I thought these were “standard” 104BCD. I’d take the cranks off to check, but there’s a chainguide in the way. I want to replace these for a 30 or a 32T, but I’m not sure how to work out the BCD.

Hopped on the RaceFace website, but they have multiple BCDs (for doubles and I think 5 bolt BCDs?) which is confusing me.

http://www.raceface.com/components/cranks/turbine/turbine-crank/

I definitely have the normal Turbines, not the fancy direct mount Cinch version.

Anyone care to help me out please?

Some were 104 bcd, some were 120…

On that site, the vivid green cranks are 104bcd, all the rest are 120bcd.

I’m pretty sure 3×10 are 104, 2×10 are 120. My 4arm 3×10 are 104.

They made a 2×10 doubles using the 104bcd as well. The chainline was slightly different according to the website

I have a 5 arm 110bcd square taper Turbine.

Thanks for the responses so far!

The cranks came on a new bike. It looks like it will take a double, but is set up as a single ring. I’m trying to avoid having to remove the chain guide to have a look because I want to avoid tinkering with it if I don’t have to.

here

Measure the bcd yourself? it’s not hard.

How would a chainguide stop you measuring BCD?

Just run a ruler (or better a vernier) across 2 of the bolts diagonally measuring bolt centre to bolt centre.

Triples are 64/104, doubles are either 64/104 or 80/120 depending on size of rings. It’s not super easy with a ruler given the crank is in the way but you’re only trying to work out if it’s 104 or 120, not measure it exactly – and that will be obvious.

Tried to measure the BCD, but I can’t get a 100% accurate measurement because of the curve of the spider. Wish I had some Vernier callipers. Perhaps this is an excuse to get some!

I tried the adjacent bolt measurement as well, but I can’t get an accurate enough measurement with a tape measure. I’ll dig the ruler out this afternoon and have a go.

Assuming they’re 4 bolt, if you can get to two opposite bolts, then just measure across the bolt holes, centre to centre. They’ll be either industry standard 104mm or SRAM 2x specific “standard” 120mm.

Good news and better news! It’s 104mm BCD and a 32T.

Means I have the option of taking the 30T with me as a backup, but I don’t need to buy a weird BCD chainring.

Told you that 4 hours ago