3-Door RS Cosworth hub bolt pattern?

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3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Sat Oct 21, 2017 10:29 pm

Didn't find anything in a short search... Does anyone know if the RS rear hub bolt pattern is the same as the stock XR? I'm looking at swapping from Wilwoods to TBird TC rear calipers so I can get a real e-brake for the street. Don't know if old TC caliper brackets would work, or if I'd have to have custom ones machined.

TIA,

John

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by John Brennan » Sat Oct 21, 2017 11:54 pm

Both are 4x108, so, yeah. Scorpio rears are basically the same as RS (as is the Master), and you can use a Cossie e-brake cable... all factory parts.
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Sun Oct 22, 2017 12:48 am

Thanks John,
The wheel bolt pattern is the same, but the rear bearings in my setup are significantly larger than any XR I've worked on. So, larger bearing, larger hub = wider bolt pattern? This is what I had to do for Wilwoods on the rears. Been a long time, but I kinda' recall that the old TC brackets wouldn't work. :?

Sorry, guess the photo attachment didn't work...

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by John Brennan » Sun Oct 22, 2017 1:29 am

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by jkxr4ti » Sun Oct 22, 2017 8:42 am

I think what John K is asking is about the bolt pattern of the bearing carrier to sta so he could use a turbocoupe adapter bracket. I beleive they are the same even though the physical bearings are larger but he was looking for input on those that know for sure.

Is that what you meant John?
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Sun Oct 22, 2017 1:01 pm

I think what John K is asking is about the bolt pattern of the bearing carrier to sta so he could use a turbocoupe adapter bracket. I beleive they are the same even though the physical bearings are larger but he was looking for input on those that know for sure.
Exactly. Again, its been several years, but as I recall when I put large Wilwood calipers on the rear, I couldn't use the TC adaptor/bracket I had because the bolt pattern was different. Ended up with this:
100_2543.JPG
100_2543.JPG (643.21 KiB) Viewed 412 times


Then again, I'm not sure if that was really the reason, or if it was something else related to the Wilwood calipers. Been working on too many other cars since then...

Yep, that's a real FMS race suspension, with spring perch delete and ribbed reinforcements all over the place. Even the rear crossmember is doubled wall tubing. Weighs a ton.

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by timxr8 » Sun Oct 22, 2017 4:24 pm

Bolt pattern is the exact same (53mm PCD, 94mm top spacing and 90mm bottom spacing). Don't know why you couldn't use the TC brackets. I recall that the little pilot lip that goes inside of the STA is a little bigger on the Scorpio/Disc Sierra, but the hole was a little bigger on those brackets too. No clue.

Just wondering, why are you using the TC? I know that you want a parking brake, but if you were willing to go that far with the Wilwood (looks like SL), then why not just add an external parking brake? You're going backwards. Also, did you match the piston area? Which Wilwoods were you using in the back?

Funny thing is, I realized a couple years ago that the standard Sierra/Scorpio rear mounting height is perfect for the Wilwood Superlite calipers on the back with 11.75" Circle track rotors. Simply 12mm offset plunge in the original holes to go from the 3.5" to 90mm. Tap the hole in the bearing carrier, and boom, you have 11.75" rotors and 4 piston calipers in the back. Exactly what I'm doing on mine and adding a little bracket for the MC4 parking brake caliper.
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by timxr8 » Sun Oct 22, 2017 4:27 pm

Are those the WRC bearing carriers?
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Mon Oct 23, 2017 3:49 am

timxr8 wrote:
Sun Oct 22, 2017 4:27 pm
Are those the WRC bearing carriers?
Yep. Used FMS WRC rally set-up. The only "stock" thing on it is the anti-roll bar and its bracket pins (I welded those on). It has the extra brackets for the rear mount anti-roll bar, but that requires swapping the fuel tank to a fuel cell to get room for mounting brackets.

Everything on it is double-skinned, and ribbed, like the rib over the spring perch-delete-plate in the photo. Its really heavy.

The last smog test I had, with the battery in the back, a set of golf clubs, and this rear suspension, the tech told me its in the "250-300lbs range" over stock XR rear weight, and wouldn't test it... CA now measures rear/drive wheel weights on the dyno rollers. So, we had to back it off the dyno and lift it so he could verify I had the battery in back, and that the rear hadn't been swapped out to a Vette or 944 rear trans/diff, or some 4x4 setup out of an F150.

I guess CA thinks consumers routinely do sneaky swaps from automatics to manuals, or 4x4 conversions... I get that different gearing could mess with emissions at specific RPM's (especially in the testing range), but I could just as easily have only had golf clubs and groceries, or a couple cases of oil, or beer in the trunk, and that really ain't any of the tech's or CA's business.
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Mon Oct 23, 2017 4:10 am

timxr8 wrote:
Sun Oct 22, 2017 4:24 pm

Just wondering, why are you using the TC? I know that you want a parking brake, but if you were willing to go that far with the Wilwood (looks like SL), then why not just add an external parking brake? You're going backwards. Also, did you match the piston area? Which Wilwoods were you using in the back?
I might be cheap, but not backwards. :D

I don't want to invest in a custom 2-caliper bracket, and besides I can't find any spot or smaller caliper which will fit, or expand to fit a 1.0" wide rotor. And, a hydraulic e-brake on the same line might be great for rally, but its hardly a separate "safety" device, or even adequate parking brake if you have a leak... Anyway, the rear of the car is way heavier than stock with all the reinforcement the full suspension has, and far too much unsprung weight for the street.

So, just keeping it simple. If I'm gonna' have to add some weight to get a TC e-brake, then that's OK. Better than the car rolling into the neighbor's new Denali (ask me how I know).

Basically, just getting my ducks in a row... practically no time to get to work on the car, so when I do get the chance, I don't want any SNAFU's and have to put it all back together until the next available time.

Yes, just wanted a parking brake. Tried a couple different things to cobble an e-brake gimmic onto the Wilwood. Even thought about a Go-Kart solid rotor on the diff flange (strictly for parking, not a real e-brake), a la the old Land Rover e-brake system.

I can't tell you the exact model # of the Wilwoods on the rears without pulling them off, though they are Superlites. Been too long to remember. Got them from a NASCAR team on eBay. Did all the math to size the pistons vs. the front Wilwoods, weight transfer calcs, etc., etc., etc. The fronts are pretty damn big pistions on 1.25" x 12.25" rotors, and these rears are 4-piston staggered (different pairs of piston diameters), on 1-1/8" smaller diameter rotors, with line proportioning valve. Works phenomenal. Ben Martinez flipped over them after driving the car, when he still had his AutoX XR.
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Mon Oct 23, 2017 4:11 am

timxr8 wrote:
Sun Oct 22, 2017 4:24 pm
... Exactly what I'm doing on mine and adding a little bracket for the MC4 parking brake caliper.
Pic?

Did you use the same bracket you made for your 11" solid rotor rear kit?

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Mon Oct 23, 2017 9:14 pm

These are the front calipers,
016BFC58.JPG
016BFC58.JPG (591.12 KiB) Viewed 375 times
and,

1.25" x 12.8" rotors
00BE5B30.JPG
00BE5B30.JPG (180.73 KiB) Viewed 375 times
and the rears,
0158FA18.JPG
0158FA18.JPG (405.47 KiB) Viewed 375 times
The rear calipers are also for 1.25" rotors, but I had a shop copy the profile of the brake pads, and make me 0.25" AL blanks, machined down to 0.22" thickness. These go between the caliper pistons and pads, taking up 0.5", which allows me to use the 1.0" Cossie front rotor (actually, 0.92 something").

For those interested, those sleeves around the lug nuts are for corresponding steel sleeves machined into the Compomotives, like you see in the "How To Prep..." book. Snug fit when you're installing the wheels, but it ain't moving. The Compomotives are MO's, 17", came with the whole suspension, and each weighs a ton. Guess they didn't want any rocks to blow out rims. But, it adds a lot of unsprung weight for a street car.

Personally, if I had the time, I'd try to build my own tubular STA's to get rid of as much unsprung weight as possible. But yet again, I don't have the time, let alone finding the correct STA for sacrificing the hub portion. :(

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by timxr8 » Tue Oct 24, 2017 9:56 pm

Unfortunately, I have no pictures yet. I'm still trying to get everything set up in my garage.

Anyway, makes sense on everything. Those Factory parts that were reinforced are pretty ridiculous in weight. I know Tony W is looking at those WRC carriers, but can't justify the price.

So you're looking for a caliper to fit onto those rotors in the back? 24mm wide Front 2wd Cossie (283mm) right?

The TC use a 45mm (1.77") piston, so it's about 2.46 sq in piston area. That should give you a good comparison. The Stock Scorpio/Sierra/Cossie use a 43mm, which is about 2.25, or about 9% smaller than the TC.

I know the newer Taurus (13+) use a vented rotor in the back with a nice size pad and 43mm piston. Bolt pattern is the 90mm, same as the Sierra, but a M12x1.75 bolt. I don't have any measurements of the height thought. I'll see if I have a pad I can measure my extra set and double check the width this weekend if I can find them. Just a thought.
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Re: 3-Door RS Cosworth hub bolt pattern?

Post by john keefe » Wed Oct 25, 2017 1:27 am

Tim, found my old calculations on bores, line pressures, CG & weight transfer, etc., etc..

My rear Wilwoods are dual pistons @ 1.25" & 1.0" staggered; fronts are 1.75" each (x4 per caliper). For comparison, the stock RS fronts are @ 1.378" bore per piston.

What I calc'd out before was that the combination of Wilwood's front + rear needed 25% more pedal travel to move the pads 0.01" than the stock RS fronts + TC rears (1.77" bore). But, comparing torgue on the WW rears (+RS rotor) vs. TC rear (+TC rotor) was fairly even (1.9% produced by the TC calipers on TC diameter rotors (vs. WWd's on RS diameter rotor).

Recalculating, switching to the TC rears would require 6.4% more pedal travel. Noticeable, but probably not drastic enough to consider going to a different master cylinder bore. But, that combination using the RS rotor on the rear produces 22.1% more rear piston force, and about 14% increase in torque being applied on the rotor at the pad centerline.

That seems like it would be a noticeable difference in rear brake bias. And, not sure if the in-line bias adjuster could dial that out and leave room for further adjustment if needed.

Right now it feels like a really good combination, and a good range of bias using the line-force valve. On the other hand, the Vargas caliper seemed to work fine with heavier Mustang Cobras. Then again, they deal with a smaller diameter rotor than the TC, which requires larger rotors for its greater overall weight, right?

So, now it seems to be a debate of more rear brake bias and a longer pedal travel vs. a parking brake. Hmmm... :? Now I'm confused. Have to think on this one.

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Re: 3-Door RS Cosworth hub bolt pattern?

Post by whitelx » Wed Oct 25, 2017 10:51 am

john keefe wrote:
Wed Oct 25, 2017 1:27 am
On the other hand, the Vargas caliper seemed to work fine with heavier Mustang Cobras. Then again, they deal with a smaller diameter rotor than the TC, which requires larger rotors for its greater overall weight, right?

1993 Mustang Cobras use the same rotor and caliper as the turbocoupe. 1994-2004 Cobras use an 11.65" vented rotor with a 38mm piston. The 94-04 GT/V6 use a 10.5" solid rotor with a 38mm piston.
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