Proportioning valve advice

[atxz06]

I have a 77 Corvette (stock 4 wheel disc) that I'm installing Wilwood 14" front and 12.19" rear.

Spoke with Wilwood on the phone and was told that due to the size discrepancy between the front and rear that I either shouldn't need to run a proportioning valve or to install it on the front if I really felt the need.

I'm not brake expert by any stretch but wanted to run a sanity check on this advice. (I'm limiting myself to 12.19" in the rear so I can run 15s with drag slicks if I so choose)



Should I be ok leaving the stock proportioning valve plumbed in?

Thanks

[Apogee]

First off, I would never recommend installing a proportioning valve in the front circuit on any pro-touring application...or really almost any application for that matter. You want predictable, linear behavior from the front brakes and your front brake requirements only go up as you stop at higher rates of deceleration and transfer more weight to the front of the vehicle.

Without the piston areas of the calipers you're running, I'm just guessing that Wilwood's recommendation was based on the assumption that your front brakes with your current setup will overpower the rear, so adding an adjustable proportioning valve to the rear circuit won't gain you anything because you'll achieve front lockup first, not rear, hence eliminating the need for the prop valve. Why they would suggest adding one to the front is beyond me and you would have to ask them about that.

You haven't said what you're working on, however by leaving any proportioning valve in the rear circuit, you're reducing the pressure to the rear brakes above the knee point which means that you're even further reducing their effectiveness and contribution to the system as a whole.

You could stagger your pad compounds and run a more aggressive compound in the rear to try and make up for the lack of piston area and rotor diameter, however that can be a little trickier than it sounds due to variations in pad coefficients of friction with temperature.

Kinda off topic, but what do you call a dual pro-street/pro-touring car? Pro-String? Pro-Tweeting?

Tobin
KORE3

[atxz06]

Thanks for the feedback. Sounds like I'll need to assemble the system and perform some live tuning to get it dialed in based on how it behaves.

*laugh* I've wondered about the answer to your off-topic question as well given that's what I'm building. There isn't really a dedicated forum for "pro-tweeners" like myself that live in the void between pro-touring and pro-street but want to incorporate ideas from each so I bounce around a bit and pick up the relevant pieces as they apply.

[Apogee]

Sure, no problem. Live testing should tell you more in a matter of minutes than keyboard quarterbacking, but post up what you find and I'm sure myself and others would be more than happy to throw our $.02 in the mix.

Pro-Tweening...I like it, although it makes me think of 11-12 year old professional Justin Bieber-stalkers. We'll have to let the P-T masses try out the options and see what sticks.