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View Full Version : Straight Gauge vs. Butted


davids
09-24-2004, 04:09 PM
While helping my wife buy a bike last weekend, I had the opportunity to go for short rides on two different Serotta Ti frames, a Fierte and a Legend Ė opposite ends of the Serotta Ti spectrum. The rides were short, the bikes didnít fit me all that well, I was riding platform pedals and wearing sneakers and chinosÖ All that said, they didnít feel all that different to me. Now, I know that I was in no position to truly judge the bikes, and my purpose isnít to even compare the two bikes.

But the experience got me thinking. If I understand correctly, given the state of the art, tube butting is not done (or is not necessary) to tune the frameís ride; Ride tuning Ė engineering the relative compliance of a particular tube, or of the frame in a particular dimension Ė may be accomplished by varying the diameter of the tubes.

This seems to be reflected in the design choices made by at least one of the premier Ti framemakers, Moots, whose Vamoots is only made as a straight-gauge frame (Most of what Iíve read about this frame is that it rides and performs like a dream.)

If thatís the case, the only function of butting is to reduce the overall weight of the frameset.

If, for example, I had Seven build me an Alaris and an Axiom with the same ride characteristics (using their 4 parameters Ė Handling, Drivetrain Rigidity, Vertical Compliance, and Weight-to-Performance Ratio), they should ride the same. Only the Alaris should weigh about 6 oz, or 170g, more. Iíd save $700 by going with the Alaris, which I could spend on better, lighter wheels, or a custom-made suit, or possibly bothÖ

Some of you may think Iím just being cheap. Guilty as charged, but get some perspective - Iím fortunate enough to afford a high-end bike every few years, not every few months. The price difference between a highly butted frame and straight-gauge frame is significant for me.

So, am I missing something here?

dgauthier
09-24-2004, 04:44 PM
If that?s the case, the only function of butting is to reduce the overall weight of the frameset.
(. . .)
So, am I missing something here?

Yes, that's correct, and no, you're not "missing something". On the old forum, the man himself Tom Kellogg said exactly the same thing.

Peter
09-24-2004, 07:31 PM
You could look at butting in the opposite way: The tube ends are thicker because the heat of welding reduces the tube's strength at the heat affected area. Making the tube thicker at the ends leaves you with a proper strength tube after welding.

vaxn8r
09-24-2004, 09:01 PM
Another analogy is the CF Calfee.

3 bikes, all designed to ride, handle, and feel exactly the same. The Luna cost $1,400, Tetra 2,000 and Dragonfly $3,000. The Luna is about 4 oz heavier than the Tetra which is about 8 oz heavier than the D-Fly. There are a few marginal differences and the higher 2 models are customizable. But the man (Craig) himself says they are meant to feel and perform the same.

Some would claim the D-Fly feels different than the other two, more "metallic". I have heard these claims though I've never ridden one. Craig says it may or may not be true. I think when you slap down $3-3.5K for a frame without fork you oughta feel something special.

va rider
09-24-2004, 09:20 PM
Well, I would certainly defer to Captain Kirk or e-Richie on this topic.

But, unless you are racing, save the $$ and go with the straight tubes.

davids
09-27-2004, 08:55 AM
Well, I would certainly defer to Captain Kirk or e-Richie on this topic.

But, unless you are racing, save the $$ and go with the straight tubes.
I was kinda hoping to hear from our resident masters... I've changed my subject line in hopes of attracting them!

Thanks for the comments, guys!

Jeff N.
09-27-2004, 09:21 AM
Moots can also keep the weight down because, along with tube diameter choices, they also use varying wall thicknesses. Jeff N.

va rider
09-27-2004, 11:51 AM
You forgot DWF, too. He also has ALOT of knowledge about framebuilding. Check out anvil bikes website for some of his insight.

This forum really is fortunate to have guys like this providing insight.

Oops and I almost forgot the Jerk. He too, with his pro racing experience, can give you the straight scoop!

davids
09-27-2004, 12:02 PM
Moots can also keep the weight down because, along with tube diameter choices, they also use varying wall thicknesses. Jeff N.
I assume that all of the high-end builders would have access to a wide variety of tube, with different wall thicknesses. My understanding is that larger-diameter tubes allow thinner walls with comparable stiffness.