When in 12 gear (smallest sprocket) and when in trail or turbo whilst also putting my own max power down the chain sometimes skips a few teeth.

[RIngrey]

Given that the crankset is new and correctly aligned can anyone explain how I can sort this issue?

 

[urastus]

Your cadence must be very low, however:

The b screw adjuster on the derailleur - this adjust the amount of chain wrap around the sprocket. On a 10 tooth sprocket there isn't much for the chain to connect with (6 or 7 teeth?) I've actually removed mine because it also seems to effect ease of gear change.

Work on a higher cadence, which will probably mean staying in lower gears. This will also be better for your knees. For example, I've geared my bike down - it did have a 36 tooth chainring, it now has 32. I'd be doing about 40km/h in top gear pedaling; my assistance cuts out at 25km/h. So I'm never in top gear with assistance. I'm guessing your system is geared higher - most are.

 

[Gary]

6 or 7 teeth?

MOAR like 4

 

[maynard]

Like new? Or new ? Sounds like wrecked cassette.

 

[Funkeydunk]

I agree with Maynard, it’s almost sure to be a worn cassette

 

[RustyIron]

In the interest of maintaining my disagreeable nature, I will stubbornly disagree with everyone on this. If you're having a problem on the first or last cog, the first thing you should always consider is the limit screws.

The limits are there to keep the derailleur from moving over too far and pushing the chain off the end of the cassette. Oftentimes, people will set up the limits to hold the derailleur perfectly aligned with the cog. This is not necessary, and sometimes it inhibits perfect operation. Remember, the limit is there to keep the derailleur from pushing the chain off the cassette, nothing else. The derailleur has to move pretty far to do that. Back off the limit screws so that the derailleur can move past the cog, but not so far that the chain could run off the cassette.

On a cable operated drive train, especially those with a little wear, proper adjustment of the limit screws will allow for better shifting and running. Anyway, the limits are the first and easiest things to look at. If they're wrong, it's obvious. If they're ok, then you can move on to less-probable possibilities.

 

[Mikerb]

The OP did not mention the chain. A new cassette with even a part worn chain can cause slippage on the smallest cog. Always best to change both at the same time.
Chain wrap on the smallest cog is minimal so correct B tension is important.

The OP did not explain why the cassette was changed................was it changed because of slippage problems?

 

[urastus]

In the interest of maintaining my disagreeable nature, I will stubbornly disagree with everyone on this. If you're having a problem on the first or last cog, the first thing you should always consider is the limit screws.

The limits are there to keep the derailleur from moving over too far and pushing the chain off the end of the cassette. Oftentimes, people will set up the limits to hold the derailleur perfectly aligned with the cog. This is not necessary, and sometimes it inhibits perfect operation. Remember, the limit is there to keep the derailleur from pushing the chain off the cassette, nothing else. The derailleur has to move pretty far to do that. Back off the limit screws so that the derailleur can move past the cog, but not so far that the chain could run off the cassette.

On a cable operated drive train, especially those with a little wear, proper adjustment of the limit screws will allow for better shifting and running. Anyway, the limits are the first and easiest things to look at. If they're wrong, it's obvious. If they're ok, then you can move on to less-probable possibilities.

"Given that the crankset is new and correctly aligned "

 

[urastus]

Like new? Or new ? Sounds like wrecked cassette.

The hanger could be bent too - but he says everything is aligned

 

[John Beedham]

Slipping ... sounds like others have said ...worn 12 th gear ... it's the smallest cog so 10-12 teeth on it its going to wear out faster that a 50T 1st gear ... you may be able to purchase the 12th gear cog ... you should, be otherwise what a waste !!!

 

[sqzer]

i had same issue with shimano xt 12 speed, check rear derauiller hanger if it is really straight and try to play with b gap screw. can eliminate most of issue. if it does not work probably you need new drivetrain

 

[oceanskipper]

Are you sure it’s not the freehub failing to engage properly and giving the impression that the chain is slipping?

 

[1oldfart]

Real simple, adjust or ask your shop to adjust your derailleur so you are never on the smallest cog.
It is useless, no Ebike needs 12 S 10 or even 9 is plenty.

 

[WubbleU]

Slipping ... sounds like others have said ...worn 12 th gear ... it's the smallest cog so 10-12 teeth on it its going to wear out faster that a 50T 1st gear ... you may be able to purchase the 12th gear cog ... you should, be otherwise what a waste !!!

Fixed it for me. Didn't bother changing chain, just the sprocket.

 

[WubbleU]

Real simple, adjust or ask your shop to adjust your derailleur so you are never on the smallest cog.
It is useless, no Ebike needs 12 S 10 or even 9 is plenty.

Yes, my smallest cog gets absolutely no use at all even though it's working fine

 

[Gary]

Being slow AF is now something Emtbers flex about?

m'kay

 

[Kiteboy]

Made my own hanger adjustment (and measuring) tool for less than $20.00. My hanger looked straight but after checking it I found it was indeed bent. Used the tool to straighten it and fixed my chain skipping problem on the smallest sprockets. It's amazing what a tiny bend in the hanger will do to your drive train performance.

 

[Tribey]

Quick link on the wrong way.

 

[thewrx]

yep, check chain strech, b-screw, hanger bent, sprocket worn, wrong gear/cadence.

Replace in order: chain, d-hanger, cassette, derailur, rider.

 

[WubbleU]

Being slow AF is now something Emtbers flex about?

m'kay

All uphill from here

 

[WubbleU]

Yes, my smallest cog gets absolutely no use at all even though it's working fine

To be clear, I spend too much time on tarmac roads and smallest does actually get most of the wear. Makes sense that the smallest sprocket wears most when so much force has to go through each tooth relative to the other sprockets.

 

[crazyethnic]

bent hanger.

 

[Gary]

Makes sense that the smallest sprocket wears most when so much force has to go through each tooth relative to the other sprockets.

Generally a rider will output lower peak power (torque) while in the smallest sprockets as they will generally spinning at a decent cadence and maintaining decent momentum rather than sprinting from low speed, accelerating from mid speed or grinding climbs (Generally lower cadence but with higher pedalling forces). But the addition of a motor does for many riders often means they will pedal at slower cadences allowing the motor to output higher assistance.

The smalest sprockets wear faster for two main reasons. firstly chain wrap means only 4 or 5 sprockets are sharing the load from the chain and secondly the sprocket is turning the chain over each tooth at a faster rate.
And because of the very small number of teeth in contact with the chain a relatively small amount of sprocket tooth wear and chain wear will mean the chain will slip over the smaller sprockets under high load. Up your cadence and you'll not only spend far less time in the smaller sprockets but you'll also put less force through the drivetrain while in them. It doesn't actually take long to train your body to be comfortable pedalling at far higher cadences (90-120rpm) and doing so will improve both your riding experience and fitness greatly.
Also. if you spend a lot of time on tarmac in top gear. swap out to a larger chainring.

Most Emtb riders could do themselves a favour by not running wide range cassettes with 10t small sprockets at all and unless you really really need a massive cassette running the narrowest range cassette their trails can be climbed with. On normal mtb trails a reasonably fit/able and not hugely heavy rider simply shouldn't need a 50t cassette sprocket with 250w of extra assistance. A smaller range cassette actually allows the rear mech guide pulley to be run far closer to the cassette increasing chainwrap greatly. and with greater chainwrap/tooth coverage the smallest sprockets will still run smoothly without chainslip when the drivetrain is far more worn than it ever would with a 10t sprocket and long cage mech designed to cover a 42t range (10-52t.) Shifting is also far faster and smoother the closer ratio cassette you run.

 

[1oldfart]

Generally a rider will output lower peak power (torque) while in the smallest sprockets as they will generally spinning at a decent cadence and maintaining decent momentum rather than sprinting from low speed, accelerating from mid speed or grinding climbs (Generally lower cadence but with higher pedalling forces). But the addition of a motor does for many riders often means they will pedal at slower cadences allowing the motor to output higher assistance.

The smalest sprockets wear faster for two main reasons. firstly chain wrap means only 4 or 5 sprockets are sharing the load from the chain and secondly the sprocket is turning the chain over each tooth at a faster rate.
And because of the very small number of teeth in contact with the chain a relatively small amount of sprocket tooth wear and chain wear will mean the chain will slip over the smaller sprockets under high load. Up your cadence and you'll not only spend far less time in the smaller sprockets but you'll also put less force through the drivetrain while in them. It doesn't actually take long to train your body to be comfortable pedalling at far higher cadences (90-120rpm) and doing so will improve both your riding experience and fitness greatly.
Also. if you spend a lot of time on tarmac in top gear. swap out to a larger chainring.

Most Emtb riders could do themselves a favour by not running wide range cassettes with 10t small sprockets at all and unless you really really need a massive cassette running the narrowest range cassette their trails can be climbed with. On normal mtb trails a reasonably fit/able and not hugely heavy rider simply shouldn't need a 50t cassette sprocket with 250w of extra assistance. A smaller range cassette actually allows the rear mech guide pulley to be run far closer to the cassette increasing chainwrap greatly. and with greater chainwrap/tooth coverage the smallest sprockets will still run smoothly without chainslip when the drivetrain is far more worn than it ever would with a 10t sprocket and long cage mech designed to cover a 42t range (10-52t.) Shifting is also far faster and smoother the closer ratio cassette you run.

You won my best post of the month award ! Congrats !

 

[Gary]

Every post of yours deserves an award

 

[urastus]

It's amazing what a tiny bend in the hanger will do to your drive train performance.

Not really, by the time the effect of that tiny bend gets to the derailer - the derailer is out quite a bit.

 

[malc101]

If you are riding on the small sprocket a lot, think about getting a bigger front chainring to push the chain up a gear or two in the rear. I just did that on my Levo because the small gears were getting used 90% of the time. Adding 4 teeth moves it a gear or two bigger. It seems crazy that all the power is going to a 10 or 11 tooth sprocket.

 

[1oldfart]

If you are riding on the small sprocket a lot, think about getting a bigger front chainring to push the chain up a gear or two in the rear. I just did that on my Levo because the small gears were getting used 90% of the time. Adding 4 teeth moves it a gear or two bigger. It seems crazy that all the power is going to a 10 or 11 tooth sprocket.

I agree my transmission is a 10 S 36 front. I guess the 32 front are for when the assist does not work.
My 11/46 is great but i never use the 11 so i use 13/46.
Why do you use a 10 or 11?

 

[Gary]

I guess the 32 front are for when the assist does not work.

or riders who ride with a decently fast cadence.
It doesn't sound like you do.

 

[malc101]

or riders who ride with a decently fast cadence.
It doesn't sound like you do.

BLEvo reports my average cadence at 65. In trail I’m at 75. Adding 4 teeth to the front ring just moves the chain to a bigger cassette gear. No effect on anything assuming you don’t use first gear much.