Passat Syncro Vented Rear Disc Options?

[efritsch]

Hey all.

I have a 92 Passat Syncro Wagon. I recently put an ABA bottom end in it with a 268 cam and a 13lb flywheel. It already has a stage 3 charger on it. While I had the entire powertrain on floor, I ran new brake lines and converted it to a vacuum assist setup instead of ABS.

When I converted, instead of capping on master port, I went and got a 2 in/2 out prop valve for the rear. Actually the only one my supplier listed for this car, not the 1 in/2 out that was there originally. Anyway, since I have my car lowered 2" or better, the prop valve always thinks the rear end it loaded and stays wide open. I've noticed that the rear brakes get warmer than the fronts when I've been doing some spirited driving.

Since the rears are already doing enough work, I don't want to go to a bigger rear rotor and have rear lockup issues. I would like to put vented rear discs in to aid in cooling and obviously ditch the solid rear rotors.

Does any one know what needs to be done to install vented rear rotors?

Thanks in advance.

[efritsch]

Bueller?

[polov8]

Sounds like you're curing the symptoms, not the illness. The rears are getting hot because they're being asked to do more braking than they should, that's the issue, not the non vented-ness. is there no scope for adjustment or modification of the rear load based bias valve? It needs to be adjusted so it acts as it did when the car had its stock ride height.

[-RalleyTuned-]

Exactly, you have 2 options, adjust the stock valve on the beam, or replace it with an aftermarket adjustable one

[efritsch]

Granted, the valve needs to be adjusted but none the less, does anyone know if there is a way to put vented rotors on the rear?

[TBT-Syncro]

you should fix the problem, not hide it.

have you tried adjusting the sway bar position adjuster? or did you remove it with the new proportioning valve? (you probably have way too much rear bias right now)

[polov8]

Corner braking in the wet will be "interesting" if you do have the rear bias set too high!

Seriously, your rear brakes should not be running that hot, you don't need vented discs, you need to sort out the bias!

[efritsch]

Actually, corner braking in the wet is fine. If I hadn't washed the car that one day after driving it and watched the rear brakes steam, I would never have noticed the valve bias like that. It brakes really well the way it is.

I am going to adjust the valve when I get a spot at work to put it on the hoist but I would like to put vented rotors on the rear anyway. I know there was someone selling adapters to put 11" rotors on the rear but I don't feel the need to go big rear brakes.

[-RalleyTuned-]

Wait a sec...You washed your car after you had driven it and because there was some steam coming off the rotors you are assuming that you need vented rotors??

Lets get a little better into this...what else is telling you that you are over heating the rear brakes? Keep in mind a dragging caliper will heat up the rears quite a bit too, and is much more likely causing that than the rotor design.

Most cars (ours included) rely over 75% of their braking on the fronts, it may be a little less on a heavy awd wagon, but not by much. You would probably have to be on a track or repeatedly stopping from 80mph to actually over work the rear brakes on your car to the point where the heat is actually a problem.

[efritsch]

Yes, I realize steam coming off the rotors would be normal, what I noticed was more steam coming off the rears than the fronts.

And yes, I realize that the spring that actuates the prop valve needs to be adjusted.

Do I need vented rear rotors? Probably not right now.

Is the car only going to get faster as time progresses? Yes, it will.

Do I want vented rear rotors? Yes, I do.

If no one has done it or knows what will work, fine, I'll work it out myself. I just thought I'd ask first instead of reinventing what someone might have already done.

[MrDave]

The rear rotors on the syncro cars are very similar to the front rotors on A1/mk1 Rabbits and GTIs.

Making the vented front rotors from a mk1 GTI fit the syncro would require a spacer for the caliper carrier. You'd have to run thinner pads. Not sure where to find those.

I have solid mk1 rotors on the back of my syncro. $20 a pair instead of $150.

My next upgrade for the rears would be drilled and/or slotted. Probably wouldn't ever need vented rears, the way I drive.

-Dave

[-RalleyTuned-]

If no one has done it or knows what will work, fine, I'll work it out myself. I just thought I'd ask first instead of reinventing what someone might have already done.

There is no bolt on or direct upgrade to vented rotors using the same size disc. You can either upgrade to a larger vented rotor or use what you have since it is working well as it is VW did a really good job of matching the cars breaking power with the weight of the car (which has much more bearing on brakes than hp), however if you plan on adding a ton of weight then you may need to increase the braking performance.

[TBT-Syncro]

rear bias doesnt need to increase as you add more HP. Hell, with 500HP and 4 piston calipers in the front on my car, and there is still too much rear bias. I have a Wilwood adjuster to install, but put it somewhere and cant find it. lol

when you adjust the rear bias, you need to do it with the car on the ground so that the suspension is loaded and the rake of the car is in its normal position. that adjuster is really more for changing bias as the pitch of the car changes.



and as has been stated. there is no direct bolt vented rotor with the 9in rear rotors.