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I'm trying to improve the chain line for my non-boost cranks on a boost frame.
Currently the chainring is too far outboard, so the chain line when in the largest sprockets on the cassette is fairly bad.
The BB shell on the frame is 73mm and hence the HT2 BB is installed with one 2.5mm spacer on the drive side.
It occurred to me I could improve my chainline somewhat by moving the spacer to the non drive side, thereby effectively moving the drive side crank "inwards".
I can imagine the cranks will end up slightly off-center which could be bad for various reasons. But I don't really know whether it's the sort of bad that implies "oh my God you'll die" or "pfft, you'll never notice it".
Any ideas?
Non-boost cranks on a boost frame should give a good chainline. Swapping the spacer should be fine. Can you space the chainring inwards?
Currently the ring is on the outside of the spider.
If I flip it and put it on the inside it fouls the frame in the case of an oval ring I have, or gets too close for comfort in the case of a round ring.
Stick the BB spacer on the non drive side - it will certainly help with chainlind on your set up and you probably won't notice the difference in terms of crank/pedal position.
What size ring are you using?
I’d get new cranks or change ring size so that you’ve got ckearance in middle ring position. If you’ve got it in outer position, chainline will be so far out that moving inboard by 2.5mm won’t make enough difference. It’ll still be way out.
I was dreading the possibility that "new cranks" might be the answer 🙁
The oval ring is 30T I think, and the round one 32T. The frame specification is for 32T max, but I think that's assuming boost cranks.
If moving the spacer to NDS wouldn't result in immediate death I might give that a go and see how it looks. It might be "good enough" until I can afford some boost cranks I guess. I can always just avoid the twiddlier end of the cassette 😂
You're already 3mm in the right direction thanks to being non-boost, so another 2.5mm from the spacer and you're probably going to be close - possibly even further in than the "standard" 1x boost chainline.
The chain line you can achieve is dictated by the clearance of the ring, or, in some cases, the drive side crank. If you can afford to go inward by 2.5mm then deffo swap the spacer round. I’ve got three bikes with boost spacing and only one has boost cranks - which has a slightly less good chain line than the other two.
Thanks all. It sounds as though moving the bb spacer won't cause a disaster so I'll give it a whirl!