread about debating drums vs discs. This is to those who have done rear discs or who are still planning out a complete system, and haven't made this consideration.

 

[sleepydad]

Guys, respectfully, this isn't a thread about debating drums vs discs. This is to those who have done rear discs or who are still planning out a complete system, and haven't made this consideration.

welcome to the internet! ha

anyways.... I have been running Rockdawg84 concept for a while now and I have not encountered any issues with lockup.

my setup is different than Rockdawg84 parts wise and I also made some different design decisions. my design has the calipers positioned lower and if you wheel like a maniac? the calipers may get bashed. I used this design so the ford ebrake plate would be in-line with the toyota ebrake cable.

I also did re-build my master at the same time when I installed my conversion. I found my main valve seals were falling apart and this helped my braking system as much as anything I think.

I considered a prop valve but after getting it running I did not see any need for it.

I have wheeled my setup a couple of times and it worked great each time.

 

[rideexileex]

welcome to the internet! ha

anyways.... I have been running Rockdawg84 concept for a while now and I have not encountered any issues with lockup.

my setup is different than Rockdawg84 parts wise and I also made some different design decisions. my design has the calipers positioned lower and if you wheel like a maniac? the calipers may get bashed. I used this design so the ford ebrake plate would be in-line with the toyota ebrake cable.

I also did re-build my master at the same time when I installed my conversion. I found my main valve seals were falling apart and this helped my braking system as much as anything I think.

I considered a prop valve but after getting it running I did not see any need for it.

I have wheeled my setup a couple of times and it worked great each time.

Ha, right?

Being in MN, have you had it out through the snow and ice yet?

I messed around with mine at first on the gravel roads, and thought I had it set well. Then a nice blizzard / ice storm came in a week or so ago, so I took it for a drive and the back end was allll over the place. Took quite a bit more rear reduction to keep the front locking first.

 

[sleepydad]

Ha, right?

Being in MN, have you had it out through the snow and ice yet?

I messed around with mine at first on the gravel roads, and thought I had it set well. Then a nice blizzard / ice storm came in a week or so ago, so I took it for a drive and the back end was allll over the place. Took quite a bit more rear reduction to keep the front locking first.

last winter I was out on grays bay on lake Minnetonka and did a bunch of skid tests. the ABS system worked exactly like it did with drums. I have noticed with both drums and disc on gravel the back wheels will lock up at slow speeds. my understanding is ABS was designed for pavement only.

I think the safety data shows this as well. ABS is much safer on pavement, in general. on gravel or off road ABS is a mixed bag trending toward more dangerous outcomes.

you might want to be careful with the proportioning? gravel, dry pavement, wet pavement, snow, ice...

I have a 2000 lim that has tundra front and discs in rear.
I picked up a winter beater this fall 1997 that has a stock brake setup.

I want to get them both into a spot where I can compare the behavior when braking, it's really the only way to know IMO. I agree a valve might be needed in some cases, I just have not been able to compare enough to really say I'm confident one way or the other.

once you go down the rabbit hole and start thinking about all the situations and combinations I start second guessing myself.

so... also

your running a 4th gen rear axles assembly? that would be very different maybe? I don't know about that part. wider right? different calipers? do the 4th gen rears have double pistons? the rear ford calipers are pretty small really.

 

[4Runner fun]

ALL...

I'm seeing a flux of people and mentions of converting to rear disc brakes, but I'm not hearing much about anyone changing the rest of the brake system, particularly the master cylinder or lack of adding a proportioning valve...

Of course this depends on the particular rear setup, but at least add a proportioning valve inline! I added a Wilwood to mine, and with it full open, the rear discs easily locked up before the fronts (Tundra's). Dangerous! It took quite a reduction before the fronts would again lock before the rears.

I just don't want this to go un-checked.

/Rant

I'm in a little different situation, with a complete driveline swap to straight axle
But stock clearly it was disc/drum with ABS.
Now it's all disc, GM's on the rear, upgrade vented Tacoma's on the front, 1" MC. And a Wilwood proportioning valve. with 37" X 12.5 X 15 MTR's. Also I gutted the ABS completely, with the axle swap there was no provisions for it. That also caused a whole new situation with the speedo

The running gear was pulled out of another running rig, So I knew it all worked together but needed some tuning. At first there was no proportioning valve. I had a long pedal and grabby touchy rear brakes. At any speed it would bring the rears to a full skid instantly. I added the rear valve and closed it completely giving me about 43% line pressure to the rear.
After the valve it shortened the pedal, and helped balance the system but in a panic stop I still have a little too much rear brake. But it's much more manageable. I also haven't driven it in the rain or wet yet, So that's still to come.

My long term is to bolster the front brakes rather than limit the rears, And I have no baseline, but it stops well, but on 37's I would imagine it's nowhere near as good as stock. just because there was wholesale changes made.

 

[rideexileex]

I'm in a little different situation, with a complete driveline swap to straight axle
But stock clearly it was disc/drum with ABS.
Now it's all disc, GM's on the rear, upgrade vented Tacoma's on the front, 1" MC. And a Wilwood proportioning valve. with 37" X 12.5 X 15 MTR's. Also I gutted the ABS completely, with the axle swap there was no provisions for it. That also caused a whole new situation with the speedo

The running gear was pulled out of another running rig, So I knew it all worked together but needed some tuning. At first there was no proportioning valve. I had a long pedal and grabby touchy rear brakes. At any speed it would bring the rears to a full skid instantly. I added the rear valve and closed it completely giving me about 43% line pressure to the rear.
After the valve it shortened the pedal, and helped balance the system but in a panic stop I still have a little too much rear brake. But it's much more manageable. I also haven't driven it in the rain or wet yet, So that's still to come.

My long term is to bolster the front brakes rather than limit the rears, And I have no baseline, but it stops well, but on 37's I would imagine it's nowhere near as good as stock. just because there was wholesale changes made.

This is very interesting to me, as this is the next step I’ve been considering. I’m still going to test my booster by swappping with another, but my brake pedal still takes near full body weight to panic stop on pavement, even without locking it up. Which master / booster did you end up going with?

 

[4Runner fun]

This is very interesting to me, as this is the next step I’ve been considering. I’m still going to test my booster by swappping with another, but my brake pedal still takes near full body weight to panic stop on pavement, even without locking it up. Which master / booster did you end up going with?

Factory 1997 Booster 285K to my knowledge and MC is a Centric #130.44707

I had no issue with the factory MC, I think in the 3rd gens they are 1" bore factory. I could be wrong. adding a proportioning valve helped out, I was going to do a 2lb residual valve, for the long pedal. but didn't need to.

I can get some pictures if you need, My kid is driving it today.