Brake pedal sometimes is low on first press but otherwise is always high

> I went to an autocross last Sunday. Thought it would be fun to let my
> buddies see me slide around on the brick-like tires it is currently wearing.
>
> I launched, then made a few turns, accelerated, changed up to second. Then
> I needed to use the brakes for the first time on the run. The pedal dropped
> more than half the travel. The brakes worked fine, but it felt really weird
>having such a long stroke to get to them. Scared me half to death the first
>time.

>After the run, the brakes pumped right up. Checked the reservoir. Fluid
>full, as normal.

>Brakes worked normally in the marshaling lane and all the other times

Reply from: Jack W. Drews

I had the same problem with my TR4 vintage racer. It took three years and trying LOTS of things before we finally tumbled to the root cause. On the way to the solution we tried everything -- including aftermarket residual pressure valve for the front circuit.

Something is happening with the front wheels to push back the pistons in the calipers during cornering. With my car, this happened only after a left-right-left sequence of corners.

It could be loose wheel bearings, but that was not the case in my car, and is apparently not the case in yours. You could check to make sure that the nut holding the front spindle in the upright is still on tight. They have been known to loosen, hard as that is to imagine. In my case, the cause was that the rotors had been turned a couple times and were under spec on thickness. I completely solved the problem with new rotors. I have since found on my car that this problem will start with any irregularity in the rotors -- taper, out-of-true on flatness, etc etc.

NOTE FROM TERIANN:

As Jack mentioned, low brakes on on a first push can be caused by the front wheel bearings being set too loose, which they will be if you follow the instructions in the TR3 shop manual.  The published instructions are for the early drum brake TRs.  Triumph issued a service bulletin that provides instructions for adjusting wheel bearings on disk brake Triumphs.  Also be aware that the current felt pads are initially thicker than the old ones and will compress with use.    After replacing the felt pads it is a good idea to go back and reset the front hub bearing clearances after about a 100 miles.

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