jambon

Hi there,

Is it safe for a person weighing 100kg/220lbs to run a wide 46cm dropbar and an 80mm 17 degree stem on top of a carbon fork and steerer tube ?

Will this put too much strain on the carbon when putting down power and leaning weight on the handlebar ?

thanks for any insights

DrIsotope

I'm 215lbs, running a 44cm wide carbon bar on a full-carbon Cervelo fork with a 110mm -6º stem, and have around 9,000 miles on it, so I would say there shouldn't be an issue.

And as you're going 17º up, you'll have more weight on the saddle and less on the bars anyway. Regardless, round carbon fiber tube is extraordinarily strong.

HillRider

What you don't want to do is use a too large of a spacer stack between the top of the headset and the underside of the stem clamp. Most carbon fork makers recommend no more than 40 or 50 mm of spacers and that assumes a 1-1/8" steerer. For a 1" steerer the maximum is usually 25 mm.

WizardOfBoz

Probably depends a lot on the quality of the bar and stem. I'm 245# and have a 44cm Ritchie Superlogic Logic II carbon bar on a Bontrager Race X Lite carbon stem. That's 1-1/8 stem diameter. Had it about 3 years. Seems fine: no wiggle or observable flex except in the shock absorption.

I also have 1999 LeMond Zurich with a 1" threaded steer tube. Same bar, but an alloy stem. Again, seems solid.

fietsbob

As I understand Carbon fork steerers need to be short, to reduce the leverage applied to it,,

Being in a worry mode, you may want an internal sleeve of metal .. say Titanium , epoxied in place..

so if carbon composite cracks it will stay together.. long enough to get you home..





...

WizardOfBoz

Looking at your post again. I think fietsbob's point is well taken. I think that the point is lever arm, and not so much stem angle. You want to limit bending moment on the fork tube and on the stem joint. So get the correct size bike so that your stack height is 3cm (maybe 4) or less, and so that your stem length is 110mm or less. The limited lever arm limits the stresses on the fork tube and stem.

The 17 degree angle would have some effect (more or less, depending on whether your body weight is pushing the bar down, or forward) but the lengths are the key. If I'm reading your post correctly.