New Rail 7 2022 - chain slipping off of the front chainring.

[Wet Jimmy]

Hi Folks,

Wonder if any other Rail owners can chime in with advice...

A couple of days ago I picked up a new 2022 Rail 7. Hooray! Or so I thought.

On day 1, when performing a low speed turn on relatively clear and open terrain, I snapped the (to my eyes) thin 12 speed chain. I was at a parkland at the bottom of a massive hill, it was just PERFECT...

Anyway, back to the LBS, they replaced the chain for me without hassle and that was was great.

However what I've noticed now is that a few times, again, at relatively low speed and on, say, roads or footpaths (so not on trails or tricky situations) the chain will slip off the front chainring. It happened in the car park of the LBS and again, they took the bike into the workshop and assured me all was good. One of the team took it for a spin to make sure it was working.

I went for a ride today, did som offroad trail riding; not problem. But then went crusing along the road on the way back home and... chain slipped off the front ring again.

Visual inspection doesn't highlight any obvious problems.

What do you figure is going on?

It's really souring the experience of a shiny new (and expensive to me!) bike.

Cheers, all.

 

[Philly G]

Has the chain been fitted the wrong way round? The writing/markings on the chain should face outwards. Is there a slightly damaged or bent tooth on the chainring from when your chain snapped ? Check that the quick link has been installed the right way round too

 

[Wet Jimmy]

Thanks Philly.

Just took a quick look at the chain; the text imprinted on the chain (HG, Via, SJ, etc.) is facing outwards from the bike, and the quick link arrow is facing in the direction of the chain rotation, so I'm assuming that's all good.

No obvious issues with teeth that I can observe, but perhaps I have to take the chain off to properly inspect.

The quicklinks suggest single use only though, so I'm hesitant to rip the chain off...

 

[Philly G]

I certainly wouldn't be the only one who reuses quicklinks with impunity and never had an issue your problem is very strange though, your chainring will be narrow/wide (meaning the teeth are alternately skinny and fat to mesh with the narrow and wide links in the chain) , and assuming your bike has a chain guide, it should be virtually impossible for the chain to come off unless something is seriously wrong... I'm all out of suggestions I'm afraid

 

[Wet Jimmy]

I'll take note of what you said about quicklinks I've bought a couple of chains to keep as spares, so once they arrive I might pull the existing one apart and have a really good look.

Thanks!

 

[Sonnyjim]

Hi all, new Rail owner here too. I had the exact same thing happen to me on my first ride.

Had ridden some fairly rough trails for over an hour with no issues then the chain slipped off on a smooth section at the end of a trail. Refitted it and it came off again about 50m further on. Noticed the hanger had shifted and checked the bolt with a multi tool - it was very loose. Tightened up and continued riding with no issue, chain then came off on a smooth road section getting back to the car.

When home I checked all associated bolts and linkage bolts none were near torqued enough and some quite loose. Every thing now tight and I’ve gave it a 1/2 hour test and it’s not dropped again, albeit only on tarmac roads.

Guessing the checklist from the bike shop on torquing the bolts should be ignored and worth self checking.

Hopefully this might have solved the issue, did some Googling and it doesn’t seem to be a common issue.

 

[Wet Jimmy]

Hi all, new Rail owner here too. I had the exact same thing happen to me on my first ride.

Your first time experience sounds eerily like mine. It was on relatively flat and innocuous sections that my chain has slipped.

I’ll give the bolts a tweak tomorrow and see how it goes

 

[Sonnyjim]

Your first time experience sounds eerily like mine. It was on relatively flat and innocuous sections that my chain has slipped.

I’ll give the bolts a tweak tomorrow and see how it goes

Out of interest what groupset are you running? Should of been my first question tbh

 

[Mr_Price]

Is the chain length correct?
Is the clutch set? The clutch on my XT has needed a little tweaking for perfect shifting.

 

[Mikerb]

If the chain comes off coincident with using the highest gears ( smallest cassette cogs)............ie on smooth tarmac higher gears are used and on the trails lower gears are used................. it suggests a lack of chain tension either because the mech/hanger is incorretly positioned or has slipped or the mech clutch is not engaged or not working.

 

[Sonnyjim]

If the chain comes off coincident with using the highest gears ( smallest cassette cogs)............ie on smooth tarmac higher gears are used and on the trails lower gears are used................. it suggests a lack of chain tension either because the mech/hanger is incorretly positioned or has slipped or the mech clutch is not engaged or not working.

I think I was mid range when the first chain drop happened and the same with the second. I know the clutch was engaged because I disengaged it to refit the chain both times (then forgot to engage it after the 2nd time, I noticed the difference after).
I haven’t noticed any lack of chain tension but will check.

The rear hanger had visibly moved/rotated in the first instance as the bolt was at best hand tight. I’m now wondering if I’ve damaged a link in the chain as it left a gouge in the chain ring. I’ve not had time to investigate fully - what kind of idiot starts decorating a whole house days after getting a new bike

 

[Wet Jimmy]

Out of interest what groupset are you running? Should of been my first question tbh

Default / Standard for the 2022 Trek Rail 7;

Shifters - Shimano SLX M7100, 12-speed
Rear Derailleur - Shimano Deore XT M8100, 12-speed, long cage
Cranks - e*thirteen e*spec Plus, 165mm length
Chainrings - e*thirteen e*spec Plus, 34 tooth
Chain - Shimano SLX M7100, 12-speed
Cassette - Shimano Deore M6100, 12-speed, 10-51 tooth

 

[Wet Jimmy]

Is the chain length correct?
Is the clutch set? The clutch on my XT has needed a little tweaking for perfect shifting.

I can confirm clutch is in the locked position, but if it's set correctly, I've no idea...

Follow up question; how do I know if the chain length is correct? Where can I source that info??

 

[Philly G]

@Wet Jimmy I was also wondering if your chain was too long...I think this video is the best explanation and easiest method of correctly sizing a chain. Of course, once you've got it right, you can just size a new chain using the old one. Chapter @ 6:29 explains how to take into consideration chain growth due to suspension compression.

 

[Growmac]

The chainring locknut is notorious for being delivered loose, and for coming loose. Might be worth checking. Was one of the many, many things the PDI on my bike missed.

 

[DMS2610]

Just an idea, but the tension in the derailleur is adjustable, ask the lbs to check the B tension is in spec

 

[Timochka69]

Are you using the clutch in the derailleur?

 

[folmonty]

What @Growmac says about the chain ring lock nut. Also the mech / hanger might be out of spec and needs to be aligned. Special tool required to do this. Good idea to check nuts, bolts and screws with some regularity on eMTB's. These bikes do require proper maintenance to keep running well.

Hope you get it sorted out soon. My Rail 7 has worked like a dream since new with almost 500 miles of off road trail use.

 

[Sonnyjim]

An update on the issue.
Went out on my second ride and Had the chain drop on the first descent annoyingly. Found a buckled link in the chain and swapped it out with a quick link, no better and the chain became a fkn pest dropping every now and again. When back home after cutting the ride short I found that the chain ring had 6 or 7 bent teeth causing the chain to pick up slightly on the ring but only in gear 10,11,12 throwing the chain off. Presume this damage was caused by the original chain drop.
So new KMC chain fitted and chain ring teeth straightened with pliers seems to have done the trick. No chain drops today .

Apart from that and the battery deciding to eject itself a few times (now also fixed) ebike ownership has been great so far

 

[DeRailled7]

What @Growmac says about the chain ring lock nut. Also the mech / hanger might be out of spec and needs to be aligned. Special tool required to do this. Good idea to check nuts, bolts and screws with some regularity on eMTB's. These bikes do require proper maintenance to keep running well.

Hope you get it sorted out soon. My Rail 7 has worked like a dream since new with almost 500 miles of off road trail use.

100% agree.
On my buddy‘s and my own bike our chainrings on our Rail 7 came loose after a few rides. We both had the lock nut retightened at our LBS using Blue tread lock. No problem after over 2000km since.
Strongly recommend you do the same before it comes loose. BYTW the reason it comes loose is thought to be caused by the rear suspension movements. As it goes up and down it will pull on the chain backwards so ever slightly and in doing such will slowly unscrew the lock nut.

 

[folmonty]

100% agree.
On my buddy‘s and my own bike our chainrings on our Rail 7 came loose after a few rides. We both had the lock nut retightened at our LBS using Blue tread lock. No problem after over 2000km since.
Strongly recommend you do the same before it comes loose. BYTW the reason it comes loose is thought to be caused by the rear suspension movements. As it goes up and down it will pull on the chain backwards so ever slightly and in doing such will slowly unscrew the lock nut.

This last week I did a detail service on couple of Allant +7s city bikes with no rear suspension. The bikes have the "speed" version of the Bosch motor, with the crank arms off both chain ring nuts (same part) had half the torque required. Definitely use blue (med strength) thread lock. e-thirteen says forgo the o-ring and that's what I'm doing.

At some point the rear chain stays must've been changed. Thought all the bikes at local Trek dealers were 2022's but they're leftover 2021's and the chain ring has way more clearance. Those of us with tight chain ring to chain stay clearance must be extra vigilant.

 

[BobBuzz]

I´ve been having this problem with a Trek Rail 5 2022. Seems that e*thirteen have recognised that there is a problem and suggest a 1mm spacer to fix this:

Look here: https://support.ethirteen.com/hc/en...T-ON-E-THIRTEEN-E-SPEC-STEEL-BOSCH-CHAINRINGS

Really annoying and i have had to replace one chain already.

 

[Paulquattro]

I´ve been having this problem with a Trek Rail 5 2022. Seems that e*thirteen have recognised that there is a problem and suggest a 1mm spacer to fix this:

Look here: https://support.ethirteen.com/hc/en...T-ON-E-THIRTEEN-E-SPEC-STEEL-BOSCH-CHAINRINGS

Really annoying and i have had to replace one chain already.

I dont see how a 1mm spacer would fix this issue with the amount of chain deflection you get on a full run of the cassette .