I'm planning on fitting a set of Cooper S 7.5" disc brakes to the Deluxe.

I have the booster, and a tandem master cylinder, not to mention the whole shebang for the rear as well.

My question is this. Should I try to squeeze the booster in under the bonnet or not? Given that a booster is effectively only there to reduce pedal pressure, will I really need it or will my pedal be like standing on a brick, with about the same effect in retardation?

I'm keen to hear the views of those already experienced in the arcane mysteries of these round discy thingies. Anyone with highly developed muscles in their right legs from appplying un-boosted discs brakes?

I should mention that this car is already fitted with the standard master cylinder (top condition), spacer drums and all good cylinders and shoes. It stops better than the average Mini, and I've never really had a "moment" under brakes. It hasn't even faded away at turn 1 on Phillip Island, and yes, I HAVE arrived there faster than I thought was prudent.

That being said, since I'm developing close to original Cooper S power from the 1098 screamer, it's probably wise to upgrade now that I have the chance.

Oh, and don't suggest that I keep the drums and give away the disc setup to someone more deserving (you). It's just not gunna happen!

Cheers, Pottsy

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Smile Up at The Trucks!

I don't have a booster in the turbo'd mini and it stops pretty easily.

The only issue is the feeling of no brakes after getting out of a modern car. You need to push pretty well and for a daily it might be a better thing with a booster you'd get pretty strong legs otherwise

Daniel

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Mafs waz not my strong subgeckt at skkol

Pottsy,
My wife's `67 car has a Clubby tandem MC, S front discs and S rear wheel cyls.
I have a booster for it but have never fitted it- with Blackstuff pads it stops fine.
My car has single MC, and the same brakes but Greenstuffs, I've never felt the need to boost it either.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Mr Potts...people have also fitted boosters under guards and rally cars had them under the parcel shelf in the cabin.

When you say the whole shebang for the rear....I take that to mean ex-Cooper S backing plates, spacer drums, shoes, the smaller rear wheel cylinders and the right proportioning valve (all the same anyway??).

Can I suggest you find some friend with boosted disks....and ask if you can drive it with the booster disabled obviously, pick a road thats safe to try this experiment

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"Show me the Mini!"

Correct me if I'm wrong but to effectively dissable the booster where fitted you'd have to remove the brake line to the booster and instead plumb the mc directly to the line splitter on the firewall and then re-bleed the brakes. If you instead just remove the vacum feed to the booster without unplumbing it you'll just get spongy brakes.

as far as i know 1275 LS's didnt come with a booster and they wernt too bad.

I have had discs on all but one of my Minis.

NONE of them have had a brake booster, and i would not be using one if i had the choice.

Its not so much a heavy pedal, more it has no 'feel', it just feels different than what you may be used to.

I wouldn't worry too much about it .

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Cheap, Fast, Reliable. Choose two.

the sunshine has no booster and 7.5inch disks. i have never ever thought it was too heavy. they are perfectly fine. not a worry.

i have unassisted 7.5" discs on my clubby, and it stops fine with a bit of effort.. its certainly a lot more effort than a modern car and more than a mini with drum brakes, but its okay really, you get used to it.

but the cooper S had a booster, so i'm gonna fit one because i doubt they fitted it for pedal feel alone.

i dont know if the LS had a booster but it had 8.4" discs so that might make a difference.

I love them.

I have done without, and with. And with IMO, with is so much better.

IMO it feels right, and probably exactly the way it's meant to feel.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

Hmmm. The boost free votes out-number the boosters.

I should mention that I also have a full set of Goodridge stainless steel braided hoses as well, so the feel should be fine.

My main concern is whether the pedal pressure is going to be excessive in comparison to the drum setup. It seems that this won't be a huge problem, and I can plumb it in such a way as to allow adding of the booster later if I feel I need it. (The plan is to plumb the booster with flexible hoses anyway, to allow it to be moved for access)

As far as pedal lightness goes, bear in mind that I also have a Citroen DS which has a small rubber mushroom for a brake pedal. If you sneeze while braking with this you'll send unattached items through the windscreen!! Very sensitive, very light, but with marvellous feel.

Thanks for the replies so far, keep the feedback coming, chaps (and chappettes)

Pottsy

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Smile Up at The Trucks!

My experiance with 7.5 disc fitting to cars that had twin leading shoe brakes is to use the cooper s limit valve or an 850 one that was used with single leading shoe brakes and 5/8 rear cylinders as this tends to give the correct brake (balence) as the spring inside is a different length.By allso using .7 bore master cyl, 5/8 cyl on rear soft pads on front i have found much lower pedel pressure needed not really needing a booster.

Why do you reckon the braided hoses would make a difference to the feel?

Anyway consider that for many people the choice whether to fit a booster is as much a financial one as it is practical. VH44 are approx $250 exchange for a reco. unit so many just don't bother. If you do end up fitting one, better make sure its in tip top condition (don't just bang one one from the wreckers or off the shelf w/o servicing it) as as said if you loose vacum in the booster you loose much of the brakes.

On and "excessive" pedal pressure is a relative term. I'm 190cm and just under 100kg and have no probs. With modern boosted brakes its relatively easy to lock the wheels even in the centre of the pedal's travel, whereas with unboosted mini disks to really stop you have to stomp on the pedal when its almost all the way down and feels like there's no braking left then you realise there;s still plenty of brakes left.

that ain't true - it goes back to as if you didn't have the booster.... my booster split the diaphragm and I left it on for ages without it doing anything, when I took it off it felt the same (and continues to be so)

heya Pottsy, Simon from Wodonga here...

I reckon disks with no booster have about the same pedal feel as well set up and adjusted drums (as yours would be) - they just bite better

and Pottsy, please make sure you put 5/8" rear wheel cylinders in the back, as the larger cylinders apply more pressure to the rear brakes and will lock them very easily compared to the disks at the front - you will remember an occurrence about 3 years ago that might've been avoided had they been installed instead of 3/4" ones as per drum brakes

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did I tell you that I won a trophy?

Yep as Simon says- emergency braking at high speed with S discs and 3/4" rear wheel cylinders can be scary. I found this out in the wife's car at 110KMH on the F3. "Plenty sideways" as Timo Makinen used to say.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.