Big brakes

[Yeti_Man]

I've done at least two brake upgrades to pretty much every car I've ever owned. Without talking techno waffle.... The bigger set-ups offer better braking ability. End of.

[Guest BigJase88]

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?

Guessing your talking about the mk2 leon

My mk1 fr pd150 has the same setup as a fabia vrs!

Its mega poo! 288 and 232 on a heavier car! Urgh!

[vRSy]

yep, hence me quoting the disc sizes

[devonutopia]

I know mine stops quickly, that's enough for me. I am an accountant, not an engineer/quantum mechanic, so I will go with what my gut tells me is best, and bigger is best!

The advantage of my new D2 brake kit will be the calipers/rotors will be lighter than the usual VAG oem upgrade stuff so whatever effect comes in to play with lower rotating mass or whatever, should happen with me

[Jabozuma]

Whichever one you will be driving champ, you've done it all therefore from experience you know it all as well... I am sure you have better ways of entertaining yourself than posting here, you want any suggestions?

[vRSy]

Still no answer lol. Its a simple question. One word answer for each option.

I promise no more than 1 post after you answer lol

[Jabozuma]

So far all I've read here is about feelings, impressions, gut feelings etc. Which is fine.

If it makes people feel better than it is worht doing, simples

If I do not hoave hard data, quantifiable, measurable input to work with it is meaningless...

[BossFox]

I know, but my wife is away visiting family, so im home on my own bored and this amuses me no end

Well everyone who has posted with an amount of track experience/modifying experience seems to say the same.

So debating with a textbook expert seems pointless.

But if it keeps you amused... crack on.

I have actually done tests with my Vbox, so I know the answer.

[Jabozuma]

Still no answer lol. Its a simple question. One word answer for each option.

I promise no more than 1 post after you answer lol

I looked up Scirocco basic data and R will stop in a shorter distance because it is lighter, nothing to do with brakes, that is from 100mph. Take both to 160mph (attached to a whinch for example) and R will stop better becaue TSi's brakes will not cope with such high speed. The rest I do not know, watchig tv now and cannot be bothered to data mine now.

[vRSy]

The rest you dont know? Im shocked.

Last post, night all. Im off to read in bed

[Yeti_Man]

I have actually done tests with my Vbox, so I know the answer.

Well I'm obviously not as posh as you! I have a local route that I know like the back of my hand. I've shortened my stopping distances with every brake upgrade on the last four cars as I can simply brake later at a certain point, judged by the road side markers and dips in the road. When I upgraded my 288mm front setup to a 312mm setup on both my mk1 Octavia and the Yeti, I could brake later. When I've then upgraded the pads... Guess what... More improvements in stoping distance/braking point. And when I've replaced it with an entirely new four or six pot setup with larger disks... Guess what?

[vRSy]

Guess what?

Slower?

[Jabozuma]

I have actually done tests with my Vbox, so I know the answer.

Now you mentioned it, what are the answers then?

[Yeti_Man]

Slower?

Who are you? Jabozuma?! I can brake later therefore without doubt my stopping distances have been decreased.

[Jabozuma]

Who are you? Jabozuma?! I can brake later therefore without doubt my stopping distances have been decreased.

I am nobody really why?

And why wouldn't they decrease? One could explain it in many ways.

I was in the middle of writing "why your braking performance got better" but why bother, nobody is interested so what is important it got better so your upgrade worked and you obviously spent your money well Why dig ?

[Dark_Hero]

Well everyone who has posted with an amount of track experience/modifying experience seems to say the same.

So debating with a textbook expert seems pointless.

But if it keeps you amused... crack on.

I have actually done tests with my Vbox, so I know the answer.

It was your car that inspired me Richard. Your brake upgrade was just immense

[Dark_Hero]

[/size]

Most people who do the brakes I would imagine wouldnt be running the stock ditchfinders anyway.

Workingout the CSA is easy enough, provided yo ucan find the manufacturers literature on it. Most companies display it on their website though.

Take the Stock Fabia II vRS Caliper. Which has a single 54mm diameter piston. (Pi * Radius² = CSA) therefore 3.14 x 27² = 2289mm²

Now looking at aftermarket pistons sizes, Boxster 4 pots have a 40mm and 36mm piston each side: 40mm + 36mm = 1257mm²+1018mm²= 2275mm² So very close to the stock setup ~0.5% lower

So looking at comparable setups that will work with the master cylinder (Ive borrowed this from DaveB of VAGBREMTECHNIK from another forum, this guy is a brake SPECIALIST and is very very highly regarded) As said before by the Brake Guru, for some reason you only count the one side and you ideally want to be within a tolerance of Minus 0-1% and +8-9% max, so its better to use a larger CSA than it is a lower one, but only within reason:

[/size]

Bear in mind that i am comparing brake options for the Fabia II with a 54mm piston diameter. You need to find out what stock piston CSA the Mk1 fabia I vRS caliper runs.

These website quotes of "these are designed for your car" I dont believe personally. All they will do is look at their pre designed off the shelf caliper options, and hopefully select the one that is closest to the stock setup. Id wager the only custom work will be the caliper carriers.

Thanks Sy. I'll ask pb about their brakes and update with what they say

[Dark_Hero]

Ok their 4 pot rear brakes have 2x 28mm pistons

The fronts have 2x 38mm pistons

[Dark_Hero]

If my maths works the fronts would have a CSA of 2,267.08mm

So would be within the -1% tolerance

[Dark_Hero]

Do you know the piston size for the standard rear brakes Sy?

[Dark_Hero]

I've also done the working out for their 6pot 330mm front and 6pot 345mm

6pot 330mm

36 x 32 x 28 1017.36 + 803.84 + 615.44 = 2436.64 result is plus 6.4%

6pot 345mm

38 x 36 x 30 1133.54 + 1017.36 + 706.5 = 2857.4 result is plus 24% bad match

[KenONeill]

Where's the popcorn emoticon?

[Brimma]

Where's the popcorn emoticon?

If you haven't got anything useful to say, Ken..........

[vRSy]

Do you know the piston size for the standard rear brakes Sy?

Sorry mate, i only know the fronts of my car because they are sat in my garage.

I've also done the working out for their 6pot 330mm front and 6pot 345mm

6pot 330mm

36 x 32 x 28 1017.36 + 803.84 + 615.44 = 2436.64 result is plus 6.4%

6pot 345mm

38 x 36 x 30 1133.54 + 1017.36 + 706.5 = 2857.4 result is plus 24% bad match

That exactly what I mean, bigger wont necessarily mean better if the pistons arent well matched to the master cylinder.

I looked up Scirocco basic data and R will stop in a shorter distance because it is lighter, nothing to do with brakes,

Theres no need to look anything up. They are the same cars, same engines, same everything pretty much bar brakes and some interior changes.

Eitherway, I had a look at the VW Brochure from the official VW website which states:

Scirocco 2.0TSI Unladen 1373kg,

Scirocco R unladen 1419kg.

So does that mean the TSi stops quicker because its 46kg lighter?

Remember, they are on the same tyres as well. To remove the power from the equation, lets assume the 2.0TSI is running a stage 1 map (260Hp) so pretty similar now to the 265ps of the R. Also bear in mind the gearboxes are the same so no gearing differences.

[Jabozuma]

That exactly what I mean, bigger wont necessarily mean better (...)

.

Dammit, I fell off my chair when I read it .

Rhetorical question alert!

It baffles me, I am confused... I thought the consensus was that bigger is better, no matter what. Surely all those calcs regarding pistons is another theoretical load of b0011ock$ in need of prompt shooting down!

No, don't answer, I am not looking for a fight here . Have fun with your brakes upgrades, I am out of here.