Evening stw tech heads..

I’ve got a narrow wide 34t chainring on a hack bike that I’ve built and it’s now specced with a 9 speed sunrace casstte.

It’s a 9 speed chain.

When I put it in largest sprocket (1st gear) the chain drops off of the narrow wide chainring as you pedal.

It looks to me like it is peeling off the top almost like when you shift with a front mech on a double set up. Happens on smooth ground and you can see it happen as you pedal slowly

Is this the chain line plus 9 speed chain in the narrow wide chainring causing this?

Would a 10 speed chain maybe help? Can you eveb use a 10 speed chain with a 9 speed block?

Silly question, is the chain seated on the ring properly? That combined with the extreme chainline causing the issue?

Is the chainring on the inside or outside of the crank? It should be in the middle ring position if using a triple crankset.

If you have a spacer on the bottom bracket on the drive side, move it to the other side.

Yes the chainring is in the middle chainring position. Its replaced a middle ring on what was a triple crank. I have one spacer either side on the bb As it’s a 68mm bottom bracket shell frame and a truvativ crank.

Yep I’m going to move a spacer so that the chain line drops left 2.5mm.

It looks to me like chain line plus the fact the 36t on the rear is bigger than the 34t chainring so the chainlime is acting like a front mech would and causing the chain to hook off to the left.

I’m wandering if the 9 speed chain on narrow wide is compounding the issue.

Lots of questions- What cranks have you mounted your Narrow-Wide ring on, is it a double or triple crank? I take it you’re using the inner mount? Does the frame have a 68 or 73mm width bottom bracket? is the frame 135mm spaced? Firstly check if your chain line is correct- your’e after a 50mm chain line- swap BB spacers around to achieve this.

Not sure how well 9speed chains work with 10 or 11speed compatible chain rings- I haven’t tried it but I’d imagine they’d be a fair bit of play- might be ok if your chain line is ok tho.

Sorry only just saw your reply. Just make sure your chainline is @50mm.

Thanks, how do you measure chainlime?

https://www.sheldonbrown.com/chainline.html

SHELDON BROWN CHAINLINE

As above.

Beaten to it.

Just checked. Chainline is bang on 50mm.

9 speed chain on narrow wide the culprit?

Presumably not an excessively worn chain on a new sprocket (or vice-versa).

The chain is used and it is a new chainring and cassette but not sure that would cause this peeling affect? Normally that causes skipping.on the cassette under load etc which it doesn’t do. It’s fine in sprockets 2 through to 9 too. Just peels off like it’s trying to shift to a granny ring when in 1st

I’m going to try a 10 speed chain. Don’t really want to buy a chain guide, defeats the point of 1x in my view

A guide adds negligible weight and no drag if set up correctly, so won’t detract from 1x simplicity – just reduce dropped chain occurrences.

9 speed chain on narrow wide the culprit?

Most probably this, or a worn chain.

If you have a spacer on the bottom bracket on the drive side, move it to the other side.

This isn’t a good idea, as it throws off the symmetry of the chainset, among other issues. If you need to adjust a chainline then you can buy spacers / longer bolts to shift the position of the narrow wide on the cranks.