Q&A: Binding Mavic Ksyrium cassette

Q: Jim - The cassette on my Mavic Ksyrium rear wheel is binding. I first noticed this by seeing that if I spun the rear wheel by hand, every now and then the chain would suddenly start being driven by the rear wheel and the pedals would turn - almost like on a fixie bike with only one gear and no coasting feature. At first it only did this once in a while, but now it's binding all the time and when I am riding the cassette tries to turn with the wheel and this creates slack in the chain and I bet additional friction at the wheel that's slowing me down! Not good on what are supposed to be my fast wheels. What do you think is wrong, and do I have to return my wheel to Mavic for service, or is this something I can fix myself?

Thanks for any help you can provide,

Lloyd

A: Hi Lloyd,

The likely problem is lack of lubrication, or some grease that has gotten congealed and is now sticky instead of slippery, right where the cassette attaches to the hub. There are cartridge sealed bearings inside and also seals. All these things need to be nicely lubed for the cassette to spin freely and not bind or drive the chain forward. I recommend visiting Mavic's tech website at http://www.tech-mavic.com/, login "mavic-com" and password "dealer" (do not include the quote marks)

Here you'll find manuals for all Mavic products going back years, and instructions for your specific wheel (like the diagram above). Assuming you have a few basic tools (you'll probably need a 5 and 10mm Allen wrench and a way to hold the axle, such as an axle vise - or home-made version) and a little mechanical ability you should be able to fix this problem yourself by following the directions.

For a sticky cassette, you would disassemble the hub by removing the axle with Allen wrenches and then carefully pulling off the cassette (don't drop/lose the pawl springs!). This reveals the bearings and seals and you can check the grease inside and clean and lube as necessary. Use a light and safe oil (it mustn't attack rubber or plastic) on any seals because if they're dry they can cause the binding. Then reassemble the hub and you should be good to go. Or, if you'd rather let a professional handle it, any shop that sells Mavic wheels should be able to service yours for a reasonable fee.

Happy hub and cassette repairing!

Jim

Q&A: Freewheel/cassette not working/frozen

Q: Hi Jim,
This happened over the weekend (it was cold): When I tried to ride my bike on Monday the freewheel would not engage with the wheel (it just spun). I moved the bike inside (it was stored in the garage) and adjusted the quick release, laid it flat on the floor and it worked again. I am not sure whether I fixed the problem or not. I have no confidence to ride it until I really understand the problem or issue(s) (it’s a 12-mile commute). Could you give me some tips?
Thanks,
Thomas

Q: Hi Thomas,
The freewheel (also called a cassette sometimes, though the two are different things) has little pawls and springs inside that work together to drive your bike. There's usually lubricant inside, too. My best guess is that the cold weather made the pawls stick and stop catching and driving your bike. When you brought your bike inside the heat warmed up the lubricant and the springs were then able to push the pawls back in place and drive your bike again. So, I think it'll work fine for your ride.

It won't hurt to add a little lubricant. To do this, lay your bike on its side with the freewheel facing up. Then turn the crank backwards and watch the freewheel move. You'll see that the part with the sprockets moves and the part it's turning on stays still because it's attached to the wheel. There is a small crack between these two parts of the freewheel and that's where you put the lube. A light spray lube like Triflow works fine. Or you can drip car motor oil on while turning the crank slowly to draw the lube into the crack and into the freewheel mechanism. You won't get all the oil in there but you just need to get some in there to refresh any lube that's in there and keep the freewheel working.

Note that if what you have is a cassette, it's harder to get lube inside it because there are pieces that block access to places to add lube. Click here to see a nice picture on Sheldon Brown's awesome bicycle website that shows the difference between freewheels and cassettes. Luckily, cassettes usually don't freeze or fail as often as freewheels and don't need relubing very often. If you want to relube your cassette you can remove the cogs (you'll need a cassette lockring tool and a chainwhip tool) to gain access to the body and drip some lube in. Or, if you want to do a professional job, consider purchasing Morningstar Tools' Freehub Buddy tools and lube that let you flush and fully relube it!
Jim