MG Sports Cars

Comparison between stock and small Toyota(S12-8)caliper:

Thanks, Jim!

You really should weigh them while you're at it, though. ;)

Carl,I don't have the small Toyota S12-8 caliper,but have heard it is close to stock. I did weigh the large Toyota at 9lbs and the RX7 at 5lbs. .I just weighed the stock one at 6lbs.So until I get one,7lbs sounds like a good guess. The pads are about twice as big ,plus wider clamping surface.Plus vented rotor, which is about 4 lbs heavier. I have an idea you might be interested in, I need to have someone try the prototype Cressida with Mazda RX7 calipers including brackets when I'm done. Probably work really good with your new tires.



Edited 3 time(s). Last edit at 02/02/2011 06:05PM by mgb260.

Stock rotor and caliper=15lb. Cressida rotor and RX7 caliper=18lb. Vented rotor and 4 piston caliper with large pads still an upgrade with only 3lb weight penalty! Small Toyota caliper would add 2 more lbs but, would allow more variety of wheels to fit without spacers.



Edited 1 time(s). Last edit at 02/02/2011 06:04PM by mgb260.

Looks like my reply disappeared.

Anyway, Sounds real interesting, Jim. When you get ready give me a shout.

Carl, It'll be a little while but,here's the plan: I send you the hubs I have with rotors attatched, new wheel bearings/seal rebuilt RX7 calipers (with Mazda name sanded off and painted aluminum Hi-heat). You try them and if you like them, buy at my cost for parts and if not you pay to ship them back. Your master and booster should work fine. I would recommend stainless braided lines and GT rear wheel cylinder. You will need adapter fitting from 10mm x1.0 Jap to either MGB bubble flare or AN3 depending on your flex line(NAPA). Your choice on pads, I usually get the autostore ceramic ones. My cost for rotors $35 each,calipers $35 each,caliper rebuild kits $40 for both,wheel bearings/seal $30,caliper brakets,bolts,hardware $20. $ 230 total. Hubs/studs and labor free. I would use your positive comments for advertising. What do you think? I will be selling brackets for RX7 and small/large Toyota for $40 pair with bolts,hardware,concentic ring,instructions.



Edited 3 time(s). Last edit at 02/06/2011 06:02PM by mgb260.

I will likely be using my hubs as I just put new bearings in them last year & shimmed them right where I want 'em. Plus, I may be drilling them for a new PCD. My wheel search is not going much better than JB's.

Carl, That's O.K. I just thought you would be the perfect test driver for the brake kit. You know a lot of wheels are dual bolt pattern(4X100mm and 4X4.5"),some people don't like the 8 hole look though.

"I just thought you would be the perfect test driver for the brake kit."

Well, I just happen to agree. ;) Any chance all that would fit under my ARE 14X6 wheels? I like the whole concept. 'cept for gaining 3 lbs unsprung weight for the rotors. Aluminum hubs may fix that.

Should but,four piston calipers stick out a bit and sometimes use of wheel spacer 1/4" or so may be required.




Edited 1 time(s). Last edit at 02/13/2011 11:23AM by mgb260.

Typically I think you will need about 2" from the rotor to the wheel flange.

I have considered alloy hubs and may have to go that way, depending on other factors. The material cost for 6061-T6 for both hubs is around $75+shipping, then there's several hours of machine work and a half dozen set-ups involved. I doubt I could complete the job in an 8 hour day, just to give an idea of what it takes. That'd make for some expensive hubs unless you could find some off another car that'd work.

JB

I measured my parts and am exactly 2" and the caliper sticks up 1/4" and that litte bump about 3/16" more. Can't grind down as it is a fluid passage. 2 1/2" would be better. Looks about the same as the picture above. RX7 stock rotor to wheel is 2 1/2". I might have to use a 1/2" aluminum spacer between hub and rotor for this one and look for a similar rotor with a 1/2" taller hat. RX7 Turbo II stock had a 10.85" diameter rotor and used 14" wheels.



Edited 1 time(s). Last edit at 02/14/2011 11:19PM by mgb260.

Would this be the smaller Toyota caliper?

Thats the one for the solid rotor, Carl. Notice it has one small and one large piston to even out pad wear. Even though both my larger ones have even pad wear with equal size pistons. Not nearly as bulky as the RX7 or Large Toyota (S-12 W). Check out the picture of the RX7 above. I am doing brackets for all three. Both Toyota' would be the same. I just wasn't planning on a spacer for the larger ones. It will work fine, though. The height of the Cressida rotor is 40MM and 52MM or aproximately 1/2" more would be ideal for the larger calipers. The S12 - 8 solid rotor caliper bolt right on the MGC like your picture and the TR6. There are 2 different S12-8 , one for solid rotor (76-84 Toyota 4X4 4 cylinder pickup) and vented rotor version like my kit(86-88 Toyota 4X4 4 cylinder pickup and Four Runner). Here's a picture of the vented rotor one on Cressida rotor on TR6:




Edited 4 time(s). Last edit at 02/14/2011 08:26PM by mgb260.

I'm going to start looking around locally for some plate to make brackets out of. Should I be looking for 1018 steel plate 5/16-3/8?

You want to try your rotor and caliper on first to determine thickness,or use measurements. I would recommend 2 1/2" between wheel mounting face on hub and rotor. Your bracket might end up on either side of stock mount. Use a minimum of 1/4" steel and if over 1/2" use 6061 aluminum. Here is the best internet supplier of metal: [www.onlinemetals.com]
This template is for a Volvo conversion but gives you an idea. The RX7 holes might end up lower or higher and not straight across. I slide the caliper up or down until the ear is close to the stock mount to determine thickness of bracket.Remember the caliper must be centered, I use equal shims in the caliper slot to center. Also grade 8 bolts and hardware, blue locktite on threads.
Here is a steel bracket used on a BMW:




Edited 6 time(s). Last edit at 02/15/2011 05:21PM by mgb260.

picture of RX7 pad shims:

Hi. Great thread. I have a TVR 3000M over in Seattle and I just started looking at front brake upgrades. The small and large Toyotas fit but seem HEAVY so have been looking at Wilwood's. But, I like the idea of the RX7 aluminum calipers. I have a '87 RX7 turbo rally car which I've run both rally and on the track and can attest to the quality of the Mazda brakes. Any thoughts on fitment? I'd be going with the cressida rotors. Thanks!

BTW, I can do the FEA stress analysis on your design work. I just need a .dxf

Jim, I'm getting in late on this deal, what's the center to center dimension on the mounting lugs for the Small Toyota caliper for the solid rotors? Looking for an upgrade for my Midget, but need to cram everything inside a 13" wheel so smaller is better. Midget mounting is same as MGB I beleive at 3.25" center to center.