What size is the Syntace X12 axle O ring?

This is a question I'd asked myself when I found my X12 Syntace O ring ripped in half during a recent service. Disappointingly, the O ring had only lasted 9 months and I hadn't removed my wheel all that much during that time. With little doubt that I'd need to replace it again in 9 months, I thought it best to get a few spares in.

Unfortunately, Google was of no help and whilst I had found forum posts of people who had found replacement O rings, no one had bothered to share the size. Syntace certainly didn't offer much in the way of information on their own design and I didn't want to buy a complete new axle for the sake of something that should cost in the region of £0.30.

Finding the one ring to rule them all

O rings are measured with an internal diameter (the hole), outside diameter (the distance between two opposite outside points) and then finally the cross section (the thickness of the ring). With a ruler I took a rough measuring of the old O ring and ordered a selection of similar sizes, in different materials, from Polymax to then compare them to the original.

Different qualities of O ring

It's worth noting that there are different materials for O rings which offer different properties. The closest feel to the original was Nitrile, but in the end I opted for EDPM O rings as they are hardier in the natural elements; perfect for UK weather. And now that I have the right size, I can easily order new O rings as needed.

The Syntace X12 O ring size has an outside diameter of 17 mm, internal diameter of 12 mm and then a cross section of 2.5 mm.

The EDPM O rings, which I could only find in British standard sizing, ended up being slightly larger, we're talking 0.12 mm, and still fitted just fine.

Want a Syntace X12 O ring for free?

Contact Syntace direct and they'll send you some in the post, for free! Neat. You may need to explain why you need replacements, I explained how they fell apart within 9 months, but they were posted quickly and with a minimal of fuss.