Tom's 40mm brakes

[Fatboy 18]

I found prior to fitting the 40mm rear calipers the braking on a gen 2 seemed to be 70/30 to the front. I got fed up with locking the front brakes under medium hard braking.
1st mod I did was to fit stainless brake lines. I did not notice any difference but it seemed a sensible mod over the stock lines, next was to fit the 40mm upgrade.

Having fitted the 40mm brakes it changed the balance of the car to 60/40 to the front, I could still lock the brakes but also the rears were now making a big difference. So for street driving they are perfect.

Brake fade at track events was another story. I found after a few laps that sometimes my brake pedal would go to the floor due to the fluid overheating, at the time I had the OEM fluid in the car. I then swapped that out to Motul 660 brake fluid and also spent some considerable time making / fitting the fluid recycle system for the front brakes. Since doing that I no longer get any issues with brake fade and have now dropped form Motul 660 fluid to 600. Note I am using Baer 13" 2 piece slotted rotors.

If I was starting over from scratch, I think I would go to larger rotors Gen 3 calipers, Gen 2 front calipers on rear and the parking brake kit (but its not cheap and is relative to your budget). upgrade the brake fluid to Motul 600, but my car came fitted with the Baer 2 piece rotors so I just continued to upgrade what I had over time when cash allowed.

Below is a pic of my car with pretty much full lock up (running Toyo R888s) turning right and drifting slightly sideways into Hammerhead on the UK Top Gear track 2 up, and was braking from 150mph fast (in a sprint event, I left the braking right until I hit 150mph in a headwind and was running out of runway fast!). The thing is, no brake fade and I felt confident in what I was doing. From experience I certainly cant say that about the stock brakes I would have been off the end of the runway and probably into the next 2 fields! The sticky tires helped me get round that bend too

[MrCreosote]

Not a good idea. You will basically just have front brakes

Didn't one of the front upgrades have smaller diameter pistons?

[TTSnake]

Not a good idea. You will basically just have front brakes

So I can't balance the system with a proportioning valve?

[Fatboy 18]

Didn't one of the front upgrades have smaller diameter pistons?

No.

[GTS Dean]

Just removing the spring from the OE prop valve will give you a significant improvement in performance for ZERO dollars other than fluid bleed. I've done that AND gone to the 40mm caliper mod and STILL have OE front calipers. I have something like SIX THOUSAND track miles on my car.

[MrCreosote]

Only if you have extra rear braking. You only put the Pvalve on the rears. If you don't have enough rear, then the pvalve isn't going to fix that.

[MrCreosote]

I experimented a lot with incremental fluid, pad compound, brake bias and rear piston diameter before coming up with what I've run for 20 years with a lot of track time and road miles under my belt. I pulled the nut off the rear proportioning section of the combination valve and removed the proportioning spring, then screwed the cap back on and did a full bleed. Braking improved noticeably. I then went to the 40mm kit and found that I could get them to actually make enough temperature to experiment with pads again.

If most of your driving is street, a matched set of pads is not a bad thing because you will likely never experience the dynamics and temperatures of track driving.

What I like is a rear pad that has really good initial bite, medium torque and not too much increase with temperature. I like fronts that modulate really well with progressive temp increase and good release properties to combat front lockup. Having the rears less sensitive to pressure and a slower release helps the back end be more predictable with trail braking. When weight transfers to the front, you don't want too grippy a back pad or you may loop it. If you have adjustable shocks, adding a little more rear rebound and front bump stiffness will give you better initial weight transfer control under braking to use the rear performance improvement.

I know absolutely nothing about picking out pads. I know I don't want fade and I know race pads don't work until they get nice an toasty. I'm trying to remember, but I think I have EBC Greens in my 96 GTS (should probably be Reds). With Tom's which I just got and stock fronts, what would you recommend in pads? EBC good enough? Mixed colors maybe?

Thanks,
Tom

NOTE: I've done a little track time, maybe 10 days total and doubt I'll do any more. A day's shifter kart class in FL changed me - on the way home, I was drifting my $72k 2000 GTS (most I ever spent on a car was $7k at that time), that I had driven to FL during a snow storm from Pittsburgh starting with 90 miles on it, around a 270* rte 826 on ramp in North Miami Beach, beating on it like a rented mule. Doug Levin told me about the class and I ended up staying in FL 9 weeks instead of 2. Bike Week was awesome as well as Sebring. Sebring is whole other story.

[TTSnake]

Just removing the spring from the OE prop valve will give you a significant improvement in performance for ZERO dollars other than fluid bleed. I've done that AND gone to the 40mm caliper mod and STILL have OE front calipers. I have something like SIX THOUSAND track miles on my car.

You mean that annoying high compression spring that makes it impossible to reinstall the valve stem?

[goggles Pizano]

On the road so all I can do is this. you remove the hex bolt and remove the spring inside.

pvalve.jpg