MK4 brake upgrade

[dylan8]

just a thought... if you were to upgrade the front two brakes on a car (for example a 2lt Bora) to bigger brakes, eg 312mm of a Audi, can you swap the existing front brakes onto the rear...? weather its to keep a similar ratio in size front vs back, or just to put something slightly bigger on the back to fill the wheel out a bit more

Can't say iv paid much attention to the brakes on my car before so have no idea at all

[Manaz]

You need to deal with the handbrake at the rear, so the front and rear setups can be quite different, and are likely incompatible with each other.

Brake bias can be an issue, but less so than the front/rear differences.

[dylan8]

didn't think of the hand brake, good point!
So with the brake bias, whats happens when you just stick big brakes on the front and leave the rears? surely that cant be great either when they are so tiny on the back?

[Manaz]

The R32 had 334mm fronts and 256mm rears - the Bora V6 4Motion had the same rears, but the fronts were only 312mm, so there's some allowable variation in front:rear ratios. Most of your braking's done at the front anyway, so unless you're making huge changes to one or the other, you probably won't have a significant negative impact.

[dylan8]

The R32 had 334mm fronts and 256mm rears - the Bora V6 4Motion had the same rears, but the fronts were only 312mm, so there's some allowable variation in front:rear ratios. Most of your braking's done at the front anyway, so unless you're making huge changes to one or the other, you probably won't have a significant negative impact.

ok, so refer to the comparison you made between the r32 and 4mo, would they have something set up differently pre front brakes? like a booster, or more pressure etc? i probably need to under stand more about how they work first.

You upgraded your brakes didn't you...? think its worth it?

[Golf Loon]

Most Mk4 rear brakes are the same Dylan.
Only the 4wd ones are different on the back.
Most braking is done wiith the front, so that is where the bigger stoppers usually go.
Rear rotors are a different shape from fronts so that wont work either.

[dylan8]

Most Mk4 rear brakes are the same Dylan.
Only the 4wd ones are different on the back.
Most braking is done wiith the front, so that is where the bigger stoppers usually go.
Rear rotors are a different shape from fronts so that wont work either.

I get that braking it mostly done with the front.
Was really wondering about swapping the smaller fronts to the rear, weather it was just visual or actually would help at all. But if its not going to fit then thats that. Thanks for the answers guys!

[JVLR32]

Its a good question? U still need to play with master cylinder size to get right balance for the brakes to run effiecent, can be done thou

[gavs]

Found this article the other day about brake size increases etc, it's got a bit of basic physics teminology and formulas in it, but it's still pretty to understand.

http://www.mgf.ultimatemg.com/group2/brakes/big_brakes/Big_Brakes.htm

For those who can't be bothered reading it ( I did because i'm in the middle of a bigger brake upgrade!) it comes down to the fact that only 1 thing slows you down and it comes from 3 things. The thing that slows you down is friction and it is a constant figure, no matter how many factors you change. The 3 things that cause this friction are:
- Tyres
- Brake Pads
- Gravity

So, no matter how big your brakes are, they will still slow you down at exactly the same rate due to the balance of the car and how it is affected by gravity. The performmance upgrades that bigger brakes give you are (1)initial retardation and (2)heat disipation.

(1) Think of your brake system as a lever. The rotor is the lever arm and the calipers the clamps that stop that lever. If you have ever tried to undo a super tight bolt, you know that the longer you make your lever arm, the easier it is to undo, this is the same with brakes, the larger the rotor=a larger lever which in turn gives your brakes a stronger initial clamping bite even though the friction coefficient stays the same.

(2) Heat is the worst enemy of a braking system so by going to a bigger rotor, your brake can dissipate the heat easier and more efficiently meaning that the next time you need a hard stop, the rotors will have cooled down more than a small rotor, giving you better wear characteristics, something that comes in handy at the end of the Reefton spur or on a reacetrack.