The main advantage of the o-ringed type over the lip seal type is that the o-ring set-up will NOT suck air into the system, as the lip seal ones do. The in-out motion of the pistons as they ride on the rotors while driving creates a pump...which sucks air in past the seals. Eventually, you have to constantly bleed the brakes. With the o-ring seals, this doesn't happen.
In your case, whichever type of seals you decide, you should at the very least do both calipers at the same time, whether front or rear. Fixing a leak on one side can sometimes cause the other side to start leaking. It's a little known effect called "Murphy's Law".....
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Joel Adams
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