hsea17

I think to switch to a 50-34 Crank from 52-36 as I image that it is a better solution for problem knees as it has been said here and there that with a 50-34 crank every rpm will feel easier. What is your experience?
Thanks & Regards
hsea17

Polaris OBark

I went for 165 mm crank arms on a 46/30T crankset (GRX). The shorter crank arms are easier on your joints. The lower gearing helps if you want to spin up an 18% grade.

Bill Kapaun

Ditto- shorter cranks are easier on the knees.
IF you want lower gearing, don't upshift, use a lower gear OR change the cassette to one with larger cogs.

Duragrouch

Yeah that's a small percent difference. In going from a 52 single, I went 50/34 because the low was more important than the high, I needed the low to spin up the steeper hills here, I'd always spun up hills, never pushed hard when sitting. That said, I have now learned to climb while standing, legs straighter, so way easier on the knees. Key is not too low a gear for too fast of a cadence, not too high a gear requiring pulling hard on the handlebar, but in between so I just need my weight on the pedal, maybe 50 cadence. But yes, cranks a bit too long can cause knee problems, more than a bit too short. But of late, crank-length calculators have been changed to recommend a shorter crank than in the past for a given height or inseam. Spinning favors a shorter crank, climbing while standing allows a bit longer crank.

34 or 33 is as small a ring as will go on 5x110mm BCD. I like the suggestion above for 46/30 if you can't go larger on the cogs, but that 30 will require a smaller BCD, I don't know if the 46 will be on the same BCD or larger.

hsea17

Thanks for the replies. I think I will change whole crank. Tried one of these crank calculators and it show crank arms max 168. However, I will measure my inseam again with some help because I not sure if my measurement was accurate!
hsea17

oldschoolbike

Look for a 46-30 crankset option. It will allow you to keep the current cassette and rear derailler and still buy you a useful drop in gearing. I am using that on a 135/74 mm BCD triple with just the middle and inner rings mounted. There is considerable leeway for further lowering of gears, with just chainring changes, with that arrangement. Specialities TA makes almost any ring that is technically possible and reasonably useful.

Iride01 

Shorter cranks are only easier on the knees if you already push a easy gear or will be encouraged to keep a higher easier cadence because they are shorter. Even if only 5mm. I've run a 165mm crank most all my life. But I also keep a cadence around 80 rpm for most cruising and climbing.

You question of will a 34/50 crankset be better on your knees than a 36/52 will depend on if that allows you to run the easier gear combos for your knees. But if on your current crankset, you are muscling yourself up hill at a low cadence and have a lower ratio available to select that will allow you to have a higher cadence, then that's all you really need to do is shift to that easier cadence. If you are running out of gears to keep that high (70 plus rpm, 80 plus is better) easy cadence while climbing, then that 34 ring might benefit you. As will a cassette with a larger tooth count for the low sprocket if your RD supports that.

<added well after initial reply>
If your knees are getting old and having some some issues with range of motion, then shorter cranks might also be a solution. Even so, be certain that you aren't just pushing too big a gear ratio at too low a cadence.

wheelreason

Assuming the same cassette, the difference will be minimal.

Steel Charlie

I went from 53 to 50 on three bikes and now I have regular use of 6 of the 9 cogs. Where I usually ride the grades are short and relatively steep. I can coast off of 53/11 so coasting off of a 50/11 is NBD and that's the only place I see the 11 anyway. I have a 14-25 on one bike with 30/39/50 and it is just great for my antique body.
YMMV of course


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Barry2 

For those subscribed to the thread wondering where my post went. I deleted my original post due to a "math before coffee" issue.

Barry

13ollocks

Inseam length is only one factor to consider when deciding crank length - regardless of inseam, shorter cranks will result in less knee- and hip flex, which might be preferable or beneficial. Just because a calculator arrives at 170mm, for example, doesn't mean that 165mm won't be a better fit for your particular joints.

Iride01 

Adding to what 13ollocks said, I think that crank length calculators should be looked at as telling you what the maximum crank length is you should consider. Not what crank length will be ideal for you.

urbanknight

Yep, if you're really looking to get some easier gears, this will make a noticeable difference, and you're apparently getting a new crankset anyway. 36 to 34 is such a small difference, I wouldn't change that unless the chainrings were worn and I wanted to keep the cranks. Another bonus is the chainwrap is the same so you know it will work and at most you will MAYBE have to take a few chain links out.

FBinNY 

A distinction without a difference. You're talking about lowering all the gears about 4% or so without changing the range. So, what'll happen is you'll quickly enough adapt and select the same (roughly) rations your legs are used to. Unless you're currently riding either the highest or lowest gear, the ONLY difference is the exact gear choice for any condition.

BTW, just a quick reality check. While the way to prevent knee issues is to ridelower gears, you do this, not by changing the bike, but how you use it. So save the dough and focus on what's between your ears.

oldbobcat

Personally, I can live without 52/11 and the crawling difference between 34 and 36 is so small that I prefer 50/36. I use the 36 more than I used the 34, and the drop from the 50 feels more like dropping to a 39 from 53.