Polyurethane f-drive O-ring kit

[mbrST1100]

Hi,

possible improved O-ring set for the final drive of ST1100/Pan-European:

http://www.ebay.co.uk/itm/331238013646? ... 26_rdc%3D1

[alans1100]

Hi,

possible improved O-ring set for the final drive of ST1100/Pan-European:

http://www.ebay.co.uk/itm/331238013646? ... 26_rdc%3D1

Part numbers for those match the ones for the 1100 final drive list so they should be ok but he has a limited supply

[mbrST1100]

...they should be ok but he has a limited supply

Which is why I posted the link

Its not that I'd seen any frequent failures of the OEM O-rings (as long as hub-centre (AKA bearing boss) and drive splines are not FUBAR), but the price is tempting and why not test more rigid materials as nitrile for a change?
I've ordered 2 sets, will report once they've arrived...

[WJBertrand]

I'm a little concerned that they are described as thermoplastic. Rubber and silicone o-rings will be a thermoset material. Themoset materials are chemically cross-linked and cannot melt or dissolve so they are generally quite chemically and heat resistant. Thermoplastic materials are subject to melting and dissolution (in the presence of the right solvent). Urethanes do have superior abrasion properties to rubber or silicone, but there shouldn't be much of that going on unless the rear wheel is misaligned with the final drive. Urethanes are a unique class of polymers that can be made either as a cross-linked thermoset or as a thermoplastic, so to me it's a bit curious they chose a thermoplastic type for this application. The only reason I could see to do that is they can be cheaply made by injection molding that way.