Why not one on both sides? Why have one at all? Is it a mfg deal to allow other component setups? Does a half inch shift in wheelbase really have a significant impact on the handling? All that I can see that it accomplishes is making it more difficult to install/center the rear wheel.

Was this on an indexed-shifting bike? I think the point here was to make sure the axle ended up in the same place every time, ensuring that everything played together consistently. Part of the reason why vertical dropouts eventually took over.

You could have one on each side, and adjustment screw equipped dropouts do just that. By having at least one it provides a reasonably repeatable wheel placement and its easier to pivot off one side than just have both sides float to place the wheel.

The horizontal dropout design is a legacy from single ratio bikes and then the Campagnolo "Cambio" shifting systems. It was expected essentially. There is also the truth that making a vertical dropout frame requires a bit more effort, things must be more exact. Plenty of frames of "top tier" quality require one of the adjustment screws to be a bit more set back to have the rear wheel sit straight.

85 Nishiki Cresta.....suntour symetric shifters. Wouldn't the axle be in the same place every time by simply pulling it to the rear of the drop out?

The reason it's only on the right side drop-out is because , I think it's the back side locating mount for a derailleur hook. It fits on the inside of the drop-out and the hook is on the outside.

...maybe? There's no guarantee that the back of the dropouts are aligned perfectly enough that the wheel will end up straight if you do that. And the ideal spot for the rear wheel is somewhere in the middle of the dropouts anyway -- putting it back further increases the chain gap, and having it too far forward reduces the wrap angle on the freewheel/cassette cogs. Putting in a dropout spacer (which is probably cheaper than drilling/tapping the dropouts for adjusting screws and supplying said screws) is a convenient way to make that middle position the default, while still allowing the user to align the wheel.

Position of the axle in a horizontal dropout can be critical to rear derailleur performance.

True, but the OP's picture shows a "fixed" spacer - ie non-adjustable - so effectively its just a shorter horizontal dropout in his case (and in this case not for the derailleur claw since you can see the dropout has an integrated hanger).

I supposed one could move the spacer forward and tighten, but most of them seem designed to fit right up against the closed end of the dropout. And what if the optimal position for the RD is further back than the spacers allows (I know, take it out!)

My similar Miyata Two-Ten has them on both sides. And the right side one is not part of the derailleur. I'm stumped too. Best guess is they do the same thing as adjuster screws - - to have a quick setting for keeping rear wheel angle straight. In fact, I think they can even be adjusted a bit. But I was wrong once.

The drive side spacer maintains a proper relationship between the cogset and the derailleur pulleys by putting the axle in the middle of the dropout... these really date to a time when derailleurs did not always have an angle adjustment screw / B screw which made axle position critical for optimal performance.

I guess my issue is the extra attention required to align the rear wheel, but how often does that happen on a touring bike? I'm finishing up the rehab and so the rear wheel has been on and off much more than it will usually. Chain wrap had not occurred to me and a half inch has a significant impact. I may have a bike or two that need these.

no.

All early PX10s, PR10s and PA10s have two. Also all of the early Gitanes I'm familiar with. My Japanese Peugeot MTB with Suntour dropouts has two. They make it quick and easy to install the wheel straight.

Some bikes only have one. That means that you have to make sure the tire is evenly spaced beween the stays.

I prefer two, but can live with one.

Not to say never, but I have never seen the case where having the axle at the back of the dropout makes for better shifting. It has always been the case shifting is better in the vertical dropout position.

I imagine the horizontal dropout is a legacy to when derailleurs were uncommon. There was no derailleur to pick up chain slack and the horizontal dropout allowed to pick up slack less than a half of a chain link. Try making a fixed gear bike with vertical dropouts. It is a dance between the chain, front ring and rear cog that usually doesn't work out well.

Agree with both points....and also referring to 65'rs comment, these things were in use for years, and it seems to me if a frame builder wanted to keep the axle in the optimal position, they'd have been spec'ing vertical dropouts a lot sooner. To me looks like a chintzy engineering bodge, and also speaks to the thought that the average owner has no ability to adjust things correctly.

Anyway, I suspect the consensus is correct in that the horizontal dropout was a holdover from the fixed/coaster/IGH days where some adjustability was needed in the drivetrain, and fashion (or fear of changing fashion) kept builders using them forever; and for those frames that didn't spec the high end adjustable dropouts, sticking an ugly spacer in was a suitable course of action (/Flame suit on)

Obviously it is a cheap-out as compared to having adjuster screws, but also is more robust against rough handling or corrosion.

There is a bit of extra time spent when trying to get a pair of these axle-stop things adjusted to keep the wheel centered. Sometimes I even use a few swipes of a rattail file to achieve the final adjustment.
Also, these things seem to get knocked out of adjustment on occasion, from their contact with the axle.

My biggest beef with this type of adjuster is that, since it is on the driveside, you sometimes get interference with the freewheel on wheels where you have carefully optimized the axle spacing to achieve the minimum of driveside axle protrusion.
So, after trying to build the strongest wheel (for best rim dish and shortest axle protrusion for less stress on the axle), upon installing the wheel, I end up having to spend much extra time sculpting the nut or bolt-head portion of either the claw hanger or the axle stop with a Dremel grinder, so that the rotating freewheel body won't bind against the hardware on the inside face of the dropout. This has been an issue with the various Asian freewheels that I prefer.

I believe that a single axle stop is always put on the driveside because of the chain tension being applied there, otherwise it would make more sense to perhaps use a single axle stop on the non-drive side, since the driveside axle would end up in the right spot as the wheel was centered.
The driveside chain tension really doesn't make centering the wheel (with the axle stop installed on the non-driveside) that much more difficult however, as long as one heaves down on the saddle with their shoulder while centering the wheel and tightening the nuts or the QR.
I use knees, toes, shoulders and hands in different combinations when working on different-sized bikes, in order to settle the wheel in straight while securing the axle. Some are not so easy, especially when dropout alignment is sloppy or when the axle nuts use fixed, integral toothed washers.

Yes, but that's not necessarily the optimum position for the wheel to maximize shifting performance.

On frames lacking an integral derailleur hanger on the dropout, the bolt-on "claw" acts as the spacer, and the non-drive side slot would have a spacer to help ensure proper wheel position.

But so few claw-mount bikes even have the non-driveside adjuster, no? I know that I've had to add a few on...


Country of origin seems to be a big factor, as I think Grand Bois mentioned.

---My Schwinn Supersports have claw only, while my older or cheaper French bikes have the claw, plus an axle stop on the non-driveside.

---Then there's my Austrian Steyr Clubman, with claw only.

---Lastly, a couple of my Japanese bikes have an integral derailer hanger dropout, with a cast-in axle-stop in the driveside dropout only.

Hey Thumpic, you are second guessing on Old stuff, and asking answers

about what choices of small parts some one else made . in the past.

why are you worried so? take it off and be done with it.

..not so important, particularly on Friction shifted Bikes ..

You simply pay attention to where you put the axle in the dropout when the QR gets tightened.
they make pieces like that for those who dont have a care about that stuff,
you apparently do care, so its not required.


new bikes with Vertical Dropouts are benefitting the index shifting,
by having the wheel backin the same spot,

and if the QR is not really tight ,. the axle wont pull forward. ..
like can happen with Horizontal ones.

For those of us who try to get the most performance out of older bikes, who select parts carefully, and who may go to the trouble of adjusting the A-B tension ratio of more difficult-to-adjust derailers, having the axle positioned foreward accurately can be well worth tinkering with imo.

Friction shifting has so much potential today with the availability of modern chain and cabling.

Schwinn installed a Huret ref. 849 dropout spacer on the non-driveside of Super Sport, Sports Tourer and Superior models with forged Huret dropouts. You can see one on this '75 Sports Tourer:



This subject was previously discussed here: https://www.bikeforums.net/showthread...-Position-Safe

I can't quite see, but did these dropouts have a Huret tensioning stop along the bottom, or was it perhaps campag-style for any modern derailer?

I like the better forged dropouts, but sort of prefer the painted forks that came on the 1971 plain-dropout model SS's that I've found.

Those dropouts had the Huret "4:00" stop vs. the Campy "7:00" stop on later models. Schwinn used forged dropouts on the Super Sport for several months into '71, so there were examples made with the forged dropouts *and* painted forks. So far the latest one I've documented had an "FG" (June '71) frame.

Thanks for confirming that! I have long believed that it only either was one combination or the other!

And it seems like it would be quite easy and minimally cosmetic to sil-solder a stop tab anywhere along the bottom edge of a derailer hanger, if someone wanted to change between Campag and Huret.
Ok, so I'm sort of a Huret freak, and for no particularly good reason. I'm reasonably happy with the claw, and with keeping my kickstand and my all-steel crankset, since those rings shift so well even with 9-sp chain.
At least with the claw, one can adjust the derailer's B-pivot position to match a smaller freewheel using a file, with the result then being reversible by installing a new claw.
The long-cage Allvit usually found on these Supersports also have a thicker claw-tab to hold the derailer more vertically, so as to clear a 32t cog, and the shifting can thus feel lazy.
I always change those out to a standard Allvit claw and then file it some to match the particular freewheel's largest cog, either 26t or 28t.