My big brake upgrade experience

[TCJBOLDIE]

When I upgraded my front brakes from single piston sliding calipers clamping onto (IIRC) 260mm discs over to a 4 piston 294mm disc combination that would fit inside the 15 inch wheels on the car at the time they had to be tested and approved and signed off by engineer and an engraved modification plate fitted in the engine bay and paperwork forwarded to the Transport Department.

There was an improvement but I found that the rears were locking but never the fronts under hard braking at the track.

Put simply when I braked the rears had 100% pressure applied to the discs and the fronts approximately only 80% which was not ideal so I had a WILLWOOD bias adjuster installed in the engine bay ( it is not road legal in the cabin where anyone could change the setting without the owners knowledge )

This allowed me to progressively reduce pressure to the rears and allow more pressure to the fronts until I found the ideal setting so now I can apply more pedal pressure without locking the rears and stop shorter OR brake harder much later safely.

Another benefit is that there are no hi performance pads available for the rears of the car in the pic whereas there are many different pads for the fronts and the adjuster allows me to adjust the front to rear pressures IF needed to allow for different friction levels between the pads.

http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx

 

[TCJBOLDIE]

Forgot to add that the brake master cylinder had to be bored out and fitted with a stainless steel sleeve and piston to allow for the additional capacity needed by the 4 pot vs single pot calipers to keep the brake pedal height the same.

 

[obi_waynne]

Good post, thanks for sharing your experiences and it's worth noting your findings.

 

[TCJBOLDIE]

Thanks Obi San

The front discs are from an M/bishi Evo redrilled to fit my PCD and the calipers are from a Skyline fitted to custom adapters.
I now have changed to 17 inch wheels I can fit say 330 diameter discs but seeing that I am more than satisfied with the stopping power of what I have now have no plans to do so.

 

[obi_waynne]

At a certain point the grip the tyres have outweighs any advantage in braking power. You're probably near the limits there anyway but obviously bigger brakes last longer, fade less and dissipate heat more quickly than smaller ones so it's not all about pure stopping power.

 

[TCJBOLDIE]

You nailed it

 

[TCJBOLDIE]

Forgot to add that I have had custom tapered adapters that fit over the openings in sides of the spoiler that have a flexible hose that directs cooling air to the centre of the front discs.

 

[obi_waynne]

A word of warning to those ducting cold air to the brake discs, think about water. The last thing you want to do is start collecting water from rain/splashes and throwing these at the brake discs.

I'm only saying this because I saw a badly modified car with low intakes just behind the wheels which flipped the air onto the discs and it would have caught pretty much every speck of water the tyres threw up.

 

[T9 man]

Cheers for that Obi