FarHorizon

I've searched BF, Google, & Sheldon Brown's site for about a half-hour, now, but can't find the answer I'm seeking.

I have a Nishiki steel-tube frame. I need to buy some clamp-on cable stops & guides. I've loaned my calipers to a friend & can't measure the diameters directly. The bolt-on clamps come in various sizes.

So what is the OD of the top tube? Of the down tube?

Thanks - FH

dabac

The pressed-metal - not the CNC-ed or cast ones - tend to have a bit of fudge room.
Cut a thin strip of paper. Wrap around tube. Mark where it begins to overlap. Remove, roll out flat and measure with a ruler. Divide by Pi. Go shopping.

JohnDThompson 

A traditional, non-French, non-mountain bike road frame will have a 1" top tube and 1-1/8" down tube.

Retro Grouch 

If you have a big crescent wrench, clamp it around the tube that you want to measure. Measure the distance between the jaws.

FarHorizon

MOST EXCELLENT idea, @dabac - Thanks!

FarHorizon

Alas - no large crescent either...

Retro Grouch 

I'm 90+% confident JohnDThompson is right because he usually is. 90% isn't 100% and I've been stung on odds like that before. If it was my bike, I'd use dabac's method to measure.

IthaDan 

Wrap a piece of string/dental floss around the tube. Measure that length, divide by Pi. I'd be rather surprised if the diameter didn't come out to be 1 1/8" or 28.6mm.

E: or use a piece of paper like dabac said.

FBinNY 

Nishiki steel frames conform to the traditional steel frame standards John posted earlier. 1" top tube, 1-1/8" down and seat tubes.

FarHorizon

Thank you kindly - Mr. John D. Thompson was correct - 1 and ⅛ inch diameter = 28.6 mm

fietsbob

Nobody Measures anything for them selves It seems .
1" 1.125" ,1,25" 1.5" unless the frame is French from a particular Era


then its 25.28 ,30 something ... just rounding off the equivalent Fractional size. to the nearest whole MM.

IthaDan 

To piggyback on this- ever notice how prevalent 25.4mm, 28.6mm, 31.8mm and 34.9mm are for sizes? That's because the sizes translate to 1" 1.125", 1.25" and 1.375"

I'd love to hear the story of why a metric dominated industry follows imperial tubing sizes so closely, I have a feeling it's something along the lines of the campagnolo 10mmx26tpi axle threading- Stock availability after the war and new, 'superior' [fractional inch] allied machine tools.

LesterOfPuppets

I'm sure there are plenty of reasons why tubing manufacturers are/were reluctant to go metric.

IthaDan 

Right, but why would columbus (for example) have ever been imperial in the first place?

fietsbob

The French Metric Breakaway was swallowed up by the Fractional tube Peloton and then they had to either Join the rest, so as to have an export Market , or quit.

LesterOfPuppets

I obviously don't have any details or clear answers but it could be because they wanted to make tubing that would fit the most commonly available lugs, headsets, BBs, etc. Or perhaps they originally purchased their tube making equipment from a supplier that only produced stuff in English units...

I guess both of those could possibly apply, but both are just guesses of course.

FBinNY 

You have to factor USA and UK dominance in bicycles prior to WWII. That established numerous standards that others followed for convenience in cross fitting of parts and frames.

Until fairly recently, people were reluctant to depart from standards because the cost of tooling to make multiple versions of things was too high. So lug makers in Italy produced to UK standards because they wanted to sell their products to folks who used Reynolds tubing (regardless of where). Then tube makers followed suit so they could sell to people using those lugs. Everyone was happy to play the follow the leader game, because life was easier that way, so things like FD clamps, bars, stems etc tended to follow imperial standards (even if described in metric terms).

As long as we're dealing with lugged steel frames, there will be resistance to depart from the established imperial standards, after all, who goes first? Welded frames would be easier to change to alternate dimensions, and as we know, that cat is out of the bag with carbon fiber, but it still crates issues for the likes of clamps and clamp-on accessories.

You car argue Metric System superiority, but in many cases, the benefits are minimal compared to the cost, confusion, and hardship a changeover would entail.

As an example, the first ISO standard for BBs was so-called Swiss standard 35x1 with right/left threading. This was intended to combine the R/L benefit of the British system with the politically correct metric thread. Naturally it made a world of sense especially because Switzerland was such a major producer of bicycles. Naturally the bike world totally disregarded that, and slowly migrated to the BSC standard. Eventually the ISO came around and recognized the BSC standard as the ISO standard.