Rear Disk Brake Conversion Pt 1

[Rockdawg84]

[MENTION=53470]Rockdawg84[/MENTION]

Hey Sam....

Just wondering....

Did you have to change the MC or the booster when you went to these calipers/discs in back?

Just trying to figure out if I need to budget for a Wilwood set up or something out of a Tundra or similar. Some guys on Pirate were swapping in Tacoma boosters with Tundra MCs....but I think the bore size wasn't significantly different (like the metric equivalent of 1/16").

[MENTION=144462]Sean K.[/MENTION]

I didn't change my MC out. It is a little softer than stock but I have never needed to give it a second pump. When I need to change out the MC I will upgrade to a Chevy Avalanche MC as I have read that it is just right. I will try to find the thread where I read that.

 

[4x4runner2002]

did you use the same setup? mustang calipers? more inform please?

I know it's been a while, but yes I used the same set up as the op.

 

[Sean K.]

I know it's been a while, but yes I used the same set up as the op.

Did you keep the factory T4R Master?

 

[4x4runner2002]

Did you keep the factory T4R Master?

Yes I have the factory master, but I have an 02 so it's the bigger more complicated master. The pedal feels fine and I have tundra brakes up front.

 

[Sean K.]

Yes I have the factory master, but I have an 02 so it's the bigger more complicated master. The pedal feels fine and I have tundra brakes up front.

Thanks for the info! Much appreciated.

 

[IBallEngineer]

[MENTION=53470]Rockdawg84[/MENTION]

Hey Sam....

Just wondering....

Did you have to change the MC or the booster when you went to these calipers/discs in back?

Just trying to figure out if I need to budget for a Wilwood set up or something out of a Tundra or similar. Some guys on Pirate were swapping in Tacoma boosters with Tundra MCs....but I think the bore size wasn't significantly different (like the metric equivalent of 1/16").

Sean, for the record, I went from 7/8" to 1"(FZJ80) bore master cylinder on my FJ62 and it was a huge difference.

Surface of a circle is Pi x Radius squared. Even a 1/16 added to 1" is an 8% increase for a 1% radius increase. I don't really know pressure formulas but I know the increase is exponential, not linear.

But from a quick search it appears we already have 1" bore in the 3rd gen which ought to be enough.
:shrug:

 

[Sean K.]

Sean, for the record, I went from 7/8" to 1"(FZJ80) bore master cylinder on my FJ62 and it was a huge difference.

Surface of a circle is Pi x Radius squared. Even a 1/16 added to 1" is an 8% increase for a 1% radius increase. I don't really know pressure formulas but I know the increase is exponential, not linear.

But from a quick search it appears we already have 1" bore in the 3rd gen which ought to be enough.
:shrug:

But apparently, it's not since lots of users are reporting soft pedals.

Wilwood makes a 1 1/8" that *appears* to have the same bolt pattern as what I have (haven't taken it off to actually get a precise measurement). It's also dual reservoir, which is kind of nice....though that could be a little more complex in terms of adjusting brake bias.

The other option would be (obviously) factory MC offerings.

 

[Kryptoroxx]

But apparently, it's not since lots of users are reporting soft pedals.

Wilwood makes a 1 1/8" that *appears* to have the same bolt pattern as what I have (haven't taken it off to actually get a precise measurement). It's also dual reservoir, which is kind of nice....though that could be a little more complex in terms of adjusting brake bias.

The other option would be (obviously) factory MC offerings.

There is also an offering from inch worm that might work. They have a toyota to gm brake booster adapter. 1.25" bore which will definitely be large enough for a full disk setup

Sent from my SAMSUNG-SM-G870A using Tapatalk

 

[Jaysen4runner]

Who selling the rear brackets for disc brake conversion?

 

[Rockdawg84]

Who selling the rear brackets for disc brake conversion?

No one. you get to make your own. honestly it is super easy. Get the dimensions from the diagram: cut the plate, drill some holes and grind the edges to make it look pretty. You Can Do It lane:

 

[Sean K.]

There is also an offering from inch worm that might work. They have a toyota to gm brake booster adapter. 1.25" bore which will definitely be large enough for a full disk setup

Sent from my SAMSUNG-SM-G870A using Tapatalk

Thanks very much for the tip.


Here's a link for anyone interested:

Toyota Booster to GM Master Cylinder Parts

 

[Rockdawg84]

As I have been working on my rear full float conversion and came across an issue that we should all be aware of.

IF YOU ARE USING MONTERO ROTORS. You will have to countersink the back of the rotor for the rotor to sit flush on the flange. I don't know how I missed this before but the studs have a flare at the base that keeps the rotor from sitting flush. I have searched and cannot find a stud that doesn't have the flare and is long enough. Here are some pictures.

You can see the Flare here:


Here is a comparison to an 85 front stud.





here is how far they each go down into the rotor.



and this is the result. I have the rotor on upside down so that you can see the gap.



It is possible that you could have the rotor sit even across the studs and not have a problem but most likely is that the rotor will not sit even. Since I haven't found a stud that will work I have decided to get a Carbide countersink bit to cut the bottom of the rotor so it will set flush on the flange.

This is what I ordered.

 

[Kryptoroxx]

As I have been working on my rear full float conversion and came across an issue that we should all be aware of.

IF YOU ARE USING MONTERO ROTORS. You will have to countersink the back of the rotor for the rotor to sit flush on the flange. I don't know how I missed this before but the studs have a flare at the base that keeps the rotor from sitting flush. I have searched and cannot find a stud that doesn't have the flare and is long enough. Here are some pictures.

You can see the Flare here:


Here is a comparison to an 85 front stud.





here is how far they each go down into the rotor.



and this is the result. I have the rotor on upside down so that you can see the gap.



It is possible that you could have the rotor sit even across the studs and not have a problem but most likely is that the rotor will not sit even. Since I haven't found a stud that will work I have decided to get a Carbide countersink bit to cut the bottom of the rotor so it will set flush on the flange.

This is what I ordered.

Good Catch! Mine are still sitting in a box sadly....

Sent from my SAMSUNG-SM-G870A using Tapatalk

 

[Rockdawg84]

Good Catch! Mine are still sitting in a box sadly....

Well the good news is that you will only have to do it once now

 

[Kryptoroxx]

I actually have heard of another rotor being used as well but I can't recall it. Some of the Facebook groups have definitely done the rear disc now.

Sent from my SAMSUNG-SM-G870A using Tapatalk

 

[Rockdawg84]

yes [MENTION=144462]Sean K.[/MENTION] is going to use 4th gen rear rotors. I bought a set and was going to try them since they are vented but the hat depth is shorter and I would have to of reworked my bracket and felt like it wasn't worth it for now.

 

[Sean K.]

yes [MENTION=144462]Sean K.[/MENTION] is going to use 4th gen rear rotors. I bought a set and was going to try them since they are vented but the hat depth is shorter and I would have to of reworked my bracket and felt like it wasn't worth it for now.

I'll try and check to see if the 4th Gen rotor works with the factory Tundra studs I'm running. I would guess they will be similar to the studs on a 4Runner.

 

[phattyduck]

Does the Montero center bore match the 4Runner center bore? If so, just drill out those holes all the way through. Those studs should never be side-loaded by the brake disc anyway. Even if the bore doesn't match, you should have a centering ring on there to keep the rotor centered...

-Charlie

 

[Sean K.]

I'll try and check to see if the 4th Gen rotor works with the factory Tundra studs I'm running. I would guess they will be similar to the studs on a 4Runner.

Just checked....no drilling necessary....axle flange and lug studs fit flush to rotor hat.

 

[Rockdawg84]

Just checked....no drilling necessary....axle flange and lug studs fit flush to rotor hat.

That's good to know. So a different bracket and the 4th gen rotors will work great.