how much does weight affect shifting?
 

I've always wondered this because shifting on the repair stand never matches up well with road performance. I figured it was my own ineptitude, but today one of the best mechanics at a particulalry sharp LBS tuned my RD but when I went to ride it, it dropped a chain into the spokes on my first shift.

so I am wondering whether lots of weight like mine (275#) makes a real difference to a shifter. setup is 10-speed Shimano

Technique matters - are you shifting under full load? That's not the best strategy. pedal easily when you're shifting.

What do you mean dropped a chain into the spokes?

I mean I shifted to the top cog and the chain overshot and landed in the spokes. I fished it out, but I once destroy a wheel this way.

Like he said, shifting under any load is a bad idea, and the heavier the load the worse it gets. Shifting my bike on the stand, it is dead silent. No matter what gear I'm in, if I'm riding then I'm constantly trimming to get it to stop making a faint noise, so it could just be a difference of stand vs. real use if you're not shifting under load.

I had a problem with derails when shifting to the small chain ring. I was easing off a lot when shifting. The guy at the LBS suggested keeping at least a little force on it while shifting, and it helps.

I'd suggest that you need to get the stops set properly on your derailleur or you may loose another wheel, derailleur and the hanger. Shifting under load does make shifting harder but even under a load it shouldn't drop off the inside cog between it and the spokes. That tells me that your derailleur is dangerously close to the spokes in your rear wheel.

Weight doesn't matter.

How fast the cranks spin and what sort of pressure is involved make _huge_ differences, as does where the other derailleur is positioned when you're shifting. You may also over-shift more or less when actually on the bike than when you work the lever on the repair stand, although your particular failure is an incorrect low limit setting on the rear derailleur or maybe a bent hanger (as the derailleur rotates about the upper pivot the bent hanger means it's moving in and out too).

You set the rear derailleur up so that with the chain on the small (double) or middle (triple) ring the screw is 1/4 turn out from where it's far enough in to cause problems shifting to the largest cog when you pull the cable with your hand.

+1.....find a better mechanic. I'd bet you that chain will drop on the stand as well if the mechanic had tested/simulated the inner shift properly.

Better set that low limit screw properly and soon, like right now. ;)

OK, don't tell me, he's a real sweet guy who is really nice to you when you go into the shop so you take him twinkies once a week. All that is fine but it doesn't do squat as far as preventing expensive damage to your wheel, derailleur and frame. :D

On thing I have learned is to shift at the right time which means, for example, if I have to shift on a climb, I shift when the right leg is starting the up stroke. Takes the pressure off the drive train.

+2

hey.... dont bring twinkies into this!!!!!!!!!!!!!!!!! :)

Technique is everything. I started out around your weight and thought the same thing until someone on a group ride talked to me about my shifting timing and technique. Now most of my shifts are smooth as glass but I still get a clunk if I'm too slow downshifting on a steep hill or if I shift while trying to accelerate. Anticipate the gearing you'll need and shift while you still have plenty of momentum going up hills or into the wind. Soft pedal for one full crank rotation during a shift whenever possible, with some practice you can even do this during a sprint without a loss in acceleration.

I guess I'm not aware of a bike that is mechanically sound that would toss your chain into your spokes. You might have a worn/broken derailleur, have it looked at by a better mechanic. You shouldn't have to change cycling technique to keep your chain out of the spokes. Could be it's just a simple adjustment.

The guy I go to has about a 50% rating on Yelp. Those looking for a "sweet guy" totally rip the shop. Those like me, willing to learn something, and don't mind a little gruffness now and then constitute a "following".

Chain in the spokes and poor shifting are two different issues. The chain in the spokes could be caused by a damaged derailleur or hanger as you stated, but is more commonly caused by poor adjustment of the limit screw. The L limit screw should be adjusted to allow easy shifting into the largest cog but no more. I usually do this by tightening it down while turning the pedals until the RD shifts into the second cog. I then back it off until it shifts back into the largest cog plus about 1/4 to 1/2 turn. I've never lost a chain into the spokes yet with this practice.

Poor shifting can be a derailleur problem, an indexing maladjustment, worn cog/chainring/chain, or poor technique. If the bike is mechanically sound and properly adjusted, shift problems are often associated with shifting under load, cross chaining, or poor timing.

I consider setting the DER's on the bike stand as a prelimenary adjustment.
It seems I typically need to give the barrel adjuster a partial turn to get things in the "sweet spot".

I haven't had a twinkie grade school!!!LOL

I had a twinkie high school! :D