Comparison of alternative front drum brakes

Post by **Peetee** » Mon Feb 25, 2008 4:40 pm

Can't quite picture where the snail adjuster is but could this be compensating for the shorter cylinder in the Wolseley? (Roy described how fitting Minor cylinders meant lengthening the backplate slot).

Post by **alex_holden** » Mon Feb 25, 2008 5:01 pm

I have the original (knackered) Wolseley cylinders and a spare Minor cylinder here so I will take some careful measurements before modifying the backplates. It seems to me the position of the bottom of the slot on the back of the cylinder is the most critical location because it's the fixed pivot point for the opposite shoe.

Post by **paulk** » Mon Feb 25, 2008 7:16 pm

Looking at the set I've got the slot to front of piston dim on both the Minor and original wolseley set is the same. its just the back of the piston that is different.

Post by **alex_holden** » Tue Feb 26, 2008 2:54 pm

Just measured a couple of them. When fully closed, the measurement between the front and back faces is 1.692" on the Wolseley cylinder and 1.72" on the Minor cylinder. So there is a difference (0.028"), but not as large as the difference between the adjuster cam sizes (0.1").

More measurements to come later, but it looks to me like to do a decent job of the backplate conversion you need to move the large bolt hole about 0.1", the small hole about 0.06", and extend the slot in both directions. If you leave the small bolt hole where it is and move the large hole by 0.16", the back of the cylinder is going to be about 0.06" closer to the drum than with the original cylinders.

Post by **bmcecosse** » Tue Feb 26, 2008 4:10 pm

I certainly didn't do that - I left the large hole and top end of slot - and just deepened the slot and redrilled for the small hole. All goes together fine - and this set is on 8" snails - and are adjusted up on only 3rd or 4th click - but they are new shoes. So - many clicks left - and experience with the other set I removed is that shoe wear is almost negligible - so I rather think this lot will see me out!

Post by **alex_holden** » Tue Feb 26, 2008 4:17 pm

If you leave the big hole where it is the back of the cylinder will be 0.1" further from the drum than with the original cylinders and the front will be about 0.072" closer (which will probably make up for using the smaller 8" Minor adjusters). I'd be a bit concerned about what moving the pivot point does to the geometry.

Post by **bmcecosse** » Tue Feb 26, 2008 6:36 pm

I really don't think 0.1" is significant - and remember the shoe slides in the cylinder end and the adjuster slides too on the cylinder nose so the whole lot self centres on the drum. Believe me - it works.

Post by **alex_holden** » Thu Jul 10, 2008 5:01 pm

Just taking another look at this and I was surprised to discover that the original Wolseley cylinders have a bore of 0.795" compared to the Minor's 0.935". I'm sure I have previously read that they were the same!

Not that I'm complaining, as it will give a lighter pedal. This may be another advantage of changing to Minor cylinders.

Post by **bmcecosse** » Thu Jul 10, 2008 6:52 pm

You are right there Alex - my set now on the car with Minor cylinders do have lower pedal pressure - although the other W cylinder set was by no means excessive. I had just put it down to the new shoes on this set - and have not compared bore sizes.