Hi All,

I'm building a new bike with an '06 Bianchi San Lorenzo aluminum frame. I'm 6'3" 198 lbs. and I think I'm powerful but I'm probably not. I'm considering using 105 or Ultegra but I'm not sure there is a difference.

I currently have a Cervelo Soloist with 105 components and I haven't missed a shift in 1,600 miles. Are 105 cranks as stiff as Ultegra cranks? Are there big differences in crank stiffness? Stiffness is what I'm going for.

Thanks,

Mickey

Hi All,

I'm building a new bike with an '06 Bianchi San Lorenzo aluminum frame. I'm 6'3" 198 lbs. and I think I'm powerful but I'm probably not. I'm considering using 105 or Ultegra but I'm not sure there is a difference.

I currently have a Cervelo Soloist with 105 components and I haven't missed a shift in 1,600 miles. Are 105 cranks as stiff as Ultegra cranks? Are there big differences in crank stiffness? Stiffness is what I'm going for.

Thanks,

Mickey

Ultegra cranks are alleged to be the stiffest in the Shimano range, but the real question is whether or not you could even discern the difference. The answer to that is probably not. Any "flexing" you feel is likely flexing of the frame at the BB.

Ultegra cranks are alleged to be the stiffest in the Shimano range, but the real question is whether or not you could even discern the difference. The answer to that is probably not. Any "flexing" you feel is likely flexing of the frame at the BB.

I'm a bit skeptical that crank stiffness get one any more power or speed, though I admit I do like the feeling when I step down on a stiff crank. I have to disagree with this post, especially with experience on my MTB crank. I replaced a stock XT with a Race Face, and difference in stiffness was incredible. I'd even call it brittle. And the bb--an XT square taper-was the same.

There are lots of things that may or may not be stiff in a drivetrain, and may or may not be felt.

I'm a bit skeptical that crank stiffness get one any more power or speed, though I admit I do like the feeling when I step down on a stiff crank. I have to disagree with this post, especially with experience on my MTB crank. I replaced a stock XT with a Race Face, and difference in stiffness was incredible. I'd even call it brittle. And the bb--an XT square taper-was the same.

There are lots of things that may or may not be stiff in a drivetrain, and may or may not be felt.

Well, you'd be surprised by how little any crank flexes under a rider....

I'm a 200# + pound power rider, who has been riding and racing since the 50's. I've never felt a crank flex. Ever. BB and other parts of frames? Yeah, they flex, but cranks - nah.

I'm a 200# + pound power rider, who has been riding and racing since the 50's. I've never felt a crank flex. Ever. BB and other parts of frames? Yeah, they flex, but cranks - nah.


Interesting.
But I definitely knew the difference when I went from my old Truvativ Stylo's to a set of Shimano XT's on my MTB.

I'm a 200# + pound power rider, who has been riding and racing since the 50's. I've never felt a crank flex. Ever. BB and other parts of frames? Yeah, they flex, but cranks - nah.

I'm a 225lb rider with SRAM Force on a Scott CR1 Pro....I get a little bit of flex on the cranks and a bit on the frame. Makes it quite "compliant" for riding. If it didn't give a little, I think it would be too uncomfortable to ride....

The Flash

So school me please....How does one decipher crank flex from frame flex or percieved frame/crank flex that is really wheel flex or shoe flex? :idea:

brewster

So school me please....How does one decipher crank flex from frame flex or percieved frame/crank flex that is really wheel flex or shoe flex? :idea:

brewster

For me, it's based on my experience....

Wheel flex is the easiest to determine....it will hit the brake pads and/or frame...

BB flex causes the chainring to bow outward and the chain will hit the FD when pedaling hard.

Crank flex gives me the feel that the pedal is going to swing under the bike, but only while seated. If I was standing, I would say it was more BB flex...

Shoe flex is a mushy feeling when sprinting...

The Flash

So school me please....How does one decipher crank flex from frame flex or percieved frame/crank flex that is really wheel flex or shoe flex? :idea:

brewster

Change one variable at a time, as any researcher would do. As I noted earlier, on my MTB I traded a '96 for a Race Face--same square taper bb, same everything else. The difference in how the crank feels, even after 10 years, still amazes me. Recently I switched my Stronglight road crank for a Shimano compact and the difference in rigidity is immediately apparent. Obviously, if you change your shoes, your wheels and your bike all at the same time you might have some trouble......

You are now schooled.