Clydesdales/Athenas (200+ lb / 91+ kg) - phantom upshifts?

question: is upshifting under a load more likely with a heavier rider, or is this more of a factor of the condition of the bike and cables? My GF is having a lot of problems with this in her bike and I'm concerned that the bike might just not be stiff enough for her. She's wanted to "do something to get in shape" but hadn't found what that was until I convinced her to drag out her old bike (maybe 3-4 year old Trek crossover type thing) and go on a ride with me, and I think she really took to it but I'm concerned that it really won't be fun for her unless she can trust her equipment. Unfortunately for her she is simply built large, she'd be anorexic at what most people would consider a normal weight for someone of her height. (I'm in kind of the same boat, but don't have near the problems with my Cannondale CX bike. I'm about 195 at the moment, and again, don't particularly want to lose a whole lot of body mass but have only had 2-3 of these shifts and I ASSume that if I simply lube the cables and adjust everything correctly that the issue will go away.)

I seriously hope that the answer isn't "buy another bike" because that probably would be a turnoff for her...

Check your cable tension. That would be my first suggestion, that it may just be time for a tuneup. ;)

Cable adjustment makes all the difference in the world. You should have the barrel adjusters that can fine tune it. I had the same problem, and fixed it with the barrel adjusters at the brifters on my bike. It really doesn't take much of an adjustment to fix the problem. If you don't feel comfortable with it, take it to the LBS and they can do it in a few seconds.

Cable adjustment makes all the difference in the world. You should have the barrel adjusters that can fine tune it. I had the same problem, and fixed it with the barrel adjusters at the brifters on my bike. It really doesn't take much of an adjustment to fix the problem. If you don't feel comfortable with it, take it to the LBS and they can do it in a few seconds.

And, if you don't know how to do it, ask them to show you. It's a simple adjustment and easy to do.

I would highly recommend learning how to make simple adjustments and repairs to your bike. It's very gratifying to ride a bike that you know how to tweak.

http://cdn.overstock.com/images/products/P3649106.jpg

On my old $100 mountain bike, it would do that when the thingie was adjusted so that it was sort of in-between gears. It would stay on one or the other, but could pop off one onto the other when you put some power into it. Along with some unpleasant grinding gnashing noises, I might add. Part of that was cheap components that flex under load, part was being out of adjustment, part was my Clyde strength at work :)

Up shifts occur as you release tension on the cable.
It may be that you need to add a bit of tension to the cable adjuster. Give it 1/2 turn and see what happens.
You may also need to clean/lube the cables if they are sticking a bit.
This is a much simpler problem than if you were getting phantom shifts in BOTH directions!

well I posted too soon. started to clean it up today and noticed that the chain was completely mangled - twisted a good 20 degrees at one point. Unfortunately my next guess which was that it needed to be lubed at the bottom bracket was a non-starter as this bike actually has full length cable housings from the shifters to just before the derailleur. Got a new chain from bike shop; needed an excuse to go there anyway as she wanted some gloves and I needed some other little bits. I guess I'll just have her ride it again and see if it's any better and if it's not hand it off to a bike shop for a "tune-up." I have no idea if the mangled chain was a result of or the cause of the problems.

Dang thing looks like it's brand new too...

You might need as new cassette too, a mangled chain can cause heavy wear.

please don't tell me that... ASSuming she mangled the chain yesterday (I think I know when it happened, just not sure) and not before it probably only has 3-4 miles on it like that though.

I assume it's a SRAM cassette as most of the other stuff is SRAM; are they interchangeable with Shimano stuff?

Follow up: finally stopped raining long enough to get a ride in yesterday evening and the problem is gone with the new chain. I guess it must have been mangled before and I didn't notice it.

Even more amazingly, she called *me* from work and wanted to know if we could go for a ride as soon as she got home. I dunno if it's some weird drive to get in shape, or she's actually enjoying riding, but I'm not going to argue with it. I just hope she gets more comfortable with it soon as her riding speed is, um, a little "sedate" but seeing as she's essentially just starting out I can't complain too much at the moment.

please don't tell me that... ASSuming she mangled the chain yesterday (I think I know when it happened, just not sure) and not before it probably only has 3-4 miles on it like that though.

I assume it's a SRAM cassette as most of the other stuff is SRAM; are they interchangeable with Shimano stuff?

Most of Shimano gear is interchangable. A rear cassette if needed should not cost you too much money.

Just take a good long look at the chain links and the rear cassette. SRAM componates can take a little more abuse than the lower end equipment.