"My experience of big brake upgrades"

Pete Humphries details his experiences of brake upgardes...

Over the past few months I've had a lot of questions from people who want to upgrade the brakes on their TVR but aren't sure about the best way to do it. I seem to have tried most of the popular upgrades on the V8S so I thought I'd share some of the lessons I've learned along the way.

Why upgrade?

The original brakes on the V8S were 240mm single pot calipers/vented disks at the front and single pot calipers/non-vented disks at the rear. These are identical to the brakes fitted to early 4.0 Chimaeras and Griffiths. Newer cars have basically similar brakes but with larger vented rear disks and slightly bigger calipers. These brakes are perfectly capable of stopping the car, the limiting factor is how quickly they can dissipate the heat i.e. how often you can use them before the pads overheat and fade, or the brake fluid boils in the calipers. In normal use on the road, this should not be a problem. But when the car is driven hard on the track with an aggressive braking style, it is possible to overheat the brakes. The warning signs are having to push the pedal harder, increased pedal travel or, in extreme cases, a pedal that goes to the floor as the brake fluid boils. The excessive heat may also warp or crack the disks that can cause brake judder. The sensible action at this point is to ease off and give the brakes a chance to cool, and not push quite so hard in future. But once the brakes have been overheated like this they never fully recover, and I find it's usually necessary to replace the pads and fluid. Replacing brake pads, disks and fluid after track days quickly lost its novelty value so a few years ago I started what turned out to be a long succession of brake upgrades.

How far to go?

Brake upgrades can be expensive, and there's no point spending more money than you need to. But if you're going to upgrade the brakes, it's worth deciding how far you're going to go and replacing the brakes once. Doing the upgrade in lots of small steps like I did is very expensive! There seem to be three conventional upgrades:

Stage 1: Fluid/Pads/Disks/Ducts/Braided pipes

There are some inexpensive changes that will improve the heat dissipation a little. If your brakes are marginal these changes may be enough to keep you out of trouble.

DOT 5.1 fluid allows your brakes to operate at higher temperatures without boiling. It absorbs water relatively slowly so it doesn't need to be replaced any more frequently than the normal DOT 3 or DOT 4 fluids. Best of all it's fully compatible with the normal fluids so there's no need to flush the system or replace the seals.

You can also fit harder compound brake pads. These can work at higher temperatures without fading, but there's a compromise - the higher temperature rating they provide, the less likely they are to work well from cold. Avoid "race" compounds, "fast road" are the ones to go for. Make sure you follow the correct bedding-in procedure for your particular pads. For example Tarox XF pads have a very high temperature rating and work well from cold, but if you don't put them through the correct heat cycles while they're bedding in they don't work at all well. Mintex 1144 pads are far easier to bed in but don't have such a high temperature rating and don't quite have the grip of the Tarox pads.

I've also used Kevlar 'Green Stuff' pads with mixed results. The high-temperature performance is phenomenal and they just seem to work better and better the hotter they get, but they don't work very well for the first few minutes on cold winter mornings, and the disk wear is significantly greater than normal.

You can also fit grooved or drilled disks. These are a direct replacement for the standard items, and they're claimed to disperse gases better during braking, reduce pad glazing and improve heat dissipation. They have the disadvantage that they wear the pads faster, and drilled disks can be prone to cracking if they're severely overheated.

Braided pipes will also help improve the feel by preventing the normal rubber pipes from expanding slightly under pressure leading to a softer/soggy pedal feel.

The final change is to fit air ducts to direct cold air to the brakes. On fast circuits these can noticeably improve cooling, on slower circuits I found little benefit.

The uprated components are typically only a little more expensive than the standard ones. On my car I would guess these changes improved heat dissipation by roughly 25%.