Looking to buy a new MTB crankset. I have always used 175mm I believe, either because they were what was provided on a stock bike or when I bought some they were what was in stock and it was what I was used to.

However, I have always used 170mm cranks on all my road bikes following a bike fit several years ago.

So should I stay with the 175mm or step down to 170mm. I am a XC jey-boy type so I don’t think clearance is a big decider – Are there any other factors I should consider? Would one or the other be easier on my aging knees.

Thanks
Gary

Depends on your riding style (spinner/lumblin), inside leg length etc

Calculator here

According to that calculator I should be using cranks off a child’s bike. Although that probably suggests I should be stepping down to a 170mm

Probably more road orientated for faster cadence as I came out at 166.6 with an inside leg of 32″.

Shorter cranks with less leverage would undoubtedly be easier on the knees. I notived a big difference when I tried 180mm on a singlespeed and was much happier on 175mm.

I too had this dilema when buying a new crankset for my HT build,

I’m 5’11” with a 32 1/2″ inside leg and fitted 170mm cranks and they feel just fine and dandy

5mm makes **** all difference unless you have seriously dodgy knees. all the change in length does is adjust the gearing slightly. but you are riding a geared bike so it dont matter

I’m riding 180mm cranks. I don’t know anyone else who does. Why I have them isn’t so important but frankly I can’t tell the difference between them and 175mm cranks.

Shorter cranks are better for spinning the gears, longer for better leverage, that’s why ‘standard’ road bike cranks are 172.5mm, and mtbs are 175mm.

Though as most people above say, you’d probably never notice the difference.

Crank length doesn’t alter gearing