TR2/3/3A Brake System Performance Expectations

[mastaphixa]

The biggest complaint I have with the '60 TR3 I'm working on is the brake system performance. I'm not sure if I have a problem, or perhaps the car is just behaving like they all did "back then". I have read any number of threads describing the sort of thing I am experiencing when I drive the car. The first press of the brake pedal is very long in stroke (almost like the calipers pistons are moving toward the rotors) with just a bit of braking at the bottom of the stroke. The next press brings brakes into the picture but after a lot more pedal travel than I am comfortable with. The pedal doesn't go soft, but the braking action is after SO much travel on the pedal, I'm just not confident in the brakes. Do some of you get a good firm pedal after an inch or two of travel or am I trying to achieve something the car just can't do?

I have bled the brakes with a vacuum pump. I've replaced the MC (no change in behavior of the brakes). Bled it at the MC output. Adjusted the rear drums. Gutted the 5 way. I've made sure there is slack in the push rod when the pedal is relaxed. Pulling up on the emergency brake doesn't make things better.

I'm all ears. Do I just expect to much?

Thanks in advance for advise!!

 

[TexasKnucklehead]

I don't think you are expecting to much.

I think the owners manual talks about the possibility of extra brake travel during 'spirited driving' -or (in my experience) when on very rough roads. If the rotors flex, they will push the caliper pistons back farther into the caliper, so it takes extra movement to push them back into normal position. I suppose a loose wheel bearing or warped rotor could cause the same thing. I also have that valve gutted. Rarely do I have excessive brake pedal travel. And it always gets solid braking long before the pedal hits the floor. I know some people switched the front to a Toyota system, but also hear that if your brakes are working properly, there's not much difference.

Make sure the rear brakes are properly adjusted. That seems to have the biggest affect on pedal travel. When you slam on the brakes, all 4 wheels should skid. The pedal should never need pumping, unless it needs bled -or that rare wheel flexing thing.

Good luck, let us know what you find.

 

[TR3driver]

IMO you definitely have something wrong. I can't move the pedal more than 2" or so unless I really stand on it (which might get to 3").

How old are the soft brake lines? If you pump the pedal up with the car not moving, does it go back down again while sitting still? Have you checked that none of the caliper pistons are stuck?

I've never had much luck with vacuum bleeding; have you tried doing it the old fashioned way with two people? (One opens the bleed valve, the other pushes the brake pedal down, then the first closes the bleed valve and the 2nd lets the pedal up.)

 

[number6]

I agree with Randall. Check the flex lines. If MC is good, the fluid is going somewhere, either expanding the flex lines or there is still air locked in the system.
I never had any luck vacuum bleeding, try the old fashioned way, pump the pedal.

 

[sp53]

Yes there is something wrong. Did you rebuild the master or put on a new one? The back brakes need to be tight, so the travel on the E brake is just a few clicks. Sometimes getting the correct wrench with some length for leverage helps get that last click on the adjustment of the rear brakes and like Randall suggested the calipers are not all working. And yes with the 5 way gutted the pistons will contract by rattling. I have about ¾ on an inch or less play on a rock hard pedal with Girling 4 brake fluid. I have also run synthetic without much difference, but some loss of braking pedal with the synthetic on a tr3.

 

[Geo Hahn]

Not much to add except I would be tempted to put the guts back into the restrictor and see what effect that has.

My TR3 has the best brake feel of any of my British cars - really rock hard and that is with DOT5. I have never messed with the restrictor so I cannot say whether it is intact or gutted. I have tried both ways multiple times on my TR4 and can only say that it makes a difference but each way has advantages and disadvantages.

I do have braided stainless lines on the TR3 and those may help. I didn't plan to do that but when I ordered new 'rubber' lines TRF was out of stock and Albert (bless 'im) offered to send me the braided s/s lines (no extra charge) to get me back on the road. Now I'd be reluctant to use anything else.

 

[malbaby]

All of the above plus....Have you checked the pedal linkages to see if there is any free play, as any small amount of wear will be magnified at the pedal pad. Also, as an experiment, adjust the push rod so there is no free play at all.

 

[Sarastro]

If you eventually get a hard pedal, it's probably not bleeding or soft lines. I would first look at the rear brake adjustment and the adjustment of the plunger at the master cylinder. I think your car has two adjustments at the master cylinder, one for the pushrod length and one for the pedal stop. If the pedal stop is too far in (i.e., towards the firewall), you just don't have enough range of pedal motion, and the brakes don't come on until your foot's almost to the floor. It's a common problem with Bugeye Sprites, which have a similar setup.

If those check out, take a look at the front brake calipers. Dunno about the TR3, but in some cars the piston seal distorts too much, so the piston cannot come to rest, as it should, with the pad almost in contact with the disk. Then the seal just pulls the piston back when you take your foot off the brake pedal. This is a universal problem in early Porsches; I've seen it occasionally in modern cars, too. The solution is to rebuild the piston with (we might hope) better rubber bits.

Sorry if I'm making any incorrect assumptions here; I'm a TR4 person, not TR3.

 

[sp53]

The brakes on a tr3 are a simple system. Only the early cars had the pedal stops. Get a new quality master cylinder; tighten up the rear brakes make and sure all your pistons on the caliper are working. I would rebuild them and the purpose of the 5 deal is to keep a little pressure on the front pads to the disk, so you do not have slop, but I have talked to people who have gutted theirs out and they found no difference. You can check the piston movement by pushing the piston back and put in an old pad and watch the piston come out. BUT and again and anyway a brake job should be a complete rebuild hoses and everything.

 

[TR3driver]

My experience has been that the effect of disabling the valve only shows up after fairly hard cornering. Lots of folks never drive their TRs that hard, so they won't see any difference. It is "real", but only results in the pedal being lower than normal, not by enough to have to pump the brakes (tho it can be momentarily disconcerting as the pedal sinks past it's usual location with no apparent effect).

But that is why I asked about the problem showing up when not driving. If it does, that would also rule out some other possible causes, like bad wheel bearings, warped brake rotors, hubs that don't run true, etc.

BTW and FWIW, there is an aftermarket fix for the spindle flex that the valve was meant to overcome. It was originally developed by a vintage racer ("uncle" Jack IIRC) and is still sold by TRF under P/N HP661. It will also work on the later TRs (through TR6) that did not have the RPV from the factory. I'm told that the uprated spindles and spacers solve the problem nicely, but haven't (yet) tried them out for myself.

 

[CJD]

Another thing that can cause what you describe is if the brake disc has runout, or "wobbles". The wobble will kick the pistons into the calipers, and they have to be pushed back out on the next application. It can be caused by dirt on the hub, a burr, or a bent disc and/or hub.

 

[DavidApp]

I presume this is the 5 way people are referring to?


Is there some type of piston/valve in the black portion? Do the rear brakes connect to the black portion?

David

 

[TR3driver]

Yup, that's it. There is a residual pressure valve inside the black portion, that is intended to hold a small positive pressure in the entire braking system (not just front or rear). The line from the MC goes into the top; the brakes connect to the 3 ports on the bottom (5th port is obviously the brake light switch). Here's a photo of the inside of the valve (sorry the colors are so odd, but you get the idea)

 

[DavidApp]

Hello Randall

Thank you for the info.

I probable need to take it apart and check it out.

David

 

[mastaphixa]

Thank you all for your input. Good stuff as usual. I revisited the rear drums and was able to tighten them up a few more notches. That helped, some old fashion bleeding really helped. I have a good firm pedal now. I am going to bleed it one more time as it's not as good after a long drive as it is at the beginning. Reeks of a little air in the lines. Even at that, I have more confidence in the brake system. I just discovered the brake lights aren't working, so I'll be getting that right before I drive it again. Thanks again all. Have a great weekend.
Steve in Newnan

 

[TR3driver]

FWIW, I finally gave up on the hydraulic switch and hid a mechanical switch on the pedal. The hydraulic ones kept taking more and more pressure to activate, I had 3 of them fail in less than 3 years.
Just a quick and dirty fix, but only took an hour or so even after I bent it the wrong way the first time and it's still working fine after 7 years or so.

 

[DavidApp]

Are you using DOT 5?
I have read somewhere that it can be difficult to bleed as DOT 5 tends to trap small air bubbles. Giving a spongy brake pedal.

David

 

[glemon]

Although no one ran with it, someone mentioned switching to Toyota calipers, that is a fairly straightforward swap, but the dual piston design takes more fluid volume to move, so your pedal will go lower still if you fit them.

 

[TR3driver]

Are you sure about that? My understanding is that the pistons are smaller, so the total area (and hence volume) is the same. Otherwise, the swap would upset the front/rear brake balance, which would actually degrade overall braking performance.

 

[martx-5]

The pistons are smaller, actually there are two size pistons in the Toyota calipers. However, the total area of the four pistons is a bit larger than the two pistons in the TR. Below are the sizes of each and the total calculated area of both calipers. Note that I don't show the area of individual pistons, only of them x2...

Original TR3
2 x 2.125" = 7.09” sq in

Toyota 4-Piston (79-83 4WD pick-up no diesel 820-821)

2 x 1.333" = 2.79” sq in
2 x 1.683" = 4.447” sq in total = 7.237” sq in

I have the Toyota calipers on my car, and before I put in dual masters, I didn't notice any difference in amount of pedal movement.