Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Brakes

It depends on the weight balance front to rear. For example the mk1 MR2 that NeilM and I Hillclimb is light on the front weight is 40% front and 60% rear axle. Now under normal braking everything is fine but if you want to stop quick regularly, especially in the wet or damp it is easy to lock up the front. After a bit of research on MR2 race forums we found that the best way to resolve this was to fit a brake bias valve on the fronts, not the usual way to do this. The valve is set to about 20% more to rear! it is a progressive valve so under normal braking split is 50/50 but if you brake hard it will be 40% front and 60% rear roughly. The effect of this is it helps get the nose down on the front suspension just as the front brakes start to exert force. Anyway it works and I would guesstimate that we have shortened the braking distance by about 35% from standard set up.

As said earlier on a MOG under braking the weight transfer is more up front hence rears locking, however the rear axle is pretty heavy and can act as a pendulum and induce tail hop. I experience this in my plus 8, a experience. This can be induced by accelerating in a turn and the quickly braking and then turning the opposite way to correct. The car will tail hop from side to side, or snake, I would not recommend trying it unless in a very open flat area off road. If you brake harder the tail will come right round, the way to get rid of it is accelerate out of it.

Braking balance is generally biased to the front. The reason is that under braking the weight is transferred forward. To my knowledge it is never balanced to the rear.

Another reason for this bias is that braking in corners or in wet and particularly icy conditions, locking the rears will actually cause the rear to accelerate causing the rear of the car to try and overtake the front and the car spinning.

If the front brakes aren't locking before the rears, check that greasing the kingpins hasn't been done over-enthusiastically. Too much and too frequent enthusiastic greasing can easily cause large amounts of grease to lie at the base of the mainsprings close to the calipers with a good chance that it will end up on the brake disc.

If you're an enthusiastic greaser, take the trouble to remove the excess otherwise it'll do it itself but in a way that's not in your interest.

Cadence braking - that's a great skill Graham and a little known and lost driving technique. I remember John Cooper and Giacomo Agostini battling it out at the Post-TT races at Mallory Park; both cadence braking into the Hairpin. You could see daylight alternating between the front and rear wheels as they used this technique to maximise braking without actually allowing the tyres to lock up and loose grip.

A correct to my earlier post.

Brake balance is generally to the front even for single seater race cars and mid engined cars. Front/rear weight distribution will affect the amount of braking bias but this will always be in relationship to the weight distribution.

Brake bias using valves and adjusters is always dependent on the braking surface area (pads and shoes) remembering that the effectiveness of calipers is dependent on caliper size and the number of actuating pistons. Brake linings are notorious for their poor contact area especially after a reasonable amount of wear.

Took the Morgan for a run and did several emergency stops.
The rear improved both braking evenly.
The front also appeared to be better as well, which points to lazy rear cylinders and possibly grease on the discs though I do have gaiters.
I find the brakes on the +4 very unresponsive with little feel unlike my older 4/4's. Light pressure has very little effect and the danger then is that you stomp on the pedal too much.
I will take the advice of the forum and fit braided hoses and better pads when the brakes are overhauled.
Occasional heavy braking will also be added to the to do list.
Titus

Brake balance - wots that then?

The vintage three wheeler does not link the front wheel brakes with the back. Front brakes are on lever with crude ratchet and not really that good; the back is on the foot pedal and can just lock the back wheel on dry tarmac. However, locking the back wheel on a trike tends to require new trousers for the occupants.

Quite a few cars though have the lever and pedal the other way round, some link them, and some cars are converted to hydraulics (original is cable). My car is standard apart from a floating pivot point on the fronts.

Martyn, in your case brake balance is down to your skilful co-ordination between hand and foot. You've obviously mastered the technique either through design or desperation when someone's pulled out in front of you.

Titus, I suspect that your gaitors are positioned around the lower rebound springs. The grease generally accumulates at the bottom of the mainspring where it meets the damper blade plate and top of the stub axle. It's worth keeping an eye for excessive build up. I have seen Morgans with circa half a pound of grease sitting there gleefully contaminating the inside of the brake disc and inner pad.

Yes I agree brakes are generally balanced to the front and is normally correct, I was just trying to explain the if weight distribution is not front biased then this will have an effect on braking in creating conditions. Most cars setup is fine and Morgans should be fine as they are.

Enjoy sprinting the MR2 - it's great fun.

Have you thought about increasing the tyre contact patch by going a size larger in diameter or width. As you say, the dedicated forums are a great help.

We run with rep mini-lites 15" by 6.5 with silver stone RRs, may change these next season to Avon a015 slicks for dry, they are Hillclimb stickies. For wet we have set of oz 16" with toyo proxies.

Our main issue is that we need a LSD with lower gearing so we can get up to 90mph in 3rd and then just use 2 and 3rd for most of the hill, minimising gear changes. Also we need to strip some weight off the car, trying to do this and keep road legal so we can avoid a trailer. Budget is tight so it's a bit at a time

Great fun though, and made some good friends.

It sounds as if you know what you're doing. Budget is always a problem; however it's always greatly satisfying when your results are better that someone else with a bigger budget. Also, doing the development yourself is extremely satisfying.

Have fun!