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Horizontal Dropouts: Why??

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Horizontal Dropouts: Why??

Old 04-30-22, 06:26 PM
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jolly_codger
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Horizontal Dropouts: Why??

As I was working on my winter project (`85 or `86 Schwinn Peloton modern build) I got to wondering why horizontal dropouts continued to be used so long. I can understand bikes before the widespread use of the modern rear derailleur needing the ability to adjust chain tension. I can't believe the purpose is to be able to vary wheelbase because i bet 99% of riders wouldn't be able to discern a difference of about an inch. Was it for frame builders to have room for error for slight mis-alignment? And don't get me started on the whole adjusting bolt & spring that end up seized since no one regularly fiddles with them. When you do get them out, the cursed little spring disappears to the black hole underneath the toolchest and you get to pay for an overpriced replacement set. There a lot of smart people who are regulars on this forum and I am counting on them to school me on the lowly horizontal dropout and the reason(s) for their reign lasting so long.
Cordially,
John
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Old 04-30-22, 07:32 PM
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My take is that in '86, Shimano and Suntour et al, were fervishly design/dancing to find the winning (indexed) drive train so some frame builders took those cues to heart, including a variable axle position in a horizontal dropout.
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Old 04-30-22, 07:58 PM
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Originally Posted by jolly_codger
...I got to wondering why horizontal dropouts continued to be used so long... Was it for frame builders to have room for error for slight mis-alignment?
John
Yes, frames built curing the classic era with limited and somewhat primitive tooling required horizontal dropouts with screw adjusters (or some kind of adjustment) to get the rear wheel to center. Any error in chain stay length gets magnified at the tire end of the wheel at almost a 3 to 1 ratio. Even today's modern and expensive fixtures don't guarantee a center wheel result.
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Old 04-30-22, 08:57 PM
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Originally Posted by Doug Fattic
Yes, frames built curing the classic era with limited and somewhat primitive tooling required horizontal dropouts with screw adjusters (or some kind of adjustment) to get the rear wheel to center. Any error in chain stay length gets magnified at the tire end of the wheel at almost a 3 to 1 ratio. Even today's modern and expensive fixtures don't guarantee a center wheel result.
i agree that a "horizontal" dropout allows a bit of error that won't be seen, but one of the definite origins would go to the first Campagnolo shifting mech, the Cambio Corsa and its children. There the teethed dropouts HAD to match left and right, Campagnolo even made a tool to assist.
about 1952-53 the Gran Sport mech was accepted enough to supersede but the. Basic design, now without teeth and with a forged derailleur tab, initially with 4mm adjusters, soon revised to 3 mm set the stage as THE defacto Italian dropout of choice.
then the advantage of integral no tool required adjusters was the standard.

it was so accepted that it became the signifiers of a quality frame, not always the case but helped. Marketing! Lygie, Atala, Italvega, Legnano all exploited it. The fork was short changed, but the rear dropouts were tops.

If Campagnolo had not taken a half hearted view of the "vertical" dropouts things may have moved faster. But builder alignment would still need to be better than with horizontals.
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Old 04-30-22, 09:19 PM
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Originally Posted by jolly_codger
Was it for frame builders to have room for error for slight mis-alignment?
Yes. It also offers versatility, allowing a frame to be readily used without any chain tensioners: this allows fixed gear, and also means that nothing kludgy needs to happen to support other non-derailleur drivetrain setups.

I think a better question is why *not* use horizontal dropouts?
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Old 04-30-22, 09:46 PM
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Originally Posted by repechage
i agree that a "horizontal" dropout allows a bit of error that won't be seen, but one of the definite origins would go to the first Campagnolo shifting mech, the Cambio Corsa and its children.
I'm not sure that that can be well-characterized as an "origin." The Cambio Corsa was a rare example of a derailleur that required a horizontal dropout, but it's not where horizontal dropouts started. For early bicycles, horizontal fixtures for the rear wheel were the norm, since they're the most minimal way to provide the ability to tension a chain. Track ends were initially more common, but by the 1930s, "modern" horizontal dropouts were making their mark; this meant that they were being used with all kinds of drivetrains, including derailleurs. For instance, here's a 1934 advertisement for Cyclo, showing their Witmy derailleur being used on a bicycle with horizontal dropouts.
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Old 04-30-22, 10:14 PM
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Additionally, horizontal dropouts can be used to adjust the relationship between the upper RD pulley and the large cog on the cassette/ freehub.
Pulling the wheel farther back into the dropout allows the use of a larger rear cog, all other things being equal..
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Old 05-01-22, 03:59 AM
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Horizontal Dropouts - Why Ask Why?

Horizontal dropouts probably date back to the 1880's with the introduction of Chain Drive Safety Bicycles - as opposed to "Penny Farthing" High Wheeler Ordinary bicycles.


A 1925 illustration was the earliest image of a modern style Horizontal Dropout that I could find.

There were several reasons for using Horizontal dropouts. The first and most obvious was for adjusting the chain to the proper length. Next was to adjust for chain wear. The early chains were probably made of lower quality steel than modern ones and wore faster. They were also probably a lot more expensive to replace by modern standards too.

Horizontal dropouts can reduce the necessity for accurate chain stay lengths. Many bikes that we assembled or worked on during the 70's frequently had differences in the lengths of the chain stays by up to 10mm, especially entry level Bike Boom models.

The problem wasn't limited to cheap bikes... One busy Saturday afternoon in 1977 someone brought a brand new all Campy Bob Jackson into the shop complaining that it pulled to the left. He'd just bought it from a mail order house in SoCal. It was black with ivory panels. The pin striping, lug lining as well as the decals were perfect! Out of curiosity and to quickly get rid of him I took it out for a quick test ride. After 50 feet I brought it back. The bike not only pulled but it wanted to go in a circle to the left.

I put it up on the stand an immediately saw that the left chain stay was almost 3/4" (20mm) shorter than the right. The fool started to give me a hard time about a bike he bought somewhere else so I quickly showed him which way the door opened!

Back on topic, I remember an early 70's ad in a bike magazine claiming the the head tube angle of their bikes could be adjusted by the position of the rear wheel in the dropouts thus adjusting the handling. Yes it's very possible if the slots in the dropouts are positioned at a significant angle relative to the ground...

Vertical dropouts have been in use for decades. They require a considerable more amount of attention to make sure that the chain stays are the same length an the dropouts are accurately positioned relative to each other. With the advent of Shimano's SIS system hub widths became more standardized and with it rear triangle positioning.

Most builders in the US used frame jigs so frame alignment issues were significantly reduced. Most UK builders and many on the continent took less caution in their construction. Just braze it and cold set it! The famous UK builder Jack Taylor bragged that he never measured anything... He just "eyeballed" the tubes then coldset them for alignment afterwards!

Dropout adjuster screws were a feature developed for quick wheel changes in competition. All of the replacement wheels were built to the same amount of dish and so on. Pull the old wheel out, put the new one in and move it back to the stop screws. 10 seconds and gone!

One other thing, I was always puzzled buy the cheap stamped steel dropouts used on some high quality British frames like Mercian, Holdsworth and so on ...

Finally the answer that I got from some esteemed folks in the UK... Those dropouts allowed an owner to use SS, Fixed Gear, and an Internal Gear Hub like a Sturmey Archer or... a Derailleur on a claw hanger ??? All of those could have been done with Campagnolo or Zeus forged dropouts. Penny Wise and Pound Foolish???

Simplified answers...

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Old 05-01-22, 05:18 AM
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Old 05-01-22, 05:41 AM
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Tradition... That Too!

Originally Posted by Bianchigirll
….


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Old 05-01-22, 06:17 AM
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Originally Posted by HTupolev
I'm not sure that that can be well-characterized as an "origin." The Cambio Corsa was a rare example of a derailleur that required a horizontal dropout, but it's not where horizontal dropouts started. For early bicycles, horizontal fixtures for the rear wheel were the norm, since they're the most minimal way to provide the ability to tension a chain. Track ends were initially more common, but by the 1930s, "modern" horizontal dropouts were making their mark; this meant that they were being used with all kinds of drivetrains, including derailleurs. For instance, here's a 1934 advertisement for Cyclo, showing their Witmy derailleur being used on a bicycle with horizontal dropouts.
In the 1930s, derailleurs were the exception, not the rule. Even flip-flop hubs were an expensive upgrade. But even with a normal hub, horizontal dropouts accommodated whatever gearing a user wanted.

Post WW2, it was an interesting time. Campagnolo dominated the Italian market, but Simplex made inroads in Italy by using Coppi. I don't think there was much cambio corsa outside of Italy & and maybe some Swiss builders. And some French builders, at least Herse, were using vertical dropouts soon after WW2. When the Gran Sport was the derailleur in 53, Campagnolo ruled the roost. Whatever he wanted to make was then the standard. But from 45-53 (arguably 51 when the GS first came out but didn't dominate until 53), anything could have happened. It was an interesting period in bike history.
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Old 05-01-22, 06:56 AM
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Originally Posted by HTupolev
I'm not sure that that can be well-characterized as an "origin." The Cambio Corsa was a rare example of a derailleur that required a horizontal dropout, but it's not where horizontal dropouts started. For early bicycles, horizontal fixtures for the rear wheel were the norm, since they're the most minimal way to provide the ability to tension a chain. Track ends were initially more common, but by the 1930s, "modern" horizontal dropouts were making their mark; this meant that they were being used with all kinds of drivetrains, including derailleurs. For instance, here's a 1934 advertisement for Cyclo, showing their Witmy derailleur being used on a bicycle with horizontal dropouts.
the "need" for the Campagnolo form factor " horizontal " dropout was gone by 1953 and still endured for decades.
there were others, no question. Gloria had a handsome frame end.
Campagnolo set the standard to which others copied. Availability? Marketing? No matter.
Campagnolo did have market dominance.
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Old 05-01-22, 08:36 AM
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The reason that horizontal persisted for so long was that there was no need or desire to change them. Bicycles. particularly high grade bicycle were steeped in European tradition, until the outsiders ( Japanese and Americans) invaded their turf.

The high grade European bicycles were built on the artisan philosophy. An apprentice serves with a master craftsman, who teaches him the "correct" way to build a bicycle. One did not deviate from the master's method. While this approach results in fine product, it also stifles innovation. Whatever creativity a novice has at the start of his apprenticeship, is often diminished to point of near non-existence by the time they are ready to set up their own shop. Besides, why change something that works perfectly fine.

There is also the matter of sporting regulations, which often discourage innovation or at least limits it. When recumbent bicycles and bicycles with streamlined fairings demonstrated that they could shatter existing records, the UCI promptly banned them. When derailleurs started being popular with racers, Desgranges banned their use in the Tour de France for almost a decade. For a while, he even issued standard bicycles to every competitor, so that no rider gained an advantage due to his equipment. When disc wheels were introduced in the mid-1980s there was a huge outcry to ban them. Whenever, some outside-the-box-thinker, such as Graham Obree, came up with a revolutionary idea, they would often create new rules (or interpret existing rules) to make it illegal.

The net result of the deep tradition and regulations was that innovation was typically incremental. There were exceptions but it was rare. Whenever there was true innovation, it was rarely widely accepted by the consumer, if it had not trickled down from the ranks of pro cycling.

Things started changing with the arrival of the Americans and Japanese at the high end of the sport. They were not mired in the European mindset. They pushed the boundaries, within the rules, and found commercial success, to the point where the Europeans could no longer sit on their laurels, They were forced to innovate or die. The late 1970s started what would be a golden age of innovation in the cycling industry.

One of these Japanese innovations is what led to decline of popularity for the horizontal dropout. Shimano's SIS indexed shifting system proved to be major commercial success and led to many copies. However, correct chain gap is one of the critical parameters for optimum performance of indexed shifting systems. Reports of poor indexing could often be traced to an owner or mechanic who had inadvertently changed the axle position in the dropout, thus altering the chain gap. The move to vertical dropouts mistakeproofed this parameter and drastically reduced indexing related complaints.

As to the origin of horizontal dropouts, I strongly suspect the origin was prompted by the invention of the pneumatic tyre. An axle slot with the opening at the front end makes it easier and quicker to remove and install the wheel. Frequent punctures were an accepted fate on early, unpaved roads, so the advantage of quicker wheel removal and installation was substantial in competition. It became de rigeur when racers started utilizing flip-flop hubs, with a fixed fear on one side for relatively flat terrain and a larger freewheel on the opposite side, for ascents and descents.

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Old 05-01-22, 09:12 AM
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Hmmm. It would take Shimano a number of generations of index shifting to spec out a derailleur mounting tab that migrated away from the Campagnolo standard. Even then it was not much. I think there is a turning point soon though with the changes seen in the most recent mechanisms.

like the braze on shifter bosses, that battle was done with The 7400 group, Shimano adapted to the "Campagnolo" standard. Doing a nice job of encapsulating it.
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Old 05-01-22, 10:06 AM
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I understood dropout design to be mostly driven by race needs. Track ends that open to the back and are still used on track bikes and now, many single speeds and non-velodrome fix gears have been around since the first chain driven safety bikes. Horizontal dropouts opening to the front came along to make wheel changes faster and easier, especially with the then brand new concept of derailleurs. (Note - derailleurs were driven by racing. Racers had been changing gears in mountainous races for probably two decades before the first derailleur but it was by stopping and flipping the wheel around to a different cog. Those bikes HAD to have a horizontal slot for the hub to set the chain "tension". (Tension in quotation marks because it is always the proper chain slack that is sought.) After the freewheel was adopted for racing, a chain tensioner (basically a derailleur that doesn't shift) could be used. Now, I have never learned whether European racing adopted freewheels before the derailleur that required them. I know racing on the road stayed fix gear in this country until the derailleur took over in the 30s (by which time US racing was basically dead).

The word I heard when I was racing in the mid-70s was that vertical dropouts had taken over in pro racing because wheel changes were faster. Indexing had nothing to do with it; in fact it was years before it even existing at the racing level. My 1979 Peter Mooney wold have been vertical dropped except I requested horizontal dropouts. So I could run fix gear if I ever chose. (For the first 38 years, I second guessed myself on that many times. - until I set the bike up fix gear. What a ride! Now is a road fix gear in the elegant English tradition with a second life as a triple crankset gravel bike.)

The discussion I see there is interesting but misses the driving timeline of pro racing. The vertical drop switch was driven there before Shimano was even a player in the pro road scene, never mind SIS.
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Old 05-01-22, 10:24 AM
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The primary reason to have horizontal dropouts is to discourage too much power output at startup. If set up correctly, with the proper quick release (preferably a blingy external cam version), the rear axle should slip slightly so that the rear wheel locks onto the chain stay and dumps the rider.

Modern dropouts, or modern thru-axle holes, emasculate the cycling experience by removing this simple reality check, and this is why such bikes are disqualified as vintage.
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Old 05-01-22, 10:28 AM
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Originally Posted by jolly_codger
As I was working on my winter project (`85 or `86 Schwinn Peloton modern build) I got to wondering why horizontal dropouts continued to be used so long. I can understand bikes before the widespread use of the modern rear derailleur needing the ability to adjust chain tension. I can't believe the purpose is to be able to vary wheelbase because i bet 99% of riders wouldn't be able to discern a difference of about an inch. Was it for frame builders to have room for error for slight mis-alignment? And don't get me started on the whole adjusting bolt & spring that end up seized since no one regularly fiddles with them. When you do get them out, the cursed little spring disappears to the black hole underneath the toolchest and you get to pay for an overpriced replacement set. There a lot of smart people who are regulars on this forum and I am counting on them to school me on the lowly horizontal dropout and the reason(s) for their reign lasting so long.
Cordially,
John

Keep your hands off my horizontal dropouts. I LOVE them.

Yes, I actually do love them.
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Old 05-01-22, 10:50 AM
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Horizontal dropouts are what allowed me to calm the steering response of my 1979 Fuji Professional.
It's a big 59cm and with steep angles, though fits me perfectly with the original, oddly-short (9cm) Nitto Crystem (but which leaves relatively little weight on the front tire).
Moving the axle back 1cm (after photo was taken) definitely made a quite-noticeable improvement, now it's a favorite ride of mine!

Horizontal dropouts also can accommodate wheel-clearance issues, such as when a frame gets bent or a spoke breaks out on the road!
Also useful for accommodating fenders in some cases.
One concern might be that the rear brake pads may contact the tire after axle is moved, so re-positioning the pads may be necessary.

One more (theoretical) advantage might be that a derailer mounting claw can be used in a horizontal dropout slot if perhaps the original hanger becomes damaged or was "Drewed".

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Old 05-01-22, 11:30 AM
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Originally Posted by T-Mar
..... Besides, why change something that works perfectly fine.
I'm assuming that this comment was made with tongue in cheek??

For the most part, it did. Still, most of us have had paint rubbed off of the inboard side of the left chainstay after the axle slipped. This was more of a problem with chromed dropouts. The problem was largely fixed with good quick releases, and serrated locknuts on the hub axle helped maintain a good grip on the dropout too.
A quick photo showing the locknut on a Campagnolo Record hub...




Another issue with horizontal dropouts relates to fenders... having to slide the wheel forward to remove it usually means that the front of the rear fender has to be spaced further out than otherwise needed. Not a functional problem, but it does look goofy.

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Old 05-01-22, 11:44 AM
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I personally find horizontal dropouts give me the ability to ride different tire sizes and with varying chainstay lengths. Useful on a couple on a couple of '80s bikes that will take 33mm cyclocross tires (aft-most position), or 25mm road tires with a tighter rear triangle. Believe me = I can tell the handling differences between knobby 33s and supple 25mm tubulars inched toward the seattube. For those who can't appreciate the versatility or tell the difference between a fat or skinny tire - well, ... sympathy for you all. Vertical dropouts = best reason for N+1+1. Enjoy.
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Old 05-01-22, 12:25 PM
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Originally Posted by HTupolev
I think a better question is why *not* use horizontal dropouts?
Because the hub can slip on these drop-outs. If you tighten the QR too much then the bearings start to bind.
The vertical/fixed dropout is much more foolproof.
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Old 05-01-22, 01:56 PM
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Originally Posted by 79pmooney
I understood dropout design to be mostly driven by race needs. Track ends that open to the back and are still used on track bikes and now, many single speeds and non-velodrome fix gears have been around since the first chain driven safety bikes. Horizontal dropouts opening to the front came along to make wheel changes faster and easier, especially with the then brand new concept of derailleurs. (Note - derailleurs were driven by racing. Racers had been changing gears in mountainous races for probably two decades before the first derailleur but it was by stopping and flipping the wheel around to a different cog. Those bikes HAD to have a horizontal slot for the hub to set the chain "tension". (Tension in quotation marks because it is always the proper chain slack that is sought.) After the freewheel was adopted for racing, a chain tensioner (basically a derailleur that doesn't shift) could be used. Now, I have never learned whether European racing adopted freewheels before the derailleur that required them. I know racing on the road stayed fix gear in this country until the derailleur took over in the 30s (by which time US racing was basically dead).

The word I heard when I was racing in the mid-70s was that vertical dropouts had taken over in pro racing because wheel changes were faster. Indexing had nothing to do with it; in fact it was years before it even existing at the racing level. My 1979 Peter Mooney wold have been vertical dropped except I requested horizontal dropouts. So I could run fix gear if I ever chose. (For the first 38 years, I second guessed myself on that many times. - until I set the bike up fix gear. What a ride! Now is a road fix gear in the elegant English tradition with a second life as a triple crankset gravel bike.)

The discussion I see there is interesting but misses the driving timeline of pro racing. The vertical drop switch was driven there before Shimano was even a player in the pro road scene, never mind SIS.
A couple of things to the best of my knowledge.

First, open in the front horizontal dropouts appeared after WW!, maybe before, but at least a decade before derailleurs. Prior to WW1, many/most race bikes hade open in the rear/track horizontal dropouts. Also, in France, derailleurs were driven by bicycle touring, in Italy their use was driven by racing. Next, multi-speed freewheels were available and in use before derailleurs. I have seen them s early as 1923. You just had to stop your bike to change gears. And while the first generation Vittoria Margherita is only a chain tensioner, you can shift by using your fingers to move the chain from one gear to the next. There is no reason to stop and dismount so I would qualify it as a derailleur.
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Old 05-01-22, 01:58 PM
  #23  
El Chaba
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Flexibility. It’s a concept that is almost completely lost with modern bikes. When I started racing as a junior in the mid 70s, and was carefully watching everything that the better Senior riders were doing, I saw a number of them who would move the wheel forward for a criterium or move the wheel back for a long road race. I think that there is a small difference in the way a bike handles as a result, especially with a relatively short wheel based racing frame. As others have mentioned, you can also “cheat” the capacity of a racing derailleur by moving the wheel back all the way for some extra cog clearance. I think that the greatest benefit that I have experienced myself, though, was the ability to take a spare wheel that may have been dished a little off…You can tweak the positioning to get the wheel centered in the chain stays even if it is a bit off….and it gets you back in the race ( or ride)…The same thing is useful if you break a spoke as sometimes you can mess around with the wheel position to get it in a spot where it doesn’t rub….
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Old 05-01-22, 02:15 PM
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Mr. Spadoni 
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Any design that requires that use of a specific component rubs me the wrong way. Case in point….I’ve got a 1980’s bike with vertical drop outs. It originally came with 20c tires. I quickly switched to 23c after a bunch of flats. Now I run 25s on it and have to be careful that I don’t use a “wide” 25 or the tires won’t fit. Now if they had just used horizontal dropouts, I’d have some flexibility.
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Old 05-01-22, 02:37 PM
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Polaris OBark
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Originally Posted by Mr. Spadoni
Any design that requires that use of a specific component rubs me the wrong way. Case in point….I’ve got a 1980’s bike with vertical drop outs. It originally came with 20c tires. I quickly switched to 23c after a bunch of flats. Now I run 25s on it and have to be careful that I don’t use a “wide” 25 or the tires won’t fit. Now if they had just used horizontal dropouts, I’d have some flexibility.
Modular dropouts.


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