Brake upgrades
Discussion
A car should be capable of locking it's front wheels with standard brakes. So the limit of braking is tyres. Brake bias in a production car is set to ensure that the front wheels always lock first, so if you upgrade your front brakes only, then they will lock before your rears are giving their best, which could result in increased stopping distances?
Upgrading brakes generally is done to reduce fade when using them heavily, to take advantage of better tyres, or to improve feel.
Upgrading brakes generally is done to reduce fade when using them heavily, to take advantage of better tyres, or to improve feel.
MGBV8 said:
I know this is for going faster but any stopping slower thoughts
Front Only Brake Upgrades Increases Stopping Distance!
Double Dutch or not?
Paul
Only if it was put togther by a total nimrod.
If you have a decent kit and put a new brake proportioing valve in the rear circuit then you can adjust the brakes to maximise their overall effect on braking performance.
If the pads selected were designed to work at a certain temperature then when cold stopping would be longer. But when warm they should be superior to standard.
GavinPearson said:
Only if it was put togther by a total nimrod.
If you have a decent kit and put a new brake proportioing valve in the rear circuit then you can adjust the brakes to maximise their overall effect on braking performance.
If the pads selected were designed to work at a certain temperature then when cold stopping would be longer. But when warm they should be superior to standard.
In that case I think most big brake upgrades are put together by total Nimrods because very few people I've seen with brake upgrades have paid any attention to brake balance. In any case the brake proportioning valve can correct the dynamic balance but not the static balance. In other words you can use it to set the car up for grippy or slippery conditions but not both.
danhay said:
A car should be capable of locking it's front wheels with standard brakes. So the limit of braking is tyres.
This is a common misconception. I agree, that the ultimate braking force is determined by the firction between road and tyre. However, just because a car can lock it wheels, dosen't mean to say it has decent brakes, or even that it could stop quickly from high speed. With the wheels locked, the brakes are doing no work at all, all the energy is being dissipated in the tyre and the road.
Good brakes are one that can disspate enough energy as heat, that the temperature limits of the disks, pads and brake fluid are not exceeded under worst case conditions.
littlegearl said:
don't think this can be true for all cars, my mate has a Polo 1.0 and when it failed its MoT for brakes he slapped on the setup from a Golf GTi mk 1 (similar age cars) and without doing anything to the rear drums...
that thing now stops on a sixpence!!!
Yes but replacing them with half-decent polo brakes would have had the same effect.
The tyre limits your braking capabilities, once it locks it looses 90% of it's traction, so having bigger brakes will not reduce stopping distances, it'll just make it easier to lock them.
_Al_ said:
don't think this can be true for all cars, my mate has a Polo 1.0 and when it failed its MoT for brakes he slapped on the setup from a Golf GTi mk 1 (similar age cars) and without doing anything to the rear drums...
that thing now stops on a sixpence!!!
Yes but replacing them with half-decent polo brakes would have had the same effect.
The tyre limits your braking capabilities, once it locks it looses 90% of it's traction, so having bigger brakes will not reduce stopping distances, it'll just make it easier to lock them.
Having bigger brakes can reduce stopping distances under the right conditions. Bringing a v-fast and heavy car down from high speed will be easier and quicker with bigger brakes because they will resist fade for longer. Example: Something like a Merc S-class or any big heavy uber saloon. Stopping a car of say 1,800kgs from 170+ will generate masses of heat, even just one stop. Larger brakes will help disipate that heat better and suffer less fade.
Still, granted, under most normal conditions faced in everyday driving, this will not be an issue.
Paul
A few numbers ball park based on a MGF
OE brakes 60% Front 40% Rear
Upgrade front now 70% Front 30% rear
Maximum front tyre grip at point just before lock up 1500lbs
So OE Front 1500 rear 1000 total 2500lb of stopping force
Upgrade Front 1500 Rear 650 total 2150
Nearly 15% reduction in stopping force!
The assumptions are on the limit braking and a matched properly working system to start.
Also looking for a good explanation of tyre grip in relation to braking from high speed to low speed when the wheels hopefully fronts lock.
Paul
OE brakes 60% Front 40% Rear
Upgrade front now 70% Front 30% rear
Maximum front tyre grip at point just before lock up 1500lbs
So OE Front 1500 rear 1000 total 2500lb of stopping force
Upgrade Front 1500 Rear 650 total 2150
Nearly 15% reduction in stopping force!
The assumptions are on the limit braking and a matched properly working system to start.
Also looking for a good explanation of tyre grip in relation to braking from high speed to low speed when the wheels hopefully fronts lock.
Paul
MGBV8 said:
I know this is for going faster but any stopping slower thoughts
Front Only Brake Upgrades Increases Stopping Distance!
Double Dutch or not?
Paul
If you use your car hard it is invariably (or usually) the front which suffers fade..... big brakes reduce this and give improved 'feel'.
However if used wrong (ie allowing the tyres to break traction by just massing the pedal) they will increase stopping distance.
I had a serious misbalance of brake bias on my car which resulted in my front locking severly (no rear brakes in mid engined car).....
At a 0-100-0 timed event not only did I manage to flat spot one tyre horrifically, I also managed to rotate one of the front tyres 3 inches in the rim... guess which one had the best stopping time?
So everyone is right and it proves that Brake tuning is as much an art as engine tuning.
MGBV8 said:Good set of numbers Paul, which illustrate the problem admirably.
A few numbers ball park based on a MGF
OE brakes 60% Front 40% Rear
Upgrade front now 70% Front 30% rear
Maximum front tyre grip at point just before lock up 1500lbs
So OE Front 1500 rear 1000 total 2500lb of stopping force
Upgrade Front 1500 Rear 650 total 2150
Nearly 15% reduction in stopping force!
The assumptions are on the limit braking and a matched properly working system to start.
Also looking for a good explanation of tyre grip in relation to braking from high speed to low speed when the wheels hopefully fronts lock.
Paul
Upgrading brakes is generally aimed at getting rid of fade, or increasing feel, or to account for better tyres. I would hope most cars are capable of stopping from their max speed at least once without suffering fade?
But if you're going to take your car on a track, or attack a challenging road then you might well suffer from fade in a standard car. (Unless it's a Porsche!)
When you look at the improvements manufacturers make to brakes for their higher performance models, it is usually bigger discs, or vented discs etc...basically reducing heat build up to prevent fade.
MGBV8 hit the nail on the head- most people only upgrade their front brakes and it is often lost potential or money wasted. Sure, the fronts will work for longer but some of the weight at the rear of the car is not being braked. Best solution is an adjustable brake bias valve. Fit this and you can use all the brakes to their maximum.
For instance, not enough rear bias and the fronts will lock at comparatively low brake force.
Too much rear bias and the rear will lock on too early and the braking will become unstable.
If you get it right, the fronts will still lock at large brake forces, but a harder shove on the pedal may still be able to lock the rear as well.
I have found this to be the cheapest effective brake modification there is (apart from good servicing). People I know with identical cars have tended to note how much better a standard system with a bias valve is over expensive performance brakes.
My point is that all cars (TVR excepted) tend too have not enough rear brake bias and stopping distances are therefore larger. This is now being overcome by Electronic Brake Force Distribution in newer cars which ensures excellent braking all the time.
For instance, not enough rear bias and the fronts will lock at comparatively low brake force.
Too much rear bias and the rear will lock on too early and the braking will become unstable.
If you get it right, the fronts will still lock at large brake forces, but a harder shove on the pedal may still be able to lock the rear as well.
I have found this to be the cheapest effective brake modification there is (apart from good servicing). People I know with identical cars have tended to note how much better a standard system with a bias valve is over expensive performance brakes.
My point is that all cars (TVR excepted) tend too have not enough rear brake bias and stopping distances are therefore larger. This is now being overcome by Electronic Brake Force Distribution in newer cars which ensures excellent braking all the time.
Remember the brake bias valve doesn't correct the static balance, if the static balance is wrong then using the bias valve you can balance the brakes under heavy braking or light braking, but not both. (Having the balance right under light braking is very important when you're cornering near the limit of grip.)
MGBV8 said:
Alpha
As most prob most lower cars then the rears may require an upgrade rather than fronts.
Paul
I think the chimaera/ griff tends to suffer the oposite problem, over braked on the rear, under braked on the front.
the typical tvr smack is heavy braking, weight transfers forward, back lifts, rear wheels lock, back over takes front and car heads for the nearest solid object.
Upgrading the fronts on my chimaera massivley reduced the brake distance and the feel / controlability of the brakes.
We suffer the same problem on the Race tasmin running standard brakes, the back is adjusted right down to cope with the poor performance of the fronts. soon to be addressed with 304mm disks and ap 4 pots, which will allow me to put more pressure on the back, and increase total braking power..
So you are correct in saying an imbalanced brake setup front or rear will screw the overall braking performance
a good brake setup will offer modulation (feel) braking power and fade resistance. Just having lots of power but no feel ( i.e. over assisted) will be usless as all you will do is lock wheels.
G
edited to add
on a race car you want both axles to lock up together, road cars are generally set so the fronts will lock first, to prevent a spin.
>> Edited by Graham on Wednesday 28th January 22:00
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