TiHabanero

Building a touring frame with a TT RC2 9-6-9 57.5 top tube and TT RC2 58 9-6 seat tube and only have an HOX Platinum down tube that is 8-5-8. The bike is intended for loaded touring. Based experience, do any of you see a problem with stability, shimmy or other when loaded using this light of a tube? Rider weight is 230, loads not to exceed 40 pounds, mainly on rear wheel. Will have front panniers, but only in use on cross country ride where load will certainly top 50 lbs. due to water and food requirements.

Andrew R Stewart 

Diameters? Andy

TiHabanero

Standard road diameters. 25'4 TT, 28.6 DT and ST. Will not be using any oversized tubing.

Nessism

I'd use something thicker. 1.0/7 maybe? 1.0 straight gauge?

Andrew R Stewart 

I have made a number of touring frames for myself and the wife over the decades. Traditional diameters with typical .9/.6 tubing. The early ones all shimmed when fully loaded (we carried over 70lbs each over Ebbits and Pacific Grade passes back in 1991). By the late 1990s I did the #3's, still with traditional diameters but now 1/.7 tubing (and thicker blades too). Better loaded stability but still some shimmy. Fast forward to a few years ago and generation 4 was produced with OS1 diameters and 1 1/8" steerer, the tires did go down to 26" though too. I hit a homer with this one. Solid and stable with over 80 lbs yet still nice to ride unloaded.

My take aways- I would never make another touring bike with a 1" steerer. I attribute a fair amount of the more solid feel of my #4 's to their stiffer steerers. There's not too much discussion as to the fork's contribution to the bike's handling (and I'm not talking about rake).
I would not want to make a loaded touring bike with less then .6 tubing walls in the center sections. Dent resistance being a big consideration. I've watched baggage handlers load our bikes onto trucks, planes, trains and boats and cringed at the bumping about they saw.
I like what's considered medium/long trail. My bikes have ranged between mid/upper 50's to mid/low 60's on MM of trail with 71 to 72,5 degrees of head angle.
I can scrape my front pannier bottoms on a U turn before I'll strike a pedal. So low BB heights are it. One spends a lot of time straddling the bike while doing that tourist's procrastination thing (drinking water, looking at the map, taking it all in around you). My #4 has about 10.3" of BB height.
"One bolt one job" My braze one are numerous with each bolt only having one accessory attached. No fenders on the same mount as the rack uses.
Last points aren't about the frame. Use components that are a generation or three old. Chains not too skinny, Shifters that are separate of brake levers. Cable routing outside of the frame with all the stops slotted to make field service easy. Bike weight is vastly over rated when fully loaded.

I have other opinions but these are some of the biggies. Andy

Doug Fattic 

Using a 1 1/8” down tube with 8/5/8 wall thickness for a touring frame will not work well - at all. Before OS tubing became available because of the popularity of mountain bikes, Columbus SP tubing was a popular choice for a touring frame. It has 1/7/1 wall thickness for the main tubes and the blades and stays are decently heavy too. Another option is OS 9/6/9 tubing.

What happens with lighter tubing is that the frame will sway around when pedaling under load making things seem unstable. In the 70’s I built a frame with Reynolds 531 standard tubing that had essentially a 1/7/1 (actually 19/22 wire gauge thickness) with a 9/6/9 top tube and I was not pleased with how flexible the frame was when loaded. And like Andy I’m not a very big or heavy guy. I then made another touring frame out of Columbus SP and was entirely happy with the results when it was loaded down with panniers and other gear.

TiHabanero

Thank you all for the input. One other frame I used RC2 for the whole thing. 9-6-9 main tubes, standard diameter. Used for commuting with loads never exceeding 20 lbs. It has done fine, however I know adding 40 or 50 more lbs to the bike will dramatically change how it deals with the weight. Looks like I need to order up some more tubes.

Seems I am getting spare tubes laying around here. Not sure how it happened, but I have some RC2 seat stays and head tube. Add to that some main tubes. Sure will find use for them some day.