To follow on from a post yesterday I have seen a great big brake upgrade by pb brakes.

Admittedly it will be partly for looks but also I would be looking at doing track days too.

Would I need to keep the rears smaller than the fronts for balance or could I get away with having them both the same size?

I like the idea of 330mm fronts and maybe 330mm rears too.

I currently have the 312 and 256 brakes behind 17" wheels and the rears do look a little pathetic.

Anyone in the know able to share some wisdom?

There does need to be a certain balance with brakes, it all depends on the calipers your running,

If you have 330mm 4 pots up front and the original caliper spaced out on the rear to but using a 330 disc or what might be easier is to use the 312 discs on the back with the original rear calipers if you have vented octy rear calipers as i believe i have read somewhere that they fit thickness wise and get some spacers for calipers to move them out then you keep the handbrake aswell then

Your rear wheels do less of the braking work on front-engined cars. Bigger rotors -> heavier rotating mass -> poorer acceleration, handling and fuel economy.

Your call.

I wouldn't want to go too big on the back due to the extra revolving weight.

Bare in mind the front/back balance is built into the car, so keeping the rears a little bit smaller is probably the best idea. (IMO)

I know when I put the Brembos on my Fabia the rear did fidget under hard braking, but I kept the stock rear calipers and fitted bigger discs which made it well balanced, giving more braking force per revolution.

I had a look at the PB brakes too. Very impressive I have to say.

If You do not upgrade tyres the only thing bigger rotors and callipers are going to do is to run much cooler at track days if set up correctly. EDS systems provide dynamic brake force distribution making better use of brake upgrades. I believe vRS Fabia 2 has this system.

If You do not upgrade tyres the only thing bigger rotors and callipers are going to do is to run much cooler at track days if set up correctly. EDS systems provide dynamic brake force distribution making better use of brake upgrades. I believe vRS Fabia 2 has this system.

I don't agree with that.

In my experience upgrading the brakes with bigger rotors and callipers results in more stopping force, particularly from higher speeds often seen on track days where the car is not already on the limit of grip of it's tyres. (which can be case at lower speeds)

EDS is not on the OP's car I believe.

Braking torque of a brake assembly should be matched to tyres grip based on speed, weight (including dynamic weight transfer) and speed. If tyre grip doesn't change and your OEM brakes have enough braking torque to lock tyres at the highest speed you will be braking from them the only thing bigger brakes (if set up correctly, i.e. with lower pressures) are going to do is run much cooler and lower the unsprung rotary mass. I am not saying you should lock your brakes of course, it's just a telling sign that braking torque of your brake system exceeding the braking torque your tyres ca handle so no need for an upgrade bar lower temps or looks .

Braking is a complex subject. Lowering your car will make it tail happy for example as less dynamic weight transfer will occur. Just putting more powerful brakes at the front will increase your stopping distance ore front brake bias ) but will make or car much more "planted", stable under braking-a subjective feeling of better brakes .

Braking torque of a brake assembly should be matched to tyres grip based on speed, weight (including dynamic weight transfer) and speed. If tyre grip doesn't change and your OEM brakes have enough braking torque to lock tyres at the highest speed you will be braking from them the only thing bigger brakes (if set up correctly, i.e. with lower pressures) are going to do is run much cooler and lower the unsprung rotary mass. I am not saying you should lock your brakes of course, it's just a telling sign that braking torque of your brake system exceeding the braking torque your tyres ca handle so no need for an upgrade bar lower temps or looks .

That's not what you said in your post earlier where you specifically said "If You do not upgrade tyres the only thing bigger rotors and callipers are going to do is to run much cooler at track days if set up correctly"

You are now adding if you have the ability to lock the wheels. Which is COMPLETELY different.

As I already said, if you are not on the limit of grip (ie, can't lock the wheels) then a big brake kit will improve braking from higher speeds typically seen on track days.

I did start to read your most recent post, but it was going off on another tangent about suspension... so I skipped it as it's not relevent to the question by the OP or my point about your post that was incorrect.

My brembos are my favorite modification. Look great and really take some stick on track without fading at all! A bonus of a nice pedal feel means even round town driving sees an improvement, love 'em.

Braking is a complex subject. Lowering your car will make it tail happy for example as less dynamic weight transfer will occur. Just putting more powerful brakes at the front will increase your stopping distance ore front brake bias ) but will make or car much more "planted", stable under braking-a subjective feeling of better brakes .

OK, I read it.

Are you suggesting just putting more powerful brakes on the front increases the stopping distance?

I wasn't sure what "ore front brake bias )" meant.

I am not having a go here, but sometimes I do wonder how much of your detailed and numerous posts are based on personal experience.

Thanks for all the responses. Looks like the 330 front and 286 backs that they offer will be the ones to go for

OK, I read it.

Are you suggesting just putting more powerful brakes on the front increases the stopping distance?

I wasn't sure what "ore front brake bias )" meant.

I am not having a go here, but sometimes I do wonder how much of your detailed and numerous posts are based on personal experience.

More front brake bias - typo .

Yes, that is exactly what it will do if the braking torque will not be kept the same where no other upgrades took place. Reason for it is less braking going through your rear tyres to put it plainly.

BTW, I am not suggesting anything, that's simple physics 1oh1 for you. And it does not come from personal experience. That's what the written we'd was invented for so I can take other peoples experiences and learn from them. If everything was to be based on personal experience only we would still be in the caves mate...

More front brake bias - typo .

Yes, that is exactly what it will do if the braking torque will not be kept the same where no other upgrades took place. Reason for it is less braking going through your rear tyres to put it plainly.

BTW, I am not suggesting anything, that's simple physics 1oh1 for you. And it does not come from personal experience. That's what the written we'd was invented for so I can take other peoples experiences and learn from them. If everything was to be based on personal experience only we would still be in the caves mate...

Well I disagree with that too then.

That's not what you said in your post earlier where you specifically said "If You do not upgrade tyres the only thing bigger rotors and callipers are going to do is to run much cooler at track days if set up correctly"

You are now adding if you have the ability to lock the wheels. Which is COMPLETELY different.

As I already said, if you are not on the limit of grip (ie, can't lock the wheels) then a big brake kit will improve braking from higher speeds typically seen on track days.

I did start to read your most recent post, but it was going off on another tangent about suspension... so I skipped it as it's not relevent to the question by the OP or my point about your post that was incorrect.

You are right, if you are not at the grip limit i.e. not able to lock wheels then bigger brakes will improve your braking no doubt about it.

Bigger brakes if set up correctly means that the braking torque stays the same. Pistons apply less force equals less friction density equals less temps so runs cooler. Because braking torque was maintained and not increased brake bias will not change and braking distances will be the same. All will be the same but temps lower.

If not set up correctly and braking torque increases then brake bias changes, you get better brake "feel" but because rears are braking less so your braking distance increases. We are still within friction envelope of the rubber.

Well I disagree with that too then.

You are free to do so of course..

I'd urge you to read up on some physics behind braking systems, analyse the equations to see what is dependant on what. Work through it yourself and then read the conclusions the author reached to see if convergent. If not ad you still disagree keep reading.

This way I cured myself from many ridiculous misconceptions car tuning world is infested with. The worst kind are people who "spent their lives" doing it - no matter how many hard facts you show them nothing sways them in their life long convictions... Rarely one has the opportunity to go there and show it in practice how his should be done. Don't take it as being co€ky or big headed or arrogant or the such.

I put few of my own thought through theories into practice despite the biggest authorities in the game renouncing me and they had to eat their hats. Sadly I am too lazy to do anything about it...

I just lost the will to continue on this thread, reading loads of info copied and reposted.

Work to do... cars to fund.

See you at How Fast? in 9 days.

Yep, see you then .

BTW, those things are in hard copy books, very little on-line . So nothing is "reposted" .

Work to do... cars to fund.

See you at How Fast? in 9 days.

I am just on train back from a meeting do posting ...

This is very similar to a recent thread in the Fabia II section.

Jabo is insistent that bigger brakes on stock tyres equates to a greater stopping distance, which i could potentially agree with if the stock tyres are terrible and have no grip, but as you have said, where these bigger brakes really perform is higher up the speed range, where tyre grip isn't at its grip limit.

@ the OP.

Before purchasing any big brake kit, you need to look into what the piston cross sectional(CSA) area is on the uprated brakes.

Once you know the CSA of the stock caliper, you want to ensure the accumulated CSA of the pistons on a single side of a caliper(ie a 4 pot brembo caliper = measure the CSA for 2 pistons from the same side) are as close to the stock setup as possible. I think Dave Brown from VAGBREMTECHNIC said the tolerance on Piston CSA should be within: - 0% +8%. Outside of this range you run the risk of weaker brakes and very poor pedal feel.

This is very similar to a recent thread in the Fabia II section.

Jabo is insistent that bigger brakes on stock tyres equates to a greater stopping distance, which i could potentially agree with if the stock tyres are terrible and have no grip, but as you have said, where these bigger brakes really perform is higher up the speed range, where tyre grip isn't at its grip limit.

No, you turned this on its head by omitting the most important info. Statements like the above are simple b0011ocks.

If you fit bigger brakes (no matter what tyres you have) and those brakes have more braking torque than previous ones you will be shifting bias forward and rears will brake less so despite fronts braking more (let's take away tyre grip factor) overall you will have longer stopping distance.

If OEM brakes on OEM tyres are able to lock the tyres at any speed ( have enough braking torque to go over grip limit at all loads all speeds) then installation of bigger brakes will not improve anything but make them run much cooler than stock brakes, braking will not be any different. That is provided braking torque will be the same as the stock ones which means pistons producing much less pressure as there is 4 times as many of them as stock and diameter of the rotors is larger. That CSA thing by D Brown is exactly that I think (not 100% sure) where it is called to stay as close to stock as possible (I will spare you hydraulics theory I think). I think it keeps the same fluid pressure but works with adjusting the areas. It all goes back to Mr Newton and XVII century .

There is also a fine point of how consistent brakes can hold an amount of braking torque at a level just before breaking traction but this changes with speed, and temperature. Driver's "feel of the brakes" and "where the grip is under braking" comes t oplay big time here. The best brake pads have flat friction coefficent temp curve. Carbon brakes have horrible curve as they only work between iirc 800-1000C - Brakes too cold no braking whatsoever .

Thanks for that.

Now you can go back to F1 paddock lol

Thanks for that.

Now you can go back to F1 paddock lol

Any time mate, anytime

Question for you though

• Seat Leon Fr/Seat Leon Cupra: Both have identical weight, identical tyres, identical wheels, identical rear brakes, identical master cylinders, identical everything that is except front brakes: Fr has 312mm brakes, the Cupra has 345mm brakes.
  
• Seat Ibiza Fr/Seat Ibiza Cupra (Racing brake upgrade): Both have identical weight, identical tyres, identical wheels, identical rear brakes, identical master cylinders, identical everything that is except front brakes: Fr has 288mm brakes, the Cupra has 312mm brakes (with 3 extra pistons)
  
• VW Scirrocco 2.0TSI/VW Scirrocco R: Both have identical weight, identical tyres, identical wheels, identical rear brakes, identical master cylinders, identical everything that is except front brakes: TSI has 312mm brakes, the R has 345mm brakes.
  
• BMW have similar examples, as do Renault and Ford etc, but i cant be arsed looking at them just to prove a silly point.
  

The question though is, of the above, when running the same tyres, rear brakes, master cylinder etc, all exactly OEM with no unsanctioned modifications, which cars have the best stopping power?