2x to 1x upgrade: looking for help (AKA too many standards!)

There are so many standards out there, some apparently going by different names, and I’m getting a little lost in the jargon. So, I’m looking for some help from mechanics, home or professional, who can help me navigate.

The original: 2017 Felt Surplus with FC-M627B cranks and Shimano BB92 bottom bracket. When looking at new cranksets, I see 68/73, 83, & 100mm BB options, along with 24mm and 30mm spindles. The Shimano web page actually doesn’t give full specs about what spindle it has nor the BB width for which it’s compatible. I think the replacement cranks should be 83mm with 30mm spindle, but looking for some help or confirmation before I buy anything.

Thanks!

All Shimano cranks are a 24mm spindle and BB92 uses the same spindle length as a 68/73mm external BB. With BB92 the BB shell of the frame is wider but the bearings are press fit into the shell which works out to be the same overall width as 68/73 plus the width of the spacers and external bearing cups and bearings.

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What @gtrguy said ^^

A 100mm BB is the size of a threaded bb that you would find on a fat bike.

If you are only looking to swap from 2x to 1x, you should be able to simply replace the current chain rings with a narrow-wide chain ring and leave the cranks/bb alone.

If you’re looking to upgrade the cranks, then that is a whole other can of worms. Depending on the cranks, you could re-use the current bb. If you went to a Raceface crank with a 30mm spindle (they also make 24mm spindle cranks), then the bb would need to be updated to suit.

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In this case, isn’t there a chainline issue? Or, get a 104 BCD chainring with a spacer or two to push the ring into the centre more like a proper 1x system? :thinking:

Glad I asked though, since I was wrong about 24mm vs 30mm spindle. :slight_smile:

The OneUp rings come with spacers so you can adjust your chain line to optimize it. Highly recommended.

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One possible issue I overlooked is the derailleur. It doesn’t look like that one has a clutch to help keep tension on the chain. Some people have done a 1x conversion without a clutched derailleur and it has worked fairly well, but it’s not as ideal as using a clutched derailleur.

Like @brightwhite said, OneUp includes spacers to help correct the chain line as needed. I believe Wolftooth has the spacers built in to correct the chainline (on the oval rings at least, maybe round rings too).

I think that was one of the early Deore RDs that did have the clutch.

Looking at the picture it’s got the circle cover with Shimango printed on it.

You can get away without a clutch derailleur, but you will drop chains in rough downhills. If you can put a top mount chain guide on, it should be fine.

The bike does have a clutch derailleur; handy! I do like the look of the OneUp chain ring and spacers included, plus I’ve been really happy with the Two-Ten dropper that I bought from them. New chain ring with existing cranks it is. Thanks all!

You could also consider putting an extended range sprocket on the rear cassette too. One-up do a 42T

Already on the way; that one I had no tech questions about. :wink: