TR6 TR6 Brake Upgrade

[bobh]

Hi,

I recently completed an major upgrade to the brakes on my TR6. The master cylinder was beginning to leak slightly around the input rod. These are the things I did
1) Had the MC sleeved and rebuilt
2) Stripped and painted the vacuum booster
3) Installed the 7/8 wheel cylinders on the rear
4) Installed the 4 piston Toyota calipers on the front
5) Relaced all hoses with stainless braided hoses
6) installed finned aluminum drums on the rear.
7) Filled the MC with Dot 5, Silicone brake fluid
8) Bled the entire system. After all air bubbles were gone
We pumped 2 more times per corner to ensure no air remained.
9) Adjusted the rear brakes

When I test drove the car the pedal would first go nearly to the floor. When I release the pedal and pump a second time the pedal firms up and everything works fine.
I have not bled the system after the test drive

With all new hydraulics I didn't expect anything other than a firm pedal.

The rear brakes seem to be working fine. In fact almost too well. I painted the aluminum drums with silver Hi Temp caliper paint to keep the aluminum from oxidising and make them easier to clean. On the initial test drive while bedding the front pads the heat generated by the rear drums caused the paint on the drums to discolor. They are now the color of a lightly toasted marshmellow.

Does anyone have any ideas why the pedal is not instantly firm?

Considering the rear brakes appear to be functioning fine. I'm wondering about the front calipers/pads. I'm thinking of removing the springs that push the pads /cylinders back into the calipers, or having some shims laser cut to position the pads closer to the rotor.

Thanks,
BOBH

 

[DNK]

Frequently with Dot 5 you need to bleed a second time

 

[TR3driver]

One of the down sides of DOT 5 is that it can form tiny bubbles of air when agitated; which are too small to see but still compress under pressure. I find that it helps to wait some time after adding to the reservoir, before trying to bleed the brakes.

Anyway, my next step would be to bleed again.

If your MC is working properly, then the pressure is the same both front and rear, no matter which end needs more displacement to come up to pressure. So having the rear brakes get hot while you were deliberately getting the front brakes hot is perfectly normal, and doesn't tell you which side has air or whatever. Due to the design of the MC, the pressures will only be different if one of the MC halves has run out of travel.

 

[trrdster2000]

BobH, I'm a little concerned about the heat in the rear, check to see if you are getting a release on the rear. Possible a broken spring in the master or a rear return action. Do you still have the proportion value in the system, see if it is centered.
I had this problem one time and the tube at the wheel cylinder had a kink in it and was holding pressure.

You can check by jacking the car up after a run and releasing the bleeder and see if there is pressure.

Wayne

 

[davidk]

As Wayne said, do check to be sure that the shuttle in the PDWA is centered. I have the same setup you have installed. I didn't have an issue bleeding them, but you'll know when it's right, they're very balanced all the way around.

I'm looking for a set of finned aluminum drums for my Six. Where did you find them?

 

[booley]

I'm looking for a set of finned aluminum drums for my Six. Where did you find them?

https://www.wbclassics.com/content/al-fin-brake-drum-triumph-tr4a-tr250-tr6

 

[DNK]

Now "THAT" is a can of worms

 

[bobh]

Thanks guys. I'll try bleeding them again and check for kinks in the hoses.

I bought the aluminum drums 5 or 6 years ago. They are made by Brembo. I bought them from a place called Buy Brakes.com. I don't see them listed there anymore. The part number is Triumph p.n : 88-210578. I have the Brembo drawings if any of you would like them. Let me know your email address and I'll send them. I got them from another board member several years ago. As far as I can tell they are no longer made. I see some Polish postings online but don't know if they actually have them.

DavidK,

Does your setup have a firm pedal everytime you apply the brakes?

Thanks Again,
BOBH

 

[tdskip]

BobH - my rebuilt TR4a system with DOT5 does the exact same thing. Letting it sit while traveling for work, will bleed it again this weekend.

 

[davidk]

Thanks BobH. Yes, a very firm pedal every time.

 

[davidk]

Booley, thanks for the lead, but $400 for the pair is more than I want to spend!

 

[hondo402000]

when you worked on the brake booster, on the front where the MC bolts, there is a small screw with a ball on the end and a lock nut, did you touch that? it makes contact with the Master cylinder and there is a clearance between it and the MC, too much clearance and you will have a greater peddle travel. I bought a new brake booster and there were no instructions on how to adjust it, and when I bleed the brakes they would go half peddle before getting firm, I kept adjusting that ball screw out about 1/4 turn at a time till I got a firm peddle at about 1/2 inch travel. Also I got my wildwood calipers and 7/8 rear wheel cylinders and uprated front axles for my TR6 last week from goodparts and plan on installing them on Saturday, and in the instructions from Goodparts he recommended dot 3 or 4 brake fluid and in his opinion said not to use silicon brake fluid, something about the air bubbles and the fact that silicone would not absorbe moisture like dot 3 and 4 and the moisture would separated and under hard braking boil and then you would have no brakes. I know dot 3 and 4 will also absorb moisture over time but I guess the only difference is its distributed in the fluid and not a clump of water at the lowest point?

hondo

 

[trrdster2000]

Hi all, as information, Autozone does show the finned brake drums that are steel for the 1976 280Z. With a little bit of grinding they work fine, and only cost around $80, paint a high heat aluminum, if you have spokes and you have the upgrade.


Wayne

 

[bobh]

Thanks again guys.

When I bought the aluminum drums they were around $70 each. This was in the same time frame that TRF had a batch. Since then I've read that Brembo was no longer making them. It seems like they said they needed a minumum order to run another batch. The number escapes me but it was high. That may explain whi WB is asking $400 per set.

Hondo,

Thanks for the input.
I didn't make any adjustments to the booster. When I removed the MC I could see the small amount of brake fluid that leaked had removed the paint in the very bottom of the recess where the rod protrudes. I used a wire wheel to strip all the paint off the outside of the booster and a little sand paper to get into that recess. I etched the entire outside with "Aluminum Jelly". rinsed and dried. Then painted with VHT semigloss black caliper paint.
If beelding a second time does not solve the soft pedal issue I'll check the rod on the booster.

I've read several comments on the internet about bubbles in silicone fluid. Some peopple are completely againts using DOT5. Others like it for cars that are not driven often. Some use it because it does not remove paint. I decided to use it for both reasons.

When I decided to use DOT5 i was undecided on how to purge the system of the old fluid. More research indicated that DOT5 does not mix with the older fluids. Since there was only a small amount is the pipes and the PWDA I decided to just fill with DOT5 and bleed.
As advertised the old fluid came out on blobs before the clean DOT5 and the usual large bubbles started flowing. I can imagine there could be some turbulance withing the system considering the size of the bubbles coming out. That could have caused the tiny bubbles mentioned in Randall's response.

If I can get a helping foot I will try to bleed again this weekend. Whenever I do I'll post the results.

Thanks again for the replies,
BOBH

 

[DryGuy]

BobH -- I have the identical build and the same problem. Did you find an answer? I am about to launch into this head first -- HELP - thanks DryGuy

 

[Geo Hahn]

BobH has not been on the Forum since last year so likely no help from that corner.

The point made about DOT5 needing to sit quietly to allow bubbles to escape is quite true in my experience. I fill the reservoir to the top and wait a couple of days before doing the bleed. Even during the filling care must be taken - pouring the fluid down the blade of a very clean screwdriver is one way to minimize the introduction of air.

 

[Foura]

When I had the 3A in the 70s(??!!) I had the same problem. The first application of the brakes in the morning, the pedal would go to the floor. Fine for the rest of the day. It turned out to be the wheel bearings. When they were loose, the brakes would cool overnight and the pads would be at an angle to the disc and would need a long push to get them roughly parallel to the disc. Adjusting the bearings fixed the problem.

 

[bobh]

Sorry guys. I retired at the end of Jan this year. I've only visited the forum a few times and never logged in. Also have not driven the TR lately. I still need to bleed the system again. I did buy some speed bleeders that need to be installed. Still need an extra foot to ensure the bleed goes well. None of my neighbors have any interest in cars. Certainly zero interest in working on them. After it cools down a little I'll get back to the TR. Cooler weather and retirement should be a great opportunity for some driving.

BOBH

 

[tdskip]

Good luck, and as someone with the same set up it is worth the hassle. Pedal should be firm, if not yiu have an issue somewhere still.

 

[Marvin Gruber]

Bob,
I'm in Florence, Al. About an hour away from you. I 've got a couple of TR6s and a barn full of parts. Let me know if I can help.
Marv