# What are the advantages of double and triple butted ti frames?



## sdlesko (Feb 28, 2010)

Arn't they mainly for strength/stiffness without increasing weight too much? For a guy like me, 5'10" 160 lbs, i don't think there is an advantage...so why would I pay more for a frame like that?

Thanks
Steve


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## rx-79g (Sep 14, 2010)

sdlesko said:


> Arn't they mainly for strength/stiffness without increasing weight too much? For a guy like me, 5'10" 160 lbs, i don't think there is an advantage...so why would I pay more for a frame like that?
> 
> Thanks
> Steve


It's primarily for weight reduction. Straight gauge and butted tubing can be exactly the same outside diameter and have the same wall thickness on the ends, but the wall thickness of the butted tubing in the center is thinner. Butting can save up to a pound, but usually it saves less than a half pound between a butted and straight gauge frame of the same design titanium frame.

Since the outer diameter does most of the heavy lifting, thinning the tube wall doesn't have much impact on ride or stiffness.


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## bikesdirect (Sep 9, 2006)

sdlesko said:


> Arn't they mainly for strength/stiffness without increasing weight too much? For a guy like me, 5'10" 160 lbs, i don't think there is an advantage...so why would I pay more for a frame like that?
> 
> Thanks
> Steve



steve

I think the real question with Ti is manipulated tubes vs straight tubes
most Ti tubes which are DB are also manipulated in shape
and Ti frames can be greatly improved with shaped tubing

If the goal is comfort, handling, quickness, durability and lightness all combined in one package; Ti can be on of the best materials you can use; especially when special tubes are used. However, it is much more expensive to build DB manipulated tubing Ti frames than a just plain guage round tubing frame.


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## PSC (Mar 10, 2004)

Here it is from an expert:

http://www.spectrum-cycles.com/623.htm


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## rx-79g (Sep 14, 2010)

PSC said:


> Here it is from an expert:
> 
> http://www.spectrum-cycles.com/623.htm


I'm glad you posted this. I don't buy into tube shaping being better, either.


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## RussellS (Feb 1, 2010)

sdlesko said:


> Arn't they mainly for strength/stiffness without increasing weight too much? For a guy like me, 5'10" 160 lbs, i don't think there is an advantage...so why would I pay more for a frame like that?


A non-butted straight gauge tube will be stiffer and stronger than a butted tube if the same size diameter and thickness on the ends where the non-butted section is. The non-butted tube has more metal in it so it will be stronger and stiffer. But the butted tube does not lose too much stiffness or strength from the butting and does lose some weight. So generally its better to have butted tubes. Particularly with bicycle tubes that are already big enough in diameter to be stiff and strong enough whether butted or not. Look at steel frames. No one builds good bikes with non butted tubes. Everyone builds good bikes with butted steel tubing. In the past I've read about custom frame builders using straight gauge tubes for the downtube to get a stiffer/stronger frame for heavier sprinter riders. And using Columbus SP instead of SL for the downtube for bigger frames. The thicker downtube was stronger/stiffer for bigger bikes and bigger riders. But today when you can have 3 inch diameter downtubes, its not necessary to not use butted tubing. Long ago everyone had to use 1.125 or was it 1.25 inch downtubes because that is what the lugs were. No choice.

Some folks might say butted tubing rides better than non-butted tubing. Livelier, springier, etc. Don't know.


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## rx-79g (Sep 14, 2010)

RussellS said:


> A non-butted straight gauge tube will be stiffer and stronger than a butted tube if the same size diameter and thickness on the ends where the non-butted section is. The non-butted tube has more metal in it so it will be stronger and stiffer. But the butted tube does not lose too much stiffness or strength from the butting and does lose some weight. So generally its better to have butted tubes. Particularly with bicycle tubes that are already big enough in diameter to be stiff and strong enough whether butted or not. Look at steel frames. No one builds good bikes with non butted tubes. Everyone builds good bikes with butted steel tubing. In the past I've read about custom frame builders using straight gauge tubes for the downtube to get a stiffer/stronger frame for heavier sprinter riders. And using Columbus SP instead of SL for the downtube for bigger frames. The thicker downtube was stronger/stiffer for bigger bikes and bigger riders. But today when you can have 3 inch diameter downtubes, its not necessary to not use butted tubing. Long ago everyone had to use 1.125 or was it 1.25 inch downtubes because that is what the lugs were. No choice.
> 
> Some folks might say butted tubing rides better than non-butted tubing. Livelier, springier, etc. Don't know.


When making this comparison you need to keep in mind that heavier butted steel tubes aren't just heavier in the center section, they are heavier all around:

Columbus SL steel - .9 ends, .6 center span
Columbus SP steel - 1.0 ends, .7 center span
Titanium butted - .9 ends, .55 center
Titanium straight guage- .9 straight 

The point being, the tube end thicknesses do more to make a tube stiffer than the center. If you made a tube that was .9/.7/.9, it wouldn't ride much differently than the SL tube.

Titanium tubing is still largely sourced from aerospace suppliers and equipment, so tube thicknesses of .9mm are the norm. .9 also seems to be what most builders see as the minimum wall thickness for absorbing welding heat damage. When ti is butted, the center of the tube is thinned, but .9 is left on the ends. Since the tube ends and outer diameter are the same between ti butted and straight, they ride pretty much the same.

And since Ti is 57% the density of steel, there is a much smaller weight penalty for leaving a straight gauge compared to doing the same for steel.

That 57% demonstrates what you have to do to make a steel bike as light as Ti. Since steel is stiffer than ti, if you can get the same stiffness by reducing the circumference and tube walls by a total of 57% of the whatever the Ti tube is, you'll match the weight. That's what S3 manages to do with very thin walls - but at the same outer diameter as Ti tubes you'd need to be butted at .51mm on the ends and .31 in the center. Which is why we didn't see this kind of steel tubing until the advent of air hardening tubing.


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## M77PT (Mar 6, 2009)

triple is better than double because it's more.


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## Bob Ross (Apr 18, 2006)

rx-79g said:


> Titanium tubing is still largely sourced from aerospace suppliers and equipment, so tube thicknesses of .9mm are the norm.



Totally OT, but now I'm curious: What are aerospace industries using titanium tubing with 0.9mm thick walls for?


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## rx-79g (Sep 14, 2010)

Bob Ross said:


> Totally OT, but now I'm curious: What are aerospace industries using titanium tubing with 0.9mm thick walls for?


Despite 11 years in aviation, I couldn't tell you for sure. Here's supplier's chart with .9mm wall tubing right in the middle of the range:
http://www.superiortube.com/tubing_sizetbl_metric.html

Titanium tubing is principly used for rigid hydraulic lines. If you're implying that .9 is thin for hydraulic supply lines, I can only guess that the thinner stuff is used for either return lines, oil lines or bleed air systems.


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## PlatyPius (Feb 1, 2009)

Moron Tubing - More on the ends. (a la Ibis)


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## Bob Ross (Apr 18, 2006)

rx-79g said:


> If you're implying that .9 is thin for hydraulic supply lines...


Oh no, didn't mean to imply that at all. What I should have asked is "What are aerospace industries using _any_ titanium tubing for? "


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## danl1 (Jul 23, 2005)

sdlesko said:


> Arn't they mainly for strength/stiffness without increasing weight too much? For a guy like me, 5'10" 160 lbs, i don't think there is an advantage...so why would I pay more for a frame like that?
> 
> Thanks
> Steve


Here's an answer. It's an answer about steel, but the two materials are similar enough that the fundamental answer remains the same. In fact, any differences would be magnified in steel, owing to it's greater density.

http://www.habcycles.com/m7.html


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## rx-79g (Sep 14, 2010)

Bob Ross said:


> Oh no, didn't mean to imply that at all. What I should have asked is "What are aerospace industries using _any_ titanium tubing for? "


Hydraulics. One 747 has a couple thousand bicycles worth of ti hydraulic line.


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## frpax (Feb 13, 2010)

I submit that if there were two frames, each identical in size and geometry, and one was made from butted tubing and the other from straight gauge, that you could not tell the difference, except on the scale. 

Build up both frames with identical components and the same wheels and ride one, then the other, and I still say you wouldn't be able to tell.


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## rockdude (Apr 3, 2008)

frpax said:


> I submit that if there were two frames, each identical in size and geometry, and one was made from butted tubing and the other from straight gauge, that you could not tell the difference, except on the scale.
> 
> Build up both frames with identical components and the same wheels and ride one, then the other, and I still say you wouldn't be able to tell.


You can't make this argument with tapered Ti.


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## Kerry Irons (Feb 25, 2002)

*Steel butting*



frpax said:


> I submit that if there were two frames, each identical in size and geometry, and one was made from butted tubing and the other from straight gauge, that you could not tell the difference, except on the scale.
> 
> Build up both frames with identical components and the same wheels and ride one, then the other, and I still say you wouldn't be able to tell.


You can make that statement if you like. I ran that experiment with steel frames many years ago, and it was relatively easy to tell them apart.


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