Hi All,

As soon as my garage isn't freezing anymore, I'm switching front calipers on my '00 FXDX. My plan is to install a set of GSXR radial calipers with Speed Merchant brackets, braided lines, and the stock dual-disk master cylinder. I have all of the parts ready to go, but here's my question: The master cylinder was designed for DOT5, the calipers were designed for DOT4. Obviously all of the components will be fully flushed and cleaned either way, but which fluid should I use? I prefer the feel of DOT4 (which has less compressability than DOT5), but I'm not sure whether seals and gaskets in the master cylinder are made of something that will degrade if a silicone-based fluid isn't used...

Thoughts?

Thanks!

 

On my FXDXT I switched to the '08 and up HD touring calipers (made by Brembo), which use DOT4. All I did was thoroughly flush the stock 11/16" master cylinder and lines out with denatured alcohol (before hooking them up of course) filled with DOT4 and bled the system. No issues and I know others here have done the same.
The denatured alcohol is cheap, so run a bunch through. I ran a couple bottles.

You could also get a rebuild kit with new rubbers on eBay for about $15, tear it down, clean everything really well and flush the lines.

 

Thanks a million, that's what I'll do. I'll just have to remember that the front and rear systems will each use different fluid, and make sure that no "helpful technician" ever decides to top off the mc if she's ever in the shop for anything (although "the shop" is usually only my garage)!