Boxer Motorsport Brake Issue ‘83 911SC

[cuoffroad2]

Hey group, I have a ‘83 911SC with aftermarket Boxer Motorsport brakes. I have had the car a year and am not sure exactly when they were put on the car. I can’t find much of anything about these brakes online and it looks like the company went out of business in the mid 2000’s.
The issue I am having is that the right rear caliper seems to be rubbing harder than it should against the outside of the rotor while I am driving. Lately when driving, after about 10-15 minutes, it starts to clamp down on the rotor making it difficult to drive. After the car cools down the caliper releases itself.
I have posted pictures of the rotor and caliper below. I am trying to figure out if the caliper is bad, if the brakes just need to be bled, or if anyone can think of something else that might be going on.
Thanks so much for the help!

[Uwon]

This is no easy fix. All the signs of a frozen caliper in need of R&R. PMB is a good place to send them to for a nice refurb.
Johan

[GaryR]

I would say look at the price of brand new OEM calipers vs. a PMB rebuild and make your decision there. OEM brakes with upgraded fluid\pads are more than adequate and parts are readily available..

[Uwon]

Refurbished (and finished in red) those calipers will look really good and work great. OE calipers are blah looking.
M2CW
Johan

[GaryR]

Originally Posted by Uwon

Refurbished (and finished in red) those calipers will look really good and work great. OE calipers are blah looking.
M2CW
Johan

LOL, nice looking! But when they are all pretty and red (which are invisible behind almost any wheel BTW) you will still have some oddball brakes you can't get parts or (an assortment anyway) pads for..

[David Inc.]

Is nobody going to ask about those mile wide spacers?

[GaryR]

Originally Posted by David Inc.

Is nobody going to ask about those mile wide spacers?

it's obviously a wide body, but yes I'm not a fan.. Custom wheels with the correct offsets are much better for the car\axle bearing I would think.

[jjeffries]

I too saw those spacers and felt sympathy for the wheel bearings.

Maybe the flex hose is failing internally? What does the fluid look like? Etc ... basic diagnostics.

Depending on how mechanical you are, you could disassemble that caliper and see what you find. Maybe with some careful measuring you'll find the seals and dust boots are off-the-shelf? Then you could do a 4 wheel/caliper refresh.

Or, the caliper may be toast and you'll need to go for a larger repair.

Best of luck to you,
John

[cuoffroad2]

Thanks everyone! I think I will start by taking the caliper off and seeing if cleaning it out helps and see how the boots look. And yes, the wheel spacers are huge! I have attached a picture of the car. If you have anymore thoughts let me know. Thank you!

[jjeffries]

If you don't already have one, it would be prudent to buy yourself a Motive Bleeder and run a couple of cans of a good DOT4 fluid through the system, at all four caliper bleeders. If you have a good air compressor in your garage/shop, you could obtain a vacuum bleeder instead; the Motive is the less expensive route. Maybe you already have one?

Do you have any service/repair history on the car?

John

[acme911]

If your planning to keep this car. Not knowing history of maintenance. Personally I would replace the calipers with stock, replace rotors, brake lines and rebuild master. If one caliper has gone bad chances are the others might fail soon. And when your done you’ll know exactly what shape your brakes are in.

Long story short. After installing a rebuilt engine and going on a lengthy tuning drive. Hitting triple digit speeds. It was fun. But, when I got home it hit me that my brakes and suspension where still over 40 yrs old. Ordered parts the next day.

2 cents worth.

[cuoffroad2]

I don’t have service records on the car, but I know it was well maintained. These brakes were installed between 15-20 years ago. It sat for about 4 yrs in a garage before I got it. I am inspecting it to see if all of the lines were replaced at the same time and what shape they are in. He did a good service on it when I bought it which included a brake fluid flush. I agree that with this one going out it probably means the others aren’t far behind. My goal right now is to see if I can safely get to winter and replace things then, so that I can enjoy driving it this fall.

[porsche930dude]

Originally Posted by GaryR

it's obviously a wide body, but yes I'm not a fan.. Custom wheels with the correct offsets are much better for the car\axle bearing I would think.

Stress on the bearings is caused by the increased offset regardless of how it's achieved.

I would first test if it is in fact the caliper. Apply the brakes to get it stuck and release the bleeder. If it releases then its not the caliper. Also check the sliders as that is most likely the culprit. If it is the caliper piston take it apart pull out the piston clean it all up and put it back together again. Its not hard to do. If it has damaged seals and you cant figure out replacements then consider new options.

[Ian Comerford]

Originally Posted by porsche930dude

Stress on the bearings is caused by the increased offset regardless of how it's achieved.

I would first test if it is in fact the caliper. Apply the brakes to get it stuck and release the bleeder. If it releases then its not the caliper. Also check the sliders as that is most likely the culprit. If it is the caliper piston take it apart pull out the piston clean it all up and put it back together again. Its not hard to do. If it has damaged seals and you cant figure out replacements then consider new options.

I agree with this version and would add that you should try exercising the calipers pistons which is simple to do. You can buy a simple and cheap tool to push the pistons back into the caliper with the pads removed. Then replace pads and push the pedal to move the pistons back out. I do this on my car every winter and it takes just over an hour to do all four. It keeps the pistons working freely and helps negate dragging pistons caused by lack of use.
https://www.machinemart.co.uk/p/disc-brake-piston-spreader-0---65mm/

[Locker537]

Originally Posted by cuoffroad2

I don’t have service records on the car, but I know it was well maintained. These brakes were installed between 15-20 years ago. It sat for about 4 yrs in a garage before I got it. I am inspecting it to see if all of the lines were replaced at the same time and what shape they are in. He did a good service on it when I bought it which included a brake fluid flush. I agree that with this one going out it probably means the others aren’t far behind. My goal right now is to see if I can safely get to winter and replace things then, so that I can enjoy driving it this fall.

I like that you state your goal.

I would start by removing the pads and inspecting the caliper. See if you can push the pistons back in. It should take some effort, but not something you need to grunt doing. Give everything a good cleaning with brake cleaner. Inspect and come up with a plan.

I agree with the long term solution being to return to original calipers and rotors. For an SC, you can upgrade to Carrera 3.2 calipers and rotors without having to change anything else.

Granted, we don't know if your car has a different master cylinder or some other parts that may add to the project.

[Mahler9th]

If your car has a vac booster the issue may not be the caliper... it may be the booster. Especially with symptoms that seem heat related.... they may not be heat related, they may be vac related.

Ask me how I know....

[Mahler9th]

Vac boosters may or likely have check valves...

[cuoffroad2]

Thank you everyone for the responses. I am going to remove the caliper this weekend, clean it out, inspect the pistons, etc and see what’s going on. Will get back with an update when I have one.

[pa911]

Most likely the hose on that side is swelled up .