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Discussion Starter · #1 ·
I'm 6'6" -- Bike shop is telling me a I need a new Bottom Bracket and a new big tooth cog - so it seems to me like maybe I should be looking at a new crankset...

Right now I've got an SRAM rival OCT 50/34 GXP ... might get same ... any other suggestions?

I've got a 10sp Microshift setup...
 

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Sadly Shimano does not make an Ultegra 6800 in 180mm. They do make a Dura Ace 9000 in 180mm. (11 speed cranksets work just fine with 10sp) They are $350 at Performance. The nice thing is there is a wide range of chain rings should you want to switch ratios.

I have always found Shimano's clamp on style arms to be more secure than the single bolt arm attachment of SRAM. I have seen too many of those single bolts become loose.

For an economical solution I think SRAM is your best bet.
 

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Discussion Starter · #3 ·
Sadly Shimano does not make an Ultegra 6800 in 180mm. They do make a Dura Ace 9000 in 180mm. (11 speed cranksets work just fine with 10sp) They are $350 at Performance. The nice thing is there is a wide range of chain rings should you want to switch ratios.

I have always found Shimano's clamp on style arms to be more secure than the single bolt arm attachment of SRAM. I have seen too many of those single bolts become loose.

For an economical solution I think SRAM is your best bet.
Great thanks for that advice.
 

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I'm 6'6" -- Bike shop is telling me a I need a new Bottom Bracket and a new big tooth cog - so it seems to me like maybe I should be looking at a new crankset...

Right now I've got an SRAM rival OCT 50/34 GXP ... might get same ... any other suggestions?

I've got a 10sp Microshift setup...
Have to ask the obvious question: Why do you think you want/need 180 mm cranks?
 

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Have to ask the obvious question: Why do you think you want/need 180 mm cranks?

He's 6'6". That doesn't totally explain it as inseam is the more important issue here.
 

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inseam is the more important issue here.
Precisely. According to the developer of the Kirby Palm Crank Length Formula (Mr. Kirby Palm), he might profit from an even longer crank. Assuming a 36" inseam (I), applying the Palm Factor would have him on an L(mm) = 5.48 x I(in) = 197.28 cm crank. Lots of leverage there, no doubt.

Bicycle Crank Length
 

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Precisely. According to the developer of the Kirby Palm Crank Length Formula (Mr. Kirby Palm), he might profit from an even longer crank. Assuming a 36" inseam (I), applying the Palm Factor would have him on an L(mm) = 5.48 x I(in) = 197.28 cm crank. Lots of leverage there, no doubt.

Bicycle Crank Length

Is there even such a thing as a crank that long?

While one might benefit from a longer crank as far as leverage goes, one would still be OK with a shorter one. The opposite is certainly not true as someone who has a crank too long for their inseam could be causing unnecessary knee strain.
 

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Is there even such a thing as a crank that long?
Zinn offers them up to 220 mm.

Zinn Cycles::custom bicycle cranks :: extra Long bike cranks :: short bicycle cranks | Zinn Cycles website

Don't take my previous post too serious. Kirby Palm theories are a bit of a joke. You need to click on the link to see that.

Personally, I don't believe crank length makes much difference to road performance. Pros generally don't ride custom-length cranks. It seems illogical to assume that pros ignore a performance advantage if it existed.
 

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I run 180's on my XT equipped 29'er XC bike. I'm 6' 5" with a 34" inseam (long torso, average leg length).

I could probably benefit from 180's on my road bikes too, but 175 has been working for me. One of these days, I might try a set of 180's on my gravel bike, just to see how that plays.
 

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Precisely. According to the developer of the Kirby Palm Crank Length Formula (Mr. Kirby Palm), he might profit from an even longer crank. Assuming a 36" inseam (I), applying the Palm Factor would have him on an L(mm) = 5.48 x I(in) = 197.28 cm crank. Lots of leverage there, no doubt.

Bicycle Crank Length
If i go by that formula, I'd be on 186's. I think that's a bit too long, just from a toe and ground clearance standpoint. Unless the bike is specifically designed for cranks that long, you could run into issues with pedals clipping or your toes and front wheel colliding.
 

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I run 180's on my XT equipped 29'er XC bike. I'm 6' 5" with a 34" inseam (long torso, average leg length).

I could probably benefit from 180's on my road bikes too, but 175 has been working for me. One of these days, I might try a set of 180's on my gravel bike, just to see how that plays.

Interesting that mountain and hybrid bikes come with longer cranks than the equivalent sized road and touring bikes. My mountain (17in. medium frame) and hybrid (56cm frame) came with 175mm cranks while my two road bikes came with 172.5 cranks and my steel touring bike came with a 170mm crank (all 56cm frames).
 

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My guess is that is because, generally speaking, you benefit more from the extra leverage on a mountain bike, and cadence isn't as critical, so there are fewer downside(s) and more upside(s) to having the crank a bit longer. Plus, also generally speaking, bottom brackets are a bit higher, and toe clearance is not an issue.
 

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Plus, also generally speaking, bottom brackets are a bit higher, and toe clearance is not an issue.
Ahhh, that would explain things. Mountain bikes tend to have the highest BBs in order to clear obstacles, while touring bike have the lowest BBs in order to keep center of gravity low for stability of heavy loads.
 

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touring bike have the lowest BBs in order to keep center of gravity low for stability of heavy loads.
At very low speeds and at a standstill, this is correct. But a higher speeds, a higher center of gravity increases stability of a two-wheeled in-line vehicle. This is why high-wheelers are so easy to keep upright (once you're up there and cranking away!) and recumbents are a little more difficult to keep upright and going in a straight line. The principle at work is the "inverted pendulum" if you're interested in the physics.

Some touring bike designers also feel that being able to put your feet on he ground while seated in the saddle is a good thing, especially if you're on a fully loaded bike.
 

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At very low speeds and at a standstill, this is correct. But a higher speeds, a higher center of gravity increases stability of a two-wheeled in-line vehicle. This is why high-wheelers are so easy to keep upright (once you're up there and cranking away!) and recumbents are a little more difficult to keep upright and going in a straight line. The principle at work is the "inverted pendulum" if you're interested in the physics.

Some touring bike designers also feel that being able to put your feet on he ground while seated in the saddle is a good thing, especially if you're on a fully loaded bike.
Well I doubt that many people doing loaded touring are riding very fast.

As far as recumbents, I know someone who has two of these. The one with the handlebars out in front was fairly easy to get moving. I found it impossible to get the one moving with the handlebars down at the sides. This is an example where steering only, not body English, is used to keep balance. I just couldn't do it.
 

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Discussion Starter · #16 ·
If i go by that formula, I'd be on 186's. I think that's a bit too long, just from a toe and ground clearance standpoint. Unless the bike is specifically designed for cranks that long, you could run into issues with pedals clipping or your toes and front wheel colliding.
My inseam is about 35 and 1/2 - and I was onboard with the Zinn thing - was going to get a Flite 747 with 200mm cranks - but thought I'd baby step it first.

I can see why if you were a younger tall competitive road cyclist you'd want longer cranks - but my legs and knees are not recovering like they used to - I need to start getting my cadence up I think and save my knees and wondering if I should just back down to 175.

Trying to find longer cranks is also a pain. I don't know if SRAM makes any new 180 rivals - old ten sp versions were/are 150-180 w BB. I don't want to shell out 400 for a Dura Ace just to get extra 5mm although I'm sure they're wonderful.
 

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I can see why if you were a younger tall competitive road cyclist you'd want longer cranks - but my legs and knees are not recovering like they used to - I need to start getting my cadence up I think and save my knees and wondering if I should just back down to 175.
If your knees are talking, then yes, by all means, err on the side of a shorter crank. It sounds like 175 is a prudent choice for you.
 

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Precisely. According to the developer of the Kirby Palm Crank Length Formula (Mr. Kirby Palm)
Yeah, and that formula was debunked more than a decade ago. There are LOTS of formulas for crank length, but none of them are supported by actual data. Even Zinn, who makes very long cranks (because he likes them) did a study that showed no correlation between crank length, leg length, and performance.
 

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It would be really hard to quantify 'performance' based on crank length. There are so many factors involved.

My 4' 11" girlfriend could obviously not ride comfortably on my 175mm cranks. In fact 165mm was uncomfortable for her. We put her on 145mm on her road bike (152 Sugino's on her Surly LHT commuter) and she is soooo much more comfortable. Her pedaling motion is so much smoother, and her cadence is just naturally much higher (averages ~100-105). I can't say if her performance improved. We aren't racers, so we don't have any advanced performance metrics. Don't really care. What matters is she is comfortable on the bike, and can ride longer, and more frequently without dealing with hip and knee discomfort.

For me, at 6'5", 175mm might be a tad on the short side. My cadence averages about 85rpm. I can, and do go higher on occasion, but my legs are long an heavy, and running a higher cadence feels unnatural and uncomfortable. Running a shorter crank, in my case, wouldn't make sense, and there are of course practical limitations how long a crank can be.

180mm is right at (or maybe slightly beyond) the limit for most stock frame designs. Frame parameters like BB drop, HT angle, Fork Rake, etc... factor in to how long a crank a given frame can support without clipping and toe clearance issues. At some point it becomes unmanageable.

Leonard Zinn makes (made?) bikes for extremely tall people, and designs frames and cranks specifically to accommodate them. I'm pretty sure he has some basic guidelines he uses, but it's probably mostly 'that looks about right' sort of thing, and not actual science that he's using to make his designs.

Most people don't give crank length much thought. We (my G/F and I) learned the hard way that mass-market bike manufacturers don't give it much thought either. We've seen Small and XS frames with 170mm cranks on them. My G/F clipped a pedal on a XXS Focus Izalco that was on the display floor with FSA 170's. At that point we didn't know enough to ask about crank length, and the sales people who sent her on the test ride didn't think about it either. She crashed, but not seriously, and fortunately, she wasn't hurt (slightly bruised ego) and the bike wasn't damaged. Lesson learned. When we asked the manager at the bike shop why such long cranks on such a small bike, he replied 'they just put on whatever they have'.... yikes...
 

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He asked for a "good" crank with no mention of a budget limitation and we know he's got a bunch of money burning a hole in his pocket from the Microshift savings. How has no one mentioned Clavicula? Is there anything else that's more good?
 
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