TR4/4A Brake question on the TR4

[doughairfield]

I finally found the time to get my brakes put back together on the TR4. On the front I did new braided steel brake lines, new pads, pistons and seals on the calipers. On the back I did new brake shoes, cylinders and springs on the drums. I bled the whole system twice today, but my pedal travel is still pretty far before it really firms up. You can't get the pedal all the way to the floor anymore, and a couple quick pumps really firms everything up at the top of the pedal, but after a short minute, it's back to the way it was. And I put in a new master cylinder about 6 months ago.

Granted, I don't have anything to compare the brake feel too except for how it was before and I wasn't blessed to have been born early enough to drive cars in the 60s. Is this just how it is or is there still an air bubble hiding out somewhere?

 

[HerronScott]

Doug,

If it takes several pumps to firm up, it sounds like either there's still air in the system or possibly the rear brakes are not adjusted correctly.

Scott

 

[TR3driver]

I think the moderator may have deleted it, but there was a thread just a few days ago about a defective new brake MC.

Should be very firm, especially with the braided lines. Did you change the rear line as well as the fronts? It could be ballooning.

 

[Andrew Mace]

If it takes several pumps to firm up, it sounds like either there's still air in the system or possibly the rear brakes are not adjusted correctly.

 

[doughairfield]

I did change the rear tube out and replaced it with a steel braided line as well.

After reading Scotts reply, I went back and read the manual again and may have found the problem. The manual says to run the adjustment screw all the way in and then back off one notch to free the drum. The first time I misinterpreted that and ran the adjustment screw out so the pads were all the way in. I went back and ran the screw in until the drum would not turn, then backed it out until the drum would turn with a little drag. The pedal feel is much better, not quite what I expected but engages firmly at least a 1/4 of the way in.

I'm going to bed the new brake pads and then try and other bleed session. Maybe moving it around out on the road will help any air left in there shift around.

 

[Andrew Mace]

I often find that adjusting the rear brakes involves 2-3 tries, with a bit of either pedal or handbrake lever in between to re-centralize the shoes as necessary. Beyond that, the rear shoes also might need to bed in a bit.

With the new wheel cylinders in the rear, are they lubricated so that they will slide easily? That also can make a difference.

 

[HerronScott]

Doug,

Glad to hear that it's better at least. As Andy indicated, I would certainly try adjusting the brakes again after letting them bed in some to insure that they really are centralized and that they aren't adjusted out too far.

It's been a long time since I've driven my TR4A but as long as you have a firm pedal without excessive travel you should be in good shape. I do seem to recall there being more travel in my TR4A and my wife's Spitfire than on cars with servo-assisted brakes, but could be faulty memory. Maybe someone who's driven theirs in the 21st century could offer a comparison.

Scott

 

[doughairfield]

Well I took the TR4 out for a spin to bed the brakes and the pedal travel is still pretty excessive. It will stop but I don't have much farther to go before I hit the floor board. Is excessive pedal travel typically air in the system? Also, if I pump the pedal, I get a moment of firm pedal at the top, is that also a symptom of air in the system or a problem with the MC seal?

I feel like there is still air in the system, but I bled the system twice and didn't encounter any air the second time around.

I have heard about doing a reverse bleed on the system as sometimes that can move the air bubble out. Anyone found reverse bleeding to be effective?

 

[3798j]

Doug - I used the Phoenix Reverse Bleeder (basic kits run $60-$70) to do the notoriously difficult Ford Ranger hydraulic clutch. It worked well as advertised. Having said that, you probably won't be glad to hear that I've always bled the TR4A's brakes either the conventional two person way or with the use of a MityVac with no real difficulty getting a firm pedal.

 

[angelfj1]

I finally found the time to get my brakes put back together on the TR4. On the front I did new braided steel brake lines, new pads, pistons and seals on the calipers. On the back I did new brake shoes, cylinders and springs on the drums. I bled the whole system twice today, but my pedal travel is still pretty far before it really firms up. You can't get the pedal all the way to the floor anymore, and a couple quick pumps really firms everything up at the top of the pedal, but after a short minute, it's back to the way it was. And I put in a new master cylinder about 6 months ago.

Granted, I don't have anything to compare the brake feel too except for how it was before and I wasn't blessed to have been born early enough to drive cars in the 60s. Is this just how it is or is there still an air bubble hiding out somewhere?

Doug: You have a PM