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    • CommentAuthorparkman14
    • CommentTimeJan 29th 2010
     
    Is it all about personal preferance? I mean the difference between 165 and 170 is barely visible. I know that track frames have higher bottom brackets and stuff, but other than that, is it about inseam size or heiht? I'm almost 5'10 and I run 170s.
  1.  
    There have been studies and most of them show little to no consensus. The theory is that short arms are good for cornering and cadence, long arms are good for climbing and hard pedaling (the longer the arm, the more force -- a simplification, but someone else is welcome to expand on it).

    170 is probably about right for you. If you're a low cadence guy, longer arms work better; if you're a high cadence guy, shorter arms will serve you better. Also, since you're riding fixed, shorter arms help prevent pedal strike.

    I wouldn't go longer than 170 on a fixed bike unless you are trying to break the sound barrier on a flat, straight track.
    • CommentAuthorparkman14
    • CommentTimeJan 29th 2010
     
    Well ya. Thank s_d
  2.  
    I have found that it is about personal preference as well. But I factor my height in too, just to get rid of a variable when adjusting my set up to fit me.

    I ride a pair of 170mm Carbon Pro's on the track for a little more sprinting leverage, and 165's for commuting (it makes me feel better when I do corner more sharply).
  3.  
    My road bike (the only bike I own which is fully assembled, I might add) has 172.5mm arms. They're too long, but they came with a bike I bought, so I ride them. The pedals do strike in turns occasionally, but the pedals are CB Mallets, designed for DH, so I don't blame the arms much. I would love to swap them for a similar 165mm set -- there's an Ultegra set on eBay now which will work 1:1 with my setup, but they're silver!!! Otherwise I use 165s or 170s, depending on the bike and purpose.
    • CommentAuthorparkman14
    • CommentTimeJan 29th 2010
     
    Well, I'm going to upgrade the Kilo cranks to 165, but it's my Suntour cranks that are 170mm. The GTB or whatever frame I get will definately have higher bottom bracket geometry than my kilo so I should be fine
    • CommentAuthorwes m.
    • CommentTimeJan 30th 2010
     
    I have ridden every size from 165 to 175. For road riding I like 170s, 175 for mtb, I'll ride 165 on a fixed gear if the pedal/bb drop combo make pedal strike a serious issue. After about 5 minutes of riding I stop noticing the difference in crank length. Theoretically, the concept of gain ratios says that crank length doesnt matter (well, sort of) so I guess you should ride whatever is most comfortable for you.
    • CommentAuthorlatron
    • CommentTimeJan 30th 2010 edited
     
    I'm 6'3" with a 35" or so inseam and have 175 on everything except my road bike, which has a 170. It feels a bit like a clown bike when I first get on, but seems to accelerate better than my long-crank bikes. Sheldon preferred short cranks over long, while others have come up with formulas that supposedly produce the "ideal" crank length. One fellow suggests 5.48 times inseam, which gives 191.8 for me. Kinda tough to find, if indeed it would even be a good idea. I did get a 180 triple recently and am going to try it out, but I know that for some, long cranks = knee pain. Basically, whatever works for you.
    • CommentAuthorSkidMark
    • CommentTimeJan 30th 2010
     
    I think 175mm is right for someone over 6' tall.

    There were BMX cranks in 185mm,190mm and I think 200mm.

    The knee pain could be from not moving the seat forward 5mm to compensate for the extra length of the crank, or not moving the seat down 5mm to compensate for the extra length.

    If I ever replace the cranks on my track bike they will be 170mm, and when I build my own frame it will be designed for 170mm cranks (5mm less bb drop).
    • CommentAuthoreaglerock
    • CommentTimeJan 30th 2010 edited
     
    Posted By: latronSheldon preferredshort cranks over long, while others have come up with formulas that supposedly produce the "ideal" crank length.One fellowsuggests 5.48 times inseam, which gives 191.8 for me. Kinda tough to find, if indeed it would even be a good idea.

    One of the advantages of Sheldon's gain ratio formula for measuring gearing is that the gain ratio calculation includes crankarm length and tire width, both of which affect gearing and neither of which is included in gear inch calculation. I never had nerd experience with gear inches (back when gear inches was all there was, I was not bike-nerdy), so I adopted the gain ratio system when I first started calculating this stuff.

    Generally speaking, for equal cog/chainwheel ratios, longer crankarms reduces gearing. For example, let's use the gearing I rode on for most of a 10-mile ride at about 1AM this morning:

    Tire - 700x23
    Chainwheel - 50T
    Freehub cog - 15T
    Crankarm length - 172.5

    Gain ratio - 6.5
    Gear inches - 87.6

    If we change the crankarm length to a trackier 165, the gear inch calculation remains at 87.6. But the gain ratio increases to 6.7. Similarly, if we change the crankarm length to a mountainy 175, the gear inch calculation still remains at 87.6. But the gain ratio decreases to 6.4.

    Generally speaking, longer crankarms gear you down (it takes longer to rotate your feet around the circumference of a larger circle), while shorter arms gear you up.

    BTW, latron: There's an eBay auction for a TA Pro V crank, English pedals with a 53T ring closing in a few days. The seller originally listed it as 175, but I emailed to check on the pedal threading, and now he's saying it's 185mm. If monster cranks are of interest to you (or any of the other giants hereabouts), PM me and I'll send the URL.
    • CommentAuthorlatron
    • CommentTimeJan 30th 2010 edited
     
    Thanks for the heads-up. Will look at it but most likely pass -- rode TAs for a while but got aggravated and gave up on them. Love the look and history, but didn't appreciate the pointlessly nonstandard specs, questionable design (to change the large chainring, you have to disassemble the entire thing), marginal materials, and poor shifting. Vintage is great, but there are limits. I will keep my eyes open for more bolts for you, though.
    • CommentAuthoreaglerock
    • CommentTimeJan 30th 2010 edited
     
    Posted By: latronI will keep my eyes open for more bolts for you, though.

    Thanks for that. I rummaged around at Velo Sport, and came up with one Frenchy nut (long-shafted for triple rings) and a standard M6 bolt with a tapered head and a Nylock nut. I pulled the crank, bolted the uglybolt in, tightened another bolt...and tore the head off the nut. After a brief explosion of profanity and tool-hurlage, I pulled out the hex bolt for the torn nut and installed the new Frenchy nut. So at this point, I'm still one bolt shy. I'm on my way to the hardware store to get a dozen M6 bolts and Nylock nuts; the crank can just look butt-ugly for awhile. At least I can be confident that stainless M6 construction bolts won't shear off.

    Sugino must have made narrower bolts for the PX, since it accepted TA chainrings. I have an email in to Velo Orange, saying I'll buy a set of nuts - but only if the ones they have are made of better steel than the old TAs.

    Posted By: latron(to change the large chainring, you have to disassemble theentire thing)

    As part of this process, I took the opportunity to switch out the 52T for a 50T. If the drama goes on long enough, I'll swap out the granny, too (from 34T to 30T or less; Rene Herse charges basically $ 1.30 a tooth).
    • CommentAuthorlatron
    • CommentTimeJan 30th 2010 edited
     
    Posted By: eaglerockRene Herse charges basically $ 1.30 a tooth

    Yours or theirs? :~)

    For your enjoyment (or further tool-hurlage), here's an illustration from The Dancing Chain of what was supposedly the original ancestor of the TA crank. Designed by Albert Raimond of Cyclo in 1925 and named the "Rosa" after his wife, it featured the 50.4mm BCD and large-chainring-as-spider design. Check out the right-hand setup: The medium chainring is outside the large one. Shifting fun!

    Image Hosted by ImageShack.us

    Also note the five-arm design. I assume TA went the six-arm route (thus the really weird five-on-six pattern) because even they found the five-arm setup too wobbly.
    • CommentAuthorMancha150
    • CommentTimeJan 30th 2010
     
    In regards to the crank length, since I began riding my bike, I have had 175mm crank arms. The bowery came stock with 175s (not really sure why since it was meant as a fixed gear), and I recently upgraded my cranks, but still use 175mms (it was actually a really tough decision). My girlfriend has a pista with the stock 170mm (if I am not mistaken) and I got a chance to try hers out for a short ride. It felt kind of wierd (we are both 57cm), and I guess this justifies my opinion (being able to notice the different feel).

    I have been told by a few people that it makes more sense to have 172.5 or 175mm if you are going on long commutes. I personally have never had any problems with my 175mm omniums. I actually feel really comfortable with the long pedal stroke. Only when I had straps and cages did I very few times have the problem of having the pedals scrape the ground on sharp turns (they were kind of bulky and I reached out a lot). My main problem is toe overlap, which is caused by a few other things. I actually felt I could go faster for longer (for my purposes...long commutes) with the 175s. I have never raced on the track and dont intend to with my current bike, so I guess if its any help, I dont really think that if you intend to commute with your bike you will have any problem with 175mms (or 170-172.5). But I think its really just about preference. People with 165mms are probably used to them and would feel their speed reduced switching to 172.5s or 175s, regardless of what they use them for. I mean, I have a hard time feeling comfortable with free wheel bikes now because I havent ridden one in 3 years, but if I had a road bike it wouldnt be long before I thought it was much more comfortable than a fixed gear. So i think you see what I mean. Hope this helps
    • CommentAuthorlatron
    • CommentTimeJan 30th 2010 edited
     
    Posted By: Mancha150In regards to the crank length

    Always good to bring a thread back to the original topic.

    Posted By: Mancha150I have been told by a few people that it makes more sense to have 172.5 or 175mm if you are going on long commutes.

    Depends on the kind of commutes you're doing (flats? hills? both?) and the cadence you prefer. I like my bike with 170s for the flats, as they spin better (higher cadence), while the 175s work well for bigger loads and more variation in terrain (lower cadence, more shifting).
    • CommentAuthoryobaby
    • CommentTimeApr 19th 2010
     
    Hi guys

    I wanted to ask your opinion on something relating to crank length on a fixed speed. Im making the transition from a road bike to a fixed speed and was unsure about crank length. i currently ride a 175mm length but have been made aware about toe clearance issues on fixies. I originally thought i should go for the 170mm seeing as Im 6.1 and have long legs, the toe clearance issue makes me think i should go for a 165 to help ease this. Im aware that you can never truly remedy this as fixed gear/track bikes aren't meant for road use but a "best of solution" is what Im after. Basically, Im sure I'll get used to 165mm and II'l take this over constant pedal strikes and toe's clipping the front wheel unless of course the 170mm are a better solution. ( My inseam is 35 and 3/4 inch or 91cm )

    (er not sure If I've just answered my own question here)
  4.  
    You could go with either.

    Since you're taller, your frame will be taller, and the bottom bracket shell will probably be higher, so I think running 170mm cranks would not be a problem. As far as toe overlap goes, if you're getting a frame with track geometry, there will be toe overlap no matter what, but you will get used to it and adjust to avoid this after riding your frame for awhile.

    I'm 5'5" and I've raced and commuted on 165mm, 167.5mm, and 170mm cranks on various track frames and hadn't had any issues.
    • CommentAuthorwes m.
    • CommentTimeApr 19th 2010
     
    By toe clearance do you mean clearing the front wheel or clearing the ground when cornering? Clearing the wheel is something you are going to need to learn how to deal with. Striking a pedal on the ground is a legit issue though. If you are riding a conversion you may want to go with 165s depending on the bottom bracket drop. If you are riding a fixed gear specific bike you should be able to get away with 170s without a problem.
  5.  
    ^This, totally.
    • CommentAuthorparkman14
    • CommentTimeApr 19th 2010
     
    My 170s are fine. I'm going to try some 165s though just to see if i like spinning so much.
 
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