Chain dropping off chainring after rear wheel upgrade.

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Chain dropping off chainring after rear wheel upgrade.
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flag backmuirboy
Posted: Aug 19, 2022 at 12:13 Quote
Hi, I'm wondering if anyone has had similar problems to me and can offer any solutions.
I recently replaced my rear (27.5' 148x12mm BOOST) wheel after damaging my old rim on a rock. I bought a Nukeproof wheel and when I fitted it to the bike the brake disc was about 1mm further out towards the outside. I adjusted the caliper to the full extent and the disc was still hard up against the pad. I thought there was a problem with the manufacturing tolerance in terms of the position of the disc mount flange and so I exchanged this wheel for a Spank wheel....same problem! I pushed the pistons fully home and replaced the pads and I only managed to solve the issue by finding a brake mount that had the holes slightly offset to the correct side which gave me the tolerance required. I still don't understand why the new wheels would be different to the old (WTB) one. Anyway....the reason I tell you this is that the wheel is now spinning freely but the chain is now constantly dropping off the front chain ring!
I've checked everything i can thing of; no damage to the chainring, cassette, chain is in good condition and every link pivoting fine. Chain line is straight in about the middle sprocket (and this is when it tends to come off). I've checked the pulley tensioner /clutch is working well. Also, when I originally damaged the first wheel, after changing the tube I managed to get off the mountain no problem and the chain stayed on fine (it was very rocky). I am stumped! Something has obviously changed....any ideas? Any help much appreciated.
flag kiranseligman
O+
Posted: Aug 19, 2022 at 19:15 Quote
backmuirboy wrote:
Hi, I'm wondering if anyone has had similar problems to me and can offer any solutions.
I recently replaced my rear (27.5' 148x12mm BOOST) wheel after damaging my old rim on a rock. I bought a Nukeproof wheel and when I fitted it to the bike the brake disc was about 1mm further out towards the outside. I adjusted the caliper to the full extent and the disc was still hard up against the pad. I thought there was a problem with the manufacturing tolerance in terms of the position of the disc mount flange and so I exchanged this wheel for a Spank wheel....same problem! I pushed the pistons fully home and replaced the pads and I only managed to solve the issue by finding a brake mount that had the holes slightly offset to the correct side which gave me the tolerance required. I still don't understand why the new wheels would be different to the old (WTB) one. Anyway....the reason I tell you this is that the wheel is now spinning freely but the chain is now constantly dropping off the front chain ring!
I've checked everything i can thing of; no damage to the chainring, cassette, chain is in good condition and every link pivoting fine. Chain line is straight in about the middle sprocket (and this is when it tends to come off). I've checked the pulley tensioner /clutch is working well. Also, when I originally damaged the first wheel, after changing the tube I managed to get off the mountain no problem and the chain stayed on fine (it was very rocky). I am stumped! Something has obviously changed....any ideas? Any help much appreciated.

I assume you have a narrow wide chainring? If so, I have seen some poorly machined chainrings where you can actually put the chain on wrong and it will always drop the chain and make weird noises. Try to shift the chain on the chainring so the inner link is On the next tooth, if the ring allows it.
flag privateer-wheels
Posted: Aug 19, 2022 at 19:47 Quote
backmuirboy wrote:
Hi, I'm wondering if anyone has had similar problems to me and can offer any solutions.
I recently replaced my rear (27.5' 148x12mm BOOST) wheel after damaging my old rim on a rock. I bought a Nukeproof wheel and when I fitted it to the bike the brake disc was about 1mm further out towards the outside. I adjusted the caliper to the full extent and the disc was still hard up against the pad. I thought there was a problem with the manufacturing tolerance in terms of the position of the disc mount flange and so I exchanged this wheel for a Spank wheel....same problem! I pushed the pistons fully home and replaced the pads and I only managed to solve the issue by finding a brake mount that had the holes slightly offset to the correct side which gave me the tolerance required. I still don't understand why the new wheels would be different to the old (WTB) one. Anyway....the reason I tell you this is that the wheel is now spinning freely but the chain is now constantly dropping off the front chain ring!
I've checked everything i can thing of; no damage to the chainring, cassette, chain is in good condition and every link pivoting fine. Chain line is straight in about the middle sprocket (and this is when it tends to come off). I've checked the pulley tensioner /clutch is working well. Also, when I originally damaged the first wheel, after changing the tube I managed to get off the mountain no problem and the chain stayed on fine (it was very rocky). I am stumped! Something has obviously changed....any ideas? Any help much appreciated.

If your freehub and hubshell are binding up, it can force your freehub to spin even when your cranks are not moving, in turn creating slack enough for your chain to drop. Hard to tell if this is the case.

Pictures/video would be helpful.
flag backmuirboy
Posted: Aug 20, 2022 at 1:34 Quote
Thanks for the replies. The free hub is spinning smoothly (I did have that issue before on my old wheel) but good suggestion.
Kiranseligman, I haven't been as careful as I should have been when remounting the chain on the chainring...it is a fairly basic crankset and slightly worn so that's definitely something to check carefully. That's really helpful, thanks.
flag TimMog
Posted: Aug 20, 2022 at 5:29 Quote
Are you absolutely sure your frame is boost? Disc being very off, and then problems with chainline sounds very much like you've got a boost wheel in a non boost frame

What bike is it?
flag kiranseligman
O+
Posted: Aug 20, 2022 at 5:31 Quote
TimMog wrote:
Are you absolutely sure your frame is boost? Disc being very off, and then problems with chainline sounds very much like you've got a boost wheel in a non boost frame

What bike is it?

I mean would be tricky to install as the frame would be pretty big or too small.
flag privateer-wheels
Posted: Aug 20, 2022 at 6:10 Quote
kiranseligman wrote:
TimMog wrote:
Are you absolutely sure your frame is boost? Disc being very off, and then problems with chainline sounds very much like you've got a boost wheel in a non boost frame

What bike is it?

I mean would be tricky to install as the frame would be pretty big or too small.

Is actually pretty easy to install a boost wheel in a non-boost frame. The cassette and brake spec are the same so it makes no difference to either. Your chain line will just be justified a few more mm towards the bigger cogs of your cassette. Some frames you need to pry the drop outs open a little, but others slide in without any force at all. My old Canfield Riot was 142mm, and took 148 without even having to open up the stays, almost like it was made for 148.

I've known several people to do this intentionally, but you need a longer axle make it work safely.

Bottom line though, is that a boost wheel in a non-boost frame will not interfere with the brake, nor will it interfere with shifting in the middle of the cassette. It may cause things to shift a little worse at one end of the cassette or other though. Unlikely that it would cause the chain to drop off the front ring. I actually own one boost frame with a non-boost chainring because is shifts better in the climbing gears.
flag barp
Posted: Aug 20, 2022 at 9:14 Quote
privateer-wheels wrote:
My old Canfield Riot was 142mm, and took 148 without even having to open up the stays, almost like it was made for 148.

That's really weird. When you put a 142 mm wheel in that frame, did it visibly squeeze down around the hub's end caps as you tightened the thru-axle?
flag eshew
Posted: Aug 20, 2022 at 9:20 Quote
Another thing to consider would be cassette... If it's a SRAM driver. Did you tighten it to 40nm... Which is 30 ft-lbs? Approx 8x tighter than a stem bolt for reference.

If you don't tighten it all the way it sits outboard and causes all sorts of problems.
flag privateer-wheels
Posted: Aug 20, 2022 at 13:26 Quote
barp wrote:
privateer-wheels wrote:
My old Canfield Riot was 142mm, and took 148 without even having to open up the stays, almost like it was made for 148.

That's really weird. When you put a 142 mm wheel in that frame, did it visibly squeeze down around the hub's end caps as you tightened the thru-axle?

It was definitely a loose fit until you cinched the axle down with a 142.
flag kiranseligman
O+
Posted: Aug 20, 2022 at 14:40 Quote
privateer-wheels wrote:
barp wrote:
privateer-wheels wrote:
My old Canfield Riot was 142mm, and took 148 without even having to open up the stays, almost like it was made for 148.

That's really weird. When you put a 142 mm wheel in that frame, did it visibly squeeze down around the hub's end caps as you tightened the thru-axle?

It was definitely a loose fit until you cinched the axle down with a 142.

That’s what I meant- it’s not gonna fit perfect there’s gonna either be a bit of wiggle room or if the wheel is too big it’ll be very tight.
flag TimMog
Posted: Aug 20, 2022 at 15:33 Quote
photo

I still think you might be putting a boost wheel in a non boost frame. What would really help would be telling us what frame it is...
flag privateer-wheels
Posted: Aug 20, 2022 at 16:52 Quote
TimMog wrote:
photo

I still think you might be putting a boost wheel in a non boost frame. What would really help would be telling us what frame it is...

Definitely that would give us an answer.

But again, aside from an additional 6mm between the flanges, the brake mount and cassette standards are the same between 142 and 148 hubs and frames. The only thing it would really affect, is that you would have a chainline that is 3mm more inboard than is standard for boost. That and your axle would be too short. I would be surprised if this was the issue.

photo
flag barp
Posted: Aug 20, 2022 at 19:23 Quote
privateer-wheels wrote:
barp wrote:
privateer-wheels wrote:
My old Canfield Riot was 142mm, and took 148 without even having to open up the stays, almost like it was made for 148.

That's really weird. When you put a 142 mm wheel in that frame, did it visibly squeeze down around the hub's end caps as you tightened the thru-axle?

It was definitely a loose fit until you cinched the axle down with a 142.

See, now I'm just wondering what the actual distance between the rear dropouts on that frame was... Guess we'll never know though.
flag privateer-wheels
Posted: Aug 20, 2022 at 19:44 Quote
barp wrote:
privateer-wheels wrote:
barp wrote:


That's really weird. When you put a 142 mm wheel in that frame, did it visibly squeeze down around the hub's end caps as you tightened the thru-axle?

It was definitely a loose fit until you cinched the axle down with a 142.

See, now I'm just wondering what the actual distance between the rear dropouts on that frame was... Guess we'll never know though.

Closer to 148 than 142 I think. Definitely no undue stress on the frame, that is for sure.

Definitely a few people did this to their Riots and Balances. There are a few threads dedicated to it out there, I think on MTBR. I've had customers do it with other bikes as well. You are only moving each stay by 3mm outwards. That's a fraction of a mm flex at the yoke.
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