Shifting problem

[OakLeaf]

Well thank goodness for Sheldon then.

I don't know why the forum software is only showing a thumbnail of the chart at 80 rpm ... but you can click on the link for the 90 rpm chart.


Shifting under load (i.e. avoiding same) isn't that complicated. Catrin, has someone already explained that to you? The bike won't shift smoothly if you're putting a lot of pressure on the pedals, which makes the top of the chain super tight. Shifting under load can cause the chain to drop, it puts excess wear on the drivetrain, makes an awful noise while you're doing it (but not afterward), and can even cause immediate damage in extreme cases. When you shift, you need to be pedaling, but back off the pressure and soft-pedal. Ever shift a car without using the clutch (or with a worn-out second gear synchro )? You know how you have to get your RPMs in the right place to sync, then take your foot off the gas while you throw the gearshift? Same idea.

It can be tough when you're climbing a steep hill and realize that you've waited too long to downshift. The hill was steeper or longer than you realized when you chose your gear, and now you're going 4 mph at 45 rpm and you have a lower gear that you really want to grab. I know I occasionally wind up in that situation. When you shift, take as much load as you can off the pedals without falling over...

Still ... I can't see how shifting under load would pull the FD out of alignment unless the clamp was loose to begin with - especially on a steel frame where you don't have to be quite so ginger about the clamp torque. And I really don't think a FD could be so twisted that it would make noise all the time, but still allow you to shift into all three chainrings.

[KnottedYet]

Well thank goodness for Sheldon then.

Yeah! Can you put up the link? I gotta run catch my bus.

[OakLeaf]

Linky. You can plug in your gearing (stock cassette or custom) and wheel size and get gear ratios, gain ratios (if you put in your crankarm length), meters development or speed at a selection of cadences in mph or kph.

[Catrin]

The reason I've taken to using my big chain on flattish ground is that my chain doesn't make noise there and behaves itself. My rear cassette is 11-34, and some of the jumps between gears are pretty large.

In some cases I have a smaller range if I jump between the chains for some of the gear progression - someone checked out the gear ratio for my bike on Sheldon's site and suggested it. I've also found that I go a couple of mph faster if I am in the big chain on flattish ground (with the middle gear on the rear). My max speed so far that isn't downhill is 19.9 mph.

Oakleaf - it rubs on the same part of the FD cage regardless of what gear I am in.

As far as cadence is concerned, I try my best to keep it between 80-95 and as generally close to 85-89 as I can. Going uphill can generally keep it in the 70's - though when I am really struggling to get up that hill I don't think to look at my cadence but am focusing purely on perceived effort. On sprint intervals I am paying attention to my HRM (it is mounted on my bike) but can get cadence to 105 and this is typically on the big chain.

I understand about trying not to shift under load, so I try to anticipate when I will need to shift and to do it a little early, but not so early that I lose all of my speed too early. I am not successful with this much of the time but I seem to be improving.

I do try to "soft pedal" when I shift, and sometimes will even coast for the briefest of seconds while I shift and then start pedaling to complete the shift. This is a carry-over from when I first started to learn how to shift and at that time my coordination was worse and would go all over the road if I tried to shift and pedal at the same time I will pay attention to this in case I am not soft-pedaling as much as I think I am...

Thanks everyone, you have given me some things to think about and check out. Cleaning my drive train does seem a good idea, but there does seem to be more going on than that. At least my LBS will appreciate a clean bike later this week!

[OakLeaf]

Which part of the cage does the chain rub? That'll help isolate what needs adjustment.

[Catrin]

Which part of the cage does the chain rub? That'll help isolate what needs adjustment.

Standing at the rear of the bike looking at the FD, it is the upper right part of the cage. There is a part there that comes down, then goes over to the right - which is the perfect place for the chain to rub. And so it does.

Is that a good enough description? I can always take a pic tonight and post it...

[OakLeaf]

mmmkay. It sounds like your cable just needs a little tightening (just as I originally thought - after the shop repositioned the cable, everything will settle a little and need a tweak within a few rides). But two last questions to be sure.

Does it rub when you're in your very tallest gear (your 48x11)?

What about in your very shortest gear (your 26x34)?