Non-drive side rubber O-rings for Shimano HT II cranks

[Fatal Swan]

Nearly every Shimano Hollowtech II crankset I've had has somehow lost its little rubber O-ring seal (part Y1F316000) on the non-drive side. The driveside has one too, but that never comes off.

I've always just done without, as they're £6-7 to get the replacement Shimano part. But I've currently got two cranks I want to fit but are missing them, and the glory of my generic O-ring solution to rattling valve stems has given me a misplaced sense of confidence that I'll find generic replacements for the non-driveside seal far cheaper and in bigger quantities. They're so cheap that I'm prepared to buy them and fit by trial and error, which will still get me them cheaper and hopefully with a stash of spares once I chance upon the right size!

So, following some Vernier caliper work, the first size I'm trying is 24mm internal diameter (that's the size of the HTII axle, so should be a good starting point) x 1.5mm thickness. The generic O-rings I've found come in 1mm, 1.5mm or 1.8mm or larger, but 1.5mm seems about right so we'll take it from there.

Total outlay so far: £2.18 for 10 - the cheapest price for two Shimano ones is £11.98

I'm now eagerly waiting for them to arrive so that I can report back...

 

[Fatal Swan]

So, reporting back on the 24mm x 1.5mm O-rings, which arrived inside 24 hours. They're almost perfect and will do the job just fine (at 22p each) but while the internal diameter is fine, they could fit a fraction more snugly against the outer edge of the recessed bit where they sit.


They will do nicely, but I'm keen to find the perfect size, so on we go. Next thickness up is 24mm x 1.8mm, a bit pricier at £1.99 for 4, but still less than a tenth of the Shimano replacement part.

Total outlay so far: £4.17 for 14

And if these are still a bit small I'll try 24mm x 2mm...

 

[Fatal Swan]

So the O-ring saga continues. And sadly, a setback. Attempt no. 2 to find the perfect size generic replacement for the Shimano part has failed. Ordering what was supposedly 24mm x 1.8mm (https://www.ebay.co.uk/itm/274741897323), unlike all other O-ring sizing descriptions the 24mm on this one seems to be referring to the external diameter rather than the internal diameter Not my fault, but of course they're too small.

So on we go to the final attempt - 24mm x 2mm at £1.88 for 10 which are going to be either perfect or just a fraction too big.

Total outlay so far: £6.05 for 24 O-rings

 

[Spunky]

Hey. Thanks for posting this


Did you conclude the best option? I'm looking to do the same.

Thnaks

 

[Splatter Paint]

I used a smaller o-ring and stretched it over the axle.

I still haven't worked out what it seals though... water tracking down the axle into the frame or bearing?

 

[FluffyChicken]

I always assumed it was just a compression buffer.

 

[Spunky]

I'm pretty sure it does 2 things.
1 keeps moisture out of the BB.
2 provides a stand off on the interface between crank and BB.

 

[Fatal Swan]

Hey. Thanks for posting this


Did you conclude the best option? I'm looking to do the same.

Thnaks

I can't quite remember what happened to the third type I tried, I think they ended up being too big. Definitely the first type was the closest, it does the job fine, just doesn't sit as snugly into the groove on the inside of the crank as the original Shimano one.

 

[Spunky]

I can't quite remember what happened to the third type I tried, I think they ended up being too big. Definitely the first type was the closest, it does the job fine, just doesn't sit as snugly into the groove on the inside of the crank as the original Shimano one.

Brilliant thank you!!