Bicycle Mechanics - Simano Sora Hub Sealing Experiment

This idea might be of interest to other owners of bikes with Shimano Sora hubs.

For a while I have been dis-satisfied with the sealing design of these hubs. Basically this comprises a specially designed cone that has a groove around its circumference, into which are fitted two plastic washers. Shimano describe this as improved sealing on their website. Presumably the idea is that the washers fill the gap between the cone and the hub body. Unfortunately this is only partially sucessful, they are not a great fit. In wet conditions, the bearing is soon filled with an emulsion of grease and water which squeezes out past the seals, and later a rusty mess develops.

So, I decided to experiment, to see if the sealing could be improved. Since the cones are provided with a handy groove, I cut some old inner tube to make sealing washers that fit snugly in the gap between the cone and hub. It was a little tricky to get the size just right: inside diameter so that the seal squeezes over the cone and holds on in the gap, outside diameter (more critical) large enough to fill the cone-hub gap without being too tight. This does add a little friction to the bearing, but I am assuming that the rubber will eventually conform to its surroundings - this is an experiment after all and is much cheaper than having new wheels built around more expensive hubs. The modified wheel spins freely enough

After fitting the new seals, cleaning and re-packing the front hub with plenty of grease I rode today without any problems. There was certainly no sign of grease squeezing from the bearing. The real test will be some rain, but we won't have to wait long for that, it is summer here in the UK!

If there is any interest, I will keep this thread updated.

Cheers,

Ed

Ed; thanks for the idea. I'm not a sora user, but Shimano uses that same systemn several different hubs so if your experiment works, it could be applied in different ways. I assume you are using butyl tubes, right?
There are--or were-- small round punches available for making round gaskets. Something like that would be quite useful in making the washers perfectly round and might make experimenting with other materials easier.
I think it's a fine idea and hope you'll follow up on it.

It can be difficult getting sealed cones ther correct size for older models, they always seem to be changing them.
I just take the seals off current models to fit my old hubs. Maybe Ill try your idea.
You can also get O-ring silicon rubber rings of various sizes. The industrial bits catalogue at work has them, but they would be difficult to find in the shops.

You could always go to a dive shop
they have a good selection of silicon or
rubber O rings.

Marty

Thanks for the feedback!

Just to follow up on some of your comments, I considered using O ring type seals as suggested by MichaelW, and this is a definite possibiliy. Some of the reasoning behind my method is as follows:

1) It is difficult to find O rings of the exact size all the time - I do have access to lab supplies, BUT the remains of old inner tubes are free and plentiful.

2) The way I arrange the seal to fit means that it is rather like the plunger inside a bike pump, with the outer diameter deflected back toward the outside, so the sealing should be quite effective. The experiment needs to run for a while to show this.

The round punches mentioned by Ljbike are a great idea. I made my seals in this way, with a home made punch fashioned from some old 15mm copper pipe thinned at one end to form a cutting edge. Blanks were made with this tool, then the centres cut out using a smaller tool of about 10mm - Keeping the two cuts concentric was not too difficult after a couple of practice runs.

In answer to your question Ljbike, yes the material was butyl rubber, which is pretty tough stuff. Other materials could be tried - so long as they are not affected by grease/oil.

Cheers,

Ed

!UPDATE!

After 4 months of relatively consistent use, the front wheel bearing started to make ugly noises again. On disassembly there was no sign of the butyl rubber seals that I had made and fitted (see above posts). They seemed to have become completely chewed and then dissolved into the grease, which had turned black. On the plus side there was no real sign of corrosion in comparison to that seen in the past without seals. The fact that the cones were still badly pitted suggests that the materials used are not great. Wheel bearings should last longer than the approx 1400 miles they had covered.

Not to be put off, and in the name of science :D I have tried new seals, this time cut from a sheet of silicone rubber, which should (might) be more resistant to attack.

More results as they come,

Cheers,

Ed

Ed;

Graphite water pump packing material merits consideration. I became a believer in the aforementioned when managing a swimming pool. We had major problems with water linking out of the pump impeller shaft housing, called in professional pump folks to overhaul the unit. The mechanic gave us a supply of this slippery stuff, graphic impregnated cord like material that easily wraps around a shaft (axel) and conforms to whatever is snuggled up against it. I’ve seen it in large plumbing supply houses; also pump rebuilders in your area would be able to appropriately direct you. Rest assured it didn’t wear away under the extremes of 5 months continuous service and when we rebuilt the pump at the beginning of each season we simply discarded the old material and wrapped new packing in it’s place. It’s so incredibly slick and slippery that it wouldn’t add any significant friction load.

Best of luck with your endeavors...

Thanks Faith, that is a very interesting suggestion. Certainly top of the list for the next experimental material, the similarity beween a bicycle and water pump has been very close of late here in the UK... I'm in the lucky position that I was able to get a large supply (at a very reasonable price) of replacement cones for these wheels, so there will be plenty of chances to experiment.

Ed