# Deore 10 Speed Gear Change Problem



## 87s (Jun 24, 2021)

I have a new 2021 Trek Marlin 7 with the following drive train spec:


ShifterShimano Deore M4100, 10 speedRear derailleurShimano Deore M5120, long cage*CrankFSA Alpha Drive, 28T steel ring, Boost, 175mm length Bottom bracketFSA, 73mm, threaded cartridge, 122.5mm spindleCassetteShimano Deore M4100, 11-46, 10 speeChainKMC X10, 10 speed.

The problem I have is that when I change gears from 5th through to 10th, the pedals slip about 1/3 rotation and there is a loud ka-chunk as the chain hammers onto the cassette. The issue is bearable when riding at speeds of up to 10kmh 😆, but at higher speeds, sometimes it's so violent that my feet jump off the pedals. Of course, when moving from a steep incline to a more gentle one, when I change to lower ratio gears, and this happens, I lose all power and rhythm. Very occasionally there is a lovely soft click when changing from 7th to 8th, which is what I imagine to be expected. The gears changing from 10th down to 1st or from 1st up to 5th are perfect.

The shop I bought the bike from insist all that is required is a cable tension adjustment, but this has not made an improvement. I took the bike to an official Trek dealer for a gear set-up. They made adjustments to the cable tension, the derailleur and tightened the cassette (the cassette rocks a little, but I have been told this is normal with a bike in this price range. Though it doesn't seem to be any tighter than it was before the service). They also told me that all Shimano 10 speed set-ups behave like this, and 10 speeds in general; that it is normal, but, although I am not very technically knowledgeable about bikes, I have ridden many over the past 35 years and never had an issue like this which was considered normal and unfixable, especially with a brand new bike. I've ridden about 500km on this bike.

Has anyone advice or similar experiences which have been resolved?

Thanks.


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## Matt505 (9 mo ago)

Hi, did you ever discover / fix this problem, can you shed some more light on your experience.
I picked up a new Marlin 7 yesterday and on the 30 min cycle home I experienced what you described around 4 or 5 times.
I'm hoping it's the gear setup as you originally did.
Thanks


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