Front caliper difference

[Goodie]

I am in the process of renewing the front brakes on my '80 911SC. All was proceeding smoothly when I noticed that there is a distinct difference between the right and left sides. Is this normal or did the PO get creative and replace one with an non OEM caliper at some point? Three of the four pistons are pretty much siezed, so I couldn't tell if the size difference created any braking issues. I guess the biggest problem this may cause is the neccessity of purchasing two different sets of pads/kits needed to replace/rebuild them both. The rears are both identical to the "smaller" one (on the right in the pictures). Based on the pictures, can anyone identify the larger one on the left so I can order the correct pads/kits?
Any feedback would be appreciated.

[Bill Verburg]

Originally Posted by Goodie

I am in the process of renewing the front brakes on my '80 911SC. All was proceeding smoothly when I noticed that there is a distinct difference between the right and left sides. Is this normal or did the PO get creative and replace one with an non OEM caliper at some point? Three of the four pistons are pretty much siezed, so I couldn't tell if the size difference created any braking issues. I guess the biggest problem this may cause is the neccessity of purchasing two different sets of pads/kits needed to replace/rebuild them both. The rears are both identical to the "smaller" one (on the right in the pictures). Based on the pictures, can anyone identify the larger one on the left so I can order the correct pads/kits?
Any feedback would be appreciated.

The left one is an A caliper the right is an M

The A will have 3.5" mounts and the strut it is mounted on will have matching 3.5" mounting holes.

The M will have 3" mounts and it's strut will have matching 3" mounting holes.

The front M is not exactly the same as the 2 rear Ms, though it will have the same 3" mounts and use the same small pads.

to rectify the situation you will need at least 1 front strut w/ 3.5" brake mounts and an A caliper for the side w/ the wrong caliper

[Menmojo]

No this is not "normal".
Some how you have two different calipers from two different years.
Under heavy breaking this could be a big problem!

[Goodie]

Thank you Bill!
So in short, at one point the right side strut was replaced and went from the original "A" to an "M" . Will this negativley affect the braking performance to the point where it may be a safety factor?

[Joe Bob]

Talk to Eric at www.pmbperformance.com he will probably work out a deal.

I'm betting it pulled to one side?

[Bill Verburg]

Originally Posted by Goodie

Thank you Bill!
So in short, at one point the right side strut was replaced and went from the original "A" to an "M" . Will this negativley affect the braking performance to the point where it may be a safety factor?

It's not something I'd recommend keeping but for normal street use it's ok,

They probably used the M front caliper which has the same pistons as the A so the only real difference is the smaller pad which isn't that big a deal.

I would rectify the situation though. As I said you will need at least the right front strut and correct A caliper

If you don't already have Bilstein stuts this would be a good time to get a set of 930 Bilstein struts, thy bolt in and you will not only have the HD valving but new wear surfaces, struts do wear out w/ time

[Porboynz]

Thats amazing. Fitting the later model A calipers and struts is a common upgrade for older cars with M calipers. I never heard of anyone backdating from A to M calipers, let alone only one at a time. Joking aside this indicates a serious lack of mechanical interest in the operation and safety of you braking and suspension system so I would be wondering what else has been compromised. The A and M pistons are the same diameter but running one of each would be strictly a get me home exercise if I bent a strut. The shocks are going to be completely different as well.

[al lkosmal]

With this arrangement, I would be inspecting the left font side of my 911 for earlier accident damage.

regards,
al

[will hung]

Originally Posted by Porboynz

Thats amazing. Fitting the later model A calipers and struts is a common upgrade for older cars with M calipers. I never heard of anyone backdating from A to M calipers, let alone only one at a time. Joking aside this indicates a serious lack of mechanical interest in the operation and safety of you braking and suspension system so I would be wondering what else has been compromised. The A and M pistons are the same diameter but running one of each would be strictly a get me home exercise if I bent a strut. The shocks are going to be completely different as well.

i don't think this indicates a lack of interest as much as I think it indicates, as Al points out, that the car was wrecked and this was the cheapest way to fix it.

[Goodie]

Thanks for everyones feedback. I'm on the hunt for an A strut and have lined up a couple of exchange calipers from Eric @ pmb performance (thanks Joe Bob!). I plan to replace the cartridges as well.
I did a complete engine/trans rebuild last year and have spent a lot of time in, under and over this car and have seen no signs of any major damage. But I have seen multiple examples of pretty shoddy repair technics...so this does not surprise me. I got the car for a song last year so I don't mind putting a few bucks back into it to make it right again.
Thanks again!

[Porboynz]

Glad to hear you are going to get it sorted correctly, brakes and suspension shortcuts can have sad outcomes for you or other road users. Sounds like you got a deal there so as you say investing a few dollars is all part of the fun and you will have the reward of knowing you saved another 911.