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Old 03-12-10, 06:45 AM   #1
wtgrantham
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Dropout adjusters

I have been working on vintage bikes for a couple of years but just realized I don't understand why rear dropouts have adjusting screws. When and why would you adjust the dropout???
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Old 03-12-10, 06:56 AM   #2
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Like the little "wings" on brake pads they just make wheel changes a little quicker.

They are obviously one of the things you can live without because so many bikes with horizontal dropouts don't have them.
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Old 03-12-10, 06:56 AM   #3
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You set the drop out screw to position the axle correctly WRT the RD, after that you leave it alone. Its purpose is to make wheel changes faster. With the screw in place you can simply chuck another wheel in there, tighten the q/r and send the rider on his/hers merry way. If you haven't got one you have to eyeball the alignment pretty closely before you can close the q/r. Doesn't mean much for a casual rider, but can be the difference between winning and losing in a race.
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Old 03-12-10, 06:58 AM   #4
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To adjust for chain length. When I went from 6 speed casette with 24 tooth cog to 7 speed with 28 tooth, I had to adjust the position of the wheel a bit forward in the drop out to accomodate the larger casette. With the wheel set farther back with the six spped, the chain was too short for 7 speed. The screws aren't strictly necessary since, once positioned correctly, the skewer will hold the wheel in place, but they make getting wheel positioned correctly when reinstalling a lot easier.
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Old 03-12-10, 07:52 AM   #5
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To adjust for chain length. When I went from 6 speed casette with 24 tooth cog to 7 speed with 28 tooth, I had to adjust the position of the wheel a bit forward in the drop out to accomodate the larger casette. With the wheel set farther back with the six spped, the chain was too short for 7 speed.
That's coincidental. If moving it in the dropout back the minor amount of a dropout length makes the chain too short, it was cut too short to begin with.
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Old 03-12-10, 09:34 AM   #6
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The horizontal dropout was originally for adjusting chain length, but not for derailleur bikes. They go back to the days before the invention of the derailleur when single speed bikes and internal gear hubs needed a slot for chain adjustment. The forward pointing slot was an improvement over the rear open (track) dropout for road and sped up wheel changes. When derailleurs were added, they were originally mounted with a bolted on hanger that fit the right dropout. (this is a shortened history of the evolution, which included a few side trips and unique designs that didn't last).

Whether for derailleur or non-derailleur slotted dropouts mean manual centering of the rim between the chainstays with every wheel change. The addition of micro-adjusters eliminates that step ensuring hat the wheel is correctly located every time. Later on horizontal dropouts were first shortened then done away with in favor of the vertical ones in use today for derailleur bikes. One drawback is that this makes changing a frame over to SS use more complicated.
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Old 03-12-10, 09:57 AM   #7
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All y'alls are right.

Multiple yeses. Yay!
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Old 03-12-10, 12:36 PM   #8
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That's coincidental. If moving it in the dropout back the minor amount of a dropout length makes the chain too short, it was cut too short to begin with.
Thats what I thought too so I added two links, but then the chain was clearly too long. So I took one out, but chain seemed just a bit too short. Then I tweaked the dropout screws and everything dialed in nice and tidey.
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