Anyone with Shimano 12 speed - can you test something for me quickly

[Akelu]

I've been having some troubles with my new bike and was wondering, anyone that has Shimano 12 speed, could you try put your chain on the largest gear (with most teeth), then walk the bike backwards again and again and see if the chain skips down a gear or two? It also happens if I lift the rear tyre off the floor and spin it manually. It happens after I move the bike backwards about 10-15 bicycle lengths distance.

I don't think it's supposed to do this is it? The bikes supposed to be able to move backwards without the chain coming off the right gear, right?

 

[KenX]

Same with mine (11speed), don't think it's an issue, going backwards in the biggest cog is not really in the drivetrain's remit....

 

[Mteam]

Thats normal - some bikes do it some dont, its to do with the chain line from the front chain ring and chainstay length.

Its not a fault.

 

[nickfrog]

Yes I have stopped walking my bike backwards for more than 25 metres at at time for that very reason.

 

[STATO]

The derailleur guides the chain when pedalling forward, nothing guides it going backwards, so the chain will try to run straight and jump gears. This also happens when back pedalling, but ebikes (mid motor, most/all?) have a clutch on the crank so you cant back pedal or you may have noticed it sooner. Its been an issue, to different degrees, since derailleurs were invented, just very noticeable on wide range cassettes.

 

[KennyB]

2 things puzzle me:
How you found out.
Why you would want to.

 

[STATO]

2 things puzzle me:
How you found out.
Why you would want to.

It can be an issue for some people. Loading the bike in vehicles, especially vans, when wheeling backwards the chain can end up trying to rip the mech off if it jumps a lot of gears.

My road bike has similar issue if its in the big ring at the front and big-ish at the back, the cross-chaining is fine riding but will bump the chain off the front ring and sometimes end up jammed. I dont know why, same gear set-up on other bikes dont do it, so i just make sure to drop to the small ring when i get home and am putting it back in the garage, where it will end up getting wheeled back and forward to clean or get other bikes out.

The solution is just that, if you are going to be wheeling it about, just leave it in a middle gear at the back. No issues then.

 

[Akelu]

Thanks guys, the reason I was wondering is I'm having trouble with my new bike where it's making a noise and sensation through the pedals when going uphill and putting pressure on the pedals. Motor on or off. Another bike shop had a look and pointed out how every second tooth on the chainring is more worn out and that the chainring doesn't seem to be letting go of the chain neatly causing it to bounce and make the noise/sensation. So I was just exploring this area trying to find out anything else that might reveal what's going on.

You can see a video of it happening here, would love any suggestions on what it could be:

 

[STATO]

Thanks guys, the reason I was wondering is I'm having trouble with my new bike where it's making a noise and sensation through the pedals when going uphill and putting pressure on the pedals. Motor on or off. Another bike shop had a look and pointed out how every second tooth on the chainring is more worn out and that the chainring doesn't seem to be letting go of the chain neatly causing it to bounce and make the noise/sensation. So I was just exploring this area trying to find out anything else that might reveal what's going on.

You can see a video of it happening here, would love any suggestions on what it could be:

Every other tooth on the chainring is wider, this is designed to help ensure the chain stays on the chainring. This is often why it looks like it has more wear (is the shop expereinced with modern MTB? doesnt sound like it, maybe try a different shop). Can see in the video the chain is sticking to the chainring, this is called 'chainsuck' and is often cause by very worn or dirty chains. Is the chain old, worn, dirty, not-lubed?

 

[Akelu]

To my understanding the whole bike is brand new 2021 fresh out of the box. I've had the bike for about 2 weeks now and it's been happening since the first weekend I had it. I haven't cleaned or the chain or lubed it since I got it as they told me that won't need to be done for a while. I was in the meantime going to research proper cleaning techniques and schedule etc but I didn't think it would need it so soon. The other bike shop did mention about the narrow wide chainring but they said it really looks like 'too much' had been taken off the wide teeth for how long I've owned it. They said that that looks like the exact spot where there's friction im feeling when going up hill and the chain isn't releasing properly. Attached picture.

I took the bike back to where i bought it and they gave it back and said they couldn't find anything wrong with it, although by their own admission they didn't ride it off-road where it tends to present most (especially going uphill on grass). But it seems like it's got progressively worse since then I went to the second bike shop for second opinion. Now that I can clearly point to the problem and have video evidence + another 2 techs giving second opinion, hopefully the place I bought it from will be able to fix it. It has been such a headache this situation. I will write them an email tonight with description and video included and hopefully will get the ball rolling.

 

[Pyr0]

I can't tell from the video, but the chain is on the correct teeth isn't it?
The wider links should be on the wider teeth of the chainring.
If they are not, it can make it seem like there is chain suck on brand new hardware.

 

[Akelu]

You just got me excited that it could be something so simple. But unfortunately I just checked and the narrow/wide teeth are correctly engaged with the narrow/wide chain gaps.

 

[urastus]

2 things puzzle me:
How you found out.
Why you would want to.

I found out, and figured it out - it is exactly as Stato says. I session technical sections that I can't ride. It's usually pretty steep, so I was walking the bike backwards. Now I hold rear end up or pivot bike on rear wheel to turn around.

 

[steve_sordy]

That chainring does not look like a 12-speed chainring, but I've only seen Sram 12-speed, never a Shimano one. Any chance it could be an 11-speed ring fitted in error? It would be slightly wider and hang onto the 12-speed chain.

 

[urastus]

That chainring does not look like a 12-speed chainring, but I've only seen Sram 12-speed, never a Shimano one. Any chance it could be an 11-speed ring fitted in error? It would be slightly wider and hang onto the 12-speed chain.

Yes, that chain ring is definitely hanging onto the chain. That would be my focus too - swap out the chain ring.

 

[nickfrog]

That chainring does not look like a 12-speed chainring, but I've only seen Sram 12-speed, never a Shimano one. Any chance it could be an 11-speed ring fitted in error? It would be slightly wider and hang onto the 12-speed chain.

I agree. I would investigate compatibility and research if FSA even make a Shimano 12 speed ring. And I don't just mean a 12 speed ring, as Shimano 12 speed rings have a specific profile to match a Shimano 12 speed chain. I only know of one aftermarket maker of specific 12 speed Shimano rings: Raceface. But there may be others by now. And FSA may be one.

 

[urastus]

I agree. I would investigate compatibility and research if FSA even make a Shimano 12 speed ring. And I don't just mean a 12 speed ring, as Shimano 12 speed rings have a specific profile to match a Shimano 12 speed chain. I only know of one aftermarket maker of specific 12 speed Shimano rings: Raceface. But there may be others by now. And FSA may be one.

I've been using el cheapo chain ring (32tooth) for my shimano 12x setup. It is a 12x chain ring. What I found though is that not many manufacturers state what speed their rings are for - it simply isn't stated. I'm at 500km and no trouble. It isn't going to last long, and it is thick and thin, and the teeth do look the same as the shimano 34 I took off.

 

[Akelu]

So I went to hospital today, and when I walked out I saw a bike shop across the road so I decided to take a look (since I needed a bell anyway), ended up talking to the guy there and turns out he actually used to work for Focus! Pretty wild considering I'm in Australia. So he got in contact with the importer let them know about my problem and got me in contact with another shop to check it over. They advised they think the wave shaped teeth on the chain ring might not be well suited to the chain. So I've got an Ethirteen E*spec Bosch direct mount wide narrow toothed chainring that specifically says it supports Shimano 12 speed, on the way. I saw that trek uses this chainring on their Rail bike which has the same chain and cassette as my bike so it should be good. It's not wave shaped like the FSA is.

I had some other people recommend I replace the chain at the same time. What do you think? I've done about 130km on the bike. So, new chain and new chainring on the only slightly old cassette? Is that the go? I just thought maybe this clunking has affected the chain too.

 

[IanVersion2]

What's slightly odd is that if you go to the Focus website it shows the 6.9 with a bolt-on chainring, yet yours is direct mount? I think that one you have on there is a mistake. I'd be wanting it replaced FOC personally.

FOCUS Bikes - THRON² 6.9

FOCUS Bikes is the leading premium brand of high end mountain bikes and road bikes with excellent quality - German Engineered for amateur athletes and professionals!

www.focus-bikes.com

And yes, after running a chain on teeth wider than it was designed for, I would change the chain as well. Particularly on an eMTB.

Edit. Even more odd on the Focus website is the 6.8, the chainring on that changes depending on what colour paint you choose!

FOCUS Bikes - THRON² 6.8

FOCUS Bikes is the leading premium brand of high end mountain bikes and road bikes with excellent quality - German Engineered for amateur athletes and professionals!

www.focus-bikes.com

 

[Akelu]

Nice find. I have just messaged them asking about that.

Thank you.

 

[nickfrog]

I've been using el cheapo chain ring (32tooth) for my shimano 12x setup. It is a 12x chain ring. What I found though is that not many manufacturers state what speed their rings are for - it simply isn't stated. I'm at 500km and no trouble. It isn't going to last long, and it is thick and thin, and the teeth do look the same as the shimano 34 I took off.

Interesting. I think compatibility may be OK with some non specific Shimano 12 speed ring . But it also seems to be random/luck of the draw unless the ring has been designed with Shimano 12 speed in mind.

 

[urastus]

Interesting. I think compatibility may be OK with some non specific Shimano 12 speed ring . But it also seems to be random/luck of the draw unless the ring has been designed with Shimano 12 speed in mind.

A lot of people here use deckas chain rings from ali express - they only go up to 11x. This is what I have. Initially I bought one to test, then I bought a few more thinking they may not last long. They look reversible too - I'll try that out when it starts to look worn.

 

[nickfrog]

A lot of people here use deckas chain rings from ali express - they only go up to 11x. This is what I have. Initially I bought one to test, then I bought a few more thinking they may not last long. They look reversible too - I'll try that out when it starts to look worn.

At that price it's worth a punt. What's the worse that can happen? Cheers.

 

[Akelu]

What's slightly odd is that if you go to the Focus website it shows the 6.9 with a bolt-on chainring, yet yours is direct mount? I think that one you have on there is a mistake. I'd be wanting it replaced FOC personally.

Focus has gotten back to me and confirmed that my bike was shipped with the incorrect chainring*!

 

[B1rdie]

It can be an issue for some people. Loading the bike in vehicles, especially vans, when wheeling backwards the chain can end up trying to rip the mech off if it jumps a lot of gears.

My road bike has similar issue if its in the big ring at the front and big-ish at the back, the cross-chaining is fine riding but will bump the chain off the front ring and sometimes end up jammed. I dont know why, same gear set-up on other bikes dont do it, so i just make sure to drop to the small ring when i get home and am putting it back in the garage, where it will end up getting wheeled back and forward to clean or get other bikes out.

The solution is just that, if you are going to be wheeling it about, just leave it in a middle gear at the back. No issues then.

This! Derailing while moving backwards was not a problem until I bought a van and had to load it rolling backwards where the rear wheel fits between two bars. The deraileur has to be on the sprocket closer to the wheel so it fits in there, but it moves outwards unless i lift the rear end of the bike.

 

[nickfrog]

Focus has gotten back to me and confirmed that my bike was shipped with the incorrect chainguide!

Chain guide or chain ring? I am confused now.

 

[Akelu]

Chain guide or chain ring? I am confused now.

Sorry .. chainring

 

[nickfrog]

It's a result they came clean and they are presumably sending you a Shimano 12 speed compatible ring?

 

[Akelu]

It's a result they came clean and they are presumably sending you a Shimano 12 speed compatible ring?

Yes, they want me to request a replacement ring through my dealer. They looked up my specific bike serial number and also that I told them I have a 'wave tooth' chainring, they said the wrong one is on there and to request replacement.

 

[urastus]

I'd be asking for a new chain as well due to wear. They are getting off lightly as it is. They should just be sending a new chain ring out rather than getting you to jump through more hoops. I'd also direct them to this topic on this forum, just to let them know that this community is aware of it. Mistakes happen, but they haven't really risen to the occasion.

Also, I suspect that this was actually done on purpose. Having worked in manufacturing, sometimes you just run out of stuff. They probably thought the 11x chain ring would work and get a few more units out the door. I say this because there also seems to be this weird belief that chain rings are universal - not many manufacturers / sellers state what speed their chain rings are compatible with.

How many other owners are out there are not aware of this, just accepting this extra noise from their new ebike? It will logically lessen with time as chain and chain ring get worn.