spathfinder3408

I have a Trek 800 with an 8 speed Cassette. I have worked on a lot of bikes , but I have never run into this problem. The Bike shifts into all gears from the lowest to the 7th gear. When it gets to the 8th gear the chain does not match the teeth of the gears, caused the chain to ride on top of some of the teeth. I thought the chain was worn, so I replaced it and it actually became worse. I took the cassette off and checked highest gear to make sure it was placed on right, its was and it can only fit in one position. I looked at gears from side to make sure the highest gear wasn't bent, and its straight and not causing chain to hang up. Its almost like that high gear is not the right spacing for a regular chain. I was going to try another gear to see if that fixes it. Just wondered if anyone ever had this problem before?

StanSeven

Sounds like the limit stop screw needs adjusted so the derailer extends to the 8th gear

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

Also the derailer could be bent

Al1943

The gear that is giving you a problem, is it an 11 tooth? A first position 11 requires a special lockring. If you use the wrong lockring the chain will ride on the lockring and won't mesh with the cog.

fietsbob

Cable may be too tight. top,smallest, gear is slack cable ..
return spring should pull it into that gear,
whether there is a cable attached or not.

FBinNY 

If it always used to work, but now doesn't, that's different than if you installed a new cassette.

If it's a new cassette, probably, as AL1943 suggests, you have the wrong lockring.

But if it's a new problem on an old setup, odds are that the outer limit screw is too far in, as Stan suggests.

But don't just back ff the limit and forget it. Limit screws don't magically tighten themselves. If the outer limit is now too far in, it's an indicator that the bike was dropped and the hanger got bent in a bit. That's important because it means the inner limit is now too far in by the same amount putting you at risk of over-shifting the chain or RD into the spokes.

Back off the outer limit a bit and see if that solves the problem. Then check the inner limit by shifting to low gear using direct pressure on the lower body of the RD. You want the limit adjusted so it just barely can complete the shift. Now shift back and forth to low from 2nd to low and back off the limit just enough to allow a reliable, crisp shift and no more.

BTW- at some point you'll want to have the hanger checked, but it's probably close enough that you can put that off until the next tune-up.

Jeff Wills

Did this just start happening? Has the shift quality been steadily worsening?

I'll echo all the possible causes from the others and add one: since the high gear is at the limit of the derailleur's travel, the slightest drag in the mechanism can affect how far it moves. If the hanger alignment is good (use a gauge, don't just eyeball it) and the limit screws are correct (derailleur shifts to little cog with the cable disconnected), check if there's any drag in the cable housing. In fact, if it's more than a couple years old, it's a good idea to replace the cable and housing. They get old and worn and kinked and gummy (don't we all?)- I've replaced cables and housings and had huge improvements in shift quality.

FastJake

Is this a new problem? Or something that's been going on ever since you got the bike? The advice above is good, BUT:

That caught my eye. I have a 13T Shimano cog originally from a 7-speed cassette. It is meant to be the highest gear, as indicated by the grooves on the outside to mate with the lockring. It is very narrow, and no chain would fit between it and another cog. Thus, a 1-2mm (I didn't measure it) metal spacer was included to fit between it and the next higher cog. If you are missing the little spacer, it could give you the problem you describe.

Jeff Wills

Hmmm... 13-tooth second-position cogs typically have an additional 1mm spacer. On the last position- nope. The last cog on a Hyperglide cassette is all one piece so it engages the cassette body correctly.

spathfinder3408

Its a 13 tooth. Its not riding on the lockring its riding directly on the teeth of the 8th gear. The teeth of the gear are not going in between the chain openings in sync. Its almost like the gear was made incorrectly. This bike has never worked correctly since I've had it. I was hoping it was a streched chain, but that was not it.

spathfinder3408

the spacing looks pretty tight in between the 7th and 8th gear, but it clears. I thought maybe the clearance in spacing was the problem, but the gear itself does not match the openings in the chain as the gear turns

spathfinder3408

I am going to try to switch out the cassette to see if that fixes the problem. Someone may have had it off once upon a time and put the wrong parts back

FBinNY 

Shift to any larger gear to get the chain out of the way and look down on the series of smaller sprockets. Is the space between the last and 2nd the same as on all the others? It should be.

If not, either you're missing a spacer, have the wrong spacer, or you have the outer sprocket on mirrored with the built-in spacer to the outside. if the latter, reverse the sprocket and you'll be set.

spathfinder3408

I fixed the problem. The 8th gear was worn badly, so the teeth were to thin and small. I found another 13 gear in my parts stash and changed it out. Comparing the size of the teeth compared to the one I put in, is about 1/2 the width of teeth. I probably wouldn't have noticed unless I had that other gear. The thin teeth must have been causing the syncing from being right to the chain. The bike that I bought for a song, has turn out to be the Titanic. I have almost replaced everything on it. Both derailers, one shifter, seat , chain, now 8th gear. Believe it or not the tires and wheels are good. The Bike had a ton of miles put on it by a guy that was using it for commuting. Mission Accomplished.. Yeah...... Thanks for all your input. Its good to know I have someone else to bounce ideas off of. Happy New Year

FastJake

Why does it have the grooves then? It works as a last-position cog, and its splines are recessed so that they don't interfere with the lockring. It says "G*H K*M - 13T 3 RB" on it if that matters.

Al1943

The radial grooves help grip the lockring.

FBinNY 

I don't think thats isn't 1st position sprocket. I say that because it has shift gates, which are usually only cut when there's an adjacent smaller sprocket. The serations might be to improve support for a mating 12t which partly nests into it.

Also 1st position sprockets are machined from a thick blank with the spacer built in. It may be a full width spacer or partial width requiring another thin spacer behind it.

Sprockets with built on spacers (technically called hubs, just to confuse things) are more expensive to produce, so manufacturers would like to avoid needing them, or at least make them as thin as possible. But since the 1st position sprocket overhangs the end of the cassette it's necessary to have some sort of a hub, so it doesn't hang by a thin edge.

Jeff Wills

That's a last-position cog. Second- or third-position 13-tooth cogs would not have the serrations which mate with the lockring.

Jeff Wills

Wearing out the small cog is a symptom of poor rider technique. It sounds like the previous owner just left it in "high" and never bothered to shift.

Al1943

And probably rode cross-chained causing more friction and faster wear.

spathfinder3408

It turned out the the whole cassette was to worn to function properly. The lowest gear was causing a jump or splip when pressure in a climb. Replaced cassette and working smoothly now. I have pretty much replaced everything on this bike. Both derailers, chain, cassette, seat, brakes. It felt good just rebuilding. I know I could have bought another bike for close to same amount, but its a Trek 800 and fits me good, so I'll write it off to experience. Its a sturdy bike that I plan on using for deer hunting . Out where I live they don't allow passage into Weyhauser land for hunting by vehicle. The bike is allowed. If I get a deer I can put it on a trailer I plan to get next. The bike gears go low. Put a 13-34 8 speed Cassette on it.

FBinNY 

Aren't deer kind of heavy to haul out of the woods, even with a trailer. Unless you plan on shooting Bambi, you're talking about a couple of hundred pounds, which is a lot to haul on pavement. I can't imagine what it'd be like hauling that much through the woods.

OTOH- you could always just use the wheels, but get off and push it out if it isn't too far.

Al1943

What kind of rear derailleur do you have that works with a 34 cog?

JanMM

Is there a Deer Hunting with a Bike forum on BF?

spathfinder3408

Your right deer can weigh up to 200 lbs and would be a bit much . I have seen trailers made by a guy locally that are made for touring. I am going to check those out to see if they are capable of hauling large loads. If not I may have to make something myself. With the propler set up its possible to carry a 200lb load as long as it not up hill to much. Most hunting areas rise in elevation, so coming out should be a drop. Most deer in that area are Blacktail deer and they aren't that that big. Probably around the 150lb range. If I get one I'll post the info on here. Maybe a couple pictures as well

spathfinder3408

Its a Shimano Altus C10. Its kind of lazy. Thinking of switching it out with a SRAM. Something with more spring to it.