michaelm101

I removed the original chainring and guard (2 piece with 4 bolts, each with a thick washer inside the inner guard, and a thin one inside the outer guard) from a 1x9 bike I have, to replace the chain ring with a "narrow/wide" chainring.

Since I didn't own a chainring nut wrench (I ordered on on Amazon, but it got delayed), I went to the LBS and asked to use their tool while I was in the store.
The mechanic there happily did the job for me, and discovered there was space after he tightened the fasteners.

Indeed, the three piece thing was loose and somewhat "jingly," like a tambourine. We both figured the new ring was thinner and I needed new size chainring bolts.

I came home and discovered the old ring was 1/2 the thickness of the new ring. Yes, the new ring was TWICE as thick.

This defies laws of physics. Can anyone explain what is up with that?

Thanks in advance!

dsbrantjr

Is the new, thicker ring counterbored deeper than the old one?

michaelm101

Exactly the same size hole as the original and no counterboring...

shelbyfv

Washers?

krecik

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michaelm101

Yes, I used the original washers... thick ones on the inside of the inside guard, thin ones on the inside of the outside guard...

michaelm101

The new ring with guards


The original ring...


Three of the bolts showing thick & thin washer

michaelm101

I'm thinking of mounting without guard, but I will need new bolts and then the chainline will also be off..

Is there some sort of washer width equation for this?

The thickness of outer guard plus washer is 4mm. So theoretically, I could get 4mm washers and just stick then in there, directly between spider arm and ring...? BTW, the thickness of the new ring is also 4mm.

So, to mount w/o ring without guard, do I need to order new chainring bolts for "4mm" thickness chainring?

krecik

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michaelm101

The outer bolt goes through the holes in both CRs. The holes in the CRs are the same size...
The only difference is the new ring it about twice as thick as the old one...

Bill Kapaun

Single speed chain ring replacing 9 speed chain ring?
EXACTLY TWICE?
If not, how about some "real" measurements.

What "laws of physics" are being defied?
It's your credibility.

michaelm101

Excerpted from OP:

1) Replacing front ring on my 1 x 9. There is a chain guard.

2) Old ring is 2.5mm thickness (and, when mounted it is tight with no play), I can ride the bike. New ring is 4mm thickness and when mounted is loose & jingles like a tambourine when struck with hand. The bike, I assume is not ride-able with this loose & jingly setup.

I'm not a physicist, but this does not appear to make sense from a physical standpoint.

Bill Kapaun

I'd like to see pics of both rings on both sides of the mounting holes.
Something has to be different.
Countersunk hole that the chain bolt "sits in" differently from one ring to the other?
Chain bolts backwards or not fully tight. Maybe bolts "popped in" to countersink holes after some usage?

I would expect usage in current state could result in elongating holes over time, depending on how hard & often you use it.

I think defying the law of math makes more sense.

AnkleWork

You didn't need the special wrench to remove the guard/chainring?

What's a "three piece thing"?

Never mind, I would offer no guesses based on that description.

[+1 on the law of arithmetic.]

michaelm101

1) Oddly, I was able to loosen and remove the old chainring without the proverbial special bike tool.
2) The "three piece thing" consists of: Piece #1-Outer chainring guard, Piece#2- Chainring, and Piece #3 - Inner chainring guard.

michaelm101

The holes are exactly the same diameter and not countersunk. Only difference is in the thickness.
Indeed, if things defy laws of physics, then they must also defy laws of math.
Hoping this all makes sense...

Kapusta

Either:

a) you lost a spacer of some sort.
b) you are assembling it wrong.

Have you tried re-assembling with the old ring?

Kapusta

Are all of the chain ring spacers the same OUTER diameter? You say that some are thicker than others, but I am unclear whether you mean the length of the spacer or the outer diameter.

Eggman84

Where are you measuring the chainring thickness. I believe many modern chainrings typically are different thickness where they contact the cranskset spider than at the tooth. As to defying physics, I doubt it unless you are pedaling close to the speed of light, in which case relativity might come into play (and affect your measurements in some way I am unaware of).

fietsbob

Where is the chain line right? Mounted on the inside or the outside , of the crank arm ,
or do you have to solve that first?

and in my experience it's been fine to mix chainring bolts and sleeve nuts, of different lengths,
a shorter nut on a longer bolt. so the bolt passes through the nut ..

single nut double length bolt is on my single ring - trouser guard ring set..

Last ride 76 

Sometimes the socket side of the chainring bolt does not seat perfectly in the crank. If the front bolts are long enough to connect, you will have play. Whether it is this or a different piece causing the play, something in the sandwich is not seating the way it was before. This would also explain the change in the chain line.

tyrion

Looks like the bike shop mechanic pulled the ol' switcheroo on you and substituted cheaper, thinner washers. Happens all the time if you don't keep a sharp eye on them.

michaelm101

Thanks, all! I'm expecting some short/single gear CR bolts, in addition to the special tool.
I'm gonna try and install the ring w/o the guard. Will report back...

krecik

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michaelm101

Ok. I mounted the single ring directly onto the spider with 4mm (inside width) ring bolts and all is fine. Re- indexed and all gears shift fine, but get some noise on the two biggest cogs.
I'm assuming I'd alleviate this problem by adding 3mm washers in between the spider and chainring to makeup for the spatial disparity inward, that the guard and thin washer allowed...

I thought of adjusting the low limit screw, but I think physically moving the front ring inward would be the best decision...

Please me know your thoughts.