What does butted mean?
 

I see some frames that say fully butted, some that say double butted and others that do not say anything? What does butted mean? What is the difference between double butted and fully butted? How does this effect strength and ride quality?

Also, what does butted mean for wheels?

Thanks,
Brian

Butted frame tubes are internally thicker at the ends where stresses are higher and thinner in the center. Butting makes tubes both strong and light. Double butted tubes are butted at both ends. Fully butted? I'm not familiar with the term.

As regards wheels, some wheels are built with butted spokes, which are, like butted tubes, thicker at the ends.

A tube without a butt has constant wall thickness; it is called a straight gauge tube. A single butted tube is thicker at one end; double butted tubes are thicker at both ends (each end of the same thickness); triple butted tubes have ends of unequal thickness; and quadruple butted tubes have ends and midsections of varying thickness. A fully butted frame means that the main tubes are butted with no indication as to how they are butted. My Trek 660 is made of Reynolds 531cs tubing and the sticker says "double butted frame tubes", which means that the main triangle is double butted. Frame manufactures never (at least to my knowledge) butt the rear stays or forks.

As a side note my sticker says the main frame, stays and forks are all Reynolds 531cs. Some times a bike manufacture will use one tubing manufacture for the main frame and another for the stays and possibly another for the fork-not a big deal! Richard Sach uses several different tube manufactures to construct his bikes that's why he doesn't put any stickers on his because his thought is it's not a big deal!

Butted tubes are lighter, stronger, and ride better.
Butted spokes are lighter and stronger and more reliable than straight-guage spokes.
It sounds counter-intuitive to remove metal, yet increase strength, but structures usually fail at the joins, and butted profile tubing helps to distribute stress away from the joins.

well, in members, there is a part where there is a stress concentration on a specific area, which means the area where this occurs will stressed more which makes it vulnerable to fracture.. This usually occurs at the joints. Removing material from the center actually decreases the stress concentration factor in the joints, which means a relatively stronger frame.

Depends who you ask :eek:

Butted spokes will have more stretch in the thin part so they will also give a more comfortable ride.

The butted spoke thing is controversal, according to Jobst Brandt who is one of the foremost wheel builders the straight gauge spokes are stronger; BUT I don't necessarly agree with him even if he might be right! Maybe if you weigh 250 pounds plus than a straight gauge spoke would be stronger. Don't forget spokes are solid and frame tubing is hollow and maybe that's why for frame tubing it's stronger to butt than it is for spokes. But I am not an expert in this, maybe someone else can shed more light on it.

I'm sorry but I have to...

Heh, heh, you said butt

Butt what?

...tocks :D