While I was taking the components off my bike Tuesday. I was lookin at my Dura Ace crank and notices it was a 172.5. This may not seem like a big deal but here is the deal. I'm 6'4" the bike is a XL frame. When I bought this bike it had 175 length cranks according to the spec that I checked. At the time of purchasing the bike I was new to cycling and know little about bikes. After having the bike a year the LBC said he had this crank for sale. A customer got it as a presant and didn't like a double and traded it to a triple. He didn't inform me it was a 172.5, a differant length than the original. I think XL bikes and someone of my size a 175 crank is recommended. I feel I should have been informed of the differant length.

Some sources say that with your height you need even longer than 175mm cranks. Though, they are very difficult to find.
http://www.peterwhitecycles.com/fitting.htm

Here are Zinn's recommendations:
http://www.zinncycles.com/cranks.aspx
Crank length (mm) = Inseam (mm) X 0.216

Or, more conservatively for tall riders:

Crank length (mm) = Inseam (mm) X 0.21

Every crankset I've ever owned had the crankarm length specified in a place it could be read without removing it. It was either punched/embossed on alloy or a "sticker" on my FSA and Bontrager carbon's. Granted, a sticker can be removed, but you stated the crank was DuraAce, i.e., alloy.

I doubt the shop was trying to deceive you as the arm length was readily identifiable. It sounds more like miscommunication.

The same thing happened to me... and I had spec'ed a 175 crank for a bike I had built. It was months before I noticed. At first I was annoyed, but then realized that if I hadn't noticed ON the bike, what difference did it really make?

While I was taking the components off my bike Tuesday. I was lookin at my Dura Ace crank and notices it was a 172.5. This may not seem like a big deal but here is the deal. I'm 6'4" the bike is a XL frame. When I bought this bike it had 175 length cranks according to the spec that I checked. At the time of purchasing the bike I was new to cycling and know little about bikes. After having the bike a year the LBC said he had this crank for sale. A customer got it as a presant and didn't like a double and traded it to a triple. He didn't inform me it was a 172.5, a differant length than the original. I think XL bikes and someone of my size a 175 crank is recommended. I feel I should have been informed of the differant length.

Both of you are at fault for not specifying or checking the crank length. He should have told you what it was but you should have asked/checked, also.

Are you comfortable with the 172.5 length? Did you even notice it before you looked? I bet you didn't even know they were shorter. Don't worry about it if you don't notice the difference and I bet you don't. If you just started noticing the difference after you checked the length that should tell you something. When buying anything you need to know what you want/need and make sure you're getting the correct size.

BTW, how would the seller have known there was a difference in length if you didn't tell him what length you were riding? I'll assume he knew or should have known the length that was originally spec'd on your bike but how would he know you either didn't change them earlier or wanted something different? You gotta communicate and it goes both ways but the buyer has to know what he wants and what he's getting. Ignorance is no excuse.

The same thing happened to me... and I had spec'ed a 175 crank for a bike I had built. It was months before I noticed. At first I was annoyed, but then realized that if I hadn't noticed ON the bike, what difference did it really make?

Yeah I use a 175 crank on my road bikes and MTBs, but I've been riding a 165 on the spin bike all winter and I don't really notice a ton of diff.

I also think that you might want longer than 175. I might be wrong though........

I'm not sure how much difference it can make. it's only 2.5mm

I also think that you might want longer than 175. I might be wrong though........

I'm not sure how much difference it can make. it's only 2.5mm

i think 175 is fine though he could go longer.

Too me he was just wanting to get rid of the crank that he got stuck with. It's a small shop (2 employees total) that doesn't sale 1 Dure Ace crank in 2 years or more. Did the LBC know? Tha'ts a good question. The guy that had the crank before me is alot shorter than me and rides a medium frame. I was new to cycling and didn't know much about bikes, let alone crank arm length. The length is stamped on the inside of the crank arm at the pedal hole.

The key is, do you notice a difference? If not don't worry about it. Crank arm length has been debated on this and many other forums for a long time. There have even been attempts to quantify and determine the optimum length. It's a tempest in a teapot. If you're comfortable and don't notice the difference it's a non-issue. Chances are the Dura Ace crank is better than what you took off or you wouldn't have made the switch. It's probably at least lighter, if that makes a difference to you. I think you're probably fretting over nothing.

[QUOTE= Ignorance is no excuse.[/QUOTE]

Actually, far too many bike shop employees are ignorant, and people often rely on their "expertise." I remember years ago I went to buy my first good bike, and the guy at the shop thought a 57 cm frame was just right for me. I was a teenager and didn't know anything about bikes. Well then (as now), I was 5'7" with a 29 inch inseam. That bike was was way too big. There are so may types of stores I hate going into-outdoor, camera, electronics, anything with gear--where the employees obviously got their jobs because their buddy worked there. In my town many retirees come in with money and buy businesses to have something to do. The best bike shop in the area has been driven into the ground because the couple doesn't know a crank from their elbow. At the local camera shop, I have to explain what slide film is and why I don't need 4x6s.

Some shops do this. Most don't......There is one in my area (who will remain unnamed), who had done this many times. Cust comes in and is given a price for a bike. Cust says that shop XYZ is selling the same bike for $xx. First shop says that they will match the price, but then pulls off some parts and subs some slightly used parts to replace them.
Very sad.
If the bike is less than a year old, ask the shop about this. If it's older, just learn a lesson from it.

You're reading his poast wrong. The shop didn't switch parts on him. He bought the bike with all the advertised stuff. Later, the shop (presumably the same shop) told him they had a take off Dura Ace crank and wondered if he wanted to upgrade. He bought the crank and later discovered it was a 172.5, not a 175. Seller and buyer were not clear on what was being sold and what was being bought. Seems to me it was mostly out of ignorance by the buyer but the shop should have considered the possible crank length difference. Maybe the shop was trying to dump it on an unsuspecting buyer but my guess is both the shop and the buyer didn't think about the possible crank length difference. It's not like the length isn't clearly cast into the arm and highly visible if you know to look for it. Now, back to our regularly scheduled tempest in a teapot.

I got the crank at the same shop as the bike. Ignorance was a factor. Like stated before I knew nothing about crank length at the time. I was just excited about my upgraded crank. I trust the shop to give me the correct parts for my bike and he didn't. Look at it like this.. You take your truck to the shop to have your radiator replaced. You would trust the mechanic to replace it with one that is the same size. Right? Two years later you go Advanced Auto Part to get anti-freeze, ask how many gallons of coolant you need. You get home you have 1/2 gallon of coolant left over and come to find out the mechanic put a smaller radiator in you truck. It never cause it to run hot or boil over but, still you would feel like you where took advantage of. I think anyone would think that this is bad business.

Like I said, there's blame on both sides. The truck analogy is not quite on target. Where there's a choice the buyer needs to know what size is right for him.

A better analogy would be you stop into your local clothing store and a clerk says a customer just traded in a brown suit for a black one because he didn't like the color of the brown one. The clerk thought you would look good in the brown suit. Since you never bought a suit before you didn't think to ask what size it was but liked the color and bought it. A couple of years later, after wearing the suit 50 times you look at the tag and it says size 40. Between the time you bought the suit and now you bought others and knew you wore a size 42. Now you're pissed because you were sold a size 40 suit instead of a 42 and the clerk should have known better, probably measured you. Even though you wore the brown suit a lot and it fit and worked out fine, you were mad because you think you got bamboozled by the dastardly clerk. No harm, no foul. The cranks work, don't they? You still haven't answered the question I originally posed. Do you notice the difference?

Did I notice a differance? At he time I would say no. That being I didn't know they were differant lengths. Now that I have more cycling experiance I may notice the differance but, I don't know since I've been ridding 172.5. Why are they differant lengths of cranks? For differant body types? What crank arm lengths are recommended for somebody 5'8"? 165s or 175s? How about somebody 6'7"? Would they need a crank arm of 165? Just check bicycles that are a XL or 61-63cm size and see what crank length they have. I will say 175. What advantage would I get from shorter cranks if the guy at the shop thought I needed them?

Did I notice a differance? At he time I would say no. That being I didn't know they were differant lengths. Now that I have more cycling experiance I may notice the differance but, I don't know since I've been ridding 172.5. Why are they differant lengths of cranks? For differant body types? What crank arm lengths are recommended for somebody 5'8"? 165s or 175s? How about somebody 6'7"? Would they need a crank arm of 165? Just check bicycles that are a XL or 61-63cm size and see what crank length they have. I will say 175. What advantage would I get from shorter cranks if the guy at the shop thought I needed them?

The short answer is that despite all the formulas you will find to suggest crank length, it is really personal preference and nothing more. The only thing you can say is that longer cranks tend to result in lower cadence. Studies have been done that have "proved" all kinds of things about crank length, including studies that have proved that crank length is not tied to any body proportion. There is no good study or relationship that is actually proven to predict proper crank length. Some people claim they can really tell the difference in length, while others say it makes no difference. You found no difference, and the 172.5s are working fine for you. You were not deceived. You and the shop bungled the sale a bit - they should have asked what length you needed, and you should told them what length you had. End of the day? No harm, no foul.

Here is an excerpt from the book Zinn & The Art of Road Bike Maintenance:

Generally, road crankarms come in 2.5mm length increments from 165mm to 180mm--although 167.5mm is often hard to find. Longer than 175mm can usually only be found on high-end cranks. It is possible to find 185mm and even 200mm and longer or 160mm or shorter from some small manufacturers.


Frame size Appropriate stock crank length (in mm)
less than 46cm 165mm or shorter
47-49 167.5
50-53 170
54-57 172.5
58-60 175
61-63 177.5
64 or larger 180 or longer

Given that there is no consensus on ideal crank length, I will give you a simple selection method that works well when buying stock-sized bikes and cranks.

If your riding is focused on time trials, triathlons, or hill climbing, try 2.5mm longer than the recommendations given here.

I have done numerous crank-length tests for VeloNews, and the results show that (1) there is no one crank length that works for a given body size and (2) standard stock crank lengths are arbitrary. It is worth experimenting to see what you like.

even though there are recommendations for crank length based on rider height and leg length, the most important thing is your personal preference. I know short guys who prefer 175 cranks, and taller guys who like to spin and prefer 170s. there are plenty of track racers of all sizes and levels that use 165 cranks with no problems... if you're comfortable with the cranks, then keep them.

Let's see, I'm 6'5" and ride a 63 or 64cm road bike and an XL mtb. I have 175's on my road and mtb, 172.5's on a single speed roadie, 170's on a fixed roadie, and 165's on my track bike. I have no idea what's on the spin bikes at work. I would like to think I can tell a slight difference in them, but it's probably only mental. They all work fine and I ride them all enough to know the idiosyncrasies of each.

If I was in your position, I would probably be a little perturbed that I got a shorter crank. But as has been said, DA cranks are most likely upgrades from what you had. If it bugs you that much, ebay them and buy the same cranks in 175.

I got the crank at the same shop as the bike. Ignorance was a factor. Like stated before I knew nothing about crank length at the time. I was just excited about my upgraded crank. I trust the shop to give me the correct parts for my bike and he didn't. Look at it like this.. You take your truck to the shop to have your radiator replaced. You would trust the mechanic to replace it with one that is the same size. Right? Two years later you go Advanced Auto Part to get anti-freeze, ask how many gallons of coolant you need. You get home you have 1/2 gallon of coolant left over and come to find out the mechanic put a smaller radiator in you truck. It never cause it to run hot or boil over but, still you would feel like you where took advantage of. I think anyone would think that this is bad business.


Exactly- a good bike shop would have asked you what length crank you were using and explained the differences/problems that could arise. Not saying all the blame falls on the shop, but if you want to keep customers happy, you do the right thing. If they honestly didnt even think to ask you what crank length you were using, I wouldnt trust them on a lot of other things, I'd be looking for a new lbs.

That sums it up, innergel. I ain't steaming mad over it. If I went to the LBS and had him order me one (other than having the 172.5 in hand) He would have recomended the 175 crank in my opinion. I did put it on E-bay under Dura Ace crank. Check it out, its the ugly one on there. Then I'm going to purchase longer cranks.

That sums it up, innergel. I ain't steaming mad over it. If I went to the LBS and had him order me one (other than having the 172.5 in hand) He would have recomended the 175 crank in my opinion. I did put it on E-bay under Dura Ace crank. Check it out, its the ugly one on there. Then I'm going to purchase longer cranks.
You may want to change your description to the correct 53/39 *not* 53/29 as it's there now. Good luck with the auction and getting the right stuff.

...He didn't inform me it was a 172.5, a differant length than the original...

Well for the most part I think 172.5 is the default crank length used on many bikes at least from my experience. If you do not specify something different then it comes 172.5 and as a result your LBS was selling you a standard (172.5) crank so saw no need to warn you that is was something other than the default standard in the industry (based on my experiences).

When I shop for my short wife I specify a shorter crank. When I buy for my tall son I specify a longer crank unless he needs something different based on the discipline (crits, track...). When I buy for myself I assume that I will get 172.5 but still check to make sure.

Your shop did not do anything wrong and certainly did not decieve you.

Well for the most part I think 172.5 is the default crank length used on many bikes at least from my experience. If you do not specify something different then it comes 172.5 and as a result your LBS was selling you a standard (172.5) crank so saw no need to warn you that is was something other than the default standard in the industry (based on my experiences).

When I shop for my short wife I specify a shorter crank. When I buy for my tall son I specify a longer crank unless he needs something different based on the discipline (crits, track...). When I buy for myself I assume that I will get 172.5 but still check to make sure.

Your shop did not do anything wrong and certainly did not decieve you. The default crank length on my bike a XL giant TCR is 175 not172.5 .

The default crank length on my bike a XL giant TCR is 175 not172.5 .

You didn't buy a bike, you bought a DA crank. You chose the word deceived and that is not what happened. If you dont like it or truly notice the 2.5mm impacting your performance then sell and order what you need for your body.

...your LBS was selling you a standard (172.5) crank so saw no need to warn you that is was something other than the default...

I don't think you understand. The LBS offered me the crank. I didn't go in looking to buy a crank that day or go get the crank off the selve and take it to the counter and say I wanted to buy it. He had it behind the counter and ask if I would be interested in it. He should have informed me it was a differant size than the one on my bike. Just saying if the guy respected his customer instead of just trying to make a quick buck on a returned product. He would still have my trust.

I don't think you understand. The LBS offered me the crank. I didn't go in looking to buy a crank that day or go get the crank off the selve and take it to the counter and say I wanted to buy it. He had it behind the counter and ask if I would be interested in it. He should have informed me it was a differant size than the one on my bike. Just saying if the guy respected his customer instead of just trying to make a quick buck on a returned product. He would still have my trust.

I think he got it, the fact that the LBS guy offered it to you instead of you asking for it doesn't really make much of a difference. Most likely the shop guy had the DA cranks there, knew he could both give you a deal on them and unload them at the same time, and the issue of crank length never entered his mind. No intent to deceive, just thoughtlessness. Maybe I give people too much credit, but in my experience most of the issues I've had with people in retail haven't involved them trying to screw me over or deceive me or whatever but rather just simple, honest mistakes. I can live with that, I make my share.

Side note:
its only 2.5 mm. Wouldn't different sized insoles create a difference like that? What about pedal stack?