semi-horizontal drop-outs

[AngryScientist]

what is the reason why most road frames no longer use semi-horizontal dropouts? the idea of being able to have a built in method of chain tensioning on any frame is pretty cool, is there a technical reason this style was moved away from?

[rodcad]

When researching cross frames I recall one complaint about Surly Cross Checks being the dropouts because the wheel could potentialy slip in them. Could be one reason.....

[bicycletricycle]

fender are easier with vertical dropouts

[ultraman6970]

+1 rodcad. Well the design with short dropouts looks cooler too but then if you want to put tires too big they might not fit with short dropouts.

[christian]

Indexed shifting requires a near-fixed relationship between the jockey wheels/parallelogram and sprockets in order to maximize shift performance. That's why vertical dropouts became more popular in the 1980s/1990s. Though my 1996 Merckx shifts just fine...

[palincss]

They're a royal pain in the a$$ if you have fat tires even without fenders, but with fenders and fat tires you often have to deflate the tire to remove and replace it. What's more, the wheel can slip in the dropout and get canted sideways from the pull of the chain, which can at worst cause the tire to rub against the left chainstay which will not only feel like you have the brakes on, but will also wear the paint right off the stay. Their only virtue is ease of using an internal geared hub.

[Fixed]

i asked bill shook that once he told bike builders got better and did not need to be able to move the rear wheel around .. they could put it where they wanted it . i was skeptical


cheers

[Kirk Pacenti]

Originally Posted by Fixed

i asked bill shook that once he told bike builders got better and did not need to be able to move the rear wheel around .. they could put it where they wanted it . i was skeptical


cheers

I think there may be some truth in this, but index shifting is probably the main reason.


Cheers,

KP

[christian]

Originally Posted by palincss

What's more, the wheel can slip in the dropout and get canted sideways from the pull of the chain, which can at worst cause the tire to rub against the left chainstay which will not only feel like you have the brakes on, but will also wear the paint right off the stay.

This usually only a problem if you use crappy external-cam skewer.

[Mark McM]

Vertical drop-outs first became common on MTBs, for two reasons: Many of the 2nd wave of MTB builder/designers didn't come from traditional road backgrounds, and didn't see the need the carry over traditional design features like horizontal/semi-horizontal dropouts; and the smaller chainrings found on MTBs produced much larger chain forces greatly increasing increasing the chances of the wheel slipping in the dropouts with horizontal dropouts.

(As a side note, 130 mm axle widths as discussed in another thread were also first on MTBs ... well, at least on singles, as this width had already been used on tandems.)

Indexed shifting actually slowed down the adoption of vertical dropouts to road bikes. Traditionally, the derailleur hanger bolt was positioned directly below (and sometimes a little ahead of) the axle. This was easy to manage on a horizontal dropout, but presents obvious geometry challenges on a purely vertical dropout. The semi-horizontal dropout was an intermediate response to this design problem, but eventually derailleur and dropout designs were evolved to accomodate full vertical dropouts.

(Another, smaller contributor to the adoption of vertical dropouts on road bikes was the growth in the popularity of titanium frames with 6Al/4V dropouts. It was found that traditional QR axles didn't grip these dropouts as well as steel or aluminum dropouts, causing Ti bike manufacturers to have to adopt vertical dropout designs, further promoting the move to the vertical dropouts on road bikes.)

[palincss]

Originally Posted by christian

This usually only a problem if you use crappy external-cam skewer.

Except that even something as nice as an early 90s XTR skewer can be accidentally tightened insufficiently, allowing this (i.e., wheel getting out of alignment due to chain pull) to happen. Look at the left chainstay on my Kogswell P/R and see.

[palincss]

Originally Posted by Mark McM

Vertical drop-outs first became common on MTBs, for two reasons: Many of the 2nd wave of MTB builder/designers didn't come from traditional road backgrounds, and didn't see the need the carry over traditional design features like horizontal/semi-horizontal dropouts; and the smaller chainrings found on MTBs produced much larger chain forces greatly increasing increasing the chances of the wheel slipping in the dropouts with horizontal dropouts.

It's not like vertical drop-outs first came into use on MTBs. They were a feature of French touring and randonneuring bikes in the 1950s and even before, but we didn't see many of those here in the USA.