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View Full Version : PM caliper upgrade for shovelhead questions



SauceSquatch
03-03-2016, 4:32 PM
Hey y'all. Just picked up a good used PM rear caliper to replace my stock banana caliper on my shovelhead.

Need some info and advice.

First off, do these take DOT5 or DOT3? I assumed 5...

Can i reuse my stock master and brake lines?
Right now it's all filled with DOT3 and I believe it's a smaller internal bore size in the lines. That being said if the caliper requires DOT5 can I just flush and replace the end fitting adapter to size up to fit the caliper or do I need to replace lines all together?

Sky
03-03-2016, 8:28 PM
Disassemble and clean the pm caliper . Reassemble and use dot3/4. Use new seals if the old ones look bad.
Or flush the master and lines then rebuild the master with new rubber bits so you can use dot 5.

Thing is to not mix the two types of fluid. Silicone (dot5 ) does not soak into the rubber seals like the acid based stuff will (dot3/4).
The acid will actually swell the seals making them soft and hard to re-fit once disassembled.

So seals run in dot 5 are fine to wash (with brake cleaner) and re-use with acid
But seals soaked in dot3/4 will not last long (even cleaned) if used with silicone.

SauceSquatch
03-04-2016, 10:23 AM
Thanks Sky, I'll clean it good and get a rebuild kit for the master.

I still need to figure out if I need to swap out some lines, I guess I need to take some shit apart and get the caliper out, take some measurements. This weekend I should have some garage time.

I've been reading a couple other threads on bore size, I have a stock 3/4 bore master.

I have to check when I am back home but does anyone know the bore size of this PM caliper?
67533

docmel
03-05-2016, 7:02 PM
I've run that same exact caliper with an older 3/4 bore KH master cylinder: All worked fine

SauceSquatch
03-06-2016, 7:05 AM
I've run that same exact caliper with an older 3/4 bore KH master cylinder: All worked fine

Cheers thanks Docmel, you switched over to DOT5 though right?

Or did you leave DOT3 in there?

docmel
03-06-2016, 9:18 AM
Cheers thanks Docmel, you switched over to DOT5 though right?

Or did you leave DOT3 in there?

Here's the deal IMHO. As long as you dont mix the two, you are OK. Myself, I like DOT 5 solely because it doesnt hold water, a big prob over time in a DOT 3 used system. DOT 5 has higher boiling piont, a HiPO issue, but I dont use it because of that factor. Ever see DOT 3 over the years? It gets pretty ugly.

My KH was rebuilt by me, the PM new, so I used DOT 5. Frankly, if my KH was used and still had DOT3 in it, I prob wouldve went with DOT 3 all the way