Need a little help here after trying to sort this today.
I have endeavoured to simplify the drivetrain on my daughters bike so have bought a new 9 speed chain, new 11-34 cassette and a 30 tooth superstar I/O ring.
I have salvaged an XT 9 speed rear mech and LX shifters. Admittedly, the jockey ?heels might be shot but I don't think this is causing the problem I am having with the chain climbing off the teeth of the 30t chainring when on the two smallest sprockets on the cassette.
I have put the I/O ring on the inside face of the outer ring tabs of what was a triple ring set up. The little spacer blocks are, presumably, set between the crank tabs and the sprocket, so that the threaded stub goes into the crank tabs.
I have converted my own bike to 1x10 with a race face narrow ride and have no such problems with it so I can't see what might be causing this, apart from the chain compatability and possible the chain line presenting the chain too much to the side, causing the premature mesh?
It doesn't seem the have the problem on the large sprockets on the cassette.
Any thoughts?
Cheers.
It'll be down to chain line more than likely. If you measure from the centre line of the seat tube or BB to the inside face of the chainring teeth, then you need to have a dimension of between 47 - 50mm, or 48.5 being the ideal IIRC.
It sounds like you've got about 43 as a guess, so by using your BB spacers and/or fixing the chainring to the outside of the Middle ring tabs (circa 5mm), you'll get a much better behaving chain.
Unless of course you've already done this, in which case I've no idea, except for change the jockey wheels or make sure the hanger is straight.
Ok. I'll check that tomorrow.
So if it is ok to fasten the chainring to the outside of the tabs, I presume I'll need to reverse the ring, so the etching is facing in?
I've no idea. Are the rings directional? I'm not sure they are, in fact I think their working life can be extended by reversing them.
I may be wrong, I've yet to put a narrow/wide chainring on.
There is no direction, just that they are etched on the one side, presumably the outer face.
Could it be down to 9 speed chains being a bit wider than 10 speed ones ?
Slam dunk chainline issue. I don't really understand what you're saying about how you've attached the chainring using the available bolts and spacers, but it really sounds like the chainring is set too far inboard.
Obviously, measure what you have first and then I'd wager that by Refitting the chainring directly to the outside of the middle ring tabs, you may require shorter chainring bolts, will improve things no end. You may still need to fit or remove a BB spacer (2.5mm each), presuming it's an external BB currently fitted? It'll either be 1 or 2 spacers on the drive side and the other fitted to the non-driveside. Three in total.
Have the etching facing whatever way you choose, if I understand you correctly, it sounds like you have the outer etched face currently facing inwards, away from the tabs.
Sorry for confusion.
The chainring has some spacers machined into it, which I assume are to avoid the chain clipping and jamming in the crank tabs. These arent loose spacers that can be moved around.
The etching is facing the driveside, outside, away from the seat tube at the moment, with short bolts screwed from the outside in, fastened up to the crank tabs and directly into the chainring, as 30t come with a threaded bolt hole for direct mounting rather than a plain hole need a chainring bolt and nut, as is the case on the 32t setup.
I'll report back tomorrow but thanks for the input so far.
The initial measurement appears to be around the lower end of the range suggested above.
So this suggests a chain line issue, with the ring too far inboard.
But I can't see how to move the crank out. Again, comparing to to my bike, there are spacers on the bb but on this one, there are no spacers, no flange with just short sections of bb thread visible at both sides, where the bearings protrude equally outside the shell. So can I just unwind the drive side and nip up the non-drive side to move it across?
Mechanically, probably doable but will this increase the stress on the shell if the number of threads engaged is reduced?
Ta
Most narrow wide chain rings are designed around 10 speed chain measurements, these have a slightly narrower internal widths than 9 speed chains. It may be that with the chain being pulled across to the lower cogs it is being pulled across the chain ring and then the teeth catch in the inner plate and push the chain off.
From your description i am assuming your daughters bike has a square taper BB rather than an external bearing BB. But i would not look to loosen the BB off to slide it over. The proper fix would be get a BB with a longer spindle.
If you have a 10 speed chain knocking about or can pinch one temporarily off your bike, try that as a first fix. a 10 speed chain will work with a 9 speed set up.
if you can post up some pics of the set up. instructions on how to do so are in the forum help section.
You'll gain 5mm or so by bolting the chainring to the outside face of the Middle ring tabs. What measurement would that give you?
If you have a 10 speed chain knocking about or can pinch one temporarily off your bike, try that as a first fix. a 10 speed chain will work with a 9 speed set up
+1
Hmm, I'm running an IO ring with an 8sp chain, no issues, but I am using the 32t version however.
Superstar, like many manufacturers list their rings as suitable for 9, 10 or 11 speed. I'd be pretty surprised if this was the issue. Much more likely to be a chainline problem.
9 speed and 10 speed chains have the same internal spacing so that's a red herring (the plates are narrower on a 10 speed chain so its overall width is less than 9 speed) at least as far as the chainring goes.
It's almost certainly a chainline issue with the ring too far towards the BB in the middle ring position.
Unfortunately as you're finding, with the 30t rings, you're quite limited in how much fine adjustment you can do with the chainring spacing itself since you either have to have it on the middle ring position with the built in spacer between the crank tab and the chainring or in the outer ring position with the spacer between again.
I can't see any pics or details of the chainset but that's pretty much the only option you've probably got to adjust the chainline at this point. If it is a square taper one though, the good news is that you can get a new BB with a wider axle (or narrower if there's enough clearance to the chainstays and then use the outer chainring position).
Or you could get a 32t ring which will then allow much more fine tuning (using spacer washers and wider chainring bolts if necessary)
Also check chain's not too long.
Why i think the 9 speed chain could be the issue is that as this is a child bike everything could be quite narrow at the crank/BB area, for a 30 tooth chain ring to work it is normally stood off further inboard of the crank arm spider so as to avoid interference with the chain and crank arm tabs.
These two aspects combined could explain the problem of low end shifting issues (those gears that are furthest outboard).
1st step check if the 9 speed chain is the issue, a 10 speed may for what ever reason stay on better.
2nd step see if mounting the ring backwards on the outer side of the outer tabs works any better. (Crank tab, spacer, ring and bolt from the inside out)
3rd step see if the spacer is required with the crank they are being attached to or if you could modify the crank arm tabs in any way to allow the chain ring to be run without the spacers.
4th step remove BB and see if you can source a BB with a longer spindle to sit the cranks further outboard.
for example if you have a 68x107 look at getting a 68x113 see link below.
http://www.chainreactioncycles.com/shimano-un55-square-taper-bottom-bracket/rp-prod71369
The reason i suggest the BB last is this will just move everything wider at the crank BB area and could be too wide and uncomfortable to use for your daughter.
[edit] Nemesis beat me to it. i may have given a duff steer on the 9 speed chain, but i was just going by the recommendation with my absolute black chain ring. [/edit]
thanks for all your help here..
just to clarify, this is fitted on a 17" frame spesh myka so not a kid's bike, she's just a tall 12 yo!
I thought the problem might be the chain plates snagging in the gap between the ring teeth and the tabs, as the teeth roots are lower than the tab edges, but she's just been for a razz on the road and it came off with the chain on the largest cassette sprocket.
When I hold the bike stationary and pedal slowly, it appears that the chain is being picked up by the teeth edges, then it either drops into the tooth profile, or carries on climbing up.
The crank is a suntour xcr and looks like an isis style, albeit not what I am used to seeing on an isis.
Now that it has come off on the largest, I'm a bit stumped.
I dont have a ten speed chain handy that I can try either.
and annoyingly, I did the same conversion on daughter number two's bike, using a cheap as chips 33t singlespeed crank off ebay and it hasnt dropped once!
pics will help diagnose the issue.
as the teeth roots are lower than the tab edges
^ concerns me.
you said its a new chain, your description seems to match what happens when you try an old chain on a new chainring.
I'll try and get some pictures but I'm pretty bad at doing so...if not, I'll video the set up and problem and upload it.
She did 5 miles tonight off road and not a single dropped chain!
as the teeth roots are lower than the tab edges
This is normal for a 30t and is why they have built in spacers to avoid the crank tabs.
Really need pics I think.
Thread resurrection. Did you get this fixed? Just fitted a ss 36t io ring on a 9 speed setup and it occasionally drops the chain when shifting down from the largest cog on the rear. Ring is in the middle chain ring position. Haven't ridden it yet, only tested in the work stand.