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Old 03-04-14, 05:57 AM   #1
bradtx
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Does it really matter..

..which set of lower attachment points for a rear rack are used? Any protocol? Fenders for the blue bike were attached inside the dropout.

Brad

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Old 03-04-14, 06:23 AM   #2
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I use the higher point (like the black bike) for my rack. My intuitive engineering sense makes me think this is a stronger point for weight-bearing. In reality it probably doesn't make any difference. My fenders go on the outside of the other attachment point. I think its a bad idea to mount anything inside the drop.
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Old 03-04-14, 09:56 AM   #3
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I use the higher point (like the black bike) for my rack. My intuitive engineering sense makes me think this is a stronger point for weight-bearing. In reality it probably doesn't make any difference. My fenders go on the outside of the other attachment point. I think its a bad idea to mount anything inside the drop.
I'd go the opposite to get a lower center of gravity. Because bicycles have a high center of gravity, anything to lower it is a plus.
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Old 03-04-14, 10:03 AM   #4
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I don't think it matters unless it makes it a bit easier to fit the upper rack mount. But I concur with bradtx, mount the racks outside the dropouts.
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Old 03-04-14, 11:45 AM   #5
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mount the racks outside the dropouts.
given the drive cog is on the other side , not much choice ..
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Old 03-04-14, 03:26 PM   #6
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The racks are mounted on the outside of the dropouts as there is no alternative. The fenders (RIP) were mounted on the inside and there was no drivetrain interference, actually not even close to interfering with the chain or cassette.

Thanks for the advice, I have to redo the upper attachment points for the rack on the black (Actually a dark cherry, poor photo. ) bike and I'm going to move the rack to the lower and more rearward dropout position as I think lowering the load is a good idea.

Brad
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Old 03-05-14, 04:05 AM   #7
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The racks are mounted on the outside of the dropouts as there is no alternative. The fenders (RIP) were mounted on the inside and there was no drivetrain interference, actually not even close to interfering with the chain or cassette.

Thanks for the advice, I have to redo the upper attachment points for the rack on the black (Actually a dark cherry, poor photo. ) bike and I'm going to move the rack to the lower and more rearward dropout position as I think lowering the load is a good idea.

Brad
I've always tried to go for the lower mounting point when there are two options. On the Topeak racks I use, I've sometimes cut the legs off just above the pre-drilled hole, then drilled a new one to lower the rack even further.

There are two benefits -- obviously the lower C-of-G if it matters, and more room under the seat for top-of-rack stuff. You do still need to make sure there is enough room under the rack to (a) clear the tyre and (b) still leave room for any fender you want to fit.

Attaching the stays for the fender may also require some creative bending to clear the stays of the rack. There is nothing more annoying than the tune of stay vibrating against the rack. You also need to make sure that if the bottom of the right pannier extends sufficiently far enough downward, it doesn't interfere with the rear derailleur and its cabling.

Just some observations based on experience.
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Old 03-05-14, 05:33 AM   #8
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Racks go on the top, fenders on the back, both go outside. If possible I like to have fenders mount on the rack. The structural argument is real, the center of gravity argument is a little fanciful given how much control one has over that by packing and other means. And given the influence of body weight and position.
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Old 03-05-14, 07:29 AM   #9
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Racks go on the top, fenders on the back, both go outside. If possible I like to have fenders mount on the rack. The structural argument is real, the center of gravity argument is a little fanciful given how much control one has over that by packing and other means. And given the influence of body weight and position.
The center of gravity argument isn't fanciful...for exactly the reason you give. Tiny shifts in the center of gravity can have a large impact on bicycles. For example, shifting your center of gravity rearward 4" and down 2" (roughly) doubles how much deceleration you can develop during braking. Small shifts in weight can also have an impact on the steering of the bike. And that's on unloaded bikes. Putting a load on a bike changes lots of handling characteristics. Every other vehicle that humans use work better if you lower the center of gravity and bikes are no different. If anything, our center of gravity is much higher than all other vehicles we humans use to begin with. Anything that lowers the CG is a good thing.

As for the structural argument, breakage of brazed on rack tabs is rare. Breakage of the type of mounts that bradtx almost never happens. Racks don't break that often either. What's to gain by going to the higher mounting point?
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Old 03-05-14, 09:26 AM   #10
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Racks go on the top, fenders on the back, both go outside. If possible I like to have fenders mount on the rack. The structural argument is real, the center of gravity argument is a little fanciful given how much control one has over that by packing and other means. And given the influence of body weight and position.
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The center of gravity argument isn't fanciful...for exactly the reason you give. Tiny shifts in the center of gravity can have a large impact on bicycles. For example, shifting your center of gravity rearward 4" and down 2" (roughly) doubles how much deceleration you can develop during braking. Small shifts in weight can also have an impact on the steering of the bike. And that's on unloaded bikes. Putting a load on a bike changes lots of handling characteristics. Every other vehicle that humans use work better if you lower the center of gravity and bikes are no different. If anything, our center of gravity is much higher than all other vehicles we humans use to begin with. Anything that lowers the CG is a good thing.

As for the structural argument, breakage of brazed on rack tabs is rare. Breakage of the type of mounts that bradtx almost never happens. Racks don't break that often either. What's to gain by going to the higher mounting point?
Structurally, I agree with MassiveD.

I have never seen a dropout where the two eyelets are four or more inches apart, usually they are maybe an inch or less. I am curious to know what bike has the rear eyelet 4 inches behind and 2 inches lower than the upper eyelet.

For best handling, I find that a lower center of gravity AND also putting the center of gravity as far forward as practical while still far back enough to avoid any heel strike problems is best. If my panniers are too far back or too high, the bike feels too much like a wet noodle.

Inside vs outside, on my bike with an internally geared hub I have my fender stays inside because on this bike there is a lot of internal clearance. My derailleur bikes I have the fender stays on the outside of the dropouts to avoid any problems with the chain shifting onto or off of the smallest cog.

Since I tour with a different rack than I use the rest of the time around home, I mount fenders to the dropouts, never to the rack.
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