M.arie

Hello!

I've been searching for answers to a problem with my gears recently, but can't seem to find one, so joined this forum in hopes that someone will understand what this problem is.

My bike has 7 gears, but over the last two days, the 6th and 7th have felt like they are in 4th. I checked that the chain is moving along all 7 gears and it is. However, gear 6 and 7 seem to not be working. I have to cycle slowly because of this, and can't build up speed for a slope

On the other handlebar, I can also change something. I was told that it's the chain tension, but a friend told me they're front gears (cranks?). There are three of these. He watched me while I cycled and said they are changing, but the chain rattles loudly and feels slack, so I don't like using them.

From what I've researched, I have the opinion, it could be to do with chain tension, but I thought I would ask on here first before I do something wrong. If it is the chain tension, could this be the cause for gear 6 & 7 not working, even though the chain is moving?

Thanks in advance!

cobba

The following image shows gear combination's that Shimano doesn't recommend you use.

M.arie

Thank you, Cobba! I'll try it in the morning and let you know the results.

FBinNY 

All the sprockets are on a common block with no moving parts (except when you coast), so if the chain is on a larger rear sprocket, you're definitely getting better leverage. It might not feel that way on a hill because you're also slowing down and tiring.

If the gears change and the chain doesn't slip (you'll know for sure if it does) your bike is fine, but it sounds like the engine could use some work.

RavingManiac

With a triple in front, put it on the middle chainring and see if you get all 7 speeds in the rear. If not, check the limiting screw adjustment, derailleur not bent, der. hanger not bent.

FBinNY 

I suggest you reread the OP, esprcially here where he says the chain changes to all seven sprockets.

......I checked that the chain is moving along all 7 gears and it is. However, gear 6 and 7 seem to not be working.

RavingManiac

I read, and comprehended that the first time I read it. However, it seemed unlikely that the chain could actually be riding those cogs to no effect.

fietsbob

one of my peeves, 'speeds' added are not necessarily an advance,
its just stacking in another cog, maybe one tooth different from its neighboring ones.

the Range matters , more, difference between outermost cogs.
the bigger low gear.. more teeth around the circumference of a larger cog,
will lower the Ratio,
as will reducing the size of the chainring that the pedals turn.

Pop Quiz! ..
23:53 versus a 34:22, which will make going up a hill easier?

dabac

Your question indicates a certain amount of cluelessness, so I suggest you visit Sheldon Brown first, to read up on the basics.

Flying Merkel

Guy posts an honest question, no need for internet dickheadedness.

It will make a difference when you change gear ratios. May not be a lot or enough. The left hand shifter is for the front 3 chainrings. Assuming it's a mountain bike, you won't be using the smallest front chainring very much. Practice shifting. All the sprockets are there for a reason. Bike might be needing some adjustments. Don't worry overmuch!

FBinNY 

If you've read Dabac's posts in the past, you'd know that he's not in any way an internet dickhead. His post was a sincere attempt to point the OP to a source that might help him understand derailleur systems in general, and his problem in particular.

Part if the problem is that the OP is describing an impossible situation wherein the chain changes sprockets, yet the ratio doesn't change. Also his vague understanding of multiple chainrings & front derailleurs reinforces Dabac's conclusion.

There's nothing wrong with being a newbie, and we all want to help, but often the best help we can offer is to point someone to a published source that will give a good general background, so he can pinpoint and better describe the problem, if not solve it himself.

For my part, I don't think there's anything wrong with the bike, just that the OP was never taught how to use his gear system effectively.

Flying Merkel

Bit sensitive these days to rudeness, perceived or otherwise. Mechanics is one of the more civil forums.

Koom-buy-yaw.

ZManT

"cluelessness" is a sub-optimal noun to describe someone seeking education . .. .

gyozadude

Dear OP:

Please specify what the GEAR RATIO is between FRONT:REAR.

From the post, it sounds like you may be riding with small chain ring up front on the crank set (where the pedals are) and you're shifting through 7 gears in the back. Also, when specifying "slope" you need to be specific - are you going "UPHILL" or "DOWNHILL" on the slope?

The problem here is one of nomenclature and ability to communicate withOUT ambiguity, even if you do NOT know the lingo. For example, to be specific about the gear, you need to reference whether you are specifying gear #6 and #7 as indicated on your shifter WHILST riding, or if you mean the SMALLEST and 2nd SMALLEST cogs in the rear? Or do you imply and inverted gear scale where gear #6 and #7 refer to the 2nd LARGEST and LARGEST cogs in the rear, respectively? Which is it?

If I read your post correctly, you seem to imply that you can NOT go fast on a DOWNHILL slope even in gear 6 or 7 in the rear (the 2 smallest cogs) and you thought maybe the chain tension was the issue. My suspicion is that your friend was correct. You are "cross-chaining" which is where you are riding in the small ring up front on the crankset. What this means is that you've limited your maximum gear ratio so you cannot really ever pedal that fast, so in essence, 4th gear is not much different than 6th or 7th.

What I think your friend was trying to tell you was to switch to gear 13 or 14 or gear 20 or 21, which we might think of as designations for the next set of gear ratios when you shift the front to the middle and then to the biggest outside chainrings. Of course, you noted that this makes a noise which is probably the chain rubbing against the front derailleur cage. That happens for several reasons:

a) the FD is incorrectly adjusted
b) you need to make an incremental "half shift" up or down to "trim" the Front Derailleur so it doesn't rub
c) you have an incorrect combination of Front Derailleur, Shifter, Chainring combination
d) some combination of (a), (b) and/or (c).

But do the Math. Determine the gear ratio of FRONT:REAR and the higher that is, the more speed you can achieve pedaling at a given fixed RPM of your feet.