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MG Midget and Sprite Technical - Brake improvements

Gents

In order of merit, and within the bounds of reasonable cost, what are the best improvements to make to the braking system?

Mintex pads seem to be favourable, but how truly effective are things like larger calipers and discs, can Metro/or similar bits be used as a simple bolt-on perhaps? Can anything be done to the existing system to improve matters? - apart from a good overhaul and bleed through....

Now the Metro head is on and the engine fettled reasonably well, I find I need to stop a little better occasionally...and taking my foot off the gas is not an option....

Obliged as ever

Mark
Mark O

in order:
replace fluid
new pads (& discs if necessary)
new shoes (and drums if necessary)
while fitting pads & shoes do check that the pistons in calipers and slaves are all working OK.
Peter May does various upgrade kits, see
http://www.petermayengineering.com/catalogue3.htm#catalogue3

or if you can machine up your own adapter brackets you could DIY using any handy calipers that fit inside the wheel (do the maths on piston area and F/R balance first).
David Smith

And I'd put fresh/decent tyres just after replace fluid.

Wont matter how big the discs and pads are if they lock up a pair of 15 year old, hard as rock lumps of black concrete when you so much as breathe on the pedal.
Dean Smith ('73 RWA)

I've competed in various race series, with varying amounts of power, with what was essentially a standard braking system - other than pads and fluid.

I would also recommend good quality discs, such as Brembo.
Dave O'Neill 2

Tyres are fine, front pads new Mintex. Interesting comment Dave O....It seems then a good fettle of the standard stuff (discs apart) may be more than adequate and that any upgrades are superfluous. For sure, I think it could do with a bleed at least.....
Mark O

just a question on this subjet do better flexible pipes make a difference to the brakes.
mark 1500 on the road Preston Lancs

Correct adjustment must be first priority on the list for affordable brake improvement. And with non-automatic adjustment on the rears, they do go "off" pretty quickly. But correctly adjusted I find the brakes are pretty good for normal "spirited" driving around twisty, hilly Lake District roads. I have had brake fade in the past but a switch to Greenstuff pads cured that. I have some Mitex ones to go on next, when I have finished wearing out the current set.
Guy W

I went:

adjustment (always good)
braided hoses (good)
greenstuff pads (not so good)
brake fade on the road, not tried on track
JLH big brake kit (very very good)

next is rear brakes as they gave up on track. I'm pretty much certain the original discs and greenstuff pads would have totally given up on the track, but that's with 120bhp, a heavy right foot, and a healthy dose of lunacy.
Rob Armstrong

I'd say in all but the most modified cases standard setup in good condition works well. Don't go for unnamed or budget pads! Mintex 1144 are very good with a wide operating range.

Get some ATE Blue fluid from Euro car parts and you'll know when your old fluid has been purged. It also has a higher boiling point than normal, but not as hygroscopic as true racing fluid.

They also do the same fluid in Amber-

http://www.eurocarparts.com/ecp/p/car-accessories/engine-oils-and-car-fluids/auxiliary-fluids/brake-fluid/?524770042&0&
Dan Cusworth

After a very spirited 25 minute blast round Zandvoort last September, my Greenstuff started to break up in the centre of the pad. I wondered if it was down to having grooved discs. I bought some more Greenstuff, but may get some Mintex ones next year.

On the subject of rears, the Wolseley 1500 set up is considered a worthwhile mod, if you can find them.(Hen's teeth).
Bernie Higginson

Rob A,

I'm looking into reducing effort at rear by changing the rear cylinder bore size. With all your "fancy book learnin" can you tell me :
A. What is the std midget caliper CSA
B. What is the JLH CSA

I think the rears are now working a little too hard. I've been pointed towards a bias valve, but don't trust myself to work it proproperly!
Dan Cusworth

Dan, that's interesting about Eurocarparts doing different coloured brake fluid so one can see when the old fluid is purged. I have suggested that as an idea for many years, posting the idea on this BBS on several occasions going back to around 1999. Good to see that someone has finally caught up!
Guy W

Brembo disks,KAD 4 pots, green stuff, minifin rears, stops quite well.

d brenchley

Dan

The Midget 1500 rear wheel cylinders will reduce braking at the back. There is also a 5/8" cylinder for an early Mini, which is what I was using.

http://www.minispares.com/product/Classic/Brakes/Hydraulics/Wheel_Cylinders/GWC1101
Dave O'Neill 2

Braided lines as well

d brenchley

i went straight for KAD 4 pots, and Goodridge hoses, new master cylinder, regular fluid.
Seems good enough so far, running a very mildly tuned engine though
P Bentley

Chaps

Many thanks - food for thought indeed. I too like the idea of blue brake fluid and may well invest. To add, I have braided front lines and adjusted shoes at rear - it did indeed make a difference - but agreed new shoes may well improve further. Pretty sure I have some discs hanging around too....

And are those KAD 4 pots manufactured from unobtanium -given the price? Anything about that is little more cost effective as a bolt on improvement?
Mark O

I think ??? The princes america calipers are a direct fit to the midget and are 4 pot and resonable priced

DB4 caliper ???

Prop
Prop

Nope ... its SD1 calipers, and I think its austin princess, and I may have that confused with MGB and not midget

Im late for work, and cant research it further but its a good start if you want to look into it

Also look in the arcives bill young years ago did a honda brake kit to midget that was interesting

Prop
Prop

Controversial but in addition to the above I've added a servo.
Doesn't increase the braking performance as such and it's a Marmite option; some swear by it others swear it's totally unnecessary.
I like the extra confidence it gives especially if sudden braking is required.
Jeremy Tickle

For info, based on my calcs:

numbers are piston area in square mm.

1972 original
F R Ratio
4035.67 566.77 7.12

1500 original
F R Ratio
4035.67 480.81 8.39


CURRENT
F R Ratio
3629.84 566.77 6.40

1500 rears
F R Ratio
3629.84 480.81 7.55

so fitting the 1500 rear cylinders to my current setup will improve the braking by putting more on the front, resulting in less brake fade and fire smoke and brimstone from the rears. That's the theory anyway.
Rob Armstrong

Mark
For something a little more cost effective than the KAD 4 pot calipers, you can fit Metro 4 pot calipers, the non vented variety can be fitted to standard discs or you can go the whole hog and fit the vented discs from the Metro also. The calipers require slotting of the mounting holes then they fit very well and have almost a period look about them as they are the style as the original calipers.

Somebody please correct me if I'm wrong but I believe the KAD calipers actually use the Metro brake pads, so the braking result should be the same, but with a weight penalty of course. I can let you know the weights of both types of Metro calipers if you want.

I have fitted both types with excellent results. I can post photos of both.

The vented Metro calipers are easy to get hold of, the non vented a little harder but they are around if you are a little more patient.

Ian
Ian Webb '73 GAN5

I can vouch for the Metro 4-pots. Our 1380 Minor was fitted with a Midget disc brake conversion, using a 'J' bracket caliper mount, 17 years ago and initially used Metro 4-pot calipers, standard Midget solid discs and Mintex 1144 pads.

The rears are standard 7" drums with 'competition' Mintex linings and an adjustable pressure limiting valve (modified Mini) to prevent rear locking.

On track days there was very very occasional fade, so it now has Metro vented discs and Mintex 1155 pads - no fade ever!

See attached picture below:

The 1155's give excellent 'feel' for normal road use and just work in all conditions.

With the lighter Midget, I would think 1144's would be fine for virtually any conditions.

It also has a servo, which means 'modern' type pedal pressures, and no surprises when switching from the day-to-day car to the Minor.


Richard Wale

I'm with Dean, the best way of improving emergency braking is to get good tyres. Standard brakes are well u to a single emergency stop, the limiting factor is the grip of the tyres.

Competition drivig is quite different, the heat build-up from repeated application of the brakes is much more substantial and so brake upgrades to deal with it are worthwhile.

Spirited road driving along twisty roads is somewhere in between, fresh fluid and uprated linings would be a minimum.
Paul Walbran

Another vote for Mintex - plus one for paying attention to your adjustments, including the handbrake linkages and cable.

I'm currently using Mintex 1144s bought from Peter May following a useful discussion of the options. For fast road and hillclimbing the 1155s and Greenstuff drew a shake of the revered head while the 1144s got the nod! They are much better than the unknown pads that were fitted when I bought the Sprite.

With standard front springs and shock absorbers my Sprite would dive under heavy braking, causing rear wheels to lock and skid - annoying on the track but worrying on the road when some nerk pulls out of a side road in front of you or the local chickens play chicken! Changing to 400lb springs has almost eliminated the rear-end lock-ups and the braking is much better. The ride is harsher, but not uncomfortably so.

I've heard tales of Greenstuff leaving a residue in/on disks that presents a problem if they are replaced by other types of pad with some saying that if you change from Greenstuff you will need to change the disk at the same time. I have also heard that Greenstuff pads cause more wear on the disk than other makes. I have no personal experience of these problems, nor have I met anyone else who has, so they may just be urban myths!

C
Colin Mee

Mine is all standard apart from braided hoses and Mintex 1144's. Very good on the track and road. Never get any fade and the initial bite from cold is excellent.
I used to use Greenstuff but they went off after a few thousand miles. The change to new Brembo discs and Mintex pads was like driving a different car brake wise. I was locking up everywhere to start with!

I'm thinking of going for the KAD calipers but really more for the weight reduction and bling than any expectation of better brakes. Let's face it, if you don't get fade and you can lock the wheels up then you can't get any better than that!
john payne

I've always felt that there is another aspect to brakes: how easy they are to modulate.
Trevor Jessie

I didn't like my Greenstuff much. Worked a lot better after I cooked them on a back road in Northumberland accidentally, but always gave a bit of a dead feel to the pedal. The new 260mm brakes really are a lot better, in a totally different league.

Castle Combe was OK but Croft on a hot day it was really too much for the rear ones, smoke came out and everything.
Rob Armstrong

I had to adjust the brake balance after changing from front drums to disks. (brembo , 1144, C & C parts calipers and cylinders) The rear locked up under dry conditions and hard braking. Harder rear brake linings did not help enough. So I changed to the smallest rear cylinders I could get.

Flip Brühl

Front:rear balance is essential to check and if necessary fix when doing an upgrade. If one end locks up well before the other do to a mismatch you end up with worse braking, not better, no matter how flash the brakes are.
Paul Walbran

Hi Paul
Yes I agree
I've seen lots of brake (improvements) make cars into monsters under heavy braking
Fresh fluid, good pads and always remember use that right hand pedal to go fast middle pedal to go slow
ha ha ha
willy
William Revit

Based on my relatively limited experience, I agree with Paul; getting the balance right is vital. However, the braking performance is not just down to the size and types of the components in the braking system. An understanding of how the whole chassis is performing is also important. In trying to achieve a certain change in performance, what might seem, at first, to be the obvious change might be better or more simply achieved by other means that may also enhance other aspects such as road-holding.

As I have already posted, I was experiencing serious rear end lock-ups which were due to the weight transference under heavy braking. Reducing the front-end dive by fitting stiffer front springs has kept more weight over the rear end resulting in better braking and reduced tendancy to break away. Apart from making sure that the rear brakes are clean and properly adjusted they have not been altered at all.
Colin Mee

Its is possible to create a big disc and more efficient callipers, which enhances the original rear brakes. No need for brake bias valves, uprated suspension or re adjusting the rears. So long as the rears are efficiently working we have found that drivers of std road cars, fast road cars and race cars in almost all catagories of Midget racing inc mod sports, are all finding better stopping power without fade, but most importantly ,progressive braking.
We incorporate a wide range of pad material from EBC fast road pads (standard issue) through to Mintex and Freodo fast road and race pads.
J L HEAP

Yes, I agree that it is possible and that if you get the right combination it works well when you are pushing the car hard (as I like to).

However, for most cars it won't improve a solitary emergency stop from legal road speeds - in such a case the brakes have more power than the tyres can put down. (As indicated if you can lock the wheels).

And if the conbination isn't right, it's worse than standard.

Professionals such as Jonathon have thought this through and come up with a balanced package. It's ad-hoc mods that can be a problem.

In NZ (& Aus too Willy?) if brakes are modified they have to go through a performance test. The key point of the test is that they can meet a standard of repeated severe braking not just at a certain rate, but without locking up at either end.

For the record, we have seriously uprated brakes on our K Midget so I'm not against upgrades in principle. But the only time it presents an advantage against our other Midgets with no more than std brakes and uprated linings is on the track. My rally B also has discs fitted to the back, mainly because I am old and lazy and didn't like crawling under the car to adjust the drums every special stage. BTW the B passed the test with flying colours, an average of 0.98g on worn out rally tyres.

So yes, it is possible to set them up right. If you want modded brakes, get them sorted by someone who knows what they are doing.
Paul Walbran

This thread was discussed between 22/09/2015 and 02/10/2015

MG Midget and Sprite Technical index

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