[Fot] WARNING: TRW caliper seals for TR/GT6

[JS Performance Motoring, LLC]

Amici,
       I wanted to share with the group that there might be a big issue
with the latest TRW caliper seal kits for the Girling 16 calipers
(TR4-TR6/GT6).

Cliffs notes:  New TRW caliper seals are measuring about .005" thinner in
the radial direction than the seals previously supplied in the same kits.
This appears to allow fluid to leak during hard braking/high pressure.

These seals came from BPNW, they are reaching out to TRW, no further
information available at this time.


At Mosport over the weekend, I was struggling with some odd braking on
track.  It turned out to be the brand new TRW seals in my calipers
(replaced last week).  In the paddock, and on the pace lap with cool brakes
and gentle braking, things were fine.  Once we were up to speed, the seals
were allowing fluid to leak past under moderate to hard braking.

Thanks to Heny for digging up an older set of new seals at the track - a
trackside caliper rebuild solved it.

Back at the shop this AM, I compared the multiple sets of new TRW seals to
an unused set of TRW seals from a few years ago.  These new seals are made
from a softer/glossier material, compared to a harder/duller appearing
material that I have always seen in the past.
The new seals are dimensionally smaller in the radial direction, side by
side, it's obvious that the pistons slip in the calipers much easier with
the new seals VS taking a slight press fit with the older seals.

I don't know how far reaching the problem is, but given the potential risk,
I felt it important to share with the group.

[image: 20250616_101743.jpg]


Jason Sukey
JS Performance Motoring, LLC
440.984.7720
jason at jsperformancemotoring.com
www.jspmparts.com
https://www.facebook.com/JSPerformanceMotoring/
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