pads

[cleverusername]

Brakes are adequate for normal road use.

I must intervene, the standard front brakes are rubbish.
To get decent brakes you must upgrade to something like Ford calipers on VW vented discs, as in a Trackerjack conversion.


To describe Dolomite brakes as adequate is akin to saying you must never exceed 12 or perhaps 13mph,
or to describe a coat as waterproof so long as it doesn't rain,
or to describe a thief as honest so long as he doesn't get caught,
or to describe fried breakfasts as healthy so long as you don't eat them,
etc,etc.



Ian.

They are OK for the 1500, I have never been in a situation were they wouldn't the car. Not as good as the Xantias power assisted brakes, I braked in that like I would in the Dolly, and almost went through the windscreen.

[Jon Tilson]

Sprints will lock the front wheels under emergency braking, hence my comment about the brakes being adequate for road use.

They will also produce 1 or maybe 2 fade free stops from 80 - 90 mph, as in coming over the rise on a motorway to see a holdup....an ooops moment.

I know this to be true because I've driven them like this for 25 years or more....

They WILL fade if subjected to track sessions, hence its track and rally guys that need to upgrade....



Jonners

[Hobo]

Mmmm!, how can you describe front brakes on a Sprint?
Oh yes!, a custard cream biscuit sat in a Caliper against a metal disc designed and machined by Fred Flintstone.

Having said that, most cars of that era had sh*te brakes, BMW E21 323i, Ford Capri 3.0s, I have owned both cars and they can make one easily believe that new underpants maybe required under hard braking when someone decides to stop infront of you for no reason.

The Sprint was by no means on it's own, cure - Tracker Jack set up or similar.

[lazeruspete]

80 - 90 mph


Jonners

[AndyJ]

Locking the front wheels is a sign of failure not success. It happens when the friction between the disc and the pad is greater than the friction between the tyre and the road. It happens because the driver continues to increase braking pressure beyond the point where the disc can dissipate the heat, so in other words when the brakes have reached their limits. If the discs were vented or bigger and the pads were increased in size then the brakes would be able to lose heat faster and would lock up later, stopping the car more quickly under the same conditions and continuing to work at higher levels of demand than the standard set up.
Many Dolly drivers will have found that they've never had a problem and have always been able to stop ok. Many others, like myself will have been faced with the situation where either through their own enthusiasm or the errors of other drivers they were not ok. In my case a driver, on a very busy A road where everyone was travelling at 60mph, suddenly decided to try and pull out and overtake in front of someone who was already overtaking at 60+++. The result was cars all over the place, several very near misses and only one car failing to stop in time; mine, which locked up and despite my best efforts I couldn't avoid the car in front of me. Luckily nobody was hurt, wallets were emptied though!
Dolomite brakes are woeful in demanding conditions compared to any modern car and let's not forget they are whom we share the road with. If you find yourself trying to stop as fast as others in an emergency you won't be able to and before anyone says leave room in front of you don't kid yourselves because that decision can and often is undone by other drivers in a moment.
I have a post on "what would you like for xmas" which asks for the club to look into reproduction of the ST vented brakes as they require the least engineering (compared to other options) and were a factory option so lean strongly towards originality. This would give us all access to a safer Dolly driving experience and I hope it's possible to give my proposal serious consideration. I have the right parts and would make them available for reference if it would help.
Andy.

[sprint95m]

Sprints will lock the front wheels under emergency braking, hence my comment about the brakes being adequate for road use.

They will also produce 1 or maybe 2 fade free stops from 80 - 90 mph, as in coming over the rise on a motorway to see a holdup....an ooops moment.

I know this to be true because I've driven them like this for 25 years or more....

They WILL fade if subjected to track sessions, hence its track and rally guys that need to upgrade....



Jonners

Not only do you confirm the inadequacy of Dolomite brakes you also state you are a bad and dangerous driver, guilty of speeding
and not only speeding but also travelling at a speed beyond that which permits safe easy braking within the visible road.

If we were to follow your clutching at straws then your VW Golf would still have the Austin Maxi style callipers that were found on Mark One Golfs... .

They are OK for the 1500, I have never been in a situation were they wouldn't the car. Not as good as the Xantias power assisted brakes, I braked in that like I would in the Dolly, and almost went through the windscreen.

The Xantia has better brakes because they are bigger, i.e. bigger discs, bigger caliper pistons, bigger pads, (with correspondingly bigger master cylinder bore),
the bigger servo only reduces the physical effort.






If I was the OP I would be pretty p155 off if I bought some of they magic harder pads only to discover they make no discernible difference,
as was the case when Dolomites were new.




Ian.

[Jod Clark]

Locking the front wheels is a sign of failure not success. It happens when the friction between the disc and the pad is greater than the friction between the tyre and the road. It happens because the driver continues to increase braking pressure beyond the point where the disc can dissipate the heat, so in other words when the brakes have reached their limits. If the discs were vented or bigger and the pads were increased in size then the brakes would be able to lose heat faster and would lock up later, stopping the car more quickly under the same conditions and continuing to work at higher levels of demand than the standard set up.

What?

If the brakes can lock the front wheels then you need better tyres, bigger brakes won't make any sort of difference apart from the pedal effort required to break the friction between the tyre and the tarmac. After all, once the front wheels are locked the brakes are no longer converting kinetic energy into heat and therefore, not really doing anything that a bolt can't do. Once you've got a better brake force : grip ratio, you may need bigger or vented brakes to dissipate the heat if your driving style means you're using maximum or near maximum braking all the time. In the example you describe above you needed better tyres, cadence braking technique or ABS, not bigger brakes.

[AndyJ]

If you'd read the whole thing you'd have seen I said just that. If you put the vented disc conversion on a car would the brakes improve or would you have to change the tyres too to see any benefit? I THINK NOT! You might get a further improvement again with new boots but you are missing the point. Once the (std) brakes have reached their limit in dissipating heat they stop working as well, but since the driver still wants to stop more pressure is put on the pedal but all it does is eventually to lock the wheels up. If the brakes could have dissipated more heat then they would have worked better, converting more forward energy to heat and continuing to stop the car when the std set up had long since stopped working.

[Jod Clark]

Once the (std) brakes have reached their limit in dissipating heat they stop working as well, but since the driver still wants to stop more pressure is put on the pedal but all it does is eventually to lock the wheels up.

Interesting. I've faded a few brakes in my time and have not been able to even slow down on a long downhill, much less lock the wheels...

[TKLR]

Usually brake fade occurs when the linings / pads overheat and exude gas, this results in a firm brake pedal but reduced braking effort thus unlikely to lock wheels at all as the pedal is effectively dead. The more attempts to brake, the hotter the brake material, which results in more gas build up from the material, and even less braking effort... It's the reason vented brakes work better, dissipate the heat faster so less fade, and why thin worn out discs fade faster... less material to allow the heat to escape..

Other cause is fluid boiling as it is hydroscopic (absorbs moisture) and the heat transferred to the calipers under prolonged or repeated heavy braking causes the water content in the fluid to boil forming gas pockets in the brake fluid which compress making the pedal feel soft or spongy. Either way you wont lock the wheels, far from it ! (providing of course you have anything like a decent tyre fitted)

Hope this helps..

Iain

[Jod Clark]

I think I would be right in saying that when the front wheels lock up under heavy braking then it stops being the brakes that are providing retardation, its the friction between the tyres and the road. Sure, fit an upgraded set of brakes on your car and it will feel different, sharper grab or more progressive feel perhaps. But - assuming the tyres, speed and road conditions remain the same for both setups - then standing on the brake pedal until the front wheels lock up will take exactly the same amount of braking force AT THE DISC, regardless of how that force is applied, stopping distance will be the same and maximum retardation before lockup will also be the same.

[TKLR]

Absolutely, once locked up there is no braking effort other than the friction between road and tyre...

[xvivalve]

er, wrong, when the brakes lock up sound is created, so some of the kinetic energy is converted into sound energy, admittedly not a lot, but at that point friction and sound are slowing you down

[Jod Clark]

Excellent, I hadn't thought of that. I will seek-out tyres with a higher squeal rating.

[AndyJ]

Most importantly the point I was making was that if you have better brakes fitted (i.e. vented discs) then they will stop the car more quickly which means you avoid the need to stamp on them in the first place. Vented discs will lose heat more quickly and therefore they will slow the car more quickly. I didn't want to start a somewhat confusing technical one-upmanship debate.
The standard brakes on a Dolly are not as good as modern cars, they are improved by upgrading to vented discs and I would like to see these more widely available and as close to a factory option as possible. This would make our cars safer.
As for the original thread: Pads, I have used several combinations of pads and discs and I have found high grade grooved discs with Mintex pads to be the best combination.
Andy.