Crank length

[3narf]

I assume it's more important with an SS bike than with gears.

How do I calculate the best fit for my inside leg?

I understand the point about 165mm being best for fixed (to maximise clearance in bends) so should I just buy 165mm cranks to make the bike 'future proof?'

My current cranks are 172.5mm.

Thanks

 

[Deleted member 1258]

I'm running 165 cranks on my Pearson Fixed. I'm short, 5ft 6in with 29inch inside leg, and I've found that using the short crank makes spinning down hill a lot easier.

 

[colinr]

I had 170s on my previous fixed, 165s on the current. Can't really tell the difference, but like dave r I've short legs so going shorter was a no brainer.

 

[Rob3rt]

On the road, who cares, it wont make an ounce of difference, you wont be leaning over that far. Re-leg length, again if your frame fits and your seatpost is long enough you should have enough adjustment to give you 10mm give either way to compensate for the lowest point of the pedal stroke so no need to worry about crank length really.

On a steeply banked track, it might be an issue. Manchester Track Standard is something like 11" bottom bracket clearence and 165mm cranks.

 

[McrJ64]

I have 29" inside leg too. That's the size of trousers that I wear. It isn't the same as the inside leg length that most bike fitters / manufacturers will use though. As far as bike size/crank size is concerned they use crotch to floor length so a 29" trouser lenght works out as about 31".

I use the standard 165mm cranks but have thought of changing to 167.5mm if/when they wear out. What's the difference? Probably none. At the top of the stroke, it's more difficult to push because my knee will be higher up. At the forwardmost position, it's easier to push because the 'lever' is longer. But how much difference does 2.5mm make? I don't think I'd notice really.

Good luck.

 

[ColinJ]

On the road, who cares, it wont make an ounce of difference, you wont be leaning over that far.

I've grounded pedals several times on 3 different standard road bikes with 175 mm cranks. Each time was in the same place on a very steep hill with a left turn off it. I have to keep pedalling into the turn or I come to an instant stop. I can't climb faster enough to freewheel into the turn with my left pedal up.

I once rode about 30 miles of the Manchester 100 chatting to a man riding fixed and was astonished at how far over he was leaning on bends without grounding his pedals. I asked him about and he told me that he used shorter cranks for that very reason.

So, as far as I am concerned ... you can ground pedals on the road (I have) but if you ride fixed and use shorter cranks you will probably be ok!

 

[Rob3rt]

Fair point, I did make the hasty assumption here that the op was talking about true track frames when refering to SS (thinking me means fixed?) because for single speed why would it be any different to with geared, you could still freewheel round bends with the inside pedal up? Any frame designed for riding fixed should take pedal strike into account if its worth its salt. As such track frames often have slightly higher bottom brackets. You have to lean pretty far to ground a pedal and such a lean is beyond most riders ability or normal riding conditions.

I've tried this with 2 bikes. A Fuji Track w 170mm cranks and BMX platforms and a Cinelli Vigorelli w 165mm cranks and BMX platforms. The BMX platforms were a temporary measure but they provide a good measure because they are extra wide so they amplify any pedal strike issues.

My conclusion from doing this is that if the fixed/ss is a true track frame, it will lean pretty damn far without grounding a pedal. I can lean my fixed with 170mm cranks and BMX flats on it over to such a degree that you would never reach unless you are riding a track or cycling with such a high level of ability and speed to be able to lean that far without coming off. 165mm cranks made very little difference especially baring in mind that the lean on the fuji was already beyond most riders abilities.


BTW I'm not biased to any crank length, being the "right one", I own and ride the two bikes mentioned above. Ive done a couple of thousand miles on the Fuji and not grounded a pedal yet.

 

[totallyfixed]

On my Pearson I ride 175mm and never grounded, you never lean the bike over anything like you do with a freewheel. I have long legs but have still managed 198rpm, though I should hasten to add it's not something I care to repeat any time soon. The main advantage with longer cranks for me is it makes climbing easier.

 

[3narf]

Well, it's not a track frame, just an old steel road bike.

It's interesting to hear people's views, particularly those with short legs (I'm 29.5" - 30" ish myself).

It's initially going to be single speed with a freewheel, but as I might try a fixed gear eventually, I wondered if I really should have 165mm cranks.

From the comments above I should be OK with 170mm.

Thanks!