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My commuters drivetrain is dead, time for new cassette and chainring(s)
Currently kitted out with a 2x9 sora drivetrain,
The plan is to swap the cassette like for like but go to a single 34 tooth ring upfront
Primarily concerned with the front end, I was going to drop the bike off at the LBS and get them to “make it work”
Normally a big fan of supporting the local mechanic but also keen to learn these things for myself because…well, why not?!
Pretty confident it’s and easy job to do myself but…chain line…
Some questions…
How do I get it right for the proposed new setup?
What do I need to know?
Pretty sure I’d need a narrow wide, chainring with correct BCD and desired tooth count…but then what next?!
If anyone can help shed any information/help/advice I’d be hugely grateful
That's about it to be honest. I went from a 3 to a single on my commuter, stepping up to a 40t (I think) and just installing that on the middle ring of the Deore crank. Ok, I took the front mech off too. And the shifter.
But it works. Really well. Much simpler and easier in town.
I did take the shifter off months ago but left the derailleur on and set it up as a chain guide,
Now looking to take that off too but main concern is chain drop
If I set the chain line up so that it is straight to the middle of the cassette, would that be about right?!
Would I need a chain guide of sorts still or am I over thinking the whole thing?
Arrow wide will do most of the work, won't really need a guide, unless you're very much mountain bikkng
That’s what I was hoping to be honest,
In regards to chain line, set it up so it’s straight when middle of the cassette or does it not matter so much / a better way?!
In regards to chain line, set it up so it’s straight when middle of the cassette or does it not matter so much
you had two chain rings before, some have three.
Chainline is a single speed thing really - there you've only got one cog at each and a relatively tight chain. If you've got 9 possible positions there rear cog will be and two/three portions where the front ring would be on a geared system.... then it's not that critical where a single front ring would be. If you riding would generally use more of the higher or lower gears bias it to that. Maybe. How much trouble has it caused you so for?
If you're starting out with a crankset that originally had two rings then you've only got a choice of two positions and neither will really be in the middle. But neither are far off the middle either (theiy'll be closer to the middle that the inner / outer positions of a 3 ring sent up, but not as close as the middle) So just take your pick
@maccruiskeen makes a lot of (common) sense when you put it like that…
Essentially, if I’ve got this right, it doesn’t actually matter so much coming from a 2 ring setup and as @honourablegeorge mentioned, a narrow wide ring will do most of the work to avoid chain drop anyway
Helps a lot, thanks fellas, think I’m gonna tackle this one myself and see what happens
The only trick is getting the right bolt circle diameter (bcd) for the chainring
I think it's 104 for most middle ri gs at least on mtb
Snail chainrings on ebay & amazon do some big commuters nw chainring at v reasonable prices, watch out sometimes they're direct from China so they take a while!
Edit
Like these
You'll likely need short chainring bolts
No Spice Girls jokes?
I did this from 3x9 to 1x9 and I needed spacers for the middle ring since it's normally mounted through the big ring. I put the spacers inboard of the spider rather than outboard though, so I could get a better chain line in the largest sprocket because it was on an MTB and that's where I put most of the power down most of the time. And yes, I think I did need different chainring bolts - perhaps shorter.
I did get dropped chains - not when riding rough stuff, but when shifting across the cassette quickly. A NW ring sorted it though, I did not need a clutch mech.
Thanks for the further advice
Genuinely forgot about the (probable) need for shorter bolts, now added to the list
BCD is Shimano standard 110mm so no huge worries there
Going to treat this as an experiment as such, start by setting the new chain ring up where the big one would have been, give it a week and address any issues from there
If the (warning - old school language approaching) extreme cross-over causes any chatter at the back try the front chainring in the other position.
Annoyingly sometimes this only shows up under load not on the workstand, but YMMV.
Oh yeah, bolts. I forgot I had to space mine out with some shims made from duct tape. They were fractionally too long. When I get the bike near my workshop I’ll take a mom or so off the end of them and all will be good.
Also, on the chainguide question… that never occurred to me. The Devore rear mech seems to do a good enough job of keeping tension in the system and the rest, well, just works.
Another (slight) change of plan…
I took the cranks out yesterday to have a look and to see how it all goes together,
I have a plan but, before taking tools to the cranks (wait for it…) I’m going to experiment
I’ve ordered a new narrow wide 34t Shimano chainring
I’m going to install it where the small ring should be / would be behind the big ring and ride it for a week, if no issues to address, I’m going to grind the teeth off of the big ring and keep it on like that
All being well this would result in two (three?!) things being achieved that aren’t entirely necessary but would please me to a certain extent
A) keeps the clean aesthetic of the covers(?!) ala https://ibb.co/kB2r9fy
B) gives me a bash guard of sorts (not that it’s especially needed but figure handy to have, just in case)
C) prevents some faff / expense with spacers and different bolts etc