mtandrbker

Hello all,

I have a 24 speed MTB with about 2000 miles on it and decided it needed a new chain after it started some mild skipping on the smallest cog. i adjusted the chain so it is at length just big enough to fit around the big cog in the back and the crank gear. Once I installed the new 8 speed chain it constantly skipped on the smallest cog only under load. I then figured i had a warn out cassette so i swapped the cassette. after installed the new cassette i snapped the shift cable on accident so i put on a new de-railer cable too. i have adjusted the derailer properly and it shifts perfect now however, the chain still skips under load constantly every 1/4 turn of the crank and only in 8th gear just like with the new chain and old cassette. there is a thread on here that seems to be the closest related to my problem but it wont let me post the link since im a new subscriber . its titled "skipping bike chain when smallest hardest cog" I have gone through all the replies and none seems to be my issue. i almost thought it was the free hub but i can see the chain is skipping and not the cassette. After much research i have come across a few people stating a warn crank set can cause this. I dont see how an old crank set could cause the the chain to skip on the smallest cog only and constantly but i have ruled out everything else. please let me know what your thoughts are on the old crank set.

i wish i had a selfy stick as trying to take a video of the chain and cassette while trying to ride and keep the bike steady is kind of nutty.
once the site lets me post links i will send the youtube videos . they are titled chain skipping new cassette and new chain and cassette. the 2nd video shows the bike in 8th gear and cranking fine without load.

trailangel

Verify for us your chain is 8 speed chain, 8 speed quicklink... make and model. Make and model of Freehub.
Crank?
Then we go from there.

mtandrbker

Hi,
my chain is KMC X8.99 Bicycle Chain (1/2 x 3/32-Inch, 116L, Silver) 6-7-8 speed systems with quick link
free hub is a shimano FH-RM30
crank is SR SUNTOUR 42T-34T-24T
cassette is CYSKY 8 Speed 11-13-16-20-24-28-32-42T

thanks for the help!

trailangel

Did you size the chain correctly?

terrymorse 

Found the video:

mtandrbker

Yes. i measured it so it just makes around the big cog in the front and the big cog in the back. also i did bring it down a few links just to make sure and it still skipped the same amount.

mtandrbker

[QUOTE=terrymorse;21123545]Found the video:


thank you for posting! i should be able to post links soon.

79pmooney

Did you re-rivet the chain or use a quick link? If you re-rivetind the chain, do you have any tight links?

Ben

mtandrbker

I have a quick link. i checked it when its not under load and all the chain links seem to be grabbing fine with no stiff links. i verified its not happening on the quick link

Dannihilator

Cassette is not meshing with the new chain.

Darth Lefty 

Absolutely check the high limit screw first.

But also... that's a huge cassette to be using with a triple, or a conventional rear derailleur. No reviews on Amazon means you are the guinea pig.

Leebo

A 3 x8 drivetrain uses a 42 T cassette?

79pmooney

That CYSKY 8 Speed cassette is cheap. Maybe it is well made but they may also have cut corners with careful tooth cutting which would show first on a the smallest cog. Do you have another cassette? Try it and see if the problem remains. Try a different chain, perhaps SRAM. The cassette swap is free if you have one. SRAM 8-speed chains are cheap. So you can do these experiments without spending much money.

Ben

mtandrbker

i had it out on some mountain bike trails today. it seems i have the gears dialed in and it shifts smooth. the idea with the 42T was so i wouldnt have to use the smallest cog anymore on the crankset. so i was interested to apply the 42t on a really steep hill and it was kind of a joke. if i sat down i was popping a wheeley and i was going to fall backwards if i didnt stand up . then when i stood up my back tire started spinning lol. since the rest of the drive train works so good i am starting to get convinced the 8th gear cog is cut wrong on the cassette.

Newspaper_Nick

Check the chain tension and the B tension screw (rear derailleur). If the chain has slack, it will slip. Adjust the B tension screw on the biggest cog and make sure that the rear derailleur is engaging as much teeth of the cog as possible without the jockey wheel snapping to the cog itself (it makes a noise when it does that). Then do a test ride. If it still slips, you should check the wear of your chainrings.

Darth Lefty 

Seems possible, given the usual conservatism about the capacity. But man...