Sliding Dropouts Question

[tnort...@gmail.com]

So we are currently cycle touring in Europe and I am riding the frame I built this Spring. I designed and had laser cut sliding rear dropouts in case I ever want to go IGH.

But as we have been riding Ihave time to ponder. So my pondering is should the sliding dropouts be parallel with the ground?  On my wife's Dutch touring frame they are not and. slope up

So your thoughts??

Thanks, 

Tom

NE Ohio 

Presently in Fulda,Germany 

[tho...@kokopedli.com]

a consideration is keeping the b.b. height (& frame/sterring angles) consistent when moving the rear wheel...

This is a reason many horizontal rear drops are not parallel to the ground ...

 

noMadic   Thomas

 

 

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[tho...@kokopedli.com]

I might have said that unclearly, but the fact is that the rear axle is usually not the same height as the b.b. axle height, so geometry is involved ...

 

noMadic. thomas

 

 

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[satanas]

It depend on what sort of brakes you have. On road bikes with rim brakes the dropout slots were historically angled slightly so brake reach wouldn't change much with wheel position. On track bikes with rear facing horizontal dropouts retrofitted with brakes this could be a problem if gearing varied much, i.e., with a flip flop hub and significantly different sprocket sizes. This could potentially mean needing to adjust the pads or (worst case scenario) having to use a different brake caliper. For road going fixed gear bikes IME forwarddl facing and slightly sngled dropouts make life easier, especially if fenders are involved.

If you have disc brakes or other hub brakes there's no reason AFAIK why horizontal shouldn't be fine, and that would avoid (very) minor changes in frame geometry.

Later,

Stephen

[Mark Bulgier]

Stephen wrote:

> horizontal [...] would avoid (very) minor changes in frame geometry.

I'm guessing you'll agree (based on your "very", above) that the geo changes are hardly worth talking about.

By contrast, not making you readjust your brake pads, on a bike with a rim brake, is a real thing, a practical goal.

Yes, with a typical road dropout (slanted slot), if your pedal is barely clearing the track with the wheel forward and then you move it back, it lowers the BB a little and now you're hitting, oh no!  But why not just make the BB high enough for clearance with the wheel all the way back?  Is it so terrible if the pedal then clears the track by a bit more when you move the wheel forward?  Don't even start with the angle changes causing the handling to feel different — there's never been a human who could detect such a small change.

I went to some lengths to make sure the slots were totally horizontal on track bikes, but that was a tradition thing.  I was under no illusions that there was anything special about zero deviation from horizontal.  It was just what people expected to see.  If someone later drilled the bridge for a brake, then I screwed up, the design is now suboptimal in a noticeable way, even though the rider wouldn't blame me for it. ("Hey, it's a track bike")

Fausto Coppi was mostly known as a road man, but he won a shit ton of track races too.  His track bikes had road dropouts, with the typical slanted slot and forward opening, and it didn't seem to slow him down any.  I respect that, and wish I'd had the guts to make track bikes like that.  Sensible, but trackies would have stayed away in droves.  Seems to me that trackies are even more susceptible to magical thinking than roadies. Especially sprinters, those guys are psycho.

Mark Bulgier

Seattle

[Stephen Poole]

Any difference in geometry would be measurable or calculable but, as you say, insignificant.

Having to readjust the brake when you flip the hub over or running out of slot to do so is painful though, and I've had this issue.  :-(

Later,

Stephen

[tho...@kokopedli.com]

there it is, rim-brakes, I KNEW it had SOMEthing to do with geometry...

   My mind is/was to fuzzy to remember which geometry and Mark nailed it.

The geometry of rim-brakes!   That's what I was half remembering and to fuzzy these days to pull it together...

 

noMadic. T

 

 

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