I've had a kneed pain a couple of times now as a result of riding my bikes. Both my 26 and 29 have 175mm crank arms.

I was reading that perhaps I could avoid issues if I use shorter crank arms, 165mm being a sweetspot for others with good results.

I'm not sure but as I research this, I think it's almost impossible to convert my bike to 165mm. I can't find arms being sold that will fit my existing set up.

And even if I buy a whole crankset (which seems very expensive), I still can't find 165mm.

One would think that this is an easy thing to replace. Turns out that it seems it's one of the most difficult.

I don't know if you're using clipless pedals or not but if you are, did you have your cleats installed with your natural foot positions in mind? Example, some people have to have their cleats adjusted because they're pigeon toed or opposite of pigeon toed - toes point outward.

Sometimes it takes mm-adjustments to get the fit correct.

165mm cranks are pretty rare among road bikes. I think you'd be better served with a good bike fitting. I'm a short guy and I use 170mm and 172.5mm on my road and tri bike.

Good questions.

This is for mountain bikes. I'm using flat pedals, no cleats, no clipping.

Study seat adjustments.

How high, how far forward or back, level.

In combination with other measurements, this may solve some issues.

Your issue is likely more fit related than specific to the crank arm length, although a proper fit might identify the need for a different arm length. My point is don't just swap the cranks before you have an overall fit assessment from a qualified bike fitter.

You can get 165mm arms for MTB setups, if that's what you need, but: Second the "check fit first" recommendations.

Get some good help and follow the instructions to the letter:

https://www.competitivecyclist...itCalculatorBike.jsp

This calculator got me to within a centimeter (on all the relevant/important numbers) of what a professional fit later measured. Cost-benefit in favor of "free on the Internet." Using the same assumptions/adjustments I was using 20 years ago for seat height & position wasn't working. Painful.

I rode a 100K earlier this month with a guy who was using a hybrid bike, no clips, including a mile or two of pretty good climbing. It's all about fit.

Long time cyclist here. A few years ago I adjusted one of my cleats to a different position because it felt more natural. Rode 5,000 miles, developed knee pain, needed knee surgery. Surgery was 1.5 years ago, which did not fix the underlying problem.

Now I am finally getting my knee back. The underlying problem was that your feet should face forward or slightly toed in. No toe out at all. I was slightly toed out which caused my knee to excessively twist a few million times. The knee pain was caused by the external ligaments becoming elongated, causing pain at various points around the outside of the knee.

Also, as the ligaments were now not holding the knee tightly together, the internal components were becoming damaged.

My recommendation is to check the cleat positioning, get professional help with this.

Thanks guys. I'll try to follow the fit checklist.

When did biking get so complicated. When I was a kid, a bike was basically good to go if I could pedal, steer and stop. Now, I need to adjust to the millimeter?

quote:

Originally posted by konata88:
Thanks guys. I'll try to follow the fit checklist.

When did biking get so complicated. When I was a kid, a bike was basically good to go if I could pedal, steer and stop. Now, I need to adjust to the millimeter?

I don’t recall riding 30-100 miles at a time when I was a kid. Rode to school, ride home, ride around grab assing after school until dinner, 10 miles max for the day, some liesurely, and not all at once.

J Allen is right. An occasional 30 mile ride was usually the most we would do. Now some weeks I will ride 200 miles or more, at a brisk pace.

It is my experience most people set their seat height too low, this isn't good for the knee joint.

Aside from adjusting the seat, forn to back, make sure that your knee is only slightly bent when at full extension

I see some folks like to set seat low so they don't have to dismount at a stop... this is no good.

After this, you may want to explore your pedal stroke, some folks mash the pedal instead of utilyzing the full circular motion, it has been explained to some, when your feet are in the clips, it is akin to scraping the mud off the bottom of your foot as it reaches the furthest point.

If you are not riding with simple cages and strap, you may want to consider this, it will extend the range of motion utilyzed in pedaling.

Hope some of this helps.

See if your local shop has a "Fit Kit".

https://fitkitsystems.com/bike.../the-fit-kit-system/

quote:

When did biking get so complicated. When I was a kid, a bike was basically good to go if I could pedal, steer and stop

30 miles a week ,in town, times 9 weeks in the summer in hilly old eastern Iowa, ON A TWO SPEED !, no less for 5 years.

I'm 6-2 with a 36 inseam, I tried 172.5mm crank arms and they were too short, 175mm is great.

Like the others said, check your seating position in relation to your knee position. I used to suffer alot more knee pain because my seat was too far back and my pedal clips were in the wrong place on my shoes.

I've got 165MM on one of my fixed gear bikes, 170 on everything else. Had 175 on my best bike and replaced with 170. I'm 5'11" with a 30" inseam.

Shorter cranks are generally recommended for those who like to spin at higher cadences, vs. longer for those who like to mash at lower candences. Research indicates most are able to put out more power with shorter cranks.

Shorter cranks can be easier on knees than longer cranks with proper use of gears and everything being adjusted properly. As others have stated, verify bike setup before making a costly modification that might fix nothing.

If the cranks are somewhat solid, it would be an easy mod to have new crank holes added.

I can do this if you're interested.

1. 165mm cranks are really pretty common. Have you tried googling ? A road or mtn bike ?

http://www.jensonusa.com/Shima...dEAQYAiABEgKh2fD_BwE
or
http://www.jensonusa.com/Shima...000-Single-Crankarms
http://www.bikenashbar.com/cyc...maxPrice:&pageSize:&

2. Whether it will help your knee or not is questionable. My first recommendation would be to get a fitting from a real bike shop that deals with competitive high-end bikes and understands these things. Or, with some online study you can do it all yourself; it is not rocket science. Still, there are some advantages to having an objective observer set things for you.

quote:

Originally posted by TRIO:
If the cranks are somewhat solid, it would be an easy mod to have new crank holes added.

I can do this if you're interested.

I've been wondering if I could just tap in new holes. Just didn't know who to ask. Can I just go to any bike shop if they deal with a machine shop? Any machine shop? Or are their specialists?

Thanks for the offer. I may take you up on it if I can't find someone local to do it. (if I need to go this route).

quote:

Originally posted by Crom:
1. 165mm cranks are really pretty common. Have you tried googling ? A road or mtn bike ?

http://www.jensonusa.com/Shima...dEAQYAiABEgKh2fD_BwE
or
http://www.jensonusa.com/Shima...000-Single-Crankarms
http://www.bikenashbar.com/cyc...maxPrice:&pageSize:&

2. Whether it will help your knee or not is questionable. My first recommendation would be to get a fitting from a real bike shop that deals with competitive high-end bikes and understands these things. Or, with some online study you can do it all yourself; it is not rocket science. Still, there are some advantages to having an objective observer set things for you.

Mountain bike. Thanks, I think I already checked those out. I think that those don't fit my bike (11 speed which uses a thinner chain than my 9 speed allows). Or too expensive $200+ for arms... That's getting into crankset range (which I don't see the need for either). At least not until I determine that 165mm is really going to avoid knee issues.