GSD S10 gear ratios


New Member

We have recently bought a GSD S10 (the original one, not the recently revised version.) We're finding the gear ratios don't seem quite right for us. It is rare for us to ever get beyond about halfway up the gear range, as we've usually got two kids on the back and aren't exactly going fast. I often find myself using the electric for short bursts of hills where it wouldn't be necessary if the gears went a little bit lower. I wondered if anyone has any experience of changing the cassette for a different one on this bike and how it worked out?

The problem is also exacerbated by the fact that in the two largest cogs, the chain has a tendency to rub against the tyre very slightly, which means I try to avoid using those two gears for very long at a time. I'm not sure if this is actually a fault or just a symptom of wide tyres, meaning the chain is always very close to the tyres.

Thank you in advance for any advice.


Active Member
Derailleur could be out if alignment, put it in the largest cog, stand the bike straight up, you lay down by the rear of the bike and do a visual, look at the derailleur, straight up and down? Is it straight from the rear of the bike all along up to the front of the bike? Check the hanger. Look for any bent pieces. It is rather easy to bend the derailleur if you hit a curb for example, or bent the derailleur if the bike was laid down on that side. But it is a rather easy fix. Check out boob tube on fixing a bent derailleur.
Park tool has a great site for repair advise.

Ravi Kempaiah

Well-Known Member
exacerbated by the fact that in the two largest cogs, the chain has a tendency to rub against the tyre very slightly

As @TOOSLOW mentioned above, you may just need derailleur indexing and small adjustments. Your shop should be able to fix without much issue.
Takes 5-10 mins.

Nova Haibike

Well-Known Member
An out of alignment derailleur would only really cause the chain to rub against the tire on the lower return section; the chain would be in the same position on the top regardless of the derailleur being bent or not. If it is rubbing on the top section of chain, I cannot say why or if there is another problem.

As for the gearing, the specs I read said the bike has an 11-36T cassette. Larger cassettes with lower gears are available, and those would perhaps give you more usable gears in the middle of the range.


New Member
Thank you everyone. I'm on holiday at the moment so do not have the bike in front of me, so cannot check the derailleur - but it sounds as though that may help as it is only the lower part of the chain that rubs, not the top. That said, I still think the gear ratios are not quite right even with that fixed, because even on the rare occasion I've tried to ride it "fast" with no kids or cargo on, I'm still only in about gear 5 or 6 (out of 10) when the electric assist cuts out at 15-16mph, and I wouldn't want to go much faster than that on the 20" wheels anyway.

Thanks again.


Active Member
It is a cargo bike designed for loads, top assist speed is 20 mph. I doubt there is a gear ratio problem.
Should be 11-34 cassette. With 20" wheels there could be a cassette clearance problem if you seek more range. See my post in the Tern forum. I am going to change up to a 11-42 cassette, as I need more climbing ability, will keep you posted. (check your wheel magnet position.)


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New Member
Thank you- i will watch that thread as it looks like you are attempting what I was hoping for. I hadn't realised replacing the chainring inside the motor was even possible.

BTW in UK all electric bikes have assistance limited to 15mph for legal reasons. I guess in a jurisdiction where electric assist is allowed at higher speeds then the GSD S10's supplied gear ratio would make more sense.

thank you again


Active Member
Restricted to 15mph, seems we are restricted to death everywhere around the world in every way.
Now that's freedom !

Anyhow there are options based on your comfort level.
Larger front chainrings, derestricting of the Bosch motor, different cassette's. Alone or in conjunction with one another should allow you to achieve what your after.