wall tickness for mtb top tube.

[michäel2]

Hi all,
last week i finished my first frame, a 21" 29er mtb frame, quite excited by it all. it performed as good as i could have hoped for until it fell on the ground and the handle bars dented the top tube in a seemingly innocent incident.
i see the whole building experience as a learning curve and would like number 2 to be better then number 1. As such i would like number 2 to be perhaps slightly more dent resistant.

i used a round shaped reynolds 853 top tube, 31.8 0.8-0.5-0.8 and you guessed it the handlebars end up in the middle (-:

i did some look around on the web and saw that true temper uses a similar thickness tube in there mtb tube sets as are the zona 29 er tubes either 0.7-0.5-0.7 or 0.8-0.5-0.8 regardless of the tube diameter.

i would like to go a size up for the this tube ( wall thickness wise) but not before asking what your experience are with the matter and what you prefer to use in regards to this?
number 1:
944046_10153844863964501_9092962733174419789_n.jpg

[Andrew R Stewart]

Stuff does happen. Too bad so soon after a victory. Higher strength tubes will be slightly more dent resistant as will slightly thicker walls. But stuff still happens.

The best way to not have this dent happen again would be to design an arrangement so the bars don't contact the TT or to add a reinforcing layer at the contact location. Andy.

[Peter Polack]

I'm no framebuilder, but is there any chance to find a top tube with a front butt so long as to be where the handlebar might contact the top tube? Either that or use a straight gauge tube.

The other alternative is to assemble the frame and fork so the handlebars clear the top tube when rotated. When I took delivery of my custom mountain bike frame, I made sure to use just enough spacers, in conjunction with the handlebar/stem setup, to avoid such contact as I dented my last frame's top tube with handlebar contact. Worked like a charm, was easy to do, and didn't mess with my desired position.

[Andrew R Stewart]

I'm no framebuilder, but is there any chance to find a top tube with a front butt so long as to be where the handlebar might contact the top tube? Either that or use a straight gauge tube.

The other alternative is to assemble the frame and fork so the handlebars clear the top tube when rotated. When I took delivery of my custom mountain bike frame, I made sure to use just enough spacers, in conjunction with the handlebar/stem setup, to avoid such contact as I dented my last frame's top tube with handlebar contact. Worked like a charm, was easy to do, and didn't mess with my desired position.

As I see fit as a first priority I'd say that the frame design to allow bar/TT clearance didn't change your fit set up. The same thing as you said but placing the emphasis on having the frame design follow the fit and use needs, not having TT/bar clearance be a lucky chance result. Andy

[michäel2]

no, indeed im not intending change geometry, will go up a gauge first.
wondering if any one want s to confirm what kind of tubing they prefer as a t.t.

[cardinal-creative]

no, indeed im not intending change geometry, will go up a gauge first.
wondering if any one want s to confirm what kind of tubing they prefer as a t.t.

True Temper Verus 31.8 9/6/9. Basic chromoly, easy to work, and cheap. Straight ga. .035" is also a choice.

Are you citing your original tube specs from packages offered by the distributor? If so, think outside that box and pick tubes to tune the need/design.

[jon_norstog]

Michael,

Spec your tubes for the ride you desire. .8-.5-.8 makes for a pretty decent ride on a mountain bike, assuming you are using OS tubes - say 1 1/8" TT and 1 1/4" DT. I go to heavier tubes for bikes that are going to be thrashed, for instance freeride/slalom/4X/hucking bikes.

Dents do happen. Triple clamp style forks are notorious frame-denters, for instance. Some riders wrap old inner tubes over the parts of the frame that are vulnerable. Or piece of old tire around the [arts that might inflict the dent.

Good luck!

jn

"Thursday"

[BShow]

Doesnt look like you need a ton of extra clearance... Is it just the shifters contacting the TT?? Maybe slope the top tube a bit more? Raise the stem a smidge? Are those 980 shifters that are mated to shimano brake levers? If not, you might gain a bit of clearance by using the matchmaker (or whatever its called) setups or vice versa - not sure which is lower profile. Or build a singlespeed.