Bicycle Mechanics - history of straight bar diameter vs. drop bar diameter?

Well, like the title says - anyone know why the diameters of the two bars are different? Drop bars have a larger diameter - is it because of all the twists and turns in them or is there just some historical bit about it? Or, why did they start making straight bars in a smaller diameter... pain in arse with internal hubs and drop bars since everyone is hot on twist shifters now... <shrug> just curious.

With drops, the rider, when on the brake hoods or on the drops, can generate considerable rotational torque at the handlebar stem clamp. The larger this diameter, the more effectively the friction between the clamp and the bar can counter this torque. Unless you have climbing pegs or other extensions, it is very difficult to generate anywhere near as much torque on a straight bar. All else equal, a larger-diameter bar is also stronger than a smaller-diameter bar, and component-stressing road racers all use drop bars.

By the way, it is very simple to install a shim to enable a drop-oriented stem to accommodate a straight bar.

By the way, although everything is pretty well ISO-standardized by now, in the bad old days there were two different diameters for drop bars, as well.

I have an old Raleigh road bike. The original drop bars are smaller diameter that the typical bars of today. The clamp diameter is the same as mountain bars. These origianl bars were steel.

Why, I don't know. Just a data point to consider. Drop bars haven't always been as large as they are today.

I have an old Raleigh road bike. The original drop bars are smaller diameter that the typical bars of today. The clamp diameter is the same as mountain bars. These origianl bars were steel.

Why, I don't know. Just a data point to consider. Drop bars haven't always been as large as they are today.


That's right. I recall a lot more double wrapping of the drop bars back in the "continental II" days. They are so much nicer today.

With drops, the rider, when on the brake hoods or on the drops, can generate considerable rotational torque at the handlebar stem clamp. The larger this diameter, the more effectively the friction between the clamp and the bar can counter this torque. Unless you have climbing pegs or other extensions, it is very difficult to generate anywhere near as much torque on a straight bar. All else equal, a larger-diameter bar is also stronger than a smaller-diameter bar, and component-stressing road racers all use drop bars.

By the way, it is very simple to install a shim to enable a drop-oriented stem to accommodate a straight bar.

By the way, although everything is pretty well ISO-standardized by now, in the bad old days there were two different diameters for drop bars, as well.

Well, welcome to the bad new days then. I have seen at least 3 different sizes of bars in recent years. ISO or not, this is still the bicycle business. We pride ourselves on doing something different just because we can. As a dealer, it drives me crazy. As a rider, ditto. but as an avowed Contrarian, I find this against the grain attitude curiously appealing.

I thought it was becuase the mountain biking is a more american thing, so the bar clamps are 1'' (25.4mm) and the euros were more involved in road bikeing, so they made the drop bar a metric measurement (26.0mm).

Now, however, I think that companies intentionally make different clamp diameters so tht they don't work with other manufacturers stems. I suppose it is kinda smart, becuase a bar/stem combo that is particularly stiff or high performaing might not perform as well with a different system...so people don't go around bashing their products becuase they used them wrong...plus it makes people buy both components so they make more money...

I dunno bout some of you, but I found handling a road bike in slow speeds extremely difficult because of the width of the handlebars. Maybe it was because I'm used to having straight bars on my mountain bike (and we tend to ride slow a lot).

There are still 25.4 road bars available from "Nitto" and a few French companies. It wasn't too long ago that Cinelli made 26.4 bars while 3TTT and seemingly everyone else made 26.0. This was odd because the Cinelli bars and some of those other companies were actually made in the same factory.