TrojanHorse

So I'm in the process of shopping around for cranks. I've decided I can't live any longer without a compact crank, so I'm over at fleabay all the time hitting F5.

Anyway, I've ridden 175 cranks for about 15 years and recently discovered that the cranks I thought were 175 were in fact 172.5, which is a truly minuscule difference and doesn't bother me. One of the cranks I'm watching on evilbay is 177.5 and I started wondering if that would work or if it would be comical so I did some light reading.

I'm slowly shrinking from my all time high of 6'2" and my daughter just helped me measure my cycling inseam at 35.5".

The formula I found on this page (https://www.machinehead-software.co.u...alculator.html) indicates that I should be riding a 177.7

The formula I found on this other page (https://www.nettally.com/palmk/crankset.html) indicates that I should be riding a 194.5. I found that many different web pages referenced this guy's formula

Anyway - does that cycling inseam sound correct given that I wear pants that are 32 or 33 inches inseam?

Anybody else get loooooong cranks based on one or more of those formulae care to share your experiences? I know somebody here is building up a Gunnar with really long cranks but I"m not sure if you've gotten any riding in yet to draw any conclusions.

socalrider

Long cranks are tough to find.. You need to look at Campy - they have 177.5 and 180mm cranks.. You just need to use old square taper bottom bracket..

No issues with using with 9/10 speed shimano or sram groups..

https://www.ebay.com/itm/Campagnolo-R...item3a73ac3776

laxpatrick

Yep! Have had Dura Ace 180s on my Cannondale for years. Barely noticeable. Now the 210's...

vesteroid

Seems to me I read zinn makes long cranks


But at your height I can't imagine you need them. I am 6'5" and ride a 175 and think its fine...seems you would have to worry about cornering if you are not careful.

bigfred 

Have been riding 180 Campy then Shimano DA since mid ninties. I remember being somewhat surprised by the difference made by moving from 175 to 180. Specially climbing speed. Think of it as a free 3% increase. Just think how many slowtwitch/weightweenie/41'ers would pay hundreds if not thousands for a 3% gain that didn't involve training for it.

However, if you're moving from 172.5 to 177.5 or 180, don't be surprised if it takes a little while to become accustomed to them and you may even experience some initial knee discomfort. This should pass within a week or two. It it doesn't look at your fit. Oh, and don't forget to lower your saddle the appropriate distance and perhaps your bars.

TrojanHorse

I refuse to use a square taper bracket - I just unloaded a frame that was forcing me to do that... Progress!

I have a set of 175s on the way and I'm not sure if my regular frame can support anything dramatically larger.

vesteroid - of course your response is the common one and as I mentioned, I've been on 175s forever except for a couple months this year. What's your "cycling inseam" at 6'5"? I just can't help wondering if I couldn't put a lot more power down with the appropriate sized cranks.

So Patrick - what are your impressions of 210? For that matter, how was 180? I'm sure you came from a smaller set but I'm also not sure 5 cm would be noticeable.

Rx Rider

I'm 6', I think you'll notice the minuscule difference of a real 175. I've always used 175's, a new bike came with 172.5, like you didn't think it could make a big difference. technically the 172.5 spins faster but I don't enjoy the full stretch I get from the 175, so mashing doesn't give me as much power. I don't mind swapping back and forth between the two, but I think I get more out of training on the 175's, that in turn gives me more speed on the 172.5. guessing that a 175 for you would be the same as the 172.5 for me.

brawlo

Crank length is more personal than mathematical, meaning a formula on it's own is not necessarily the answer. From track racing, a longer crank allows you to put the power down easier with a higher gear. It's one for the powerful guys that don't like to spin so much. Spinners tend to like shorter cranks as your feet/pedals don't have to travel in such a large circle. It's not really dependant on height, but personal preference relating to how you like to pedal. Apply that philosophy to your riding.

The main reason that I have heard of tall guys wanting longer cranks is to make climbing hills that little bit easier. In my experience, aside from the very tall, that is the only reason I have seen for people wanting extra long cranks.

For me, I race track on 170s at 6'5", and have 172.5 on my road bike. Both cranks came with second hand bikes, so weren't my choosing, but I must say I can't fault them. Having said that, I'm looking at a new Cervelo R3 when I can finally scrape the money together, and am going for a Rival drivetrain because I want to try out their 180mm crankset. I was looking at an Ultegra model as I have that now and like it, but the upgrade to a DA crankset in 180mm is a bit pricey.

ChuckD6421 

6'1", 33" inseam (pants size). 177.5 cranks for years including a couple racing Cat. 2.
It certainly is a personal decision and don't be swayed by those who say '172.5's have been fine for me and I'm 7'2"'. For me, they were a great change. Played around with 180's for a bit but went back to the 177.5's for good.

After your inseam length, I think you need to ask yourself if you're a "slow twitch" or "fast twitch" kind of athlete. I'm a slow twitch, more endurance than speed rider and a longer crank suits me. As you lengthen the crank, you increase the amount of torque you can apply, but the bigger circles means your cadence slows down a bit. Shorter cranks make higher RPMs more comfortable.

bigfred 

With regard to the idea that long cranks don't spin as well as shorter ones: I could agree if we're talking about sprinter's speeds that might approach 200 rpm on a bike with a fixed gear or in the highest gear available on a geared biked. However, on a geared road bike, where we're unlikely to need much in excess of 120 rpm (unless sprinting for the finish line of a race) they really aren't a limiting factor. I have no problem spinning 180 in excess of 120 rpm. On the wind trainer I think I've gotten them as high as 170 rpm or 180 rpm. Chances are rider's who's physical size warrant 180 cranks are going to run into other physiological speed limits before the cranks become the limiting factor.

I encourage any moderately tall or longer of limb riders who are currently on 172.5 or 175 cranks and who believe those are "fine", but, who haven't tried anything longer, to go do so. 5mm may not sound like much, but, when applied to both the leverage applied and to the range of movement, it has quite a noticable impact.

bladehack

Recently swapped out my 175 FSA Gossamer cranks for 177.5 Dura-Ace cranks. My cycling inseam is 38 inches...so I could have easily gone longer in the cranks since I have freakishly long legs. I haven't noticed any difference in the ability to maintain higher cadence but haven't had them long enough to notice any increase in climbing ability. Still glad I made the change since I got a good deal on the barely used cranks and greatly improved shifting performance

TrojanHorse

I still can't get my head around 195mm cranks. I didn't know Rival had 180mm cranks! I think I'll keep an eye on fleabay and see if I can get a reasonably priced demo set of long cranks to try out. I get the sense that most people who try longer cranks (and are tall) tend to enjoy them.

I used to be more of a spinner but lately, I'm happier between 80 and 90 and I can almost always speed up by shirting down a gear.

brawlo, I'd bet you could use a rival crank with your current drive train.

Thanks for all the input.

bigfred 

I'll add a caviat to my comments about "noticable" improvement. If you are primarily riding solo, and, aren't riding with regular partners or landmarking your time on a given peice of road over a period of time, you aren't going to "notice" the improvement. It'll be there, but, you won't notice it, for the same reason that "it never gets easier, you just get less slow".

TrojanHorse,

You can usually find the SRAM Apex or Rivals in a 180mm on fleabay for around $200, which is a gret and affordable way to give 180's a try. For reference I measured my inseam this morning at 965mm and my height is 1960mm. Leonard would have me on 200-210. I've been hesitant to try to fit that length on a stock frame.

brawlo

Yeah I know I could but it's a 10+ year old aluminium roadie. I just recently had to replace the BB and after some investigation it's not really worth anything second hand. So I don't really want to spend any more money on it. I plan on keeping it as a trainer. If I find the 180mm cranks to be some shining light kind of revelation, I might just change my mind though.

On a side note, there's a track racer here in Oz with 200mm cranks. His nickname is Supercrank!

laxpatrick

The 210's feel weird. I live in western Wisconsin - so lots of steep hills. Not soul-crushing mountains, but 2-3 mile steep grades are very common around my home. Honestly, after about 5 miles, I forget that I'm running the biggies. I tended to have a fairly quick cadence - I do find that I feel the "hop" where I didn't before coming from the 180's. In my opinion, the perception of torque is significant - especially coming out of the saddle. I think I like 'em, but they take getting used to. I do feel a sensation like my whole leg is part of the effort now...

I'd highly recommend that folks considering such a big jump try them out. I'm still not 100% sure that I'll love them as much as the 180's - but time will tell.

bigfred 

If you don't mind me asking (again?), what's your overall height and cycling inseam? And was your "ideal" length using Zinn's formula?

laxpatrick

6'8-1/2", 100cm crotch to floor as Lennard and others measure. So some formula suggest 2.16 in which case 215mm arms would be "ideal". I opted a tad under that with 210's. I got mine from Tom at High Sierra. Beefy but perhaps not as easy on the eyes as some designs...