Cycling UK Forum

AlanW wrote: ↑28 Jul 2023, 9:11pm l have recently fitted a sub compact 30/46 chainset, coupled with a 11 speed 11/34 cassette.

I appreciate that cross chaining isn't really advisable to do, but sometimes it's done.

With the current set up l can utilize every possible gear option. However, when on the 30 at the front and the 11 on the cassette the chain is far to slack.

I have now removed one chain link and the only gear ratio not possible is using the 46 on the front and 34 at the rear, the chain is simply not long enough now to accommodate it.

In truth its not really a problem as it's a less than ideal chain line. My only issue is that if l do go to select that ratio it will either snap the chain or worse case rip the mech off the hanger…

Yes, you should have left the chain length as it was.

I'm stuck between a rock and a hard place to be honest. If l would have left it as it was l could not use the 30 front, 11 rear combo because the chain is so slack.

Remove one link addressed the chain slack problem, but it only served to move the problem to the other end of the possible gear ratios.

Damed if l do, damed if l don't......

AlanW wrote: ↑28 Jul 2023, 9:33pm I'm stuck between a rock and a hard place to be honest. If l would have left it as it was l could not use the 30 front, 11 rear combo because the chain is so slack.

Remove one link addressed the chain slack problem, but it only served to move the problem to the other end of the possible gear ratios.

Damed if l do, damed if l don't......

So......keep the chain the same length and just don't use the 30 front 11 rear combination then. It's probably better than shortening the chain and running the risk of it snapping...

Just remember to check that you're using the big ring when you're on the flat or going down hill and keep little ring for up hill ..

AlanW wrote: ↑28 Jul 2023, 9:33pm ....Remove one link addressed the chain slack problem...

If the chain is too slack by only one link in the small/small combo I wouldn't regard it as a real problem.

It needn't be a problem. I also have a 46/30 chainring and an 11-36 cassette. I used 46x36 a lot, it's a very useful combo. Yes, this means the chain rattles on itself in the small ring and the smaller sprockets, but that's not a problem; I just change to the big ring as soon as it happens. In practice, I've usually changed to the big ring before this happens. I don't find small-small a useful combination, as the bike is set up so the large ring is not so much "large" as the "everyday ring", with the small ring being reserved for steep hills, rough ground, heavy loads.

keyboardmonkey wrote: ↑28 Jul 2023, 9:22pm

AlanW wrote: ↑28 Jul 2023, 9:11pm l have recently fitted a sub compact 30/46 chainset, coupled with a 11 speed 11/34 cassette.

I appreciate that cross chaining isn't really advisable to do, but sometimes it's done.

With the current set up l can utilize every possible gear option. However, when on the 30 at the front and the 11 on the cassette the chain is far to slack.

I have now removed one chain link and the only gear ratio not possible is using the 46 on the front and 34 at the rear, the chain is simply not long enough now to accommodate it.

In truth its not really a problem as it's a less than ideal chain line. My only issue is that if l do go to select that ratio it will either snap the chain or worse case rip the mech off the hanger…

Yes, you should have left the chain length as it was.

Yep, I have a the same issue on my tourer. If I use the smallest ring and the smallest sprocket at the same time, the chain goes slack. But so what? Nothing locks up or breaks. It is a combination I don't intend using, and I try to avoid it. So the only issue is what happens if I get that combination by mistake. And the answer is, not very much. Just a bit of noise of chain rubbling against chain, to remind me to sort out my gear selection. But if your chain is too short for a gear combo you might select, bad things could result....

Just out of interest but did you consider fitting a rear mech extender to see if that made the situation better?

AlanW wrote: ↑29 Jul 2023, 12:30pm Just out of interest but did you consider fitting a rear mech extender to see if that made the situation better?

For my set-up I did fit an extender, the only way of preventing the top jockey wheel clipping the big sprocket. It makes some of the changes a bit vague, but it is a tourer, so a second or so of delay is unimportant.

That's interesting, l don't have any issues with clearance between the jockey wheel and the 34 sprocket after l unscrewed the B screw a couple of turns.

Which is why l don't think in my instance, it's not the answer. The problem is the range that lm expecting the chain length to accommodate.

That said, lm still going to try an extender, but my expections in any sort of improvement are very low to be honest.

I've read that adding an extender can slow down changes up and down the cassette, especially when the chain gets worn so the sideways flex is greater. Worse when on the smallest sprocket when the gap between the jockey wheel and the smallest sprocket will be at its greatest.

A mech hanger extender won't help.

An extender is for when the largest sprocket is too big, and you can't readily change onto it, regardless of chain length, because the top jockey wheel is too close.
It won't have any effect on the capacity of the rear mech (i.e. how much slack chain it can usefully tension). That's mostly determined by how far apart the two jockey wheels are.

A chain should always be long enough to change onto the largest chainring and sprocket combo. It it won't, and you try to, by mistake (perhaps when it's dark and you can't just look down to check what gear you are in), there's a good chance something will break. This could be expensive, and it could also leave you stranded with an unrideable bike, phoning for rescue.

If that means the chain is so long that it's slack in small/small, then you either buy a new rear mech with a larger capacity, swap the big chainring for something smaller, or put up with it.
Putting up with it is the normal decision. Running in small/small with a slack chain causes no problems other than rattly noises and a slightly higher chance of the chain coming off, and there's almost always a nearly equivalent gear using the large chainring that you can use instead. You just take the rattling as a warning to change to the large ring, and 3 or 4 sprockets larger (sprockets first, usually).

In your case, the equivalent gear to 30/11 using the 46T chainring would be a (11/30)*46 = 17T sprocket. It may be that you've only a choice of 16 or 18, in which case use whichever feels best.

Great reply, thanks and l agree with everything that you have said to be honest.

I couldn't understand how a rear mech extender would or even could assist my problem. Hence why l asked the question before went to all the hassle of fitting one only to find out it didn't serve any constructive purpose.

I'm wondering now if a grx rear mech would fit and work better to give me the full range and not have any chain issues, lve read that they are compatible with Ultegra shifters?

AlanW wrote: ↑30 Jul 2023, 6:25amI'm wondering now if a grx rear mech would fit and work better to give me the full range and not have any chain issues, lve read that they are compatible with Ultegra shifters?

My touring bike is using a GRX 810 RD with Dura-Ace 9000 11-speed bar-end shifters. Front chainrings are 38/24 and cassette is an 11-40, and it copes with that gear range without problem, despite Shimano only rating it for a 34t big cog on the cassette.

NickJP wrote: ↑30 Jul 2023, 10:14pm

AlanW wrote: ↑30 Jul 2023, 6:25amI'm wondering now if a grx rear mech would fit and work better to give me the full range and not have any chain issues, lve read that they are compatible with Ultegra shifters?

My touring bike is using a GRX 810 RD with Dura-Ace 9000 11-speed bar-end shifters. Front chainrings are 38/24 and cassette is an 11-40, and it copes with that gear range without problem, despite Shimano only rating it for a 34t big cog on the cassette.

Excellent, just what l wanted to hear, thanks!!

Just out of interest, where did you get the 38/24 chain rings from?

AlanW wrote: ↑30 Jul 2023, 10:19pmJust out of interest, where did you get the 38/24 chain rings from?

Actually, looking at the bike, I find that the chainrings are 38/26, not 38/24. The 38t ring is a standard TA 110BCD middle chainring available from vendors such as Spa, SJS, etc. The 26t ring is a 74BCD NOS MTB stainless steel ring made by Sakae - I scored a couple of them off eBay some years ago. Stronglight still make 74 BCD steel rings, again available from the same vendors.

AlanW wrote: ↑28 Jul 2023, 9:33pm I'm stuck between a rock and a hard place to be honest. If l would have left it as it was l could not use the 30 front, 11 rear combo because the chain is so slack.

Remove one link addressed the chain slack problem, but it only served to move the problem to the other end of the possible gear ratios.

Damed if l do, damed if l don't......

Really, it IS NOT A PROBLEM if the chain 'floats' in little and little. Any resulting rattling or rubbing noises are an entirely harmless reminder to stop cross-chaining and shift the big ring now, since you are no longer ascending a hill of any consequence and could easily manage the accompanying compensatory rear sprocket shift.

Any inability to select big and big however, is a BIG problem. Not only does inadvertent selection cause untold, ride-ending damage to the transmission, but THAT gear, being the lowest you can get without shifting the inner ring and "dropping-into-the-void" as my father in law so eloquently described it, is a most necessary cross-chaining evil, one of the most-used gears on most touring doubles. Because when one requires a lower gear on a steepening hill, one does NOT have the time nor the tolerance for compensatory rear shifts. So big and big has to work, and the better it works the better, more useful and efficient bike you have - even if that means NOT using more than one of the little-little combos.

You'll not be surprised to hear that ALL of my bikes have a floating chain in the littlest one or three little and little combos, and that it bothers me not one jot or iota!