More gear problems......

[Adam4868]

I've just built up ultegra,double 10 bike.New chain and cassette.If I'm in the big ring at front and rear the chain has a tendency to come of.Ive only had it happen in this gear,and not when on workstand(only under pressure).Standard at front and 11/28 at back.Any ideas ?

 

[Racing roadkill]

Is it coming off the ring, or overshooting to the spoke side of the sprocket?

 

[Adam4868]

Coming of front ring,its almost feels like slipping then off.Ifthat makes sense

 

[Racing roadkill]

Your front mech limit screws need adjusting. There's one Philips head screw with an 'H' printed on it, and one with 'L' on it. You need to wind the screw with 'H' on it ( it'll be the one nearest the rings, not the one nearest the frame) inwards / down, until the chain doesn't come off when shifting up to big ring when riding. You can then adjust the position of the front cage with the barrel adjuster ( roll it towards the frame to move the mech out, and towards the bars to move the cage inwards) until the chain runs clear of the front mech.

 

[Adam4868]

Your front mech limit screws need adjusting. There's one Philips head screw with an 'H' printed on it, and one with 'L' on it. You need to wind the screw with 'H' on it ( it'll be the one nearest the rings, not the one nearest the frame) inwards / down, until the chain doesn't come off when shifting up to big ring when riding. You can then adjust the position of the front cage with the barrel adjuster ( roll it towards the frame to move the mech out, and towards the bars to move the cage inwards) until the chain runs clear of the front mech.

Thanks appreciate that,bike gears do my head in !!

 

[Ajax Bay]

If I'm in the big ring at front and rear the chain has a tendency to come of.

Coming of front ring,its almost feels like slipping then off.

Besides @Racing roadkill 's good advice to adjust your limit screws, it's worth avoiding large/large and small/small combinations of chainwheel/sprocket as that requires the most extreme chain angle. And this may also be contributing to your chain slipping than coming off (sideways) because the front derailleur (FD) cage is touching and pushing the chain out at that angle.
It's also possible that you have fitted too short a chain. When in large and large, what angle does the FD cage make with the vertical?

 

[Adam4868]

Besides @Racing roadkill 's good advice to adjust your limit screws, it's worth avoiding large/large and small/small combinations of chainwheel/sprocket as that requires the most extreme chain angle. And this may also be contributing to your chain slipping than coming off (sideways) because the front derailleur (FD) cage is touching and pushing the chain out at that angle.
It's also possible that you have fitted too short a chain. When in large and large, what angle does the FD cage make with the vertical?

Thanks so do you think i should just avoid large/large ? Like I say it only this one gear I have any trouble with

 

[Ajax Bay]

Avoiding large/large is normal and good practice. You're not losing a gear. That ratio is replicated with small chainring to (say) the 19t. You haven't answered the 'angle' question.

 

[Adam4868]

Sorry Ajax not been to bike since,thanks for your info/advice.So when in big/big look at front mech and look at the angle ? Cheers adam

 

[Ajax Bay]

when in big/big look at front mech and look at the angle

The angle of the cage, not the chain.

 

[Adam4868]

Will be on my list of to do things tonight thanks!!

 

[alecstilleyedye]

there's a useful phone app called bike repair, which comes in very handy as a reference when doing repairs and adjustment…

 

[Adam4868]

there's a useful phone app called bike repair, which comes in very handy as a reference when doing repairs and adjustment…

Another one called YouTube aswell,but I still get baffled with gears !!

 

[alecstilleyedye]

Another one called YouTube aswell,but I still get baffled with gears !!

try bike gears. it shows stills with arrows pointing at the relevant bits and bobs, so you don't have to rewind videos…

 

[Adam4868]

Ok I had it on workstand and the front mech looked straight.... It doesn't come off as easy,more under load when riding.But if I pedal backwards in big/big either the chain will move down on cassette or fall of front !!