alexk_il

Planning to building a custom gear ratio on my hybrid, want to install a new 11-42 2x11 speed cassette (XT?) and lower the gears on the front from 50/34t to something that is easier to push.

I think 42/26 or 44/28 are quite possible, but then I thought maybe I could stretch it into 44/26t. This would require FD capacity of 18t, RD - 49t. I hear that most rear derailleurs are quite conservative in their chain capacity specs and can be pushed by 2-4 teeth, not sure if this applies to fronts as well. I see Shimano is offering 47T RDs and 16-17t on the front.

So is this feasible or shall I lower my expectations and go with 42/26 or 44/28? Has anyone tried this? Is it worth the hassle? Though I might still try it purely for fun if it is possible.

A noob here, please be gentle 🙂

ThermionicScott 

Front derailleur capacity has a lot more to do with what the manufacturer thinks will shift well, than the potential to break anything. Some FDs are specially shaped for specific chainring sizes, so the shifting could get a lot worse if you stray too far from what they had in mind.

So if you don't need the whole range of 44/11 to 26/42, I'd probably keep the chainrings closer in size for better shifting. But pushing the boundaries would be a great learning experience!

squirtdad

most modern shimano groups are specifying no more than 16 tooth spread between front rings, as best as I can tell this does have an impact on shifting.

Also as best as I can tell shimano conservative is more with rear cogs than the front

with an 11-42 and 44/26 you would need a rear derailler that can handle both the 11 and the 42 and have wrap capacity of 49 (42-11=31) +(44-26=18)

play and push, but don't be surprised if shifting is compromised

and what ever you do, make sure big big works

Bill Kapaun

50-34 isn't typically found on a Hybrid, but rather a "road" bike.
That asks the question-
What kind of shifters & DER's do you currently have?
What brand/model bike for that matter.....

The lowest gears you are talking about are probably lower than you need unless you have a cargo bike going up hill.
A bit more realistic approach in your low gear will likely create fewer problems.

esasjl

I would decide on the big ring size based on your usual flat road cruising gear being 2 or 3 sprockets in from the 11, say the 15 or 17 tooth sprocket, to give a bit more range for slight downhills, tailwinds and when you feel good; which sprocket(s) are you in with the 50? This should give a reasonable low gear in the big ring making it used most of the time (maybe have the big ring on the chain line). The small ring can then be experimented with to give a suitable low gear to ascend your steepest hill, sitting down, and towards the end of a normal ride. If the chainring gap is large (> say 16 and the shift becomes flaky as mentioned above) I'd be tempted to go to a triple (46-36-24?) and spend most of the time in the middle ring. Once you get a feel for the gearing you have, then different systems can be compared in a gear calculator (e.g., https://mike-sherman.github.io/shift/) to indicate how you can improve your gearing for your circumstances.

xroadcharlie

IMO reliability should be high on your priority list. A popular chainring for hybrid bikes is the 46/30 for both compatability and a wide gear range.

The 30/42 combo gets you down to under 20 gear inches. Thats about 5.6 kph at 60 rpm ...walking speed. Unless you are touring with a BIG load, or climbing insainly challenging hills every day, thats plenty low enough for a hybrid bike.

On the other end you'll get 35 kph at a reasonable cadance at 75 rpm and still have another higher gear left.

kuroba

I've been running 44/28 for a few years, so it is possible (paired with an 11-36 cassette though). It's my old triple crankset that I converted to 2x with a shim to replace the smallest chainring. I use SRAM Apex levers and front derailleur but a SRAM X5 10s rear.

alexk_il

Yeah, I recently realised that 50t is way to high for my needs, was quite happy at that time to read reviews that my hybrid bike can ride faster than others till I realised that it's owner is not up to the task.

This is a Boardman Hybrid Team, 2010-2013, don't remember, CX/Gravel 35mm tires, 2x10 SRAM Apex derailleurs and shifters, FSA compact 50/34 on the front, Avid Elixir 1 brakes. I might have no choice but to upgrade the shifters and derailleurs to match the new set. Thinking of a SRAM 22 Yawn FD and XT long cage on the back. Don't think I can find all parts from the same system.

alexk_il

I have an offroad forest hill (soil, mud, leaves etc.) on my commute, I have to walk and push my bike all the way to the top. Not fun with panniers loaded with laptop, clothes, lunch boxes, etc. Hope that I will be able to get there one day on my bike. Maybe...

alexk_il

Found this insane video about 46/27t cranks. Wow, that's 19t chain capacity. Can anyone recognise the FD on this bike? Ultegra? 105?

Racing Dan

Looks like an older 6800 or 5800 Shimano FD. A 4700 tiagra FD looks just the same. Note its Band-on, making it easier to get it low enough. If you are into low gears Id suggest looking into GRX FDs, that are meant for smaller than usual road rings.

However combining a 44/26 with a 11-42 requires a rear DR with a massive 49t capacity (44-26)+(42-11). Im not sure you can easily get that. - if it even exists.

bwilli88 

That will give you a huge range.


I would go with a 39x28, better shifting on the front and still a huge range.

alexk_il

​​​​​​Thanks, ended up with 42/26. Chain capacity of FD and RD are well within the specs.

Haven't assembled yet, will do in a couple of weeks.

HillRider

I have violated Shimano's and Campy's front derailleur specs for decades. I've installed 26T granny chainrings on numerous road triple cranks initially geared 53/42/30 and 52/42/30 and more recently 50/39/30 using both makes 10-speed triple front derailleurs. They shift acceptably well even into the granny. The granny back to middle chainring shift requires some care but still works fine and you are never in a hurry for that one.

alexk_il

An update:

OK, I managed to set up the front with a Sugino replica 42/26T double cranks, 5801 and RS700 left shifter. The front gear switching is smooth as butter and generally works well with my existing 11-32T, 10 speed rear.

But.... Setting it up with 11-42 would be too extreme, I will have to drop the idea. The chain angle at 42t fron-32t rear is insanely large, the chain is twisted and clunky in that position on my short 16" frame. If I push the RD to 42t, it will shortening the upper chain section that connects large-large even more and I fear I am going the cross-chaining becoming an issue with 4 or 5 larger cogs, only 6 cogs will be usable for me in the large chainring.

Next step - I will try to set up something similar on my other bike (MTB), it should have a larger frame to start with, Maybe will go to 44t on the front, to help with the chain-twist.

Yan 

You don't need a 42t large chainring. You are not capable of riding that fast. (No offense if you happen to be a top 1% beast).

My large chainring is a 36t and I use my top gear just a few times a year. If I'm going that fast it means I'm on a downhill. Not just a regular downhill but a steep downhill. At that point I'm usually coasting.

70sSanO

You should measure your chainstay length on both bikes. Also, you might be able to fudge the chainline if you think 42-32 is more important than 26-13.

If I were set on running your setup, I’d set the chainline, (if it is possible), so the 42t is centered on the cassette like a 1x and then limit the 26t to running about half the cassette or so, 26-21 to 26-42.

John

t2p

???

alexk_il

Agree, all that 50/34 chainrings on mid level hybrids is a scam by the velo industry. Nobody is that fast, and those who are are not riding these bikes anyway.

However as I tried to explain above, my frame is too short to drop the front gear from 50 below 42. The chain just gets too twisted and stressed on the last couple of cogs with 42t in the front.
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Yan 

36-11 is 38km/h (23 mph) at 90 rpm
42-11 is 44km/h (28 mph) at 90 rpm
42-11 is 54km/h (34 mph) at 110 rpm

I assure you, nobody is hitting 34 mph on a hybrid, ever.