rhodesmk

I have a Jamis Explorer 2 (21 speed hybrid bike) I've been riding to lose weight. When I bought the bike (new) in 2014, I generally kept the gears at 2 (of 3) for the pedals and 4 (of 7) for the rear, as I hadn't owned, or even ridden, a bike in about 35 years (I'm 66 now). As I experimented with the gears, I find that, for the pedal gears, it almost never goes into first gear. For the rear gears, 7 sometimes works, sometimes not, and it never goes in to 1. The biggest issue, though, is that these issues only seem to happen while I'm riding. If I mount the bike on a rack, turn the pedal by hand and shift gears, everything works great.

Every spring I have the bike professionally tuned (at a "real" bike shop...have used two different shops depending on their spring specials), each time describing these issues, making sure I tell them it only happens when I'm riding. Every time, they come back with "we can't duplicate the issue."

Not a mechanical person here, and having never owned a gear-bike before, am not sure I want to try messing with the adjustments on my own.

Any advice? Is it normal for gears to act different when riding than when no weight is on the bike? BTW, according to some very generalized information in the owner's manual, the weight limit for this bike is 300lbs plus luggage. I weigh in at 285 and carry nothing but the clothes on my back when riding.

aggiegrads

One thing worth mentioning (that you probably already know) is that drivetrains generally don’t tolerate “cross-chaining” well. This may not apply in this situation, but is good to know if you don’t already.

If I am in the smallest chainring or middle chainring, I find that my shifts are not as good if I try and shift to the two smallest cogs. If I am on the biggest chainring in front, the largest two cogs in the back make a lot of noise. If your bike won’t “let” you go completely cross-chained, that is OK. The newest electronic systems limit those combinations electronically.

When I get to the limits, it is better to make a front shift earlier than to have the chain travel all the way across the cassette.

OldBike876

Similar weight, similar problem, even a similar bike. I bought used from a rental place and they tuned it up when I bought it, I could see that the shifts were smooth on the rack. Not so much as i rode home. It made noise, wouldn't really shift well. The bike shop I bought it from was great, they set it up and sent me on a ride around a few blocks. I came back and they adjusted it a bit, I tried, it, they adjusted it... Eventually it worked fine.

The problem was that the adjustment on the rack was fine, but with me on it the bike flexed in some way(s) preventing smooth operation. It's fixable, but might require trial, error, and experience doing it.

Iride01 

If you generally keep the bike with the gears in a particular setting then you probably aren't using the gears correctly or your terrain is perfectly flat. I have few places that I can just stay in one gear combo. But the more leisurely I ride, the less I have to shift, so maybe that's your style.

But still, you need to shift more and make sure you are used to shifting. Also, make sure that your bike shifts correctly through it's full range of gears. If not find out why and not leave it till it's a problem.

When you shift, generally you always want tension on the chain and some power in the cranks. How much? Sort of depends on speed and which range of gears you are in. You just don't want to be putting every ounce of your strength into pedaling. But at the same time not pedaling is an issue too. Might drop your chain or something.

blamester

It could be you that is causing the problem.
There is a technique to changing gears.
You have to keep pedalling but ease off on the power slightly.
If you have never ridden a geared bike it may not be obvious.

DiabloScott

No. Although sure there is a technique for OPTIMUM shifting as described by others here. I doubt you're putting so much tension on the chain that it won't release and shift.

For easier explanation though, the "pedal gears" is your crank - so you would say "small, medium, or large chainring" or "1,2,or 3 in the front".
And the rear gears is your cassette, so you would say "smallest or largest cog" or "1,2,3,,,or 7 in the rear". EG - "rear derailleur won't shift into the biggest cog when I'm in the middle ring in front"

Now, 3 in the front and 1 in the rear is a bad combo and you shouldn't use it for a variety of reasons, but the derailleur ought to be able to make it engage. What exactly happens when you try?

Your bike shop sounds helpful, maybe they can watch *you* recreate the issue and advise what you're doing wrong.