chain rubs against top chainring when in 10th gear

[borance]

Hi,

I have recently build up a bike on Scott CR1 frame and Ultegra SL components. Wheels are bontrager race lite.

When I am in tenth gear (smallest cog on block) with the chain on the smallest chain ring the chain catches on the inside of the top chainring like it is trying to shift to the higher gear. Front mech is not in contact with the chain when I get this issue.

Do I have some type of alignment issue between chainset and rear freehub or is 10th gear a no go and I should change up to top chainring sooner???

Thanks

 

[alfeng]

I have recently build up a bike on Scott CR1 frame and Ultegra SL components. Wheels are bontrager race lite.

When I am in tenth gear (smallest cog on block) with the chain on the smallest chain ring the chain catches on the inside of the top chainring like it is trying to shift to the higher gear. Front mech is not in contact with the chain when I get this issue.

Do I have some type of alignment issue between chainset and rear freehub or is 10th gear a no go and I should change up to top chainring sooner???

Does your bike currently have a 34t inner chainring? If so, a 36t inner chainring may-or-may-not resolve the problem.

Regardless, you should be shifting up to the larger chainring MUCH SOONER ...

Having the chain on the inner chainring (or, granny for those who have a Triple) and concurrently on either of the smallest two cogs is usually considered poor-form for the very reason you have created (often referred to as "cross chaining") ...

It is also poor-form to have the chain on the largest chainring and concurrently on either of the largest two cogs.

If you are compelled to cross chaining, then you need to buy a touring frame OR ride a MTB since either should have a long enough chainstay to allow the chain to clear the outer chainring if/when you have the chain on the small-small combination.

 

[borance]

I do have a 34 tooth ring and I am a mountain biker just getting into road bikes. I know on the mountain bike big cog big ring is a no no but i am used to getting away with middle ring smallest cog. I will mend my ways Thanks. Just wanted to rule out a technical issue.

 

[Peter@vecchios]

Hi,

I have recently build up a bike on Scott CR1 frame and Ultegra SL components. Wheels are bontrager race lite.

When I am in tenth gear (smallest cog on block) with the chain on the smallest chain ring the chain catches on the inside of the top chainring like it is trying to shift to the higher gear. Front mech is not in contact with the chain when I get this issue.

Do I have some type of alignment issue between chainset and rear freehub or is 10th gear a no go and I should change up to top chainring sooner???

Thanks

What you are seeing is normal with multi cog systems(lots of cogs, gotta go outboard) and big chainrings with lots of pins and such to help in shifting to it under load. Don't change anything, just don't ride in that combo.

 

[Solanog]

What you are seeing is normal with multi cog systems(lots of cogs, gotta go outboard) and big chainrings with lots of pins and such to help in shifting to it under load. Don't change anything, just don't ride in that combo.

This was a question I've had for many years but since it happens not only in one bike I thought it was normal as you have explained. In the 9th gear it does not happen but I have to adjust the trimming for the Fron dera....
So the no gos are the two big ones with the big chainring and the two smallest with the small chainring? As I said there is no issue with 39 - 13(9th) at least in my case.

 

[OldGoat]

Agree w/ above remarks re small/small & big/big being suboptimal due to cross-chaining issues. Even so, it may be possible for you alleviate your problem by slightly loosening the low stop-limit screw on the rear der. A half-turn of the screw may be enough to allow the chain to move just a wee bit further out so that it can rest fully on the small rear cog. I run a 53/39/30 triple with an 11-34 in back (I'm well over 60 and weigh too much, so have hill-climbing issues) and have no rubbing issues in any gear combo. But it took some tinkering to get the cable tension and high- and low-stop limit screws on both the front and back ders just right. On some bikes, it's impossible to get all gear combos to work satisfactorily, in which case the best and most common approach is to focus on those combos in which most time is spent--bib/big and small/small not being among them.

 

[oldbobcat]

What you are seeing is normal with multi cog systems

Absolutely correct. Now if you got that chain rub while using the third or fourth smallest rear cogs, we'd say there was a chainline problem.

 

[chas0039]

Hi,

I have recently build up a bike on Scott CR1 frame and Ultegra SL components. Wheels are bontrager race lite.

When I am in tenth gear (smallest cog on block) with the chain on the smallest chain ring the chain catches on the inside of the top chainring like it is trying to shift to the higher gear. Front mech is not in contact with the chain when I get this issue.

Do I have some type of alignment issue between chainset and rear freehub or is 10th gear a no go and I should change up to top chainring sooner???

Thanks

I had the same problem with a changeover to a Campy crank from an FSA model. I was able to find some spacers that fit between the mounting bolts between the large and smaller chainring. Totally solved the problem with no adverse effects.

Try here. They are from Campy but you could check with Branford to see what they think.