Evolution of the rear dropout
 

Hello all,

I've been wondering why over the last 25-30 years rear dropouts have gone from long horizontal, to short horizontal, to the veritcal we have on most modern frames?

I assume that the long horizontal design is a hold out from the early, early Campy derailer system. I've also read that it allows you to tweak your wheelbase and bottom bracket height. Although this seems apocryphal to me.

I was under the impression that less material = less weight

The long horizontal sort allows you to adjust your rear wheel so that it's as close to the frame as possible without touching (as this could vary with the tire), thus improving aerodynamics.

Some bicycles still have this - - I think the fancy Cervélos...?

Dropouits are the bendiest parts of the rear triangle so short ones are much stiffer.

- Indexing gears require a fixed axle position for best performance, so dropouts got shorter and then vertical.
- Lightweight QRs don't hold as well as the older style, so verticals become almost mandatory.
- The quality of production frames has gradually increased, so less need to skew the wheel in the frame.

That, and you needed the long horizontal dropout for chain adjustment on single speed bikes.

Yup. SS became rare as everyone became able to afford a reliable, good derailer, so makers stopped caring about making their frames SS-friendly. They rather made the dropouts more derailer-friendly and foolproof (loose QR, anyone?). Given how SS/fixed is spreading like wildfire, horizontal may come back from the grave. I hope it will.

Most, if not all, of the modern SS/fixed bikes I've seen use track ends. Even the ones with road geometry. The Bianchi San Jose For example.
http://www.bianchiusa.com/typo3temp/d60b7fd765.jpg

Of course. So what? We're talking about geared bikes here, and it'd be nice to see gearie frames that are SS/fixed-capable.

Oh, thanks for the newsflash! :lol:

Ah, the power of the internet is astonishing.

One thread with one question, and several answers that all sound pretty definitive.

;)

I agree that several reasons for the change are probably appropriate since things rarely change in an industry for one single reason.

However, I must throw in my vote for the origins. I strongly suspect that they were originally horizontal simply for adjustability and chain tension. They appear to me to be a hold over from when everything was single speed...

Not to adjust wheelbase, not to increase aerodynamics, not to change bb height...

Could people through the years have individually tweaked their wheel positions to accomplish these things to some degree? Sure! But i strongly suspect that none of these were factors in the original design decisions.

I thought I was the only one who knew this! I'll post more pics as I find them. :-P

Exclusively?

My thought on why frames have gone to vertical dropouts is because the modern bike buyer wants to look like a racer thus they buy racing frames. Manufactures know this, so they had to tighten up the frame geometry, and if they installed horizontal dropouts you wouldn't be able to get the wheel off due to making contact with the seat tube. My Trek 660 is an example of that, though it has long horizontal dropouts I have to flatten the tire then press the tire against the seat tube to remove it; if it had vertical dropouts it would be easy to remove the rear wheel without having to flatten the tire first.

But before anyone shoots me on those comments, I'm just guessing.

Bang!

http://z.about.com/d/politicalhumor/...rror_alert.jpg

Well at least he's a bad shot and I'm still alive! :D

ok. french touring bikes were the first to have vertical drop outs, put in place to ease wheel removal, and because horizontal drop outs only support the axle in a very minimal way, leading to axle breakage. the french touring bikes were way ahead of thier time, and colnago or cinelli, i cant remember which, were the first to reinvent, and universally popularize the vertical dropout, which again, was only used on a limited number of very high end custom french bikes. the vertical dropout has been around in this respect since the late 1930s. ostesibly old racing bikes had semi-horizontal drops for wheelbase adjustability, but its more likely they had them to ease production, and because old non indexed derailluers didnt need the accuracy of a vertical dropout. touring bikes couldnt use the semi horizontal because of all the weight carried on a touring bikes rear wheel. does that help? it has nothing to do with weight.

its not aerodynamics that short chainstays are good for, its shorter wheelbase, therefore less flex. however, super short stays make a bike handle like crap, see cervelos and how many crashes they are involved in. short chain stays good, super short, bad.

I can't see what the shape of the dropout has to do with how the axle is supported. That makes no sense to me.

I would expect that a vertical dropout helps maintain the position of the cassette relative to the rear derailleur thus keeping the shifting geometry consistent for reliable indexed shifting.

ok lets think about this: if a crank arm was supported on only 1/10th of its internal surface area, would you expect that crank arm to fail or not? the stress is concentrated rather than spread out. its simple. a vertical dropout wraps around 50 percent of the axel, spreading force around.

Better to be hunting with Dick Cheney than driving with Ted Kennedy:D

What does Storck know that everyone else doesn't?

http://www.cyclingnews.com/photos/20...D_0.8_dropouts

they know that no one riding thier bikes weighs more than 180lbs, for one thing. they know how to make light dropouts. they know that a horizontal dropout that has no adjustment snugs the rear axel against the frame, wrapping as much of the axel as a vertical drop out.

Indeed, please let's do think about this. The axle is not supported by its tiny area of contact with the dropout, regardless of whether that point of contact is curved or straight. The axle is supported (in its full circumference) by the locknut which is held against the dropout by the opposing nut on the quick release. Those two nuts, with knurled surfaces, pinch and hold the dropout. The threaded-on locknut on the inside of the dropout is what holds the axle in place. The quick release just holds that locknut against the dropout and won't let it move. The support of the axle has nothing to do with how much of the dropout "wraps around" the axle. Nothing to do with it. And most certainly, the shape of the dropout has nothing whatsoever to do with axle breakage.


Irrelevant.

then why :) do axles break far more often in horizontal drop out arrangements? the quick release is made to purely hold the wheel in place, not to provide structure. i can bend a qr in my hand. we are talking about vertical loads here, not horzontal ones.

I've been riding and racing bikes since the early 70's and I have never seen any dropout break other then in an accident. So even though the strength thing makes sense, and yes it does make sense, I've never seen a dropout break even on heavy loaded touring bikes or when clydesdales were riding on horizontal dropouts. Maybe that problem may have happened to cheap WallyWorld or Sears bikes etc but not on the better bikes. In fact most bikes I ever saw fail was when strong clydesdale types put too much torque on the frame then the frame would seperate, but most of those breaks happened to older AL frames and the frame snapped usually in the BB area.

I would appreciate not being called names. Name calling and insults have no place here. (Thanks Mods for removing the offending words)

Please stop and think for just a moment about what I said. Please. I did NOT say that the quick release bears any of the weight. It does NOT. It simply holds the knurled nuts together, and THEY (the knurled nuts), by *pinching* the dropout opening, support the axle. The only time an axle will contact a dropout in any way traumatic enough to cause it to break, is if it is LOOSE. That is not the case under normal circumstances. The locknut and the quick release nut hold the axle in place, and the locknut, threaded onto the axle, is what supports it. Can you get that? The dropout opening, whether horizontal or vertical, does NOT support the weight of the bike on the axle in any meaningful way. It's a guide for the positioning of the axle, and it provides a structure for the locknuts to grip. That is what it does. Axles typically break at the point where the bearing cone is threaded on, because that is where the stress is. Not in the dropout.

Ridelugs,
I'll take a stab at answering your question (even though you didn't ask nicely)..

Axles break more often on older freewheel hubs, where the drive side bearings are further from the dropout than the non drive side. It just so happens that these hubs are usually in horizontal dropout frames.

and perhaps to a lesser extent, if a wheel is dished incorrectly, the wheel may be placed in a horizontal dropout crooked in order to centre the rim in the frame. This may put nasty force on the axle, making it more likely to fail.

- Joel