BigPoser

I putting the finishing touches on a new build and it will have a sleeve for the ST. The ST itself is 1.125.

For a sleeve, will a 1.25 OD tube with a .049 wall work well or should I use a 1.25 OD with a .058 wall?

Thanks in advance.

Brandon

Nessism

Math suggests the thicker tube would be better.

CliffordK

1.25 = 31.75mm
.049 * 2 = .098 = 2.49mm
.058 * 2 = .116 = 2.95mm

So, your sizes are:

31.75mm
29.26mm
28.8mm

So, looking at common seatpost sizes:
31.6 & 31.8 are available (no sleeve)

You can probably source 29.2 and 28.8 seatposts, or thereabouts, but they are less common.

Let's see:
(31.75 - 27.2) / 2 = 2.275mm ==> 0.0896 tubing.

So, you might do better with either no sleeve, or some pretty thick 0.089 tubing (27.2 seatpost).

BigPoser

Thanks guys. I think I should have clarified that the sleeve will be for the outside of my ST. I'll have a 27.2 post.

Doug Fattic 

You need a 1 1/4" tube with a wall thickness of 0.058". If it is .049" there will be too much space between the inside of the bigger tube and the outside of the smaller tube for proper brazing clearance.

BigPoser

Thanks Doug. That's what I had figured. I have some here so that's good. Likely have it turned down just a tad for my liking.

Doug Fattic 

Turning it down on a lathe from .058" to around .040" is fairly common.

unterhausen

yes, turning it down is almost required, it's far too clunky otherwise.