Rear brakes

Post by **bmcecosse** » Thu Mar 12, 2009 8:08 pm

Does anyone have a rear brake backplate handy ? I need to know the size of the slot in the backplate for the rear wheel cylinder - if anyone can help would be much appreciated.

Post by **tortron** » Sat Mar 14, 2009 10:45 am

I can measure you one in the morning if noone beats me

Post by **bmcecosse** » Sat Mar 14, 2009 10:49 am

That would be great! To save me stripping out my rear brakes - but only do it if you have a backplate handy. Thanks in anticipation !
As an 'extra' to this query - can anyone confirm the normal bore size of rear wheel cylinders?

Post by **tortron** » Sat Mar 14, 2009 11:24 am

insomnia has set in (its 12.30am)

anyway im measuring a hair under 2cm by 6cm

Post by **bmcecosse** » Sat Mar 14, 2009 2:15 pm

Thanks - so 0.787 by 2.362. I'm comparing the 'slot' in a Wolseley rear backplate ( obviously with the intent to fit to my Minor !) which is a two step afair, the narrower part being only 0.700" . I didn't want to open out the backplate until I got the Minor size - in case the cylinders I have are wider than normal. They were donated by an ex TR3 owner - but are in excellent condition. Thanks again for yur help!
Just need confirmation now of what rear cylinder bore size is normal on a Minor ? These spare ones I have are 3/4" bore.

Post by **IslipMinor** » Sat Mar 14, 2009 6:32 pm

Roy,

The rear cylinder bore is 7/8" for the 948 with 7" front brakes and the 7/8" bore master cylinder, and 3/4" with the 1098 8" front brakes and 13/16" bore master cylinder.

Depending on which wheel cylinders you have fitted at the front (the original Wolesley 0.8" or Minor 15/16"), the calculated best balance combinations on a Minor are:

Wolesley 8" front & 0.8" cylinders, with Minor 7" rear & 3/4" cylinders. Using the Minor 7" rear & 7/8" will overbrake the rear severely, and using the Wolesley 8" rear & 3/4" will overbrake the rear a bit too much. The Wolesley 1500 had a higher % weight at the rear than the Minor, so the orginal design was pretty good.

Wolesley 8" front & 15/16" cylinders, with Minor 7" rear & 7/8" cylinders. Using the Minor 7" rear & 3/4" will underbrake the rear very severely, and using the Wolesley 8" rear & 3/4" will underbrake the rear a bit, but much better than using the Minor 7" with the 3/4" cylinders.

All these results are for a 'normally' loaded car with 2 people. Full load is obviously different and ideally what is required is a load compensation valve - anyone fitted one to a Minor single line system?

Post by **bmcecosse** » Sat Mar 14, 2009 10:11 pm

Thanks Richard - my feelings exactly. It's severely 'underbraked' at the rear at the moment (or overbraked at the front the pedal is very light and easily locks up the fronts !) and so having finally managed to acquire some W rear backplates, I'm now putting together the 8" rear brakes. Way back in the past - my Rally Minor had a full set of W brakes - 'stolen' from my brother's abandoned W 1500 - and they were well balanced and very powerful with no fade I can remember - but then the art of making a Minor go fast is to stay off the brakes! My problems have arisen by fitting Minor cylinders to my current set of W front brakes, and hopefully the W rears will balance things out rather better - although I suspect the pedal will still be very light. All else failing - I have a spare set of W 9" fronts with standard 0.8 cylinders all overhauled and ready to fit, and a spare set of W front cylinders to re-fit to the backplates once I convert them back to normal W spec of course! I only fitted the Minor cylinders because it was said to be a good conversion - so far - it's NOT!

Post by **alex_holden** » Sun Mar 15, 2009 8:25 am

Does anyone know where I could buy some 7/8" Minor rear cylinders?