-------------- Original message --------------
From: "Navarrette, Vance" <vance.navarrette@intel.com>
> Folks:
>
> Here is a problem I have not seen discussed very much.
> It seems like perhaps a piston is retracting too far back into
> the caliper. The first use of the brakes pushes it back out and life is
> good thereafter.
>
> Anyone else had similar issues (it seems like someone has, but
> my memory is so dodgy any more)? Is there a cure, or is it simply a
> matter of learning to live with Lockheed brakes?
I have expericnced this for years in my TR6, especially after turning the wheel
sharply as in turning into or out of a driveway. I've also experienced this
while autocrossing my TR6. Many of my racing friends have had this problem in
their TR's as well, although I never had that problem in my vintage race TR4.
Maybe I wasn't going fast enough.
What happens is that front end flexing causes the brake rotor to knock the pads
into the caliper pistons and the pistons get knocked back into the calipers.
The first push on the brake pedal after that happens resets the the pads, but
contributes little to braking. After lots of discussion, the TR racers came up
with a list of things to do to eliminate this situation. After all, it is no
fun to be heading into a corner at 100 mph only to find that pushing the brake
pedal does little to slow the car down. Several of these things are applicable
to our street cars, several of them are overkill. Here is what we discovered,
in no particular order:
Wheel bearings must be in good shape and tightened properly.
Brake pads must be evenly worn, high spots on the pads can make this situation
worse.
The brake rotors must be within spec. Thin rotors contribute to this malady.
The front hub can flex under hard cornering. There is a way to reinforce and
strengthen the front hubs to greatly reduce this flex. In addition, there have
been several runs of custom, billet aluminum hubs produced that are way
stronger than stock hubs.
The front stub axle can flex. There have been 2 mods produced to eliminate this
flex. One is a spacer kit. The spacer fits between the inner and outer
bearings, and when properly tightened, turns the whole assembly into a stronger
unit. Additionally, new stub axles have been produced that are significantly
stronger than the stock ones.
Some have added the residual brake pressure valve that earlier TR4's had.
How much any of us chooses to do depends on how much the problem bothers them.
For a street driven car, I would think that fresh, properly installed wheel
bearings, new or near new brake rotors, and evenly worn brake pads should cure
the vast majority of this situation.
HTH,
Irv Korey
74 TR6 CF22767U
Highland Park, IL
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