[mortalsaint]

I was out riding a rail trail with friends recently and took a detour on an underused horse/mtb trail. Was standing up to accelerate before a jump and the chain slipped slightly, i lost my balance and went awkwardly over the jump. Realized as I was pedaling away that my derailleur wasn't shifting right....
So, it doesn't want to shift from 6-8th-there seems to be no tension in the shifter when i try... and when i try to downshift to 4th or below the chain just jumps around 4th-2nd gears. It also seems to be oriented more horizontally than before, and the guide pulley rubs the largest cog when i try to downshift. The hangar does not appear to be bent, so would adjusting the HL screw be all that needs to be done?
Not quite sure what to do for this one

btw the derailleur is a stock shimano acera 8speed

 

[GEARHEAD_ENG]

Put the bike on a stand or flip it over. Now crank the pedals and manually pull on the cable, what happens? If it moves and shifts normally to the higher gears you may have a bad shifter. If it moves and stops against the H screw, it may need ajusting.

Sent from my SPH-L710 using Tapatalk 2

 

[AlexRandall]

I'd still be checking the hanger....with a tool.

 

[mortalsaint]

The other thing is, i just took it to the shop to get tuned not quite 2 months ago, so i dont really want to spend another 50 bucks to get it professionally checked out

 

[GEARHEAD_ENG]

Go to park tools website, they have great self help tutorials on bike repair.


Sent from my SPH-L710 using Tapatalk 2

 

[jazzanova]

Almost always when I have problems with rear derailleur shifting properly the problem is a bent hanger.
First I try to adjust the cable tension on a lever, if that does not help try the hanger. The specific park tool tool was one of my best bike related investments.
You might need to adjust the distance of the derailleur from the big cog as well if it obstruct the shifting.

Sent from my PG86100 using Tapatalk 2

 

[Handy]

DAG-2 Derailleur Hanger Alignment Gauge by Park Tools

Dear mortalsaint,

Hold you breath for just a second...ok, I think you are about ankle deep in bicycling...you paid who, what, to do whatever they did, and now your bicycle is not shifting the way you want it to ?

Time to take matters into your own hands and get about neck deep in bicycling...welcome to the website, thanks for the posted thread...been thinking about Shimano Acera 8 speed rear derailleurs all day. I must be frank, the Shimano Acera 8 speed derailleur is not the top of the line...it is not the middle of the line...in fact, the Shimano Acera M360 rear derailleur is the bottom of the line for "mountain" derailleurs. These sell for 25 america dollars, and are available in black or silver.

The derailleur hanger, it might be straight, sounds like the derailleur was shifting fine, and then the chain skipped just before you were going to take a jump, doesn't sound like you say you think you hit the derailleur on something and then it stopped working the way that it had.

Please list the other parts of your drivetrain, shifters, front derailleur, crank, number of teeth in each chain ring in the front and the number of chain rings, the cassette and the cogs of the cassette, chain, ID numbers, for example, you might have Shimano Acera SL-MC360 shifters, some front crank with 22, 32, 44 teeth in three rings, and an 11-32 Shimano Altus HG-31 cassette ?

Are you willing to buy a better rear derailleur, maybe a Shimano RD-M591 about sixty bucks and maybe some new shifters, Shimano Alivio SL-M410, about 44 dollars, and maybe a new Sram PC-890 8 speed chain, about 40 bucks, and you do the work ?

I am running those shifters and that chain with a Shimano FC-M590 crank, 22, 32, 44, and an old 1998 XTR-RD-M950. For me, it's all about the chain and the chain lube GT85, that stuff smells good !

Also, riding style, as you were approaching this jump, just before the chain skipped, was your last gear change, a shift up or shift down ?

The correct answer is you always want to be pulling on your cable into a gear to know it is solid, sometimes, downshifting, the cable or derailleur, or chain, or cable housing, gets out of wack and "it"(the rear mech) doesn't shift, until you decide it is a good time to stand on the pedals...how big was that jump ?

Keep riding and keep up the good work !

Yours truly,

Handy

Insane Mountain Bike Crash - YouTube

 

[thomllama]

............ and the guide pulley rubs the largest cog when i try to downshift. The hangar does not appear to be bent, so would adjusting the HL screw be all that needs to be done?
Not quite sure what to do for this one

1st off, you wont be able to "see" a bent hanger (well unless it's really toast ) you need a tool..

80% of all mis-shifting is do to hanger's out of alignment. But, also from the pulley rubbing comment I'm guessing the "B" screw is adj tooo close.

 

[mortalsaint]

Dear mortalsaint,


Please list the other parts of your drivetrain, shifters, front derailleur, crank, number of teeth in each chain ring in the front and the number of chain rings, the cassette and the cogs of the cassette, chain, ID numbers, for example, you might have Shimano Acera SL-MC360 shifters, some front crank with 22, 32, 44 teeth in three rings, and an 11-32 Shimano Altus HG-31 cassette ?

Are you willing to buy a better rear derailleur, maybe a Shimano RD-M591 about sixty bucks and maybe some new shifters, Shimano Alivio SL-M410, about 44 dollars, and maybe a new Sram PC-890 8 speed chain, about 40 bucks, and you do the work ?

I am running those shifters and that chain with a Shimano FC-M590 crank, 22, 32, 44, and an old 1998 XTR-RD-M950. For me, it's all about the chain and the chain lube GT85, that stuff smells good !

Also, riding style, as you were approaching this jump, just before the chain skipped, was your last gear change, a shift up or shift down ?

The correct answer is you always want to be pulling on your cable into a gear to know it is solid, sometimes, downshifting, the cable or derailleur, or chain, or cable housing, gets out of wack and "it"(the rear mech) doesn't shift, until you decide it is a good time to stand on the pedals...how big was that jump ?

Keep riding and keep up the good work !

Yours truly,

Handy

Insane Mountain Bike Crash - YouTube

Hey, thanks for the response! I was quite aware the Acera series was nowhere near top of the line, but i was hoping it would last a while till i have the money to upgrade, which i DO want to do btw.
As far as other drivetrain components, front and rear derailleurs as well as the shifters are the Acera(idk what else to say about them).The front crank is a shimano MC311 Octalink with 22/32/42 which I've also heard is pretty much junk, and rear cassette is shimano HG40 8speed(11-32t). I would love to upgrade to Deore or XT components sometime in the future.
As far as riding, i believe my last shift was an upshift trying to build speed to the jump(about a 2 ft jump). And yes, I really am about ankle deep into cycling , i've been riding my whole life but just started trying to get a little more serious in the past year or so. Thanks again for the response. I'm going to try to get one of my friends to take a look at it too and see what he thinks.

 

[Thumpy69]

Loosen the cable and unhook it completely. Move the derailluer as you pedal and it will shift by hand. Do this and see if it freely can move and shift into all gears. If not you H screw may need adjusting or its bent. Aftwards put it and your shifter in your highest gear. Screw you adjustment screw in 90 % of the way. Pull the cable tight and screw it down. Shift one gear and adjust the screw until it shifts and is running smoothly.