skanking biker

Here's the deal. I ride a entry level gf mtb for exercise about 15 mi a day. I swapped the stock tires for cross tires (select inverts). I crank on the bike pretty hard throughout my entire ride. The last 2 weekns, ive been having problems w/ my rear derailuer. specifically, the bike doesnt seem to want to shift onto the smallest cog when i'm on my biggest and middle chainring--the chain grinds for a long time and eventually (sometimes) I get a "HARD" shift. I have cleaned the drivetrain, re-lubed the chain and adjusted the barell adjuster in the back--all to no avail. In order to get a decent shift, i have to turn the barrel adjuster so far that i begin to have problems downshifting onto the bigger cogs.

Oh, and i;ve also noticed that when can get on the largest chainring and smallest cog, and cranking really hard, the chain seems to "skip"--that is there is an area in my spin where i dont feel any tension on the chain.

I know this seems like a simple question, but i am not all that knowledgable in the mechanic departments. Any suggestions short of taking it to my LBS.

neil0502

Yeah . . . sounds like it's out of whack. Here's two sources for DIY adjustment:

https://www.parktool.com/repair_help/FAQrindx.shtml

https://sheldonbrown.com/derailer-adjustment.html

Go nuts . . . but be slow, patient, and methodical.

Stubacca

Park Tool is your friend.

Assuming you don't have a bent derailleur hanger, you probably just need to adjust the cable on the derailleur, and check the limit screws.

Brad01

Which GF is it??

skanking biker

2003 red and silver wahoo

Diggy18

Couldn't that also happen if the drive-train has become worn? How long have you had the bike?

skanking biker

3 yrs

KleinRider

This is what I'm thinking, too.

If you've had the bike for 3 years and have ridden it for most of that time using the same chain/cassette/chain rings then they are most likely worn to the point that you'll never get the shifting *right*.

Diggy18

Holy crap! I'm thinking that, in order to maintain optimum shifting functionality, you should change your chain every 1500 miles or so. And it sounds like you have a lot more miles on it than that.

You should replace the chain and the rear cassette (putting a new chain on a worn cassette is not a good idea). Maybe the derailler cables and housings while you're at it. If you do that it should run like new.

I've heard that if you replace the chain every 1000 miles, than you don't necessarily need to replace the cassette each time. If you're things this way I don't know how long the rear cassette is supposed to last.

neil0502

Replace it when it's worn.

https://www.execulink.com/~dtierney/w...m#Chain%20wear

Diggy18

Cool link

skanking biker

the other thing i noticed is that if i apply a whole lotta pressue to the cranks--like say when standing on the pedals, the chain slips, i hear a big grinding and crunch sound and the chain falls off.

anywhoo--i am gonna take the bike to the lbs this weekend and probably clean teh drive train agin (although if what you say is true abotu needing a new chain--i prob will wait until i get teh verdict from the mechanic).


The overall problem is that i bought the bike as my first "real" bike in liek 20 yrs and should have bought a road bike. I ride it like a road bike except for the occassional rails to trails use.


part of me is kinda hoping something is seriously f'd with it so i have an excuse to buy a new bike.

neil0502

Should have said that in the first place.

Sounds like your chainline is seriously out of whack, the teeth on your chainrings are gonna' need serious dental work, and your rear derailleur adjustment barrel is . . . well, over a barrel.

No way that can all be fixed. I'd get a new bike.

skanking biker

the other part of me is hoping that the cable just needs tightening b/c i am strapped for cash.


Ok--about this replacing the chain thing? I heard that you werent suppossed to replace your chain unless you also replace your cassette. Is this true? seems like an aweful lot of $ for a $350 bike

Stubacca

Not true.

If you replace a chain before it is completely worn out, typically the cassette will last a few chains. If, however, you've ridden the bike for a while with a very worn chain, then the worn chain will in turn place additional wear on the cassette, so you will have no choice but to replace both at the same time. A new chain on a worn cassette (or vice versa) will not mesh properly and skip badly.

Chains are typically around $20 or less. Cassettes for low end MTBs maybe $20-40, depending on where you buy it (plus installation if you don't do it yourself).

Doesn't matter what the price of the bike... parts still wear out if you ride it.

skanking biker

Oh, no doubt----i was just musing as to the overall cost of everything i've put on the bike and repairs etc.--

midgie

With the slippage when underload and a lot of torque, I definately have to go with wear. At this point your going to have to replace your chain and the worn cog/cassette. You can't replace one with out the other, they've worn the same. Some cassettes you can't replace just one cog, if you have to replace the whole cassette, replace it with one that has independent cogs for the next time. I would take it to your LBS and let them look at it, before you start messing with your limit screws, unless your good with
derailleurs.


[edit] I wouldn't bother cleaning the chain now, waste of time if your gonna replace it.

Al1943

Since you're having problems shifting to the smallest cassette cog, and based on what you've said about adjusting the cable tension, my best guess is that you have too much friction along the shift cable. Try lubricating the cable and inside of cable housings, expecially the short housing just before the rear derailleur. Also try hosing out the shifters with WD40. Jacking around with the cable tension may be causing the chain slip on the rear cogs.

Al

skanking biker

i havent messed with the screws or cables---last time i did that i did a perfect job of f'ing everthing up--i;ve just adjusted the rear barrell adjuster.


.............this is why i need to buy that fixed gear i've been eying up for the last 4 months

skanking biker

BTW--thanx for all the info

Diggy18

Yeah, the rear cassette and a new chain would probably be around $70. If the chain got so worn that it then ground down the chainrings up front then that could add another $50 or something I guess.

Like you said, the questions is, at what point does it become more cost effective to just buy a new bike rather then repair the one you have? What if the repairs would cost half the price of a new bike? Is it worth it?

skanking biker

THE VERDICT:


Chain is completly worn. The cassette is worn, but not so bad as to require replacement. --so says the mechanic at my LBS. $16 for the chain, $8 installation charge. Unfortunately, I have to wait until wednesday to get it back

Diggy18

Isn't that the worst part? Due to repairs I was without my bike for three weeks, I was so lost for the first two weekends without it.

skanking biker

i may have to go and buy another bike tommorrow!



Its so wierd-- i feel like if i dont have my bike part of me is mising--i know its a cheapo mtb but i ride it everywhere all the time and my whole afternoon at work is spent looking forward to riding.


Oh well---i guess patience is suppossedly a virtue.

Stubacca

A quick tip for you for next time:

A chain tool costs under $10 (mine was on sale for $5). Sizing a chain is really simple, and installing it even simpler. Next time, buy a chain tool, install it yourself and you'll be up and running in less than 10 minutes. The park tool website has all the information you need for sizing and installing the chain and adjusting the derailleur (which it sounds like it may still need).