I would first like to say hello to all my fellow forum users I am happy to be aboard.

My problem...
I am having a problem with my chain slipping off while riding my road bike. It happens when i am on the big ring and pushing a big gear up hill. My chain doesn't seem to be able to handle the stress put on it and simply slips off...i am wondering has it streched It is a major problem at the minute because a few times this week it has almost sent me crashing to the tarmac.
I would appreciate any comments as to the cause of this problem and any actions needed to be taken to correct it.

Thanks in advance for any help and comments offered!!

Welcome aboard!!!

To answer your question, this is probably due to "chain stretch" and/or a worn chainring. To check chain wear, measure the distance from pin to pin between ~12 inches of chain. If there is more than a 1/16" of extra length over the 12 inches, then you chain needs replace. Someone else here could probably describe this technique better.

If the chain has stretched too much, more than likely it has also worn the chainring down, and that will need to be replaced also.

Welcome to the forums, this is probably a question for the "mechanics section"
Anyway, i`m on this with Steele-Bike , check also your cable tension and your front derialleur adjusment, if you want to do it yourself, but don`t know how it works, look at this link -->

https://www.parktool.com/repair_help/...ex.shtml#frame

They give step by step advice and orders how to do all sort of maintenance on bicycles, good luck,

Regards,

Another possibility is one or both of your derailleurs are out of alignment. Could they have had a knock at sometime? Have you left the bike some where, where someone might have been playing with the limit screws?

Which bit of Wales? I lived in and around Aberystwyth for a few years.

Richard

Welcome aboard Flea! Always nice to see UK posters.

Could you clarify a bit? You say you're in the Big ring going UP a hill? Are you talking about the front chain rings? If you are, the chain slip problem apart, shouldn't you be on the smaller rings when you're grinding up a hill? And you sure got some hills in Wales!

Coz the big chain ring with a big rear gear is forcing the chain to have too much lateral movement (see EXCELLENT diag attached!!!), and may encourage it to jump off

Chain stretch should be easy to measure - each link is an inch. measure 12 links against a good steel ruler, should be spot on 12 inches. Someone (D*Alex?) will tell us what %age stretch is acceptable ie 12 1/8 inches=OK 12 1/4 inches=too stretched.
(Ah - I've just seen Steele-Bike has beaten me to it!!)

Another possibility mat be that the chain ring is warped/bent. With the chain off, hold a pointer near the teeth, braced against the frame and spin the pedals, should quickly show you if the ring is straight or not.

How old is the bike and its drive train? the rings & rear mech do get worn and break teeth. May need replacing. If they do, you can consider changing the cog sizes to hel with them Welsh hills, and may as well replace the chain at the same time anyway.

Stew

If you chain has more than 2500-3000 miles (450,000,000 km), replace it. If not, the problem may be nothing more than adjusting the high limit screw, the one farther from the seat tube. Shift to the big chain ring and smallest cog. Turn the high limit screw until there is just 1-1.5 mm between the outside edge of the chain and the outer der cage. I was recently on a hilly ride with a ladies who's chain kept slipping off. I don't know about the chain itself, but a couple of turns on the high limit screw cured the problem.
FWIW,
Raymond

Raymond, i think your conversion may be a bit off Good advice however! I think alot of people think that chains will last forever.

We call it stretch, but actually we should say chainwear.
The maximum elongation of a chain should be .5%. This is almost exactly 1/16" over 1 foot.
Here's the measuring technique:
measure the lower part of the chain (the part that is in tension by the derailleur return spring). Taking a ruler (a metal yardstick works best), measure from the edge of one pin, to one 12" away (or 11", if your only using a 12" ruler). If the same edge of that pin is more than 1/16" past the even-inch mark, replace the chain. If you are showing more than 1/8" stretch, replace the cogs, too. If you are showing 1/4" stretch (honest, I did see this once), count your blessings, and throw the whole lot away.

Joe, I was just doing a Dave Barry (humor columnist).

Hey Ray, It's a bicycle chain,not a Saturn V rocket !!

No wonder Nixon gave up on the metric system.

A strong rider or one who rides in the weather, dust or dirt very often will have to replace his chain much more often than the 2500 to 3000 miles mentioned above. I know people who have to replace their chains as often as 1000 to 1500 miles. Sean Yates ( former pro rider- Motorola etc.) had to change his chain every 500 miles!!
Ride not the stretch
Pat

Worn teeth on your chainrings (most often caused by riding with a worn chain) will also cause your chain to jump. If the teeth on your chainring look narrow and pointed, compared to a new chainring, replace it/them.

Firstly i would like to pass on my thanks to all who replied.
I took my bike to the shop and got it sorted the chain was very badly stretched i had to replace the the front rings and rear cassette(worn out), aswell as a few other worn out parts...i freaked at the thought of being bikeless for a few days...but my god what a difference my bike now goes like dream again...i had forgotten what a nice ride it was. One thing i will do from now on is change my chain every couple of months at least.

Richard..i live in Rhayader. My usual ride is over the old mountain road (Devils Bridge) to Aber and back along the main road (Llangurig)....great ride!!!!

Thank you all again for your help....i am off for a spin!!

I don't want to soud like yer mam... But this should be a lesson to you. REPLACE YOUR CHAIN REGULARLY! A Shimano chain should be changes before 4000 km [3000 km is better] and a Campy 10-speed chain should be changed before 5000 km [4000 km is better]. This is assuming you clean your drivetrain regularly. I get 5000 km out of a Campy chain, but I am particularly anal-retentive when it comes to cleaning my bike.

Replacing a chain on aregular basis is much less costly than replacing chain rings and cogs. On the other hand, I suspect you probably only needed to replace your inner chain ring and middle cogs. The big ring and small cogs tend to get less wear in normal riding.

Bore da.

When you're in Aber pop in the Ship & Castle for a pint (I think it's reverted back to that). I've walked much of the Elan valley, but cycling it would be something else. I'm envious

Richard

Counting on mileage alone for chain replacement is a very poor practice. Always use the elongation of the chain as the indicator of whether it needs to be replaced. I have gotten nearly 6000 miles out of one chain, and fewer than 500 out of another.