minor disc brakes

[andrew.searston]

hi everyone
im considering changing my front drums and hubs to a GRUMPY Disc Brake Kit ( Marina based ) conversion, but dont want to add a servo if not needed.
what are peoples thought on this??

[chrisryder]

Many people find them perfectly acceptable without. Why not fit the discs without servo, and see for yourself?

You can always add one later if desired.

I've got a servo on my marina discs, and am very happy with them!

Alex'n'Anne on here has marina discs without servo, and is very happy with his!

Some people even have Wolseley 1500 drums. But there's no accounting for taste.

[bmcecosse]

Ahh - but they are SO much more affordable - and SO much easier to fit! And every bit as good in the braking dept -and def NO need for a servo.

[JOWETTJAVELIN]

You'll manage just fine without a servo - no need whatsoever, so much so that they were optional extras on most disc-braked cars decades ago.

[andrew.searston]

before i go and splash the cash, is their any need to modify or change the master cylinder?
and is the pedal any harder than with drums

[philthehill]

I have a Grumpys disc brake kit on the front of my Minor and have not fitted a servo or ever had a need to fit one. What I did do though was fit the master cylinder with the smaller internal cylinder diameter and which gives a reasonable increase in line preasure for the same pedal preasure. The pedal moves a bit further but it works well for me. Keep the standard Marina disc pads as they are softer and require less piston pressure to be effective. You need to remove the check valve in the master cylinder otherwise you will have a line pressure of approx 8lb/sq in which will keep the pads against the disc and ultimatly wear out both pads/disc; and possibly result in overheating of the brakes which may lead to brake failure! Master cylinder has to be removed from the chassis leg to remove the check valve though which gives a chance to check its overall seviceability.

[bmcecosse]

You DO need to modify the master cylinder for discs -probably best to buy a new one rather than hope the bore of your cylinder doesn't rip the new seals you will fit when doing the mod.

[andrew.searston]

ahh so i have to put new seals in the master cylinder. are they modified seals or just new ones, dont think the masters that old to be honest

[bmcecosse]

You need to remove the 'back pressure' seal otherwise known as the 'top hat' seal. It would seem wise to fit new seals - but if yours are in good condition, you could take a chance... Is the Grumpy kit the one with the alloy hubs - where the bearings 'have been known' to come loose........ ??

[andrew.searston]

not sure really heres a link http://morrisminorspares.co.uk/shop/pro ... 25f861bbb4

i dont want to touch the master if i dont have to, if i just leave it what will happen?

[philthehill]

The results of leaving the master cylinder as it is will be as I have stated above!
Grumpys conversion kits do not have an alloy hub. Either the Marina Hub modified or the ESM hub which is steel and does not have the top hat spacer/alternative bearing requirement.

[bmcecosse]

The back pressure holds the pads against the disc - much heat and wear - and v slow car....... What brakes do you have at the moment?

[andrew.searston]

thanks philthehill didnt see your comment. its got standard 7" drums at the moment its 1957

[LouiseM]

Is the Grumpy kit the one with the alloy hubs - where the bearings 'have been known' to come loose........ ??

There were some problems with bearings but that was years ago Roy. See ESM news item correcting inaccurate information which has been published on the web (half way down the page): http://morrisminorspares.co.uk/news.php ... 25f861bbb4

[philthehill]

The line pressure is required with the drum brakes to ensure that the cups of the cylinder seals are kept expanded and it also helps with bleeding the brakes.
You do not need the line pressure with discs brakes as they have a completly different type of caliper piston seal and you want the disc brake caliper pistons to retract into the caliper slightly so as to allow the pads clear the disc. Line pressure will not allow that to happen so then you get the wear and as BMC says "a very slow car".
Is the Grumpy's kit new? If not I would reccomend that you fit new seals into the calipers. They are available from ESM and so long as the pistons are free it is an easy job to do.
The problems with the alloy hub was with the Ford disc brake conversion and nothing to do with the Marina conversion.

[JOWETTJAVELIN]

It seems to me, that as you are considering changing to discs, and don't say anything about having a more powerful engine, that it would be aswell to give the drums a good service and keep them. They are good enough to lock wheels and send a passenger flat against the windscreen I can assure you!

The kit would always fetch a good price if you decide to keep the drums.

[bmcecosse]

If you have the 7" drums - just upgrade to 8" drums which are PLENTY for sane motoring with a standard car.. You will do this v inexpensively and the improvement is dramatic!

[IslipMinor]

the earlier master cylinder with the smaller internal cylinder diameter

A correction - it is the later master cylinder that had the smaller bore (13/16"). The earlier one was 7/8". It came in at the same time as the change to 8" front brakes and a reduction in the rear wheel cylinder bore from 7/8" down to 3/4". The changes reduced the pedal pressure required (larger front brakes + smaller m/c bore) and improved the brake balance that was too much biased to the rear with the earlier 7" front drum set-up.

And yes, you must remove the top-hat seal at the bottom of the master cylinder - I forgot when first fitting the discs 15 years ago and a local tyre fitter burnt his finger on the wheel nut when removing them for a wheel balance!

[philthehill]

Islip minor
Thank you for the correction; you are right that the smaller internal dia brake master cylinder was used post 1962.
The brake master cylinder fitted to my Minor does have the smaller internal diameter (13/16") as stated above and it works well without a servo. Wolseley 1500 brakes are fitted to the rear and the braking is well balanced and very effective and has worked well for me over many years of competitive use.