jaslynn

Hey guys, just bought a new bike. It has a pair of Shimano Deore M591 Shifters. Specs are here: https://www.bicyclesonline.com.au/201...deore-30-speed



Anyway to cut it short, the left bottom shifter (the one that uses the thumb) is extremely hard to push. I need to press it really far before it shifts the gear. In fact if I stand up beside my bike and try to press the shifter, my thumb isn't able to push in far enough to move the gear.

Is this normal? Sorry if it sounds like a stupid post but it's my first bike with shifters

Edit:

Okay when I say harder, I don't really mean more force, but moreover that it requires me to push the left shifter 2x the distance as required by the right shifter, which is extremely uncomfortable to do so. The below diagram illustrates what I'm talking about. The first 2 pictures were taken from Shimano's manual, while the bottom picture in red illustrates what I'm experiencing.

FastJake

I would stay take it back to the shop but you bought it online so that option is out..

1) Don't try shifting when you aren't pedaling! Watch the front derailer when you push the bottom thumb button. It's trying to push the chain onto a larger sprocket which it simply cannot do without the crank/chain spinning.

2) Is it hard to get to both rings (middle and large) or is it just hard to get into the largest chainring? If it's only hard to get into the largest ring I suspect the high limit screw is in too tight and you're fighting it with the shifter. If you have trouble getting into both rings something else is up.

jaslynn

I bought it from a LBS but I won't have time to go back there till the weekend.

1) Well when I stood beside it just now and tried shifting, it was impossible to shift the gear with my left thumb. I just couldn't reach far enough. However earlier on when I was cycling I was able to shift it, albeit with much difficulty especially compared to the other 3 shifters.

2) Both rings are extremely hard to shift too. However shifting to the large ring is slightly harder than shifting to the middle ring. Shifting to a smaller ring is very easy though.

FastJake

In that case the fix is simple. Take it back and have them look at it. I'd just leave it in the middle ring till you can get over there. Should be enough gear to get you around until then.

Since it's difficult getting into both rings I'm stumped. My first thought was excessive cable friction but if that were the case it would not shift back down into the smaller rings. Maybe you just have a defective shifter?

FBinNY 

I agree with that taking it back for an adjustment is your smartest option. Odds are that there's nothing seriously wrong and it only needs some simple fine tuning.

If you knew what you were doing, you might adjust it so you could enjoy it more this week. However since you don't, you risk making a simple job more complicated, or possibly damaging something causing what would was a free adjustment to become a chargeable repair.

BTW- while they do the adjustment, ask the shop to walk you through the basic user adjustments so you can do more of them yourself. Also ask if they offer free of cheap (low cost for those who think cheap refers to something other than price) bicycle repair classes, so that you can become more self sufficient.

jaslynn

Okay just to make things clear, it's not about the strength required to shift the gear. Moreover, it's the distance required before the shifter registers a 'Click' sound. I realized that it takes 2x the distance on the left shifter as it does on the right one to register a click. I also realized that if I move the right shifter the same distance as the left one, it will move 2 gears.

Is that normal?

FBinNY 

yes, it's normal. Front sprocket separation is greater than that of the rear, so the derailleur has farther to move. Also the geometry is different. What matters is the trim (chain doesn't rub the cage) on each sprocket, and the crispness of the shifts. If these are on target, than it's adjusted correctly.

jaslynn

That's what I thought at first but I'm not so sure now. I just checked Shimano's M591 Shifter Manual and it seems like only 1x distance is required for the larger gear. The above 2 pictures were taken from their manual, and the bottom picture in red is what I'm experiencing.

https://bike.shimano.com/media/techdo...9830747488.pdf

Bill Kapaun

To be clear, when you say left & right do you mean front and rear?

To shift to a smaller cog/ring, your lever doesn't require nearly as much force, since you are just "releasing" it.
When going to a larger cog/ring, you have to overcome the spring tension of the derailleurs, so it requires noticeably more force.

It also may be a matter of ergonomics. Your hand may be positioned where you don't get the best leverage. That might simply be a matter of rotating the assembly on the bar to get a "straighter push" on the lever compared to your hand position. (BTDT)

spathfinder3408

Sounds strange, but it may just require some lube put down the cable housing. I work a lot on older bike and most of the time this is the issue. Could be the person that assembled bike forgot to lube that cable. Needs to go on a bike stand so you can invert bike where oil will go down cable housing. Easy job