Gearing and crossing chain advice

[Daninplymouth]

Hi, I’m about to take delivery on my new bike. Just wanted to check on my current bike I don’t use the 2biggest on the cassette when on the larger chain ring, 52t My new bike has a large 11-34 cassette would the same apply to this or should I try to avoid the top 3gears due to the bigger gears? This will be running a 34t from ring
Thanks

 

[byegad]

I'd avoid the largest rear when on the big front at a varying aversion. The bigger the rear sprocket the less you want to be in it. Assuming a 9 speed rear cassette and two up front, you'd be right about avoiding the 3 largest.

 

[CanucksTraveller]

I'm guided largely by chain noise, I don't even think about numbers of teeth or have a mental note to avoid certain cogs. Of course I instinctively know that in the big ring I don't want to change down too far, but really it's only ever the beginnings of noise that remind me to do something about the front derailleur to get a better chain alignment.

 

[Ajax Bay]

You probably have a 52-36 chainrings so with an 11-34 cassette you can get the ratios you need by switching to the smaller ring at the front rather than clicking into the largest 2 sprockets. And vice versa: If you find yourself clicking down the cassette (towards smallest) then change up at the front before you get to the 2 smallest sprockets.
Have an eye on the road ahead and plan ahead.
The loss in efficiency is actually very small (circa 0.5%) but the chain does have to flex sideways more when cross-chaining which increases drivetrain noise and one would have thought increases wear.
This shows the overlap:
http://www.gear-calculator.com/?GR=...26,30,34&UF=2215&TF=90&SL=2.6&UN=KMH&DV=teeth

 

[Paulus]

As a general rule, do not use the largest chainwheel at the front with the largest sprocket at the back.
The same goes for the smallest at the front and the smallest at the back. If you can help it. A short while in either will not do much harm, try it and have a look at the chainline.

 

[Daninplymouth]

Sorry, may not have made my post clear. At the moment on my 11-30 cassette the highest gear I’d use on the big chain ring is 24t or 3rd down the cassette. On the new 11-34 cassette my 3rd gear down would be 27t, would riding 50-27 cause unacceptable stretch or would the long cage mechanism make the angle less

 

[Globalti]

The further you cross the chainline the more you're asking the chain to change direction four times per rotation. Put it on big ring /almost biggest cog and squint along it to where it meets the chainring and you'll see it bending, which it's not designed to do. This will wear it out fast. Noise should tell you when you're doing it.

 

[Ajax Bay]

The chain length and RD capacity will mean you can, in practice, use all the sprockets on either ring. It's just not good riding - because if you are on large/small and you need a lower gear as the hill tips up and you're already hard on the pedals, shifting to the small ring is hard on the drivetrain, and your fluency.

 

[Dogtrousers]

I'd have thought that if you're already in the habit of avoiding the two sprockets opposite the current chainring you'll be fine, no retraining needed.

I'm absolutely no expert on this but avoiding three sprockets does seem a little bit extreme, given that actually cross chaining now and then, while it may not be a terribly good idea, won't actually do much in the way of harm (unless you make a constant habit of it).

 

[ColinJ]

I'm guided largely by chain noise, I don't even think about numbers of teeth or have a mental note to avoid certain cogs. Of course I instinctively know that in the big ring I don't want to change down too far, but really it's only ever the beginnings of noise that remind me to do something about the front derailleur to get a better chain alignment.

Same here! I usually remember to change rings at a sensible time, but occasionally something doesn't sound right and I find that I am still on the big ring, when heading up onto the biggest sprockets. (That happens more often now I have a 48-tooth big ring. When it was a 53, it was a bit more obvious that I was on the wrong ring before I got that far.)

I try to avoid extreme chainlines on the inner and outer rings on my best bike, which has a 48/36/28 triple chainset. I find that the 36 works really well over the entire cassette so I can spend an awful lot of my time just on that ring.

 

[faster]

The disadvantages of using big/big are overstated in my opinion. If the bike is set up properly, just use it. It'll be fine.

Small/small, on the other hand, is a miserable combination. Avoid.

 

[Dogtrousers]

I sometimes find that roadside photos of my bike are in big/big. I've been cruising along in the big ring, decided to stop, changed down, changed down again, and then gone a bit far.

So far the gods of cross-chaining haven't struck me dead.

 

[Ajax Bay]

Actually, in efficiency terms, running large/large (52/34) is more efficient for the same ratio in the smaller chainring (36/24). The cross-chaining will lose you a bit of efficiency but running the chain round two larger diameters means that overall there is less loss running large/large. (Research available)

 

[Daninplymouth]

Thanks for the replies I won’t over think it to much and just see how it feels.
Then il be onto a whole new subject will a 11-30t be ok for the back or would I have to change the derailleur, going to try the 34t as it is quite hilly here but seeing as I have managed so far with a 30t I think it might be overkill. There is times I wish it was a little easier but I will also be losing 2teeth on the front rings so worried it might be too easy

 

[DSK]

The only thing I'll add is that I was told by a LBS that whilst one should not cross it whilst riding, its OK to use the smallest chain ring and small cassette as this puts the derailieurs in their most relaxed position and thus taking the tension off the cables.