5-lug Front Hubs?

[mgb260]

Art, That's cool! Are you going to use the RX7 calipers with a hat and 11 3/4" .81"rotor set up? You need about 2 1/2" from face of rotor to face of hub that wheel bolts on. Plus 2 .035 stainless shims. See pictures on 4 lug Cressida rotor thread on MGB page.

[roverman]

Jim N. and clan, I got convinced .81" rotors would warp, on front. I went 1.25"thick x 11.75", bout a lb. more, $31 ea. and Wilwood 4 pots @ $126 ea.  .81" x 11.75 with RX 7 pots, should work fine on rear.Car weight approx 2,800. Approx 500-600 hp. will NEED enough whoa.  Price for "cryo" is $35./ea.. I'm thinkin, "radial" holes in the hats for additional cooling ? Wouldn't ceramic or pyrolitic graphite,( 200/1 thermal flow ratio), work better for shims, less thermal transfer ?  Cheers, roverman.

[socorob]

"I don't see any problem using shims for .81 rotors.RX7 stock used 22mm(.88)rotor.Maybe they were thinking about going to 24mm and thats why the wider slot. "

Sorry to dig up this old thread, but Jim, you were right about the 24mm sizing.

http://www.racingbrake.com/RX7_FRONT_93_95_p/2099-381.htm

And from this site:
The rotor thickness has been increased to 24mm from OE 22mm for increased thermal capacity. Read more here.

1.Some brake pad manufacturers have increased their pad thickness (ie. EBC) therefore our rotor will not fit. Please verify your pad thickness is below 16mm.
2.Remove any factory brake shims from the pads before installation so that the rotor will fit in the caliper.

[mgb260]

Robbie, Thanks for verifying that. I thought it was strange that Toyota used a 22 mm thick rotor and Mazda RX7 slot was so much wider and pads always come with shims. My junkyard calipers had 3 shims on each side. One stainless(anti-squeal) and two plain steel about .030. I saw your thread on the Sunbeam Alpine board on your 4 link. Are you doing the RX7 brakes also? This thread was about to be resurrected anyway as David Townsend has done a comprehensive article on the Mustang hub/Intrepid rotor set up.

[socorob]

This weekend I just got started on my 4 link. I got the tires, brakes, gas tank, leaf springs and perch mounts removed. The rest of my
Parts should be in this week so I can start going in the back together direction with it. While I have my car up I was looking at what it would take to swap the rears for now since I have them off already. I think I could reuse my brackets that the gm calipers are on and just cut them a little shorter and drill 2 new holes in them. If everything else goes smoothly with the suspension I'll probably do that while it's apart. If it drags on I'll just put it back together as is and do it this winter.

[BlownMGB-V8]

Looks like either 22 or 24 mm rotors would work just fine with my Outlaw calipers. I was leaning towards Speedway's scalloped .81" two piece rotors as they are very light but now I wonder if someone might not be making those in a 22 or 24 mm thickness. It'd be worth paying a bit more for them if so as long as it isn't an extravagant amount. Still have some front end work to finalize before I'll know for sure what offset I want for the hats but I suppose in a worst case scenario I could turn and mill a set myself if I had to.

JB

[mgb260]

Jim B., Check out these hats on Ebay:  http://cgi.ebay.com/ebaymotors/New-Performance-Stamped-Steel-Racing-Brake-Rotor-Hat-/190499478152?pt=Race_Car_Parts&hash=item2c5aa75a88

[socorob]

I talked to a guy at coleman today, and their aluminum hats are around 70ish, and a custom made rotor for their hats are about 80ish.

[socorob]

"I plan on using 86-87 Acura Legend front sedan rotor,10.4" diameter and 20mm thick vented like the RX7 for the rear kit. Perfect match. You could just drill your hub pattern between the 4 existing holes for the front and drill your wheel pattern between the 4 holes in the rear and slip on. Not knowing the hub diameter or axle diameter of your Alpine, may or may not have to be turned down to fit. You can get fancy slotted and drilled rotors also."

I was looking on rockauto and it loks like the Acura rotors are 21mm, while the RX7 rear rotors are 20mm. The mid 90s Miata front rotors are 20mm 4 lugs. My local auto parts store had neither in stock so I couldnt put a tape measure on them to see if it would clear my axle flange. If I remember correctly, my axle flange is somewhere in the neighborhood of 6-6.25 inches. Is there any resource that shows the measurement of how large rotors are where they slide over the axle flange?

[mgb260]

Robbie, Check the Rockauto site again under Centric. It should show the dimensions. Brembo might also. Or junkyard shopping. A 1/2 mm on each side shouldn't matter. Those 8" Ford hubs might have to be turned down.

[socorob]

Rockauto doesn't show those dimensions. I guess I'll have to go jy shopping soon.

[mgb260]

Robbie, Rockauto has hub diameters on some vehicles. Looks like 5-5.5 inches most common. Wilwood lists 2 hats in Sunbeam bolt pattern(same as 79-83 Mustang 4"X4.25"), Check this link out.   http://www.revolutionbrake.com/wilwood_rotor_mounting_hat.html

[socorob]

I should have. Went with 16" wheels instead of 15. That's what's causing the problem for me. The hat for the rotor the thickness I need and will fit over my axle flange only has rotors that are too big to fit inside 15" wheels.

[roverman]

Jim N, RX7 upright ? (McPhearson strut). I need a light, strong spindle, for SLA. and tall enough to have low roll center migration, with bolt on steering arms. Jensen Healey seems too weak,(11/16" and 1and1/16") dia's. Suggestions ? Thanks, roverman.

[mgb260]

Art, Newer Mustang and Camaro are Mcpherson strut. I thought you were going double A Arm. Some Locost builders cut the strut down and weld a 3/4" bolt on top and use a Heim for upper ball joint. That is probably what the 510 with RX7 lower A arm and Supra upper A Arm did.

[roverman]

Jim, In the picture your showing "a" Supra lca.,"b"RX7 uca and "c" ? kind of spindle ? Thanks, roverman.

[mgb260]

Art, It is on a Datsun 510. I thought the article said  it was RX7. Maybe  It is Z or 510(also strut), If you do a search on Strut conversions to Upper and Lower A Arm on Locosts you might find some pics on the Heim. Or you could use a upper ball joint like this newer Mustang. They cut down the strut and use it as a spindle..

[roverman]

If I thought I could "trust" the JH spindle @ 1.5 g in 2,400# car, but if not enough, could get messy !" Wilwood, Mustang II, I feel is too heavy, but I want bolt on steering arms. update, considering "like" Mustang II, but has centerbolt at top,for wheel cylinder? Identicle ball joint sizes top/bottom(5/8") large end of tapers. N.O.S., think I can make work. What's that air bag # that works on MGB's ? Thanks, roverman.

[BlownMGB-V8]

I thought I'd revive this thread as it has so much info on brake calipers and I need to do an upgrade.

As last reported, I have XJ6 rear brakes (1-5/8 dual pot fixed calipers), Outlaw front calipers (1-3/4" dual pot fixed), dual master/balance bar with 3/4" rear and 5/8" front. The brakes are ineffective due to high pedal pressure, traced to the dual pot front calipers. I must have simply overlooked that somehow.

Earlier in this thread (page 3)  we have the XJ6 front caliper piston size as 1-7/8" 4 pot. I suspect that is the size I should be looking for which is a little over twice the piston area of the outlaw calipers.

The question is, what is my best option? I would prefer a light weight caliper, cannot really justify ones that are tremendously expensive, and as for the mounting, I can make adapters. I have 15" wheels. A direct mount caliper would be nice but it may require me to buy different rotor hats. I'm running .81" rotors but can get thicker ones from Speedway if I need to. Any suggestions?

I'm looking at the RX7 calipers, what years used the aluminum 4 pot calipers and what size were the pistons?

Also will look at the Willwood Dynalite but Max says they have caliper flex.

Jim

[ex-tyke]

A quick look on RockAuto indicates that RX7 last year was 1995. Front calipers were aluminum with two 1.0" dia pistons.
RX8 came on board in 2004 with cast iron caliper with single 2.13" dia steel piston..
Edit: For the record, my front brakes are Wilwood Dynalites with dual 1.75" pistons. (Pads are Wilwood BP-40)

[BlownMGB-V8]

Since I've been prompted for an update, first to point out some errors.
My front Outlaw calipers are 4 pot 44mm, rears are 2 pot 43mm, and I had a bad master cylinder on the front. Since then:

Using an online brake calculator from this page:
https://www.tceperformanceproducts.com/dual-bias-calc/

We were able to determine that suitable MCs would be 3/4" front and 5/8" rear and that 350lbs of line pressure at the front would be sufficient to develop .7g of braking force, with only a couple turns off center on the balance bar. I ordered Tilton cylinders in those sizes in the 75 series, which has a shorter stroke but leave much more room for line connections. I used custom made reservoirs that retain the tops of the old ones and attach with a small setscrew.

Measuring front line pressure after the install I was able to develop upwards of 400 psi at the front. Balance bar motion looked appropriate. I will not be able to road test it until I do some more tuning work on the engine but all indications are good.

Max pointed out that the 0.41 coefficient of friction on the Porterfield pads is rather low, so this gives me a path to lower pedal pressures should I feel the need. As he was talking CFs in the .75 range it appears I should be able to cut pedal pressure to about half what it is now with careful pad selection. But there is no free ride of course. Testing will determine what is needed.

Jim

Reservoirs



Tilton 75 series



Balance bar

[roverman]

Ok, once again, series II Mazda RX-7 non- turbo and turbo.  5 0n 4.5" . Inner bearing is BIG !. better than too small. Std. rotors are vented and decent in size.
                                                                                       Dems da brakes, Art.