Grooved fork top hat bushing - leakprooof seals

Need some education concerning installation of Leakproof seals for the forks.

I have seen the recommendation for the grooves in the top hat bushing, and I just can't get my head around why one should cut the grooves.

It seems to me that if oil couldn't get past the bushing body then the grooves would serve no purpose (unless grooves were cut on the inner face - never seen that recommended).

And if oil does get past the bushing body, then what does the grooves do (the oil is there so the grooves hold a bit handy?

I just don't see how it lubricates the seal better, or is there another purpose I've overlooked?

Those are dang good questions I don't really know the answer to but found my first Combat Roadholders had spiral grooves cut inside surfaces of top bushes. At the time I thought the m/c shop only serviced bike had an insightful modification. Can't say if the groove drains oil down or flows oil upward or both, all I can say is they have some detectable slack now, some 50K miles of rough and ready use its still famous for in its county of origin decades before me - and I've two sets of [4] brand spanking new properly rounded top bushes that have even more detectable slack so binned them to keep using the oil grooved ones. So maybe only one set of Roadholders ever had this done but other than possible wear endurance don't think it matters a whitworth.

The leak proof seals like some oil underneath them without the groves they tend to run a little dry. Holding oil handy up near the seal to keep it soaked no need for groves inside just a little storage up on top. Set up like this we have two sets that still work well after 20+ seasons. Do what you like you will anyway. I see my new favorite vender has them on sale in the pro molly for just about 5 bucks more. But my old one still don't leak.

norbsa48503 said:

The leak proof seals like some oil underneath them without the groves they tend to run a little dry. Holding oil handy up near the seal to keep it soaked no need for groves inside just a little storage up on top. Set up like this we have two sets that still work well after 20+ seasons. Do what you like you will anyway. I see my new favorite vender has them on sale in the pro molly for just about 5 bucks more. But my old one still don't leak.

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Thanks. I suspected it was to keep a bit of oil up there, but wasn't sure if I was missing something in the idea.

I have a set of the pro-moly on order.