slvoid

Search isn't working for me right now but I'm damn sure a lot of people have had this problem.
The thing gets pretty tight (like 1/8" of play) when the right crank is at 9, then loose enough to have like, almost 1" of play when its at 3... my regular lbs sales guy never heard of it, he said it was normal. The mechanic there said bring it in tom. in the morning and he'll see what he can do, took it to r&a and they've never heard of that problem, their only solution was chainring/bb replacement...

kyle!

maybe the chainring is crooked in the crank? or waaayyyy out of round?

operator

Swap chainring, problem exists, crank sucks k done. Repeat.

doofo

slvoid do a ****ing search boy

or listen to operator

or get over it

or just hold me

slvoid

Something tells me you missed the first line of my post. But that's ok, I'll hold you anyway.

vpiuva

Sheldon Brown has an article on this very subject https://sheldonbrown.com/fixedb.html see 'chain tension'

2manybikes

I went through the same thing, it did not seem right to me either.

Sounds normal to me. Centering the chain ring on the crank will help. But nothing will make it perfect. It happens on geared bikes too, but the chain tensioner hides it from you. You just put up with some slack in some positions. Without the derailleur chain tensioner, that's life.

There can be a huge amount of slop in the position of the ring relative to the crank. Sheldon has a way to center the rings. I used shim stock, mine is almost perfect. All the bearings and parts can have tolerance stacking one way or the other, they can add up.

Take off the chain, loosen all the chainring bolts and move the chain ring around. It can be very sloppy you might be surprised.
The derailleur chain tensioner makes this seem to go away on a geared bike, but it doesn't. It just gets corrected by the chain tensioner.

Welcome to a different way of doing things. More surprises coming.

slvoid

The thing is, the thing was fine until the bb came loose and the lbs tightened it back up again..

2manybikes

Maybe the chain was running too tight before the repair and they loosened it a little?
Did you check your axle already? Is the chain quieter now? If it's quieter that would make me think it was too tight before.

Placid Casual

Just don't ride until 9 o'clock.

JeffS

nice...

------

I would guess that they also tightened your chainring and got it on there crooked.

na975

lbs, lot of the time just screw sh$t up, save your $, fix things yourself.

mascher

I just put a new chainring on today, and no matter how I positioned the ring on the crank, the inside edges of the ring didn't line up neatly with the crank spider ones. Then it got crookeder when I put on the bolts, and sure enough, I ended up with the same problem you describe, which I'd already had to an even greater degree with a different crank and ring.

25% crank, 25% cheap chainring, 50% lousy job. At least you have someone to blame besides yourself. On the plus side, new chainring for $14.

An inch of slack ain't going to kill you, and neither is 1/8", as long as it's not tight enough to bind. I tried derailing the chain at the loosest point by hand, and I couldn't get it off of more than one tooth at the top. I was previously riding this bike with way more slack in the chain, and I still didn't drop it much with enough slack and wear to pick the chain off of the chainring completely. You're fine, don't worry about it.

slvoid

Well it gets annoying cause it's loosest at the point when I'm trying to track stand and there's a lot of slop in it.
If NJS components are as precise as they are, then the sugino bb/crank/ring, phil wood cog, and izumi v chain should all be pretty much on. Unless i happened to end up with the Bose of bike components...

doofo

more like boise slvoider

Devotion

Bio-pace?

doofo

biopace aint njs pal

dont post high ok
?

12XU

My Phil Wood cog/C-Record Crank/Chainring/Phil Wood Bottom bracket has a great deal of eccentricity. Shocking, but isn't going to kill me.

slvoid

Are you serious or just trying to make me feel better?
Who do I have to blow to get concentricity in my parts??? I'll do it, I will!

doofo

lets see what i can manage

Ken Cox

I have the same problem, and I have a Phil Wood crank bearing and a crank with a fair reputation.

My lbs says he sees this problem to some degree with almost all bikes.

Some of it comes from a slightly out of round crank; some of it from an out of round chainring; some of it from a bent crank spindle; and some of it from an out of alignment bottom bracket.

Sheldon Brown has a good chainring centering technique that often makes the whole assemblage act round.

With the chain on and reasonably tight, but with the chainring bolts almost loose, slowly rotate the crank.
When the chain gets tight, hit the top of the chain at the middle of its span with a heavy wrench or a hammer handle.
This will move the chainring in a direction that will loosen the chain at its tightest position, but may tighten it up somewhere else in its rotation.
Keep slowly rotating the crank and hitting the chain at the tight spots, but not so hard, until the chainring has centered on the crank.
During this process, slowly tighten the chainring bolts.

The above has worked for me with some cranks.

However, with my present crank and bottom bracket, and all of my chainrings (I have more than a few), the chain tightens at the one o'clock position no matter how persistently I use Sheldon Brown's method.
Hm.
I can't move the chainwheel far enough to get it centered.

However, I have discovered that if I flip the chainwheel around, so that the countersink bevels for the chainwheel bolt heads rest inboard against the star of the crank, this gives me more play and adjustment for centering the chainwheel, and Sheldon's method works perfectly.
This has given me a cheap fix for this crank, crank bearing and bottom bracket setup, which I otherwise like very much.

I suppose it might look a little weird, since the chainring bolt heads do not recess into the chainring, but I've gotten used to it.
I now have a perfect chain, with constant tension for the whole 360 degrees of crank rotation.

2manybikes

All cranks and rings have this to some degree. They have to. It does not need to be something out of round by any means.

No mater how round everything is they need to have tolerances that allow some space. It's impossible to make it go away totally, unless you want to hand file each ring to each crank. But then you need to deal with BB bearing slop. The chainring bolts and holes have to be loose fit too to account for tolerances.

The casting for the crank can shrink/or not, a few thou. maybe .010? Maybe more? If the rings are just a little short they might be .005 too small? You can't make them too tight, the rings from one company have to fit on the cranks from someone else, with the tolerances both on the high sides. It could easily be. .015 space one side that's possibly .030 from one side to the other side if you push the ring one side to another. .030 is about the thickness of an earring stud on an earring for pierced ears. That's plenty to cause the slack/tight problem. The rear wheel parts all have tolerances that could go against you, or not. That's why Sheldon has his "centering the chainring procedure.
I have a freewheel on one side of my track hub. The freewheel is worse than the chain ring, it moves around like a geared freewheel when you spin the back wheel with the bike in the stand. That's worse than the cog threaded on to the hub. All freewheels including geared do this. But because I centered my Chain ring it's not as bad as it could be on my Fuji.

slvoid

You'd think the NJS components would have tolerances of like 1 or 2 mil at worst, making the stack no more than 4-5 mils off. It seems like that thing was off by almost 15 mil's to cause all that play. Cause all those JIS components are done to such high tolerances compared to ansi/iso.

oldsprinter

slvoid, is your chain hard to get onto the chainring/cog? Izumi chains stretch relatively easily. If you're using Sugino 75 cranks (and Sugino 75 chainrings NOT Zen chainrings) you should try a different chain (eg a Wipperman).

2manybikes

I know what you mean.

It probably was off that much.

If my memory is working today each chain ring arm on my Fuji has about .012 shims holding the ring centered.