Wedge TR8 Brake Proportioning Valve

[HHL]

The Brake Master Cylinder on my TR8 needs replacing.
I would also like to replace the Brake Proportioning valve to ensure that both the Master and Proportioning valve are new and operate well.
The Proportioning valve seems to be near impossible to find. Can the original Proportioning valve be serviced/cleaned?

What are the solutions, opinions and experiences on alternative Proportioning valves?

1 TSI’s modified Proportioning valve;
2 Wedge Shop 50/50 block plus separate in-line adjusting valve;
3 Other proportional valve such as the Wilwood available at Summit Racing, (part 260-8419).

Thank you in advance for the information.

Henri
1980 TR8
1975 TR6
1971 MGB GT

 

[DNK]

Somebody was considering the Wilwood version.
Never heard

 

[Darrell_Walker]

Somebody was considering the Wilwood version.
Never heard

I was considering it (but a different one, Summit #260-11179), but never went forward as mine appears to be working fine. Also never got a definite answer on the proper adapters. But if mine wasn't working, that would be the option I would look into.

 

[Brosky]

I have the Wedge Shop block in mine. No adjusting valve needed.

I have Wilwood Big Brakes on the front with the upgraded larger size master and booster from Rimmer. Absolutely NO pedal drop with that bad boy.

 

[Darrell_Walker]

Hi Paul,

I assume the balance between front and rear is fine with this setup? No problem with the rears locking up early? Did you do both at the same time? I have the Wilwood fronts, but everything else is stock. I just wonder if there might be some more braking to be had in the back (not that I've noticed any problem).

-Darrell

 

[philman]

I had TSI modify my valve. It works fine for me, street use and some auto cross use. I have stock rear brakes and uprated front brakes (the larger princess sized disks).

 

[Brosky]

Both the master cylinder and the valve were changed at the same time. I had issues with a pedal drop that Woody said is not uncommon on cars with big brake conversions. He mentioned that he heard Rimmer was coming out with a fix in a bigger bore cylinder, so I called them. They also upgraded the booster internally, as this comes as an assembly. It was one of the first sold and the first that Woody installed. It took care of the pedal drop and the brakes work perfectly at this time.

 

[Darrell_Walker]

Thanks, Paul.

Can you describe "pedal drop"? I don't notice anything odd with my car. Do you just mean it takes more pedal travel?

 

[tr8todd]

Here are some things to consider. First off the stock proportioning valve was overly cautious about sending pressure to the rears. BL didn't want to have any issues of rear brake lockup and horror stories of cars swapping ends in a rain storm. The fact that the car nose dives under braking and it has such a short wheelbase, only make the issue worse. The solution was to give the rears very little braking at all. Stock brake systems will almost never lock up the rears. Ted was the first to come along and modify the stock PV by shimming the cylinder. It gives a little more rear brake, but nothing overly dramatic. The wedge shop block is nothing more than that- a machined block of aluminum with no moving parts. It looks good, and is a great marketing tool, but is nothing more than a tee in the line. Then there are the adjustable ones. They are great on everything but the TR8. Why you might ask. This is because the standard practice is to tee the lines evenly and then install the valve on the rear brakes, using the adjuster to lessen the rear pressure down till you get a somewhat even wheel lock up front to rear. Problem is, that when they are installed on the rear and set to no pressure differential, the rears still won't lock. The valve would give you even less rear braking as it's adjusted, but still more than what was stock. That is why the wedge shop block somewhat works. It's a simple tee and sends even pressure front and rear, which depending on front and rear brake selections may be helpful or not. On the TR8 race car which ran stock brakes, the only way I could ever get the rears to lock was to install the PV on the fronts and adjust the pressure differential down on the fronts until there was enough rear pressure to get them to lock. At that point you turn it back a couple of clicks to keep it safe and maintain more front braking than rear. If at any point you do a brake upgrade, or need to replace both the master and the PV, you should strongly consider going to an aftermarket booster, master, PV setup, and size the master cylinder bore to match the requirements of the brake piston bores. Generally a 7/8 or 1" bore is required for bigger aftermarket calipers. You can get a complete setup from Summit for less than the cost of a stock master and it will work with no "pedal drop".

 

[Brosky]

Todd about says it all. What I meant was that the pedal would actually "drop" about two inches before I had any braking action begin to happen. By that I mean that there was no action whatsoever in that amount of travel. It was just dead space in the pedal like the old mechanical clutch linkages used to be, then all of a sudden the brakes would start to work.

I guess that one could get used to it and deal with it, but it was not for me, or for when my wife tried to drive it. It's all fixed now and the brakes feel just like my MKZ.

 

[tr8dp]

Paul---
I did the Wilwood (woody big Brake conversion) on my car over the past couple months and took the car out the other day and really tried the brakes--hard. I noticed at a stoplight--my pedal had the dreaded drop also. It felt like the first 1 to 1 1/2 inches was nothing. Car stops under panic type stops but am concerned about the "drop". What again did you change on your car--booster and master? Prop. valve also? Let me know. thanks again--Daniel Perkins

 

[tr8todd]

The reason for the 2 inches of dead pedal is the front caliper pistons have a larger cross sectional area. It requires more fluid to make the pistons push the same distance. This requires more travel in the master to push the required fluid. Get a larger master and your pedal travel will be restored. A larger master used with the stock booster will be heavier to push. I would assume the master Paul has is a stock unit for either a Rover SD1 or a Jag that utilizes a slightly larger bore than did the TR7/8. I briefly looked into doing this on one of my cars, but the masters I looked at had the outlets on the opposite side of the TR8s and were too expensive. In the end I went with one of the aftermarket complete packages from Summit.

 

[Brosky]

Again, Todd has it down correctly. The booster that I got from Rimmer is a different booster (than stock) with a larger diameter bore master cylinder attached. That combination effectively reduces the pedal drop, per what Todd states above. I had the Rimmer big brake kit on the car originally and swapped it over to the Wilwood version.

During the changeover, I decided to swap out the valve, just to clean that area up once and for all.

Apparently, this has been a concern for some time, as Rimmer did not come up with the idea for no reason.

 

[Darrell_Walker]

The reason for the 2 inches of dead pedal is the front caliper pistons have a larger cross sectional area. It requires more fluid to make the pistons push the same distance. This requires more travel in the master to push the required fluid.

I guess this depends on what calipers you install. The Wilwood calipers that came from my kit from Woody this spring where Dynalite 120-6085 (https://wilwood.com/Calipers/CaliperProd.aspx?itemno=120-6805), which have a piston area of 3.0 sq inches (two 1.38" pistons on each side). I measured my stock calipers and the single piston is about 2.25", which works out to almost 4 sq inches.