LocostUSA.com

Here's a semi-hypothetical question. Assume a V6 Mazda6 drivetrain (3.0 with 5 speed manual) is used in the rear of an exo-middy. Would you:

1. Use the FWD uprights; I believe you'd have to design them to be fixed (would dealing with bump steer be more complicated?), then adapt some kind of e-brake system (spot caliper, adapt a rear caliper, use a rotor with an internal drum, etc.)

2. Would you use RWD uprights that are designed for the rear and already have an e-brake solution included, then deal with custom axles to adapt the FWD transmission to the RWD uprights?

Don't get too hung up on the vehicle choice as it's mostly hypothetical, I'm just wondering about opinions on the best course of action.

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Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

You've nailed the big questions. I think either way is possible. Bump steer is no different for a FWD being used as a rear. The same caveats apply. Hint: Keeping the steering link pivot on the same plane as the lower BJ, virtually eliminates any bump steer, provided that the tie rod is attached to the lower control arm.

I'd personally look to adapt emergency brakes (presuming you will need them for street use) or rear caliper system to a FWD setup. But then, I've never done a midi.

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Chuck.

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I have researched a good bit on the idea as well. The overall consensus of my research on wilwood spot caliper is that they are terrible. Not much holding power and tend to rattle. Other calipers to adapt would be the gm metric caliper from circle track as has literally tons of different pad options. I planned on building an upright and adapting the thunderbird caliper. Be sure to watch brake disc issues if changing calipers. Also obviously bolt patterns will be anissue if adapting to another vehicles uprights.

Thanks for all of the info so far!



I was re-reading his build again yesterday, he went through about 14 different rear brake iterations, and he's not happy with the current solution of two OEM calipers on the rear rotor. Was there anything else you wanted me to see in that build thread?

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Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

Since we're not hung up on vehicle choice...I'm making something similar with a Metro, and there was a "sport" version of that car (Suzuki GTi before VW made them change the name) that had rear discs the same diameter and thickness as the Metro fronts, so I'm adapting the Suzook calipers to the Metro front (formerly front; they're going in the back now) spindles...but then I realized how simple the wheel hub/axle carrying portion of the spindle is--it's a double row ball bearing with seals on each end--so the latest of my midstream horsechanges is to make a two piece spindle with the bearing pressed into one of the halves.

Compared to a conventional front spindle, it looks like a rear spindle will be easier to fabricate. It doesn't need to steer, and that eliminates a lot of difficulties. I went down to NAPA, the Mazda6 has a double row front wheel bearing like the Metro (except the Mazda's is 84mm OD by 45mm wide), a pretty simple arrangement, so I'm going to vote for #3--a custom spindle, which A) takes the same wheel bearing as the donor, thus saving you from any custom axle work, B) fits the control arms you devise, and C) accepts a common rear caliper that fits the front disc from your donor.

I reserve the right to change my opinion if future experience indicates that I'm full of bleep.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

Jack-

Thanks for the post. I know I've seen some build logs with custom uprights. Are there any specific examples you know of of well-made custom uprights? The only tools at my disposal are a MIG welder, angle grinder, bandsaw, and a drill press. Anything requiring milling or lathe work is outside my capabilities.

You'll have to pardon my ignorance on upright/wheel bearing knowledge, how would I go about finding wheel bearings to match my axles? I can find some basic data on the Mazda6 axles:
22.44" overall collapsed length
26 F-splines with 2 blinds inner stub style
28-spline outer stub style

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Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

Here's another thought - according to this site the '86-'91 NA RX-7 used a 29mm x 28 spline hub. What are the odds that the RX-7 upright is compatible with the FWD Mazda6 axles? Maybe the newer Miatas use something similar?

Maybe I'm really showing my ignorance here, but I'm trying to explore all possible avenues.

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Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

That was pretty much it... I haven't read through Kurt's Midlana build in a while, might want to take a look there, too...

I don't have a whole lot of personal knowledge regarding uprights and potential applications, but I do read a lot... there are a few folks on here that have built their own rear and front uprights... I'll see if I can find some links.

I don't think you need to know anything about the splines, but if you go on rockauto.com and plug in make year model and engine and go through their index to Brake/Wheel Hub you'll find Wheel Bearing and get a bunch of options such as this:

NATIONAL Part # 510010 Wheel Race; Bore=1.6535", Outer Diameter=3.1496", Width=1.7717"

Since I don't know what year you're looking at there are a couple of choices, but I think the only difference is ID.

As far as making uprights with hand tools goes, I think you'll have to do at least one machine shop operation, to bore the bearing carrier as needed for a press fit on the bearing.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

I don't think you need to know anything about the splines, but if you go on rockauto.com and plug in make year model and engine and go through their index to Brake/Wheel Hub you'll find Wheel Bearing and get a bunch of options such as this:

NATIONAL Part # 510010 Wheel Race; Bore=1.6535", Outer Diameter=3.1496", Width=1.7717"

Since I don't know what year you're looking at there are a couple of choices, but I think the only difference is ID.

As far as making uprights with hand tools goes, I think you'll have to do at least one machine shop operation, to bore the bearing carrier as needed for a press fit on the bearing.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

Consider a driveshaft mounted e-brake setup if you wanted to leave the brakes alone. Some OEM trucks and cars use a setup like that and there are aftermarket, disc versions for cars available or you could build one.

Use a donor fwd with rear disc brakes, and adapt the rear discs and calipers to fit the front hubs for use on the rear.
This allows the entire brake system with prop valve to be reused, no custom axles, the oem hand brake, and possibly $50 of machining to open up the rear rotor id to accept the front hub pilot.

Find a fwd with rear disc donor that uses rear rotors having the same pilot id as the front. Since the same wheels should fit the rear as the front, the hat offset should match the caliper to work with that wheel offset, so brackets should not be too difficult to fab.

Calipers do not work as well as drums as a parking brake. Some oems use a small drum inside the hat of the rear rotor with tiny shoes just for the e brake.

I think Snail is referring to front engine rwd versus a fwd assy in the rear. There is nothing to attach a rotor to on a fwd axle unless it is using german cvs with allen cal screws around the cv od.

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I also used Suzuki GTi calipers on my middy build. Suzuki fronts went on the front and rears went on the rear. I just had to make some adapters to get the calipers in the right position.
Here are some pics:







The only "mistake" I made was not orienting the calipers in exactly the right position with the bleed nipples exactly at the top. Bleeding the brakes is a real pain in that I need to remove each caliper, rotate it slightly so nipple is up, use a piece of plywood to simulate the presence of the rotor, bleed the caliper and then reinstall everything.

More info at http://szott.com/zot2/page1.html

How about simply putting a piece of tight-fitting hose over that nipple (dang, does that sound like more fun than it really is gonna be?!?!) and letting the fluids drain thru that? Kinda like one of those cheap one-man bleed kits I get from NAPA?

PS -- no, I'm NOT a dirty old man. I'm not old yet.

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Geek49203 aka
Tim Wohlford
Louisville, KY
Hayes front, S10 +2 rear, Lalo body.