Wedge TR7 or TR8 Master Cylinder

[tr7andtvr]

Has anyone ever swapped a TR7 master cylinder for another application? I would like to get a little more performance and something that is a little cheaper also? I know that a 240 Volvo calipers are an upgrade for a TR7 / 8 was wondering if the master cylinder was also. Any ideas?

 

[JeffYoung]

I didn't think much of the Volvo calipers actually. In race situations they didn't do much better, if at all, than the stock TR8 calipers. The big thing is heat, not clamping force, and going to a vented disc is the biggest improvement you can make (illegal for me, I have run two ducts to each side).

I also ordered a "TR8" master cylinder and brake booster one time from one of the reputable British parts houses. It ended up being an SD1 master cylinder and booster -- slightly longer master cylinder and the booster felt more boosted.

In any event, I don't think the TR8 master is the weak point in the system. It's the solid rotors and small pads. Go with vented discs if you can, and then bigger calipers (the 240s were nearly identical to the TR8 calipers).

Last, get the rears to actually work. Modify the prop valve and put some good shoe material on there. That will help tremendously in getting front brake temps down and overall brake performance increased.

 

[tr7andtvr]

Well let me go back.... I have two bad master cylinders on two diffrent cars. I would like to find a upgrade while I am doing the replacement. I would also like to find something that is less money.

 

[JeffYoung]

Hmmmm....how bad are they? Just the seals? REbuild kits are cheap.

I'm sure something else will bolt on but all I am aware of is the SD1 master cylinder and that required some modification of the pipes to fit back into the holes (how I figured out it wasn't a TR7/TR8 master). How much are Tr7/8 masters? $150 or so?

 

[tr7andtvr]

For a new one they run $150-$250. I understand the rebuild thing doesn't work real well?

 

[JeffYoung]

It depends. You have to be extraordinarily cleanly when you do it. Any dirt, etc. on the seals and you are toast. Also, your bore has to be in good shape. No rust, not worn, etc.

Another solution is have apple hydraulics rebuild them. They do extremely good quality work. Go here: www.applehydraulics.com.

 

[tr8todd]

By "upgrade" what do you mean? Do you mean a larger bore? It is important to match the bore size of the master with the combined bore sizes of the calipers and/or wheel cylinders. The best upgrade for a street car is vented front rotors and and adding discs to the back. I am working on a car for a guy now that has Willwoods in the front and Ford calipers and discs in the rear. Because of the extra fluid transfer requirements, we needed a larger master. The one on there now is a street rod cast iron unit with a 1" bore. On my street car, I have a Wilwood 1" master to go along with my Willwood calipers. On the race car, the key was to use a proportioning valve on the fronts to dial in more rear brake. That plus alot of other little tweaks.

 

[JeffYoung]

Todd makes to very important points. The best upgrades you can make to a TR7/8's brakes are to put vented discs up front (easy) and discs on the rear (a bit harder). If you cahnge out calipers, Todd is also exactly right and it is very important that you get the M/C bore diameter correct.

I would, however, respectfully disagree with putting a proportioning valve in the front line to turn down the front brake pressure and give you more rear brake bias. You need all the front brake you can get. On the 7/8, the easiest way to get the rears to work is to fix the prop valve and use higher friction rear shoes (Carbotech or Porterfield).