I've been looking for a nice SS commuter for awhile and really liked the idea of a non-cromo steel frame. But I noticed that they didn't mention that the main tubes were double butted or tapered like the stays, so I gave them an email. They replied with my answer that it was in fact, not butted. Could there be any benefit to this or is Jamis just cutting corners?

the jamis is chromoly.

What does double butting mean to you?

It's Reynolds 631 which is not chromoly. And the main tubes are straight gauge. It seems all metal frames are butted except the high-tensile ****. Butted means lighter.

Butted means that the thickness varies. It's thinner where it doesn't need to be thick, saving weight. Hi-ten carbon steel frames are never double butted or triple butted. Most but not all 4130 cr-mo and aircraft tubing bikes are double or triple butted on one or more tubes. Some tubes may be steel welded to 4130. Some tubes might be straight gauge, some might be welded to double or tripe butted tubes. There are plenty of straight gauge 4130 bikes out there. It's not easy to determine. In the old days no one tig welded hi-ten steel. If it was tig welded you knew it was 4130. Lugs of course can't tell you anything. Same goes for aluminium bikes. The trek 1.5 series for example with their "white" aluminium is all straight gauge.

Reynolds 531 is a chromium-molybdenum alloy. Very similar to 4130. (1.5% Mn, 0.25% Mo, 0.35% C) but cannot be tig welded properly. 631 is covered in the link below.

So, not all metal frames are butted except the high-tensile ones. Aluminium or 4130, there are straight gauge bikes everywhere.

https://www.worldclasscycles.com/JACKSON-HOME.htm

bfd

From the specs page "Reynolds 631 seamless air-hardened chromoly main tubes"

My Sputnik rides just fine.. it's only around 20 lbs. Feels like a feather compared to my other bike.

Reynolds 631 is a manganese-molybdenum while 4130 is a chromium-molybdenum. Reynolds 631 is air hardened and gets much stronger after cooling as a result.

531 is basically the same as 4130. 631 is an improved version of 531, so it's probably not much better than 4130. At least not enough to base a purchase decision on. Reynolds 531 is not 4130, and Reynolds 631 is DEFINITELY not 4130. Reynolds brand names (531, 631, 853, 753, etc.) all refer to both a specific model of tubings, and the specific materials used to make them. Some are available in a variety of thicknesses and butting, and some are not. They are brand names.

4130 is a specific composition of steel, often simply referred to as "chomoly". It is made into tubing by a number of manufacturers in just about any thickness, butting, etc. that you can think of.

AISI 4130 Chromoly steel chemical composition (excluding iron which is the base element):

Carbon 0.28 - 0.33
Chromium 0.8 - 1.1
Manganese 0.7 - 0.9
Molybdenum 0.15 - 0.25
Phosphorus 0.035 max
Silicon 0.15 - 0.35
Sulphur 0.04 max

No one is saying that. But to say it had no chromium in it is a misnomer. It had chromium in it. 4130 is 4130. Even 4340 is not 4130. I should have said it was a manganese alloy, but I was trying to point out (badly) that all the different tubing alloys are close recipes compared to hi-ten steel.

As a c ticket welder I should have been clearer.

only a scale can tell the difference between 631 and 4130.

What kind of scale?

someone in the frame building forum found a frame decal that sad butted hi-ten. i am guessing most of us will never lay eyes on one however.

I'm just wondering why it isn't butted and if there could possibly be an advantage to it being straight gauge. I'm surprised by the lack of butting because even there model that's a step down (Beatnik) using 520 is butted.

The advantage is that straight gauge is usually cheaper, all other things being equal.

I'm not familiar enough with their line do know why they went with 520 on a cheaper model...

I've seen some old hi-ten frames that have had stickers stating they had butted tubing as well.

beatnik

Well someone at Jamis must be confused.. this is the sticker that was on the seat tube on my Sputnik. Says 'butted' right there..

What year is your Sputnik?

'10. Only had it a few months.