old man knees and crank arm length

[blueee]

sometimes I need to pedal a mile or two across town aand it sucks and hurts my knees. i got a smaller sprocket, skinnier/faster tires ....will longer crank arms also help out?

at5'8'' Ive always ran 175mm cranks, but should I now consider longer ones for more leverage??
...I have recently heard everyone ranting and raving about 170s and 165s

[weedbix]

Depends what's aggravating your knees. If it's the pressure of pushing on the pedal, then sure, longer cranks will help. Just as you guessed, cranks are a indeed a lever

[LeonLikesToRock]

If you're riding a bmx across town your knees will probably hurt regardless of crank length.

[benward]

I have absolute shit knees and the 165 crank length has been magical. I've gone 165 on all my bikes bmx, mtb, road. I lost a little in leverage, but I got used to that quickly. Key advantage beyond feet closer together for a more centered base is on the over/top stroke since my knees do no have to bend as far with the shorter arm.

[O.G. David]

Having a higher seat also prevents you from bending them too much. Can't ride with low seat anymore.

[benward]

I was talking about standing and pedaling.

[nwcstn]

This is old but whatever, keep in mind longer crank arms will put more strain on your hips with your feet farther apart.

[weedbix]

Not to sound like couch but I'd imagine Q factor may play a part too

[O.G. David]

I was talking about standing and pedaling.

Higher seat saves my knees when landing, bottom hit the seat before my knees bend too much.

[JFax]

From 175 you can more or less only move up to 180, which would not be a massive difference. If you are riding with pegs it is also more likely that you would hit the peg with the back off your shoes when riding longer cranks.
Im 6.3 and ride 160 cranks and tend to ride for 30-60 minutes to the park. I used to ride 180 but felt that you move your legs around so much when you pedal. Have no issue with knees though, for that I would just ride a super long seatpost that you can slam into the frame when you start riding the spot.

[JohnW]

I didn't feel much difference dropping from 180 to 175 years back, nor did I feel much now dropping from 175 to 170. Just changed it for foot clearance. I used to clip my pedal on the ground coming out of fakies way back when I ran 180s and had a cassette. Stopped happening with 175s, and this time I dropped a size for peg clearance. I really don't think it would be enough of a change to help your knees any, perhaps change sprocket size instead? I notice way more difference changing the sprocket by 2 teeth than cranks by 5mm.