Travel of master cylinder piston

Post by **Leatherneck** » Fri Jul 18, 2008 10:57 am

Can somebody tell me the length of travel of T-1 dual res master cylinder.piston? Thanks!

Post by **Marc** » Fri Jul 18, 2008 11:41 am

The first tandem M/C (1967) had 15.5mm front/12.5mm rear with drum brakes; 'Ghias w/front discs were 14.0/14.0mm.
Super Beetles are 17.5/11.5mm, Type IIIs are 15.0/15.0mm.
All of these are 19.05mm bore, as is the "universal replacement" for Standards/'Ghias/Things (113 611 015BD)...that's probably the one you're interested in, and I don't have the specs for it. If I had to guess I'd say 14.0/14.0 or 15.0/15.0mm.

Standard front wheel cylinders have been 22.2mm from `65-up; rears were 19.05mm through 1967 and 17.46mm after that (I can't recall which rears `67 'Ghias had, but they're 17.46mm from `68-`74).
Supers had 23.8mm front and 17.46mm rear; Type IIIs had 23.8mm rear (early IIIs had other M/C and wheel cylinder bores).

Point is, the M/C stroke doesn't seem to have been changed in lockstep with the wheel cylinder bores, and many's the time the wheel cylinder sizes have been "juggled" (swapped F<->R, or Type III rear brakes put on a Beetle) with no apparent need for a change in M/C stroke...so unless you're doing something really strange it probably isn't going to be an issue.

Post by **Leatherneck** » Fri Jul 18, 2008 11:53 am

Don't need the bore size but the travel length that the piston covers.

I am taking a aftermarket peddle assy and installing a VW Master cylinder. Have some work to do to mount it and want to make sure the push rod length is not to long or short to push the piston in.

Post by **Marc** » Fri Jul 18, 2008 3:44 pm

Leatherneck wrote:Don't need the bore size but the travel length that the piston covers...

I gave you those. It's designed so that if the rear circuit fails the rear piston will physically contact the front piston and push it forward, or if the front circuit fails the front piston will bottom out and pressure will develop between it and the rear piston to work the rear brakes - so just add the two strokes for the maximum total that should ever be needed.
We just put a junk 113 611 015BD in the press and measured the maximum total travel at 1-1/8" (pretty durn close to 14mm + 14mm)...if your pedal will provide that much travel you should be fine.

Post by **Leatherneck** » Fri Jul 18, 2008 4:02 pm

Marc wrote:total travel at 1-1/8" (pretty durn close to 14mm + 14mm)..

I can handle that, the pushrod will be whatever length is required. Thanks Marc.