Using mustang rotors for 4.5" bc

[Longgone]

I`ve read an article or two on the idea of using 66 Mustang rotors on A-body Mopars that came with KH 4 piston disc brakes (67-69 for ex.) in order to take advantage of the 4.5" bolt circle they offer. Since both systems were made by Kelsey Hayes it doesn`t sound out of the question. I did some research and found that both share the same inner and outer bearing. The Mustang rotor is almost a 1/4" larger in diameter at 11.29" versus the A-body rotor at 11.09". I bought a pair of these rotors Bendix #141017 and took them to a local machinist. The rotors can be used if the rotor diameter is turned down to 11.09. Two other cuts must be made, the inner bearing race must be removed and the seat has to be cut down .271 deeper to allow the rotor to slide up on the spindle ,the seal cup must be cut to match. Neither the Mustang or Mopar grease seal will fit since the od on the Mopar seal is too small while the Mustang seals id is too large. I`m still searching to find the correct grease seal. I paid my machinist $60.00 for the work (took just a little over an hour for both) and the cost of the rotors was just over a $130.00 for the pair. Now I`ve got the 4.5"bc with 1/2" studs on my existing 68 disc brake spindles by using the Mustang rotors. I hope this will help somebody by providing another alternative for getting the big bolt pattern without having to (go to the 73 and up system and) change out everything.

 

[EP87]

Longgone thats cool this is the info I've been waiting for, it seams crazy to get
rid of the 4 piston caliper just to get some decent wheels. or spend a small fortune to get some after markets setup.

Keep us posted on the seals and how it works.
Thanks Richard

 

[Longgone]

Longgone thats cool this is the info I've been waiting for, it seams crazy to get
rid of the 4 piston caliper just to get some decent wheels. or spend a small fortune to get some after markets setup.

Keep us posted on the seals and how it works.
Thanks Richard

Yeah Richard the seals have been elusive, so for now I used the outer Mustang seal Rtv`ed to the inner (rubber only) Mopar seal. It`s hard to find a seal with such a large o.d. and small i.d. so I`m still on the hunt. The unicast rotor/hub assembly has worked great though, I`m very happy with it.

 

[65s]

I knew the Mustang stuff was made by KH and both systems used the same pads and pistons and stuff like that, didn't know about the rotor thing though, very cool! What do these seals looks like? Are they all rubber? What about having them made? There's some rubber places that are not totally unreasonable. I'd be into doing this and putting up money for the seals if I thought it was all going to work.

For example, Karr Rubber made some window rubber for a van I own on behalf of a group of vanners. It was like $1400 then $85 a set for each person. Small seals would be much much cheaper.

 

[65s]

Oh ya, I like my 4-piston KH's instead of single piston later style brakes because the rotor rides at the back. The later style ones ride at the front. I would have to remove my front stock anti-sway bar to use later style large bolt brakes. Your Mustang rotor thing is the answer man!

Did you have to use the Mustang backing plate/shield thing?

 

[Johnny Dart]

Oh ya, I like my 4-piston KH's instead of single piston later style brakes because the rotor rides at the back. The later style ones ride at the front. I would have to remove my front stock anti-sway bar to use later style large bolt brakes. Your Mustang rotor thing is the answer man!


So you know,you can swap spindles & calipers from side to side so the calipers are on the back to avoid the factory sway bar. :thumbup:

 

[dgc333]

Why would you go to all that trouble to use Mustang rotors when you can buy the proper rotor from Advance Auto for $85.99 each. Raybestos #76739?

 

[Longgone]

Why would you go to all that trouble to use Mustang rotors when you can buy the proper rotor from Advance Auto for $85.99 each. Raybestos #76739?

dgc333, I believe the 76739 is the small bolt pattern rotor (which is fairly common now)as found on the pre 73 cars. Summit Racing is even carrying those now. The object here was to get the large bolt pattern 4.5" without changing out the spindles, UCA, ball joint, and calipers,etc.. All of these parts have to be found and installed if you used the post 73 stuff. There`s one company www.hotrodsusa.com that has a Wilwood kit for use with pre 73 disc spindles but it`s $800.00. That`s way too much to spend just for a larger bolt pattern. This is a cheaper alternative as well as less work.

 

[Longgone]

Oh ya, I like my 4-piston KH's instead of single piston later style brakes because the rotor rides at the back. The later style ones ride at the front. I would have to remove my front stock anti-sway bar to use later style large bolt brakes. Your Mustang rotor thing is the answer man!

Did you have to use the Mustang backing plate/shield thing?

You can use your existing dust shields. When you cut the inner bearing race seat deeper it orients the rotor into just the right position. Using this rotor also eliminates the 2-piece hub /rotor set-up of the originals and is supposed to be a stronger piece. The grease seal has a metal ring that is driven into the lip of the inner bearing ,it has a rubber or neoprene material on the inside that encircles the spindle. Finding a seal drop in ready has been a hard thing to find.

 

[340mopar]

Why couldn't the Mopar one be re-drilled with the larger pattern? seems like a lot less work than trying to find bearings and seals.


Chuck

 

[dgc333]

Opps! blew right past the desire for 4.5" bolt circle. The big issue would be the lack of a seal. That would basically make the car fair weather only use.

 

[Longgone]

Why couldn't the Mopar one be re-drilled with the larger pattern? seems like a lot less work than trying to find bearings and seals.


Chuck

Since the hub/rotor in the original 64-72 is not 1 piece it makes it very difficult to alter. Generally a machinist would just rotate the hub and drill new holes in between the existing studs. On the 2 piece hub/rotor there is no material in that area so the only way to do the change is to weld up the old holes and redrill them. The wheel studs actually hold the hub and rotor together. Material has to be added behind the hub as well.This makes the hub very hard to drill. In addition when the bolt pattern is widened it necessitates adding more material in the stud area to support it. I gave this a try to start with but most shops wouldn`t touch it. One shop tried it (reluctantly) and before it was done they gave up on it, saying it was not going to be worth it. Moser used to have a machine just for these 2 piece assemblies but the room it occupied was worth more to another machine (since there`s very little call for it anymore) so they removed it in favor of a more profitable piece of machinery. I`m all for keeping things simple and the cost down and thus far this is the cheapest method I`ve found. Anyone who`s been down this road knows that choices are very limited in what you can do with this 4"bc KH disc brake sytem.

 

[Longgone]

Opps! blew right past the desire for 4.5" bolt circle. The big issue would be the lack of a seal. That would basically make the car fair weather only use.

Yeah right now a makeshift seal is all I can come up with. I`ll get the specs of the i.d. and o.d. of the seal that is needed and see if some of our auto parts guys can come up with something.

 

[65s]

There's a bearing place here where I live that is renowned for coming up with just about anything you need. They've been in business forever in the same location. I'm just not up on this stuff, although I do have the KH discs on my car. If you had the exact dimensions needed I could go visit them and see what they've got. They might just be picking from the same suppliers as your place, but you never know. There's a lot of parts here in Canada (mostly Magna made) that maybe you don't have down there.

 

[Longgone]

The specifications for the mystery seal are as follows:

O.D.- 2.506
I.D.- 1.730

If you know of any seal that fits these specs please post it here. Thanks- John

Width -.250

 

[EP87]

Longgone there's a seal warehouse in town thats been helpful before with odd ball seals. I'll give them a call with those numbers and see what they say.
Richard

 

[grimreaper]

Checked the IBI and didn't find the exact seal. Do you think a 1.687 ID will work? If so here are some to try:
1.687 x 2.506 x 1/4 National Seal 40154 or 442224 (Kelsey Hayes 54595)
1.687 x 2.506 x .312 National Seal 410154 or 6874S
1.687 x 2.506 x .375 National Seal 480363

 

[Longgone]

I do think the 1.68 will work. Thank you grim, I`m going to try the first one, since the original is 1/4 in width. I`ll let you know how she goes.

 

[Longgone]

The seal # crossed over to a 16743 and it fits! Yes it`s a tight fit but the grease is in and the elements are out. Thanks grim, here`s a couple pics of the rotors on.

 

[HemiPar]

So if we have the K-H brakes we should be able to get 4.5" BP for about $200. Depending on your machine shop prices. That sounds great to me. Sign me up.
Oh wait, my son works at a machine shop. Thanks for all the hard leg work Longgone.
Next question though. What about the stud difference ( 1/2 on front 7/16? rear) Can I just have my rear drums and axles re-drilled for 1/2 studs?
Jeff

 

[EP87]

The seal # crossed over to a 16743 and it fits! Yes it`s a tight fit but the grease is in and the elements are out. Thanks grim, here`s a couple pics of the rotors on.

longgone I checked with my local bearing house and they couldn't or wouldn't
come up with anything even close to grimreaper. But I sounds like the 16743
will work. Thanks for all the hard work, I can't wait to try it out.
Richard

 

[340mopar]

HemiPar, if you are running 4.5" pattern on the back they should be 1/2" studs, only the 4" pattern uses the 7/16" studs.


Chuck

 

[71produster]

Yeah Richard the seals have been elusive, so for now I used the outer Mustang seal Rtv`ed to the inner (rubber only) Mopar seal. It`s hard to find a seal with such a large o.d. and small i.d. so I`m still on the hunt. The unicast rotor/hub assembly has worked great though, I`m very happy with it.

Chicago Rawhide should have the seals you are looking for.

 

[Longgone]

So if we have the K-H brakes we should be able to get 4.5" BP for about $200. Depending on your machine shop prices. That sounds great to me. Sign me up.
Oh wait, my son works at a machine shop. Thanks for all the hard leg work Longgone.
Next question though. What about the stud difference ( 1/2 on front 7/16? rear) Can I just have my rear drums and axles re-drilled for 1/2 studs?
Jeff

Actually I`ve seen a guy on Ebay selling the Mustang rotors that are cross drilled) for $100.00 a pair, shipping was a flat $26.00. If your son works at a machine shop, well you`ve got it made! If you`re still running the 7/16 studs on a 4" bc in the rear then you`ll probably want to have your axles redrilled for 4.5 with 1/2" studs and get your drums bored to match. This is probably a good idea if you start putting a lot of HP to the rear wheels. Moser Engineering did mine (it took a week from the time I sent them out to the time I got them back).They are a great company and I can`t praise them enough.

 

[Longgone]

longgone I checked with my local bearing house and they couldn't or wouldn't
come up with anything even close to grimreaper. But I sounds like the 16743
will work. Thanks for all the hard work, I can't wait to try it out.
Richard

Richard, thanks for looking!