944 N/A rear discs on IRS (again)

[flat]

KaferChris,

You've done your research! Everything you mentioned is correct. Out of curiosity, keep in mind you can use your stock T1 stubaxles if you don't want to change your axles. You will also need the 944 rear hubs. The T3 hubs are not easily adapted without machining. It's easier to get the 944 hubs.

As for the rear bias:
The 944 master cylinders are typically 23mm/19mm. That is 23mm in the front circuit, 19mm in the rear. If you are going to use a stock T1 MC, then you should be alright as far as hydraulics is concerned because T1's are 19mm/19mm. It's difficult to calculate brake torque from a given hydraulic pressure in a drum system because of the leading/trailing shoe arrangement. Also, leading shoes in a drum system have a 'servo' action. Check here for more hydro info:

http://www.vdubcustoms.com/Tech/tech_brake.htm


I think you are on the right track, and if anything you hay have a little too much rear bias. You always want to setup a vehicle so that the front tires lock a LITTLE earlier that the rears on panic stops. Understeer is easier to control than oversteer. If you have too much rear brake, then you can add a proportioning valve to the rear circuit and fine tune your vehicle. There are lots of variables here (weight distribution, tire size, tire quality, weight transfer, suspension setting etc) that play a role here. I think you're on the right track.

One question though, why 944 brakes on the back on not on the front?

Easy,
Lanner

[KaferChris]

Lanner,

First off, thanks.

I built the front-end months ago and have been working on my rear suspension lately...I've got complete Type III rear brakes done-up for the car (sandblasted and painted every last piece, all new everything), but I guess the idea of not adjusting brake shoes is just too tempting...so I threw those on one of my other cars.

I figure I'll get the car running using the stock VW disc assemblies on the front, and perhaps upgrade to 944 4-pots and vented rotors in the future...

Doing all the 944 brakes will also get me away from my ~1" spacers all the way around. I was using Boxster 16" split 5-spokes (16x6 ET50's and 16x7 ET40's) but have recently picked-up some C2/C4 16" 5-spokes (16x7 ET55's and 16x8 52's).

I plan to upgrade to either Type IV CV's with the appropriate machining or Type II CV's since I'll probably one day want to put ~150-175hp down...aiming for ~120hp for now with a mild 2017.

Thanks again,
Chris

[KaferChris]

Thanks again for the advice and parts.