14" Rotors on Non-abs car with a proportioning valve possible?

[hou99gts]

On my 99 GTS, I was wondering if the following was possible with a proportioning valve to achieve the correct brake bias?

- 14" Eurotech 2 pc rotors
- SRT calipers
- Big Brake Kit to make it all work

I would really prefer this setup versus having to use a stock 13" 1 piece rotor on the rear or another vendor's 13" 2 piece rotor.

I have 19" wheels on my car, so I have clearance. Thanks in advance!

 

[Chuck 98 RT/10]

Dave and Tom!!! Get in here!

 

[hou99gts]

HAHAHA - I just called Dave before your post, he highly suggested against it, but said a few have done it. I probably won't do it, but wanted to know if anyone had done it and what their results were.

 

[Tom F&L GoR]

You'll have to fill us in on Dave's comments. From what you said, you have four large calipers, brackets to mount them, larger rotors to clamp, larger wheels to cover them and the necesary item is the prop valve. Assuming the adjustment range is large enough, you should be able to "tune" the front-rear balance.

I keep my 17" wheels so the OEM rotors fill them up

 

[hou99gts]

Dave said you can get close (within 10-15%) of the correct balance with his proportioning valve, but advised against going this route.

This is just a "what if" question, I haven't bought anything yet. I'm still considering your 40mm kit and rear caliper cover.

 

[dave6666]

One more time as I know this is an old question... Why does it work on the ABS cars like mine? Either the ABS module is regulating pressures every time you get near the brake pedal, or there is some inherent differences in the system in general. Other fluid control orifices? Master cylinder balance?

 

[Tom F&L GoR]

Dave, you can answer this, I think. Even your ABS car has a mechanical prop valve, no? It would have been sized for the OEM calipers, and in case of ABS failure, should still allow reasonably safe braking.

Find a closed course in Mexico, pull the ABS fuse, and conduct some maximum braking tests. I hope (because then it makes sense) that the rear wheels will lock incredibly early.

So what happens in your car normally is that with application of the brakes, the rears do relatively more work until the ABS kicks in, because with the same brake fluid line pressure, you are producing more clamping force in the back. Probably feels like someone has an anchor on the rear bumper rather than tipping up on your nose.

Second, and I don't know much about this, but the Master Cylinder of the 01-02 cars and the 03 and up cars was the same. But I don't see how the master cylinder creates more or less pressure in the front or back because it is in-line; not like "real" race cars with two master cylinders, one for front and one for rear. Maybe there is a relationship between fluid volume (bigger master cylinder and bigger volume calipers) and the action of the prop valve adjustment?

 

[dave6666]

The master cylinder could have 2 different bores as long as the smaller one was in the front. Dunno. Just a thought, and don't plan on dissecting mine until she drips.