Everyone knows that the
hardness of rubber compounds is measured by the Shore A durometer and the higher
the durometer, the harder the compound.
70 Shore A has long been the
standard for OEM sealing.
More is better, so if 70 durometer is
what the OEM used then I want more. Let’s improve our seals by switching to a
higher durometer. Right? Probably not, but it’s not that simple either.
70 +/-5 durometer nitrile is the backbone
of rubber sealing materials. Occasionally, to seal under higher pressures,
OEM’s will specify a harder durometer. Rarer still are the OEM’s who will
deliberately use a 65 or a 75 durometer to try capturing after-market service
Since the standard-service 70 durometer
runs +/- 5, specking in a 65 or a 75 durometer is pointless in most cases,
except to say that there is ‘something special’ in the OEM’s genuine
As for ‘improving’ to a 90 durometer,
this material is so stiff that it can’t conform to mating surface imperfections
the way a softer 70 duro can, so there’s no improvement at all. And unless
8-10,000 psi is involved there’s most likely a deleterious loss of sealing
Seal materials are often available in
durometers ranging from 50 to 90 Shore A with a hardness of 70 durometer well
established as the industry standard. It costs less, is usually readily
available, and is sufficient in most cases.
Not sure which is the best suited durometer for your repair? Talk with one of AY’s customer service agents today for guidance on the proper component or consult with our engineering departmentto design what you need today!