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Shift RD under load

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Old 01-22-09, 04:03 PM
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rdtompki
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Shift RD under load

I've asked a similar question on the road forum, but between using degrees instead of percent (engineer mis-speak) and generally getting politely abused I thought I would restate my question in the friendly confines of Clydeville. I have 105 brifters and RD on a Giant OCR1. Before I actually try shifting up/down under heavy load I'd like to find out if this really works.

situation - climbing a hill which varies from 6% to 12+% grade. comfortable sitting up to let's say 9%, but when it gets steeper I'd like to stand, but be in a higher gear 'cause the lowest gear doesn't feel right standing on the pedals. Can I shift under a load like this or do I need to get just enough momentum to back off, shift and stand? May be easier going from standing to sitting as when the grade eases I can probably accelerate a bit and downshift while I'm sitting down.

Feel free to tell me to just give it a try. After all, how much can falling at 6-8 mph hurt?
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Old 01-22-09, 04:33 PM
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hammond9705
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I always get just enough momentum to back off, shift and stand. I don't like to shift under heavy load. Not saying that the other doesn't work, it's just what I do.
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Old 01-22-09, 04:42 PM
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CACycling
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I back off when shifting as well. My wife, however, has no issue shifting under load. Of course, at 5' 9" & 130ish lbs., she isn't putting quite the load on the drivetrain as I do.
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Old 01-22-09, 05:08 PM
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It is better on the equipment to shift without the heavy load. Spinning is the best.
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Old 01-22-09, 05:35 PM
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Shifting under heavy load will likely work, but you'll wish it hadn't. The RD will sound like it's shearing teeth off the cassette and spewing them across the road... In general, I try to gain a little extra momentum so I can ease off while changing gears. Usually, a couple of big breaths and some extra effort for a couple of spins of the pedals are all that's required. The lightening-quick shifts with my SRAM Red RD and levers don't hurt, though...
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Old 01-22-09, 07:23 PM
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Thanks, all. I'll practice on a lesser grade and see how it goes. The 105 does does seem to shift well, much better than the downtube shifters I last used 20 years ago.
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Old 01-22-09, 07:39 PM
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think of it this way -- you have a clutch...it's your legs.

shifting without the clutch can be mastered, but it can also be a disaster and you'll kill a few trannies learning. doing it under significant load is even worse on the mechanics.
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Old 01-22-09, 08:52 PM
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This is the hill I'm working on. Have made it up to the 6+ mile point so far. Shooting for 1 mile/week increase in distance. Probably not much for folks who really ride in the hills, but the unrelenting nature of this is a challenge for an old guy just trying to get back into shape. It's hard to tell from the data without putting in more accurate track points, but there are some parts over 15%. The peak is a radio tower overlooking the area where I live. Should be some spectacular views. I'm going to start bring a camera. I pulled the gpx file off of mapmyride. Not very true to the road so I'll take some time to do a bit better or wait until I have a tcx file myself which should be in 6 weeks if it doesn't kill me.
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Old 01-22-09, 09:01 PM
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adrien
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you riding a double or a triple? What's your lowest gear?
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Old 01-22-09, 09:19 PM
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Road bike with a triple. Lowest gear is approx. 29 gear-inches. Ridden 1400 miles since August so I don't have a lot under my belt. Need to loose 20-25 lbs which should really help, did a lot of hill running and marathons into my 40's so I've got a good mind set for grinding away. I'm going to resist the temptation to up-size my cassette granny gear from a 27. On my normal rides I'm avoiding the small chainring to build up strength.
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Old 01-22-09, 09:50 PM
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Shifting the RD under load isn't (Or at least shouldn't) be a problem as there should be no load on it. Think of the chain route. It is pulling tight along the top run and slack on the bottom run. I shift under load all the time during stand up sprints with no issue. You do NOT want to shift the FD as it shifts the top run of the chain.
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Old 01-22-09, 10:39 PM
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Originally Posted by ScrubJ View Post
Shifting the RD under load isn't (Or at least shouldn't) be a problem as there should be no load on it. Think of the chain route. It is pulling tight along the top run and slack on the bottom run. I shift under load all the time during stand up sprints with no issue. You do NOT want to shift the FD as it shifts the top run of the chain.
You can certainly force it, with a modern driveline, but what's the point? There's nothing to gain, and you stand at least a small chance of doing the bike and yourself harm. No reason to abuse the parts when there's nothing at stake.
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Old 01-23-09, 04:56 AM
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I don't do it while "under" a load. But I do it while I'm in the middle of a load if that makes sense. If I'm standing on a climb and I need to shift, that means I'm already pushing it a bit. I just sort of time it where I soft pedal about half a crank rotation and do the shift as the pedal rides over the top of that rotation. No stress, noise etc. unless I get the timing wrong
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Old 01-23-09, 07:13 AM
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If my bike is under my butt does that count as being under load?

Save the wear and tear and avoid shifting under load whenever possible. You can do it now and again but don't make it a habit. Why not try downshifting before you hit the hill and spin your way up? Neglecting to use the small chain ring really does not impress people, your mashing your gears which is harder on your bike and harder on your knees. If you've got the gears use them.

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Old 01-23-09, 07:55 AM
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Rear derailers aren't under any load. The front is.
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Old 01-23-09, 08:35 PM
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ScrubJ
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Originally Posted by DieselDan View Post
Rear derailers aren't under any load. The front is.
Thank you!!! This is what I tried to illustrate in my first post regarding this. The greater the "load" on the chain, the more slack on the bottom run.
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Old 01-24-09, 07:05 PM
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Originally Posted by ScrubJ View Post
Thank you!!! This is what I tried to illustrate in my first post regarding this. The greater the "load" on the chain, the more slack on the bottom run.
Exactly. Your chainrings are pulling the chain toward the front of the bike. Take a coaster brake bike with a slightly slack chain, pedal it forward, then back pedal to apply the brake, then you will defiantly see ScrubJ's and my point.
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