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CHANGING TO FRONT DISCs

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You don't NEED to change anything else but if you go to a 3/4" master then you will need less peddle force for the same braking force.
I have run 7/8" masters on disk brakes and it works fine, it is just hard to lock them up.
BillM
 
I have a similar issue with pedal force for the 7/8" clutch master in my BE. I changed to a ribcase/1275 and find the clutch pedal pressure to be unpleasantly high. Gerard's Garage/Sierra is sleeving a master for me to make the clutch cylinder 3/4". Supposed to reduce pedal force by 1/3.

If you have changed to a ribcase from smooth, and you go for disc brakes, you may want to have both cylinders sleeved, or begin working out.

I'll report back when I've replaced the master.

Michael
 
I have one of Gerrard's resleeved masters and it is really beautiful (and works very well too).
Definitely money well spent.
BillM
 
Do all rib case boxes use a 3/4 slave? Mine seems to have a

I have a :
mk1 frog that was used for rallying
ribbed box with what seem like 1500 equivalent ratios
previously drum brakes, converted now to discs
a dual 7/8 master cylinder.

If it is the case that the rib case boxes use a 3/4 I'll just convert to dual 3/4's rather than messing around resleeving (probably a dual girling setup like a sebring).


EDIT:::::
Infact the more I think about it. what it is that determines the clutch slave cylinder size?

Because off the top of my head I THINK it has:
Unknown clutch fork
Mk1 release bearing
After market 9 spring borg and beck cover plate
ribbed gear box
Aftermarket gears with ratios like the 1500 box.
 
You can bolt any of the A-series clutch slaves to any of the transmissions- the boltpattern is the same for all, so there is no way to say what size you have.
The easiest way to see what size you have is to take off the rubber cover and measure the bore of the cylinder.
 
Factory angled inlet port slave cylinder is 7/8" bore. Straight inlet port slave cylinder is 1" bore. The pressure plate pressures are quite different between engines. 948 had a 6-1/4" disc with 6 and 9 spring covers. 1098 stuff is like 7-1/2" with springs (don't remember the count) and 1275 pressure plate is a single diaphram spring with a 6-1/2" disc.

By mixing and matching master and slave sizes with the stock pedal assemblies, one can adjust the effort to operate the clutch. Pedal ratios are a different story and not as easy a change. If one can weld or obtain welding services, increasing the pedal length reduces the effort.
 
A smaller slave leads to higher peddle force. Is your required peddle force to low?
Bill
 
9 spring is normal for a Sprite/Midget 948 engine. 6 spring is Morris Minor 948
BillM
 
BillM, I believe that you are mistaken regarding spridget 948 clutches, the standard pattern was six springs according to various sources (AH Spares, and the workshop manual). A common way of upgrading the Mk1 clutch in the UK was to use a Triumph Spitfire cover plate which did have 9 springs although I believe they are now as rare as hens teeth!
Graham.
 
You might be right but over here the 6 spring plate was considered undesirable and the "standard" (or at least it is what we got) was the 9-spring.
Bill
 
Talonaer said:
Do all rib case boxes use a 3/4 slave?
Click to expand...

3/4" slave cylinders were never used. All early cars used 7/8" until the introduction of the 1275, which uses a 1" slave. 1500's also use a 1" slave. If you go to a 3/4" slave, you are going to increase pedal force and the clutch is likely to become more "switch-like".
 
So I have an original, 3/4", dual M/C from a disk brake car on my Bugeye. with a smooth case tranny and early slave cylinder. Is this correct? My clutch always seemed to work fine. I know the brake bore changed with the disks, but is the clutch side the same? Would a ribcase slave cylinder provide some sort of improvement?
thanks
Mark
 
The ribcase slave (1.0") will give you a softer clutch peddle than the smoothcase slave (7/8"). If the peddle is too hard to push then it will help but I doubt that it is too hard to push. Also of you change the slave you will have to add the rubber whip connector hose which will not be so fun to add.
BillM
 
Billm said:
The ribcase slave (1.0") will give you a softer clutch peddle than the smoothcase slave (7/8"). If the peddle is too hard to push then it will help but I doubt that it is too hard to push. Also of you change the slave you will have to add the rubber whip connector hose which will not be so fun to add.
BillM
Click to expand...
Thats true about the rubber hose, I had forgotten that. And you're right...The clutch pedal isn't hard to push.
thanks
 
As I mentioned above, the introduction of the ribcase with the 1098 continued to use the 7/8" slave until the 1275 was introduced. Both bores of the 3/4" master cylinder from an early disc brake car are 3/4" and are a correct match with the 7/8" slave.
 
Gerard said:
As I mentioned above, the introduction of the ribcase with the 1098 continued to use the 7/8" slave until the 1275 was introduced. Both bores of the 3/4" master cylinder from an early disc brake car are 3/4" and are a correct match with the 7/8" slave.
Click to expand...
Thanks Gerard :smile:
 
How much real difference in stopping distance is obtained by coverting front drums to front discs?

Fred
 
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