Gear ratio question

[fbonde]

Hi guys,

A quick question about gear ratios, Can you run a 52/34 and not 36 dura ace or ultegra?

[Lucendi]

You can mix and match the chainrings on a crankset pretty freely.

The inner ring doesn't have pins or ramps, so anything should work.

[RussellS]

The only real problem with running a 52-34 crankset is the huge gap, 18 teeth, between the chainrings. This large gap may/will cause the chain to rub on the back cross post on the front derailleur when you are trying to use the small chainring and the smaller cogs. So instead of running 36x15 quietly, you will now only be able to run 34x16 or 34x17 quietly. You are eliminating one or two usable cogs when using the small chainring. May not make one iota of difference on a 11 or 12 cog cassette with a large overlap in gearing on both chainrings. But if you like to use all the cogs in back before shifting between chainrings, then it will cause some change in behavior.

[RussellS]

I should also add that front derailleurs are really designed for somewhat closely sized chainrings. 10-11-12-14 teeth difference. If you are old, Ha Ha, then you will remember when the big shift from manly 53-42 or 52-42 to girly 53-39 chainrings occurred. Long ago back in the 1980s. Many on this forum were not even born yet. But with the big shift to a big 14 tooth gap in chainrings, 53-39, there was more occurrence of dropping the chain when shifting down from the big ring to the small ring. Bigger gap for the chain to drop. Remember, the front derailleur does not closely guide the chain between chainrings. The rear derailleur is real close to the cogs and can easily, accurately, move the chain from cog to cog with exact precision. But with the front deraillur, there is a couple inches difference in the chainrings, and the front derailleur does not closely grip and move and guide the chain between rings. Front derailleur just knocks the chain off the big ring and lets it drop in the air down to the small ring. No exact guiding or precision.
And when going from the small to the big ring, the back horizontal cross bar on the front derailleur just sort of kind of picks the chain up and mashes it into the side ot the big ring and hopes the cutouts and grooves ane pins on the side of the big ring pick the chain up and move it up to the big ring. No exact precise movement of the chain between cogs. The use of a chain watcher device is highly recommended if you go to a 52x34 or even a 52x34 setup. Use a chain watcher to keep from dropping the chain.

[fbonde]

Thanks a lot, guys. When you leave in pan flat Denmark, the 52 in the front is just perfect - you are in the big ring 99% of the time - When I travel to the alps, the 34 is nice to have. I will try this solution.

[fbonde]

And when going from the small to the big ring, the back horizontal cross bar on the front derailleur just sort of kind of picks the chain up and mashes it into the side ot the big ring and hopes the cutouts and grooves ane pins on the side of the big ring pick the chain up and move it up to the big ring. No exact precise movement of the chain between cogs. The use of a chain watcher device is highly recommended if you go to a 52x34 or even a 52x34 setup. Use a chain watcher to keep from dropping the chain.

Thanks for the input.

Do you mean a chain catcher?

[DaveS]

I use a 48/31 grx crank with sram axs 12 speed and have none of the described problems, but the chain rings are factory stock and matched to shift properly. If any other little chain ring is used, the shifting may suffer because the timing is off. A grx 30T ring is about half a tooth different in timing, to go with a 46t big ring. I haven't tried a 48/30 combination yet and really don't plan to. I've never had a chain drop with either grx crank.

[sigma]

I use a 48/31 grx crank with sram axs 12 speed and have none of the described problems, but the chain rings are factory stock and matched to shift properly. If any other little chain ring is used, the shifting may suffer because the timing is off. A grx 30T ring is about half a tooth different in timing, to go with a 46t big ring. I haven't tried a 48/30 combination yet and really don't plan to. I've never had a chain drop with either grx crank.

I have a similar ratio on my gravel bike 48/30 with a 10-42 on the back and have no problems. However, when I tried exactly what the OP is suggesting an ran a 52/34 setup. I did have a consistently rougher overall drivetrain which to be fair could be user error derived. I oscillate between flat Chicago and mountaineous Utah. When I used to have one bike (clearly a long time ago), I found it easier to just swap out the 52/36 for a 50/34 and move the cassette from an 11-28 (I think) to an 11-32 with an ultegra long cage. I kept the same length chain and the cassettes were mounted on different wheels - deeper in the flatland lighter in the mountains. After the first few times, it would take me about 30 mins on a non Di2 setup to swap it all including different pads for carbon versus alloy wheels. I found the improvement in shifting worth it for me.

[RussellS]

And when going from the small to the big ring, the back horizontal cross bar on the front derailleur just sort of kind of picks the chain up and mashes it into the side ot the big ring and hopes the cutouts and grooves ane pins on the side of the big ring pick the chain up and move it up to the big ring. No exact precise movement of the chain between cogs. The use of a chain watcher device is highly recommended if you go to a 52x34 or even a 52x34 setup. Use a chain watcher to keep from dropping the chain.

Thanks for the input.

Do you mean a chain catcher?

https://www.walmart.com/ip/3rd-Eye-Chai ... lsrc=aw.ds

https://www.amazon.com/K-Edge-Pro-Chain ... 8999&psc=1

https://absoluteblack.cc/road-chain-catcher-braze-on/

Chain watcher. Chain catcher. Do a Google search using one or both of these phrases. Above are a couple of the models available.

[fbonde]

And when going from the small to the big ring, the back horizontal cross bar on the front derailleur just sort of kind of picks the chain up and mashes it into the side ot the big ring and hopes the cutouts and grooves ane pins on the side of the big ring pick the chain up and move it up to the big ring. No exact precise movement of the chain between cogs. The use of a chain watcher device is highly recommended if you go to a 52x34 or even a 52x34 setup. Use a chain watcher to keep from dropping the chain.

Thanks for the input.

Do you mean a chain catcher?

https://www.walmart.com/ip/3rd-Eye-Chai ... lsrc=aw.ds

https://www.amazon.com/K-Edge-Pro-Chain ... 8999&psc=1

https://absoluteblack.cc/road-chain-catcher-braze-on/

Chain watcher. Chain catcher. Do a Google search using one or both of these phrases. Above are a couple of the models available.

Thanks mate

[ehlpitel]

Like other folks said, you can definitely try but Shimano road FDs are rated for a max 16 tooth difference between the chainrings and although Shimano has been known to be rather conservative in their guidelines, this might be something where they're actually right. If you have a 34 tooth chainring lying around, it's definitely worth it to try and if I had a 52 tooth ring, I'd personally try it, too. I love the feeling of a 52 or 53 tooth big ring but am too much of a wimp and live in too hilly of an area to use anything bigger than a 34. If it's important enough to you and you're willing to spend some money, you could look into a GRX FD and maybe crank because the GRX FDs can go up to a 17 tooth difference, but apparently it also accounts for the different chain angle and maybe Q factor or w/e on a GRX crank, as well (problem with running GRX crank and attmepting road gearing would be finding 52/34 rings that fit- if that's possible then it might be a viable solution if you have the money.) I do have 53/39 rings lying around and at one point was considering trying out a 53/34 but that's a 19 tooth difference and would probably result in a ton of dropped chains and best case scenario, really mediocre shifting from small to big. If i find a cheap 52 tooth ring, I might pick it up just to give it a shot.

[fbonde]

Like other folks said, you can definitely try but Shimano road FDs are rated for a max 16 tooth difference between the chainrings and although Shimano has been known to be rather conservative in their guidelines, this might be something where they're actually right. If you have a 34 tooth chainring lying around, it's definitely worth it to try and if I had a 52 tooth ring, I'd personally try it, too. I love the feeling of a 52 or 53 tooth big ring but am too much of a wimp and live in too hilly of an area to use anything bigger than a 34. If it's important enough to you and you're willing to spend some money, you could look into a GRX FD and maybe crank because the GRX FDs can go up to a 17 tooth difference, but apparently, it also accounts for the different chain angle and maybe Q factor or w/e on a GRX crank, as well (problem with running GRX crank and attempting road gearing would be finding 52/34 rings that fit- if that's possible then it might be a viable solution if you have the money.) I do have 53/39 rings lying around and at one point was considering trying out a 53/34 but that's a 19 tooth difference and would probably result in a ton of dropped chains and best-case scenario, really mediocre shifting from small to big. If i find a cheap 52 tooth ring, I might pick it up just to give it a shot.

Thanks for the good inputs. I'll be trying it out. within 2 weeks. I'll let you all know

[smokva]

Like others have said, officially FD shouldn't work with such big chainring difference, but you need to check it with your setup to be sure if it works or not.

[tiz92]

I did run a 52/34 for a year on my old bike on Ultegra 6800. It worked good for 99% of the time. Chain did fall off a few times but maybe 6-8 times in 20000 km.