Wibbly wobbly....

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gtvlusso
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Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 10:44 am

Bugger - Getting that 'chain rubbing against metal' sound this morning. Have a look down at the chainset through the front mech - chainset appears to be warped, assuming that the mech is sitting straight. I adjust the front mech using the friction shifter to try and temper out the noise.....not quite managed it.

I check the chainset when I am off the bike, just to see if it is due to my loading on the chainset. Chainset appears to be true:

So, either:

Chainring bolts loose (don't appear to be)
Chainset loose on the BB axle (bolts appeared tight)

Anything else to check?

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mudcow007
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Re: Wibbly wobbly....

Postby mudcow007 » Thu Jan 10, 2013 10:58 am

ive never known of the drive side, side of chain set to come loose...

sure your cage on the front mech hasnt been slightly bent or something like that?
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dee4life2005
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Re: Wibbly wobbly....

Postby dee4life2005 » Thu Jan 10, 2013 11:10 am

Crank arm rubbing against the derailleur when in the largest chainring ??
Had this happen before, and looking down whilst cycling it's not easy to see.

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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 11:13 am

dee4life2005 wrote:Crank arm rubbing against the derailleur when in the largest chainring ??
Had this happen before, and looking down whilst cycling it's not easy to see.


Definitely the chainring warped causing the chain to rub against the mech.....strange that it is only when under load. Something loose somewhere!

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PedalPedant
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Re: Wibbly wobbly....

Postby PedalPedant » Thu Jan 10, 2013 11:13 am

gtvlusso wrote:So, either:

Chainring bolts loose (don't appear to be)
Chainset loose on the BB axle (bolts appeared tight)

Anything else to check?


Excessive play in the BB bearings?

PP
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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 11:18 am

PedalPedant wrote:
gtvlusso wrote:So, either:

Chainring bolts loose (don't appear to be)
Chainset loose on the BB axle (bolts appeared tight)

Anything else to check?


Excessive play in the BB bearings?

PP


Brand new UN55 BB - Well, less than 2 months old, still feels tight......I am wondering if I have somehow warped the crank spider.....

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mudcow007
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Re: Wibbly wobbly....

Postby mudcow007 » Thu Jan 10, 2013 11:21 am

gtvlusso wrote:I am wondering if I have somehow warped the crank spider.....


you been using

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Veronese68
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Re: Wibbly wobbly....

Postby Veronese68 » Thu Jan 10, 2013 11:26 am

gtvlusso wrote:
PedalPedant wrote:
gtvlusso wrote:So, either:

Chainring bolts loose (don't appear to be)
Chainset loose on the BB axle (bolts appeared tight)

Anything else to check?


Excessive play in the BB bearings?

PP


Brand new UN55 BB - Well, less than 2 months old, still feels tight......I am wondering if I have somehow warped the crank spider.....

If you'd warped it the wobble would still be there when not under load. If you've cracked it that could cause what you describe.

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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 11:28 am

I could be like Godzuki to DDD's Godzilla....

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rjsterry
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Re: Wibbly wobbly....

Postby rjsterry » Thu Jan 10, 2013 11:39 am

gtvlusso wrote:
PedalPedant wrote:
gtvlusso wrote:So, either:

Chainring bolts loose (don't appear to be)
Chainset loose on the BB axle (bolts appeared tight)

Anything else to check?


Excessive play in the BB bearings?

PP


Brand new UN55 BB - Well, less than 2 months old, still feels tight......I am wondering if I have somehow warped the crank spider.....


Derailleur? I thought you wuz fixed. Unless you've developed Hoy-like thighs over Christmas, it's extremely unlikely that you've bent the drive side crank/spider. By contrast, chainrings are quite flimsy especially if your chain line is a bit off, and the load is pulling slightly to one side. If your chainring bolts are a bit loose, this will allow the chain ring to move under load, which will increase the chances of it getting bent.

A more alarming thought is that the BB shell might be flexing excessively relative to the seat tube, which might mean that the frame is about to let go. :shock: Any sign of paint cracking around that area?
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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 11:50 am

My fixed days are a little varied due to an ongoing back injury and my left knee is playing up. Chainline *should* be perfect - BB matched to chainset and at 43.5mm...

Good point on the BB movement, Need to check that!

davmaggs
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Re: Wibbly wobbly....

Postby davmaggs » Thu Jan 10, 2013 11:52 am

I fitted a new BB a couple of months ago, and over the Christmas hols I caught out by the same symptoms. At the time of the repair I wanted to avoid over-tightening the screw holding the chainring onto the BB, I kind of assumed that because I needed a crank extractor to get the damned thing off then the screw wasn't really going to be required to be uber tight. I also greased the threads liberally too.

I was wrong, it had gradually unthreaded over the weeks so each turn of the pedals caused a the chainring to appear warped as it started to wobble a little on each rotation as it gradually became loose from the BB.

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The Rookie
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Re: Wibbly wobbly....

Postby The Rookie » Thu Jan 10, 2013 11:56 am

My chainring does distort under load when using highest/lowest gears at the back (so the chain tension is pulling it sideways as well as backwards so to speak), clearence when not pedaling, slight rub when pedaling, only on the downstroke, no rub when the cranks are vertical.

jds_1981
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Re: Wibbly wobbly....

Postby jds_1981 » Thu Jan 10, 2013 12:02 pm

I had similar problems. Fixed it by changing to a better bottom bracket type.
FCN 9 || FCN 5

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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 12:06 pm

jds_1981 wrote:I had similar problems. Fixed it by changing to a better bottom bracket type.


I don't think there is a better JIS square taper type BB. Must admit that I have been considering a complete new chainset and hollowtech BB

**Vintage frame with 105SC and Dura Ace 7401 mix.

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Kieran_Burns
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Re: Wibbly wobbly....

Postby Kieran_Burns » Thu Jan 10, 2013 12:09 pm

davmaggs wrote:I fitted a new BB a couple of months ago, and over the Christmas hols I caught out by the same symptoms. At the time of the repair I wanted to avoid over-tightening the screw holding the chainring onto the BB, I kind of assumed that because I needed a crank extractor to get the damned thing off then the screw wasn't really going to be required to be uber tight. I also greased the threads liberally too.

I was wrong, it had gradually unthreaded over the weeks so each turn of the pedals caused a the chainring to appear warped as it started to wobble a little on each rotation as it gradually became loose from the BB.


Exact same thing happened to my cycling mate... came gradually unthreaded. - needed tightening up fully before it was sorted
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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 12:12 pm

Kieran_Burns wrote:
davmaggs wrote:I fitted a new BB a couple of months ago, and over the Christmas hols I caught out by the same symptoms. At the time of the repair I wanted to avoid over-tightening the screw holding the chainring onto the BB, I kind of assumed that because I needed a crank extractor to get the damned thing off then the screw wasn't really going to be required to be uber tight. I also greased the threads liberally too.

I was wrong, it had gradually unthreaded over the weeks so each turn of the pedals caused a the chainring to appear warped as it started to wobble a little on each rotation as it gradually became loose from the BB.


Exact same thing happened to my cycling mate... came gradually unthreaded. - needed tightening up fully before it was sorted


Reet - Thanks dude - Chainring bolts.....Now need 8mm allen key!

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rjsterry
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Re: Wibbly wobbly....

Postby rjsterry » Thu Jan 10, 2013 12:30 pm

gtvlusso wrote:
Kieran_Burns wrote:
davmaggs wrote:I fitted a new BB a couple of months ago, and over the Christmas hols I caught out by the same symptoms. At the time of the repair I wanted to avoid over-tightening the screw holding the chainring onto the BB, I kind of assumed that because I needed a crank extractor to get the damned thing off then the screw wasn't really going to be required to be uber tight. I also greased the threads liberally too.

I was wrong, it had gradually unthreaded over the weeks so each turn of the pedals caused a the chainring to appear warped as it started to wobble a little on each rotation as it gradually became loose from the BB.


Exact same thing happened to my cycling mate... came gradually unthreaded. - needed tightening up fully before it was sorted


Reet - Thanks dude - Chainring bolts.....Now need 8mm allen key!


I think they mean the nut holding the crank onto the end of the BB axle, so I think you'll need a socket, rather than an allen key. Failed to tighten this properly myself many moons ago, and the result was the whole crank coming off mid-pedal stroke. It was the non-drive side, so no wobble to alert me. Luckily the whole thing stayed attached to my foot and I was able to bring the bike to a halt without incident.
1997 Giant Peloton 7200 - FCN 4 (5 if it looks like rain)
1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
1980s BSA 10sp

"Be there, eat sausages, gain ultimate respect"

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gtvlusso
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Re: Wibbly wobbly....

Postby gtvlusso » Thu Jan 10, 2013 12:41 pm

rjsterry wrote:
gtvlusso wrote:
Kieran_Burns wrote:
davmaggs wrote:I fitted a new BB a couple of months ago, and over the Christmas hols I caught out by the same symptoms. At the time of the repair I wanted to avoid over-tightening the screw holding the chainring onto the BB, I kind of assumed that because I needed a crank extractor to get the damned thing off then the screw wasn't really going to be required to be uber tight. I also greased the threads liberally too.

I was wrong, it had gradually unthreaded over the weeks so each turn of the pedals caused a the chainring to appear warped as it started to wobble a little on each rotation as it gradually became loose from the BB.


Exact same thing happened to my cycling mate... came gradually unthreaded. - needed tightening up fully before it was sorted


Reet - Thanks dude - Chainring bolts.....Now need 8mm allen key!


I think they mean the nut holding the crank onto the end of the BB axle, so I think you'll need a socket, rather than an allen key. Failed to tighten this properly myself many moons ago, and the result was the whole crank coming off mid-pedal stroke. It was the non-drive side, so no wobble to alert me. Luckily the whole thing stayed attached to my foot and I was able to bring the bike to a halt without incident.


yes - my typo - crank bolts. i think they are 10mm....allen fitting on my cranks. I tightened them to a fair amount of torque - like 10Nm. Will check them though.

jds_1981
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Re: Wibbly wobbly....

Postby jds_1981 » Thu Jan 10, 2013 12:53 pm

gtvlusso wrote:I don't think there is a better JIS square taper type BB. Must admit that I have been considering a complete new chainset and hollowtech BB

**Vintage frame with 105SC and Dura Ace 7401 mix.

That's along the lines of what I did. My original allez had quite a bit of flex. I eventually swapped over the bb to another square taper which turned out to be worse. Went to hollowtech and everything worked a lot better.
FCN 9 || FCN 5


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