Caliper rebuild question

[jsubbi]

I ordered some stainless-steel pistons and new seals from Bimmerworld, but the seal is a couple of mm larger than the piston (the ID of the seal is about 62 mm and the max OD of the piston is 60 mm). The part number on the seals match the ETK and BW swears it's the right piston. Does this sound normal? It doesn't seem like it would seal.

[95DayVI]

_______
GC RTAB shims, RSMs, T/S Coilover with Koni DA f/SA R & 450#f/550#r Eibach ERS
Eyeball Arm CA mounts
Sunbelt CAMS w chip for 24# injectors, Euro MAF, Conforti/ITG CAI
96+ exhaust manifolds
Euro fLoAtErS, Ferodo DS2500
accessory UDPs
M roadster lever
All done in my garage

[jsubbi]

[95DayVI]

_______
GC RTAB shims, RSMs, T/S Coilover with Koni DA f/SA R & 450#f/550#r Eibach ERS
Eyeball Arm CA mounts
Sunbelt CAMS w chip for 24# injectors, Euro MAF, Conforti/ITG CAI
96+ exhaust manifolds
Euro fLoAtErS, Ferodo DS2500
accessory UDPs
M roadster lever
All done in my garage

[ADS]

I've seen rubber seals expand. Funny thing is, brake fluid on the wrong type of rubber would do that, but obviously shouldn't to a brake part o-ring, but heat, or somebody stuffing the wrong o-ring in the bag with the right part number would be my number one guess.
Get somebody to measure a piston for you. Try a racing board (where someone may have their stock calipers off from a Brembo/stoptech upgrade) or maybe visit Pelican parts site and see if somebody there can give you the diameter spec.

Good luck.
ADS

[95DayVI]

_______
GC RTAB shims, RSMs, T/S Coilover with Koni DA f/SA R & 450#f/550#r Eibach ERS
Eyeball Arm CA mounts
Sunbelt CAMS w chip for 24# injectors, Euro MAF, Conforti/ITG CAI
96+ exhaust manifolds
Euro fLoAtErS, Ferodo DS2500
accessory UDPs
M roadster lever
All done in my garage

[ADS]

[jsubbi]

but no luck. I'm just going to have to pull my caliper and mesure the piston this weekend. I'll let you know what I find out.

[jsubbi]

That's why I suspect it's the piston, but Bimmerworld swears it's the right diameter (60 mm). I've scoured the net to see if the piston size is speced, but unfortunately no luck.

[95DayVI]

Bimmerworld are great guys but not infallible. I had one parts issue with them myself, and they corrected pronto. If you send them the pic then that's that. The only possible other solution is they put the wrong seals in the bag.

Now you gotta take that [Oops!] apart some time, and you can measure the caliper piston without a complete tear down. So do that._______
GC RTAB shims, RSMs, T/S Coilover with Koni DA f/SA R & 450#f/550#r Eibach ERS
Eyeball Arm CA mounts
Sunbelt CAMS w chip for 24# injectors, Euro MAF, Conforti/ITG CAI
96+ exhaust manifolds
Euro fLoAtErS, Ferodo DS2500
accessory UDPs
M roadster lever
All done in my garage

[95DayVI]

_______
GC RTAB shims, RSMs, T/S Coilover with Koni DA f/SA R & 450#f/550#r Eibach ERS
Eyeball Arm CA mounts
Sunbelt CAMS w chip for 24# injectors, Euro MAF, Conforti/ITG CAI
96+ exhaust manifolds
Euro fLoAtErS, Ferodo DS2500
accessory UDPs
M roadster lever
All done in my garage

[shipdriver]

[shipdriver]

right parts was the easy part...now, getting the boots to stay in place while sliding in the piston...now that is the hard part. Good luck. :o) Best Regards, Mike