Which is better large discs or performance pads

obi_waynne

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A3 1.4 TFSI 150 COD
Which would make the biggest impact on braking, larger disks or high friction performance pads?

Disks costs a lot more than pads which is the reason for my question. Is it worth shelling out for a large brake conversion kit, should I just fit some slightly larger disks from say a sport version of my car or would fitting high quality performance pads make a difference to braking?
 

TCJBOLDIE

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JB Starion
IMO it depends on what you intend doing with the car ,is it a DD or towing a horse float or heavy loads regularly then. i would fit the better pads with a higher temp operating heat range as a first option BUT be aware that some are not so good when cold so check their operating temps range and then if they weren't doing the job then upgrade to a big brake 4/6 piston conversion.

FWIW I had to install a bias /balance adjusting valve to be able to stop the rears locking when the fronts had more to give .This allowed me to reduce the power/pressure going to the rears so that I could brake harder without locking the rear wheels.
 
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old-git

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Elan & Robin Hood
Don't get the locking rears up.

If you fit better front brakes, surely they will work better without having to press harder on the pedal, yes?

In that case, there will be no extra pressure applied to the rear brakes. Couple this with the extra front braking and there shouldn't be any chance of the rears locking up.

Even when pressing hard on the pedal you won't be working the rear brakes any harder than previously.

Or am I missing something (probably)?
 
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TCJBOLDIE

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JB Starion
Steve are you forgetting /overlooking the weight transfer under HEAVY braking that reduces the weight on the rear tyres and that allows them to lock easier.?? For example the way I look at it is that before I had the Willwood bias adjuster fitted I could get say 100% brake retardation on the rears (locking) and only say 80% of the retardation the fronts were capable of before the rears locked which you/most should agree is not the best result and after trial and error adjusting and testing by reducing the pressure to the rear I can now execute THRESHOLD braking without locking any wheels.

The factory does all of the brake balance testing before cars are released to the public so IF they came out with say a 250mm front disc and you changed them to 300mm's don't you see that this upsets/alters that front to rear brake balance??


ALL dedicated race cars have a system similar to this to adjust brake balance with a lightening fuel load as they have more pressure to the rear with a full fuel load and need less as the fuel load lightens.

Hope I have explained it so all can understand
 
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Yugguy

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Makes sense. In fact dont cars have a self adjuster that alters brake fluid pressure to the rear according to rear suspension height so if you have more weight in the back you get more rear braking?
 

TCJBOLDIE

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JB Starion
I should clarify my post by saying that my track car does not have ABS.

In an ABS equipped car with a front big brake upgrade only the ABS would allow the driver to continue to apply more pedal pressure when the ABS activates on the rears BUT due to the change to the brake balance done by upgrading the fronts only not be able to get the fronts up to their maximum retardation (just before they lock) in an emergency due to the system continually releasing pressure to the locking rear wheels every time they locked/stopped rotating.

PS most drivers or should I say motorists ?? think that ABS was invented to help one brake better when it was actually to help one to steer as when the front wheels are locked the car will go where it is pointing no matter how much steering lock is applied.

PPS Getting the balance right is so important as the front brakes do app 80% or the work under HEAVY/EMERGENCY type braking situations

I might add that IMHO all the electronic wizardry in modern cars is dulling or dumbing down driver skills EG just slam on the brakes and hang on and drivers are not taught how to modulate brake pressure to achieve the shortest stopping distance in an emergency
 
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TCJBOLDIE

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JB Starion
Makes sense. In fact dont cars have a self adjuster that alters brake fluid pressure to the rear according to rear suspension height so if you have more weight in the back you get more rear braking?
Unsure about cars without ABS but having had a number of 1 ton utes without ABS over my working life I can confirm that that type of relief valve was fitted by the factory.
 
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old-git

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Elan & Robin Hood
Steve are you forgetting /overlooking the weight transfer under HEAVY braking that reduces the weight on the rear tyres and that allows them to lock easier.?? For example the way I look at it is that before I had the Willwood bias adjuster fitted I could get say 100% brake retardation on the rears (locking) and only say 80% of the retardation the fronts were capable of before the rears locked which you/most should agree is not the best result and after trial and error adjusting and testing by reducing the pressure to the rear I can now execute THRESHOLD braking without locking any wheels.

The factory does all of the brake balance testing before cars are released to the public so IF they came out with say a 250mm front disc and you changed them to 300mm's don't you see that this upsets/alters that front to rear brake balance??


ALL dedicated race cars have a system similar to this to adjust brake balance with a lightening fuel load as they have more pressure to the rear with a full fuel load and need less as the fuel load lightens.

Hope I have explained it so all can understand
I assume that your car has ABS, yes?

In that case, this will kick in as soon as tyres start to break traction. Assuming that you haven't changed the tyres this will happen at the same point regardless of the type of brakes fitted as it is down to tyre grip. Therefore the rear brakes will react the same way regardless of the brakes fitted to the front.

Without ABS, the tyres will skid at the same point regardless of the type of brakes fitted, again because of grip not braking force.

So I am saying that if you need to balance the brakes after fitting new calipers and rotors you would have needed to do it with the old setup.

If you have changed the tyres then this can have an effect on the braking perfomance due to, hopefully, improved grip and this is where balancing becomes useful.

For example. I am running 4 pot front calipers with 225/15 tyres and 2 pot rear calipers with 305/15 tyres. I am fitting twin brake master cylinders with balance bar so we can set up the braking balance for driver preference, various climatic conditions and racing type (drag/sprint or hillclimb).

Of course, this is just my opinion which has proved to be wrong on many an occasion :)
 
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TCJBOLDIE

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JB Starion
Steve you missed the first line in my post no 6 ? NO ABS

We will have to agree to disagree on some points as the way I see it is that "all the tyres will lock up at the same point"seems to overlook weight transfer that happens under heavy braking when the weight transfers to the front wheels and the rears have less weight on them so they have less grip and can /will lock up easily/sooner , whereas the fronts have far more weight on them so they will have more grip and IMO will need more pad pressure to get them to lock. yes /no???:confused::bigsmile:

I appreciate your thoughts and look forward to more of them on this subject :D
 
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davalav

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I think it also depends on the car? My self and OG had this very conversation the other day when I dropped some calipers off to be cleaned up. My car uses drums at the rear and small discs 262mm solid and single piston brakes. My car brakes fine... But is it over kill having 282mm discs and grooved and vented with larger piston brakes? No. It's not, as my front's do most of the braking (I don't know exact figures) being drums I don't think they do much in the way of braking at high speeds anyway. With a fully loaded weight of just over 1168kg my MG is quite light too, but having all that weight when braking heavy all on the front calipers causes heavier wear and having bigger brakes in general helps dissipate heat etc etc. I personally think its all down to application. On a road going car which might be tracked twice a year (Such as mine, eventually) the brakes are an ideal upgrade.
 

old-git

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Elan & Robin Hood
Steve you missed the first line in my post no 6 ? NO ABS

We will have to agree to disagree on some points as the way I see it is that "all the tyres will lock up at the same point"seems to overlook weight transfer that happens under heavy braking when the weight transfers to the front wheels and the rears have less weight on them so they have less grip and can /will lock up easily/sooner , whereas the fronts have far more weight on them so they will have more grip and IMO will need more pad pressure to get them to lock. yes /no???:confused::bigsmile:

I appreciate your thoughts and look forward to more of them on this subject :D
Yes I did but I also covered no ABS :)

Weight transfer happens whenever a car brakes. But as you are braking at the tyre's limit of adhesion the amount of transfer will be the same regardless of the size of the brakes, therefore the risk of rear brake lock up is the same.

Fitting a brake balancer allows you to fine tune your brakes, not to compensate for larger front ones, IMO. I think the confusion arrises due to the bigger brakes allowing you to reach the limit of tyre adhesion sooner so the inherent inbalance of the system is more apparent.
 

TCJBOLDIE

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JB Starion
Yes I did but I also covered no ABS :)

Weight transfer happens whenever a car brakes. But as you are braking at the tyre's limit of adhesion the amount of transfer will be the same regardless of the size of the brakes, therefore the risk of rear brake lock up is the same.

Fitting a brake balancer allows you to fine tune your brakes, not to compensate for larger front ones, IMO. I think the confusion arrises due to the bigger brakes allowing you to reach the limit of tyre adhesion sooner so the inherent inbalance of the system is more apparent.
We may be going around in circles and maybe I am not explaning the way I see it correctly' so here goes:bigsmile:

When my rears locked they had reached their limit of adhesion/grip BUT MORE IMPORTANTLY THE FRONTS HAD NOT so to be able to reduce stopping distance I had to reduce /limit the maximum pressure to the rear calipers so that I could increase pedal pressure to allow the fronts to reach their limit of grip at the same time as the rears .

This Is what I call adjusting the brake balance so that both ends or the car/tyres arrive at their maximum grip level at the same time to have a far more stable car when threshold braking .
Hope that makes sense;):confused::bigsmile:

Appreciate your replies and thoughts and have an open mind and always willing to learn more. and hear different points of view on all things.
Cheers
Rad

PS You do realise that an ABS equipped car all the brakes DO NOT lock simultaneously and only one locked wheel will activate the ABS ??
 
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old-git

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We may be going around in circles and maybe I am not explaning the way I see it correctly' so here goes:bigsmile:

When my rears locked they had reached their limit of adhesion/grip BUT MORE IMPORTANTLY THE FRONTS HAD NOT so to be able to reduce stopping distance I had to reduce /limit the maximum pressure to the rear calipers so that I could increase pedal pressure to allow the fronts to reach their limit of grip at the same time as the rears .

This Is what I call adjusting the brake balance so that both ends or the car/tyres arrive at their maximum grip level at the same time to have a far more stable car when threshold braking .
Hope that makes sense;):confused::bigsmile:

Appreciate your replies and thoughts and have an open mind and always willing to learn more. and hear different points of view on all things.
Cheers
Rad

PS You do realise that an ABS equipped car all the brakes DO NOT lock simultaneously and only one locked wheel will activate the ABS ??
In that case I would certainly suggest that you fit a brake balancer :)

PS Yes :)
 

SLEEPER

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it is very much down to the car as brake set ups vary from poorly designed to a properly set up system.
With a single master cylinder set up without any balancing system changing the calipers and discs together can affect the balance. I say can and not will because the tyres have to be able to cope with the extra braking .
A small point I am talking about changing the discs and calipers together as then you definately can increase the braking efficiency . Again though the master cylinder has to be up to the job.
Assuming it and the tyres are up to it then real gains can be made.
Ive upgraded the fronts twice and now have 343mm aps . These are more efficient so provide more "stop " with the same pressure because the tyres (888s) and the original master cylinder are up to the job.. The new front brakes changed the balance of the car.I upgraded the rears to 34 GTR vspecs and the balance returned.
This worked for me and at the moment I dont seem to need a bias valve which is probably a happy coincidence.
As with all mods it isnt as simple as above a serious brake upgrade will likely need different suspension as a full stop from 170mph isnt the same as from 70 or 120. Hopefully most cars with such brakes have also had the rest of the car improved as well.
 

TCJBOLDIE

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JB Starion
In that case I would certainly suggest that you fit a brake balancer :)

Finally we agree .It took some doing but it all worked out in the end LOL

PS Yes :)[/QUOTE

I never doubted that you did BUT unfortunately a lot of motorists haven't a clue as to how they work :sad

SLEEPER you restored the balance by upgrading the rears.

My car had 4 wheel ventilated discs from the factory clamped by single piston sliding calipers .I upgraded the fronts to 4 piston calipers and app 40mm bigger discs and had the brake master bored and Stainless steel sleeved to accommodate a slightly larger piston to cope with the larger volume of fluid needed as the 4 pots totaled up to more than the large single piston which returned the pedal free-play back to stock height
 
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Yugguy

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Just disregarding wether you'll brake quicker there's also the question of repeated braking and dissipating the heat produced. Are you therefore better off with keeping the same size but upgrading to grooved/drilled?
 

SLEEPER

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I would have thought that larger discs will be much better - more area so will cool down quicker.
Besides you question assumes the larger brakes will not be drilled , grooved or have cooling vanes (which they usually will)

re tcbs........... SLEEPER you restored the balance by upgrading the rears.

In my case it worked . Seems to be a braking package that works on lots of skylines .

The standard stagea master cylinder is known to be "man enough " for some reason they uprated it on stageas. No idea why because the stock brakes are rubbish but they did.

I forgot to add you also need decent brake pipes (obviously)
 

turbonutter69

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Braking improvement is't just down to the disks and pads.
As already said other components need to be taken into consideration too.
You can improve braking by just servicing the existing setup. And replacing the brake pipes with braided lines.
Bigger disks on alot of road cars wouldn't improve the braking at all as unless they are pushed hard they would never get up to a decent working temp.
Where as uprating the standard pads and leaving the disks alone may improve slightly,
 

old-git

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Like everything else in car modding, there are a lot of wrong ways and often more than one right way of doing something. :)
 

TCJBOLDIE

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JB Starion
I would have mentioned in another post that I have braided lines and use Motul RBF 600 fluid and have vented & slotted discs all round.

FWIW slotted is said to be better than drilled as I have seen pics of drilled discs that have been worked hard with multiple cracks radiating out from the holes.
 

TCJBOLDIE

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JB Starion
Which would make the biggest impact on braking, larger disks or high friction performance pads?

Disks costs a lot more than pads which is the reason for my question. Is it worth shelling out for a large brake conversion kit, should I just fit some slightly larger disks from say a sport version of my car or would fitting high quality performance pads make a difference to braking?
Waynne Thanks for kicking off this subject as it has turned out to be a lively discussion thread with hopefully good info to others who may be considering an upgrade.

I did get a sneaky feeling that the OG was testing me to see if I knew what I was on about :eek: but it turned out all good in the end :D
 

old-git

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Elan & Robin Hood
I would have mentioned in another post that I have braided lines and use Motul RBF 600 fluid and have vented & slotted discs all round.

FWIW slotted is said to be better than drilled as I have seen pics of drilled discs that have been worked hard with multiple cracks radiating out from the holes.
Yes, drilled holes can cause problems. Mine are drilled but also chamfered to reduce the risk of cracking. Regular checks will be in order just the same.
 

TCJBOLDIE

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JB Starion
Me? Do something sneaky? Perish the thought :)
Shame on me for entertaining thoughts like that for even a moment:amazed::embarrest:
This is why I love this site as I enjoy a bit of good natured banter back and forth and long may it continue:D
 

HDi fun

TC ModFather
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Passat 2.0 TDi
My Passat has 345mm front discs as standard (rears are about 300) and that is in to my local specialist to sort out soft initial pedal feel which I think is due to an air bubble somewhere. Second press and they come on hard and evenly. The BMW only had 312mm fronts and that stopped far better than the Passat does at this point. So we can't automatically say that bigger is better. Or, at least, it had far sweeter pedal feel.

Driver perception and confidence is subjective but very real in our own minds.

The jury is out. In my opinion a well designed factory brake system works better than a badly modified one. I've always been a fan of OEM components, especially where brakes are concerned.
 
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