Why do chains slip?

[slowmotion]

A battered soul very recently posted some pictures of the injuries he received when his chain slipped and he met some tarmac at 20mph. Ouch. I came a cropper in a similar fashion a very long time ago and I've been pretty much terrified of a repeat ever since, to the extent that I'm reluctant to get out of the saddle and put torque into the cranks. My chain has less than 0.5% wear, the cassette and chainrings are in good shape, and the indexing is OK.
So why should my chain slip every so often? Thank you.

 

[mickle]

Stiff link.

 

[Smurfy]

Mickle is correct. And it is more likely to happen in higher gears (smaller sprockets), as the chain has to bend more to fully engage with the teeth and avoid skipping.

 

[Smurfy]

I should add, the best way to check for stiff links is to put the chain on the smallest sprocket, and back pedal slowly, while watching for links jumping as they pass around the jockey wheels and smallest sprocket. And if you want to minimise the possibility, keep the chain well maintained/lubricated, or run a fixed-wheel which has no slack and so cannot skip.

 

[gbb]

A battered soul very recently posted some pictures of the injuries he received when his chain slipped and he met some tarmac at 20mph. Ouch. I came a cropper in a similar fashion a very long time ago and I've been pretty much terrified of a repeat ever since, to the extent that I'm reluctant to get out of the saddle and put torque into the cranks. My chain has less than 0.5% wear, the cassette and chainrings are in good shape, and the indexing is OK.
So why should my chain slip every so often? Thank you.

Also could be a freehub playing up....it'd give you the same sensation.

 

[Levo-Lon]

9 speed link fitted to a 10s chain..
and all of above..
usually on mtb bikes its debris small bits of twig in the cassette etc. Not so common on the road bike but anything can get in there with all the stuff lying around..

 

[slowmotion]

Thank you for the suggestions. There are no stiff links and I lube the chain regularly. Can anybody suggest how I might test the freehub for wonkiness, short of replacing it? Thanks

 

[mythste]

I had a similar problem - I thought it was one gear but on further inspection it was the top 3 cogs and the reason *appeared* to be that id buggered the chain with too much cross chaining, though it could just of easily have been a stiff link now I think about it. Either way, a new chain sorted it right out.

https://www.cyclechat.net/threads/one-gear-slippling.180502/

 

[gavroche]

Took mine to my LBS today for chain slipping. Will collect bike tomorrow and will let you know. Woman in LBS think it could be worn cassette gears when I took it in but she is going to investigate further. Might just be a simple adjustment?

 

[Smurfy]

Thank you for the suggestions. There are no stiff links and I lube the chain regularly. Can anybody suggest how I might test the freehub for wonkiness, short of replacing it? Thanks

I'm not sure you can, apart from remaining seated with a new unit until you build up confidence. And unfortunately these things can be quite sporadic, so I'd want to give it several hundred miles if I was concerned about the consequences of a slip/skip. Best advice is just to buy good quality, and give it a while to settle down before putting your faith in it. With respect to quality, I'd say generic copy is the most risky, middle ground would be good quality OEM unit, and bomb proof would be high quality after market such as Hope. For example, the Mono RS has four pawls, which is probably twice as many as most freehubs. The chance that all those will slip is minimal.

http://www.hopetech.com/product/mono-rs-rear-hub/#tech

http://www.worldwidecyclery.com/col...mono-pro-2-evo-11-speed-freehub-body-40t-only

 

[gavroche]

Well, got my bike back from lbs. The lady said all she could find was a twisted jockey wheel. She twisted it back and all seem well. No charge. Will probably try it out tonight.

 

[slowmotion]

I'm not sure you can, apart from remaining seated with a new unit until you build up confidence. And unfortunately these things can be quite sporadic, so I'd want to give it several hundred miles if I was concerned about the consequences of a slip/skip. Best advice is just to buy good quality, and give it a while to settle down before putting your faith in it. With respect to quality, I'd say generic copy is the most risky, middle ground would be good quality OEM unit, and bomb proof would be high quality after market such as Hope. For example, the Mono RS has four pawls, which is probably twice as many as most freehubs. The chance that all those will slip is minimal.

http://www.hopetech.com/product/mono-rs-rear-hub/#tech

http://www.worldwidecyclery.com/col...mono-pro-2-evo-11-speed-freehub-body-40t-only

Thanks @Yellow Tim.

 

[gavroche]

Went for a quick 14 miles ride and all is well. Gears are working properly so problem solved. If yours slips, check your jockey wheel first.

 

[Smurfy]

Thanks @Yellow Tim.

Glad to assist. Thinking about freehubs a bit more, I think it is worth considering the designs used by different manufacturers.

The Shimano design, as do many other generic copies, positions the ratchet mechanism inside the space between the cassette and the spindle. Clearly there is not much space available, so the pawls, springs and ratchet ring must be small. Here is a Shimano 105 unit, and all that can be seen is the spline for interfacing with the hub, the ratchet mechanism is crammed into a tiny annulus between the inside of the freehub body and the spindle.

Compare that to the Hope design, where the ratchet mechanism is a separate extension of the freehub body. This enables all the constituent parts to be larger. The pawls on the Hope freehub appear to be set at a slightly larger diameter than the main freehub body, a feature that is impossible with the Shimano design, and the ratchet ring will be even larger, allowing more points for quicker engagement. The pawl springs are also quite substantial, which leads people to either love or hate the hub for its loud clicking when freewheeling.

 

[slowmotion]

Thank you @YellowTim. My bike is a cheap Cinelli. It has a Miche Reflex rear wheel and a Campagnolo cassette. I would be delighted to splurge a few quid on a dogs' danglies freehub if it solves my fear of ending up on the tarmac, or gasping on the top tube. I'm still a bit cautious about getting out of the saddle. You would be too if you went through what I did, but I'm grateful for your advice and suggestions.

I guess I just need a team car and a bunch of mechanics.