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MG Midget and Sprite Technical - brake upgrade recommendations

I am contemplating a brake upgrade to my 1968 Sprite. my goal is to maintain a safe brake bias but to end up with modern effective stopping. That will mean updates to both axles, I am sure. The car is a street car not a track car. It all has to fit in the current panasprort wheels. Currently the brakes are stock configuration but up to snuff. Any thoughts and approximate cost appreciated. Hoping someone else has invented the wheel!
bew wright

Hi Bew

There are a number of options including use of some MGB components as well as use of some custom bits. The important thing is having the rest of the car in good condition and working properly, including tyres and suspension, brake lines, hoses and your master cylinder and shock absorbers (dampers), the body structure not rusty, and then choosing an upgrade that suits your use, driving style and all the bits harmoniously working together not unbalance the car. Also your budget.

You may find getting the standard car braking system in factory fresh condition, properly serviced and set up carefully with good tyres might be a revelation in how good it can be and also serves as good baseline for any modifications if needed. What use are you intending - street, racing (what type and duration)? Plus other modifications to power or weight that could influence handling as well as stopping power needed? You may just want a standard system that is working properly, perhaps with some different friction material and a servo (the latter if you want a more modern feel). Do not discount using rear drum brakes.

There is an excellent book by Daniel Stapleton that covers the subject well that is worth reading and will help you choose what way to go with a possible upgrade' and will also cost way less than a set of uprated pads or rear discs: https://www.amazon.com/midget-Austin-Healey-Sprite-Performance-Manual-dp-178711001X/dp/178711001X/ref=dp_ob_title_bk

A idea of some of the upgrade parts available, noting need to have car in good condition and a carefully combined set of modifications that work together: https://www.petermayengineering.com/product-category/brakes/


Cheers
Mike
M Wood

Mike has pretty much covered it! :-)

It is important to remember that any braking effort greater than that required to lock the wheels is wasted effort.

Or in less complicated terms, upgrading the brakes won't do squat if your tyres can't transfer that braking force to the road. So my first question would be, are your tyres good?

Generally speaking, if the standard system is in good order and you are running standard size tyres you should be able to lock the wheels if you push hard enough!

If you want a little more "bite" braided flexi hoses and a pad upgrade would probably suffice. A lot of folk recommend Mintex 1144 pads for Spridgets.

But they will always feel different to a modern car due to the lack of servo assistance. They need a good shove!

Cheers,
Malc.
Malcolm

With such a light car the standard brakes in good order should be more than adequate. As others have said, the tyres stop the car, the brakes just stop the wheels. But driving the Spridget after using a modern over-servoed car's brakes will make them feel unresponsive. Either you have to teach yourself to push harder on the pedal, or you could fit a servo. Not that a servo will improve the efficiency of the brakes, but you will need less effort to get the same result.
Mike Howlett

Brake pedal feel has a lot to do with how well the rear brakes are adjusted, these also affect the handbrake. Regular servicing, as per the Driver's Handbook, such as adjustment and changing the brake fluid along with components in good condition should keep the braking good - but different to modern cars.

If you much more regularly drive a modern car and your Sprite not enough then the braking will more different as you're not used to it.

You don't need to consider 'upgrades' unless you're dissatisfied with the whole standard braking system (including tyres) is in full good working condition.

Tyres are often overlooked many classic car owners have tyres that have loads of tread but are hard through lack of use and/or age so don't brake as well as could - and effect steering, handling, road holding and ride noise and comfort.

The production age of the tyre is in a four digit code on the sidewall (three digits is before the year 2000, 20 years ago). - http://www.tirebuyer.com/education/how-to-determine-the-age-of-your-tires

Owners also seem to fit tyres that are much more suited to small (heavier) modern city cars rather than a lightweight sports cars.

If you're Sprite isn't doing average or more modern car mileage then it makes more sense to buy tyres that offer more grip and handling, and braking, rather than those that last for long mileages.

20 + years ago I had a 1969 Sprite on 3.5" steel wheels, 145/80r13 tyres and completely standard braking and it was fine and I used the car as a daily, for commuting to work, holidays, tours and club events as well as using a moderns and other classics as well during its ownership.

Once when I went from driving the Sprite all week to driving a new MX-5 and I really noticed the difference so got into the habit of gently testing the feel of the brakes shortly after pulling off. A good idea anyway to test the brakes before you need them and when driving a car you don't know - or swapping from one car to another.






Nigel Atkins

I would concur that the standard disc setup is more than adequate for the road. Even the drums will easily lock the wheels. I have video of my Frogeye on Minifin drums locking the fronts on dry track at Castle Combe. It's on standard discs now, and with ceramic pads the main improvement is in pedal pressure. No need for expensive pad material IMHO.

Les
L B Rose

Standard brakes
Good disks (high grey cast iron brembo’s from magic midget)
Mintex 1144 pads
Normal mintex brake shoes at the read.

Perfect for road driving and trackdays.
Only possible slight down side it having to use some muscle, but then I don’t like the feel of boosters
O K

thanks for all the input. To answer a common comment/question, the car is in excellent condition overall, used for spirited street driving, very well maintained as well as rear brakes adjusted, fluid changed less than a year ago, tires are about 6 years old but with maybe 3k miles but never lock up on pavement. The peddle pressure required to stop quick is significant but I should just do a test and see if even more pressure in a panic stop would eventually haul it down. Not sure what pads are on the front though. They came with a kit of new stock type rotors from Moss so probably not the super best.
Maybe the only problem is a need to encourage my 70 yr old legs to jamb down harder?
bew wright

I had to do an emergency stop last year, standard disc and drum brake setup with braided hoses and in good condition. Tyres were Uniroyal Rainexperts.
I managed to lock the rears up. As others have said the standard brakes are very good, and it’s your suspension and tyres that are the limiting factor.
Chris Madge

Bew,
you might be correct that you just need to push the pedal more but perhaps your 6 year old tyres could be nearer the lower end of the scale or 'ditchfinders' as 3k-miles a year should, depending on climatic conditions (summer tyres loose efficiency at 10C and below) and car storage be enough to keep them reasonable.

Even cheaper rotors (brake discs) generally seem to work if not last as long as they could but pads or shoes can be contaminated or 'hard' or otherwise from storage(?) or inappropriate use or bedding-in. You shouldn't need to jamb the brakes, firm pressure for fast stopping yes.

We obviously can't comment on the pavement (road surface you have, other than over here you'd run the
the pedestrian down) but the tyres that are sold in your neck of the woods should be appropriate and suitable for emergency stops obviously.

Locking up, skidding, is the car out of control and moving rather than stopping but it takes an expert not to do it in an emergency stop situation.

Generally you will not stop a Spridget as quickly (shorter distance) as a modern car in good condition, those that are, but it should be adequate,or more, in most circumstances so you do need to find out why yours might not be adequate.

Have you driven other Spridgets that are in good mechanical order (regardless of what they look like or how shiny) and have you had the owners of such Spridgets test your brakes to se how much of a concern this is?

Braking is always number one priority, always, generally a car that isn't moving is usually quite safe but one that goes but doesn't stop well isn't a good thing.

Just thought, the footwear you use can make a big difference to brake feel, try braking barefooted and see, well actually don't.

And another thought, just as atest, when safe to do so, try braking with your left foot, as your left leg is used to the pressure of pushing the clutch (unless your clutch is very soft) and generally you have less perception about the force you are applying with it. If hard left foot braking doesn't get your nose closer to the windscreen (please always wear your seatbelt even in the land of the free) then you really know something needs sorting on your braking (tyres are part of braking remember).

Let us know how you get on, good luck.
Nigel Atkins

Another thought you could do what that guy does on TV, where really safe to do so, absolutely jump on the brake pedal to lock up to stop. Then get out and look at the tire (tyre) skid marks and see how they match or mismatch and how straight or not they are.

That's me out of ideas and now with a headache due to effort of thinking and remembering.
Nigel Atkins

Best brakes: good eyesight, concentration and anticipation.
GuyW

I'm sure that a standard system that is set up and maintained properly is, as Les said, more than adequate for the road.

However, to Onno's list, I would add tyres that are suited to the Spridget.

To maximise fuel economy and minimise pollution, combined with the fact that even the smallest modern car is far heavier that a Spridget, I believe that manufacturers are making tyres with much harder compounds. A FIAT 500 is 900 - 100 Kg, a Mini is 1200 - 1400 Kg, Spridget is around 750Kg. The braking efficiency of the heavier modern might be more than adequate with these hard tyres, but the Spridget does not have the weight to get maximum benefit.

My experience of different tyres on my Sprite only includes Toyo 350s, which are like concrete, and Yokohama Blue Earth AE01s. An emergency stop on the Toyos just turns immediately into a four wheel skid. The softer Yokos will still lock up if pushed, but give much better braking in the dry and in the wet.

I would take issue with Nigel's brake testing exercise, as stamping on the brakes is bound to promote a skid, and once the wheels are locked they are having no influence over the direction of travel. Increasing pressure progressively causes the car's weight to transfer onto the front and give much better grip while allowing the wheels to rotate and steer and still give a good idea of whether the brakes are balanced so that it brakes in a straight line.

Colin
C Mee

Colin is completely right with his comment on tyres.
Get the softest compound (lowerst wear rating) you can get.
While you will be able to lock up the modern tyres more easily (heavier cars mean harder compound and less grip with a lighter car) they won’t give you the shortest stopping distance.

I’ve mostly run Vredestein summer tyres or 4 season tyres and am happy with them, but recently their side wall design got way to modern for me.
So for the now almost finished MGA restoration I’ve bought a new set of blockley radials, they are made specifically for old cars.
I’ve had a lot of good experiences with their crossply tyres on pre wars and decided to give their radials a go
O K

Colin,
makes a good point about my poor choice of word (again) although I did put jump rather than stamp.

A more progressive quick hard push would be better, but I was hoping Bew might have seen the TV show I mean (and it's title escapes me again) for the method used.

Quite right about the transfer of weight when braking but left right, diagonal, front rear, differences in skid marks can be seen.

Whilst the locked wheel has no influence at that point in direction change of travel the delay in the locking, subject to tyres all being about the same in type, traction, wear profile and correct pressures may well be indicated by the start of the marking and how off (is it?) axis of travel from lining of steering.

I didn't say it was a great idea (more one to be, as you rightly have, rejected really) but if Bew is right that the wheels never lock up he's going to need a long wide road to try it on. They do things different in the USA - and I'm sure Prop would have approved, always a god benchmark.

Something's not right about not locking up if enough effort is put in, even poor tyres ought to be able to be provoked into it to some extent eventually.
Nigel Atkins

Nigel - apologies for the mis-quote - short term memory issues on my part, trying to remember what I had read 2 minutes previously!

Something in your reply stirred a dusty long term memory from my Open University course where, if I recall the term correctly, they referred to Limiting Friction, that is, the point immediately before that at which grip is lost.

Maximum braking effect (force?), and, indeed cornering, is to be had just before grip is lost.

That's where the driver's skill comes into play, being able to judge just how much pressure to apply and where to apply it without breaking adhesion while carrying maximum speed through the corner, and, far from being able to repeat it exactly each time, the real skill is being able to adapt to the prevailing conditions which can be changing continually.

ABS takes all the fun out of it, that's why I enjoy driving the Sprite to its and my limit (and occasionally exceeding it!) on the track.
C Mee

That's one purpose of cadence braking, though generally used on gravel surfaces to induce a bit of intentional oversteer.
GuyW

Colin,
I was joking, whichever was a poor choice or word.

If Bew has weak legs perhaps he's cadence braking without realizing it hence no lock-up.
Nigel Atkins

Bew,

If like me you also drive over servo'd modern cars the change can take a while to get the feel back when changing cars or if the pedal pressure is too much then the addition of a servo can help.

Yes I know it is really frowned on by most on this board and considered unnecessary but I find a servo useful, especially with modern driving when people seem to think your safe distances are only there so they can cut in at the very last moment and anchor their eurobox to a stop !

A servo will not improve your stopping power at all - just the pedal pressure required - a question of choice.

'In the day' when a Midget was my only daily driver I didn't consider it necessary either - unfortunately I'm a lot older now !
richard b

In a standard Spridget (disks front, drums rear) the rear passenger side wheel locks first, if I drive alone. That is not what I want so I bought a brake bias valve (adjustable): it works perfect; now the front brakes lock first.

Flip
Flip Brühl

We drive the cars faster now than when they were new. I have a 5 speed Rivergate conversion installed and go the 75 MPH speed limit to avoid getting trampled by semi-trailers. Traffic moves at 80 MPH+ with impunity and driving slower is dangerous. When I got the car new in 1971, 55 and 65 MPH were common limits with 70 MPH allowed on less frequent segments of highway.

So the braking distance the cars were designed for is now an issue.

Friction formulations vary with one extreme responding quickly but tending to fade early with the other high heat tolerant materials being less responsive initially but good in sustained braking situations. I had a Range Rover that felt like it had air in the brake lines from the factory. Brakes felt like they were not responding initially and then were OK (OEM Ferrodo pads). I changed the master cylinder to no avail. I replaced the front pads with a material that responded instantly and this felt much better in city driving situations, only to find myself in an horrendous accident when the car failed stop in a sustained high speed braking moment.

Pick your poison and drive like nobody else knows how to.

See attached factory data that was folded into the owner's manual when my Midget was delivered.
Glenn Mallory

Pretty much all covered. If you're finding pedal effort too high, fit a servo. My pedal effort (260mm vented 4 pots and 230mm solid rear discs) was way too high and I as going to bend something, so a servo was the answer, it's brought it back to standard feel. Tyres are of vital importance as mentioned, as is front pad type and rear shoe adjustment.

Rob Armstrong

I've just found out the difference decent discs make. My S80 Volvosaurus brakes were, I thought, okay with the aftermarket discs I fitted only three years ago. Then recently it developed a "kick " through the pedal from a warped disc so fished all the loose change out of the sofa and the kids piggybanks, sold my firstborn son into slavery and bought OEM Volvo discs.
What a difference! Night and day.
I still smile at the memory of the only time my daughter drove the Midget, having never driven a 70s car. She drove it roughly 30 yards into the grass going Omigod why doesn't it steer and Omigod there's no brakes!!!
I was laughing too hard to answer!
Greybeard

The late Terry Sanger mentioned to me that the brakes on the ARDS Ford XR2s IIRC that they used at Castle Combe were hard on the brakes so they tried to cut costs by using aftermarket discs and pads but found the discs more prone to warp and the pads wore out faster so in the end it proved a false economy and they went back to Ford OE parts as it worked out cheaper.
David Billington

This thread was discussed between 18/09/2020 and 22/09/2020

MG Midget and Sprite Technical index

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