Wibbly wobbly....

gtvlusso

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?

mudcow007

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?

dee4life2005

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.

gtvlusso

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!

PedalPedant

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

gtvlusso

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.....

mudcow007

gtvlusso wrote:

I am wondering if I have somehow warped the crank spider.....

you been using

Powa Awesome?!

veronese68

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.

gtvlusso

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

rjsterry

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?

gtvlusso

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

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.

The Rookie

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

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

gtvlusso

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.

Kieran_Burns

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

gtvlusso

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!

rjsterry

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.

gtvlusso

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

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.

rhext

Get a really big spanner on it and tighten the crank bolts up as much as you can. I had a similar problem, took it to the LBS, turned out I'd not tightened it up anything like enough. They put some real muscle into it and I've not had a problem since. In my case the crank bolt was working loose as I pedalled, but it's not obvious to a casual inspection because you don't put enough load on it. A big giveaway is if the chain is rubbing against the outside edge of the front mech as you push down on the drive-side pedal.

UndercoverElephant

gtvlusso wrote:

I tightened them to a fair amount of torque - like 10Nm. Will check them though.

We have a winner, I seem to recall when I installed mine it required nearer 45 Nm.

gtvlusso

UndercoverElephant wrote:

gtvlusso wrote:

I tightened them to a fair amount of torque - like 10Nm. Will check them though.

We have a winner, I seem to recall when I installed mine it required nearer 45 Nm.

45Nm is huge!! My last crankset (FSA) was only rated to 20Nm - I did 10Nm as it did not say anything in the instructions for the UN55 (and I have stripped BB crank threads many years ago), safe rather than strip the threads.

I will re-tighten though.

gtvlusso

gtvlusso wrote:

UndercoverElephant wrote:

gtvlusso wrote:

I tightened them to a fair amount of torque - like 10Nm. Will check them though.

We have a winner, I seem to recall when I installed mine it required nearer 45 Nm.

45Nm is huge!! My last crankset (FSA) was only rated to 20Nm - I did 10Nm as it did not say anything in the instructions for the UN55 (and I have stripped BB crank threads many years ago), safe rather than strip the threads.

I will re-tighten though.

A quick google suggest about 34Nm upwards to 50Nm. I'd best dig out the 'big' torque wrench!

http://www.shimano.com/publish/content/ ... 0Specs.pdf

Thanks dude.

UndercoverElephant

gtvlusso wrote:

gtvlusso wrote:

UndercoverElephant wrote:

gtvlusso wrote:

I tightened them to a fair amount of torque - like 10Nm. Will check them though.

We have a winner, I seem to recall when I installed mine it required nearer 45 Nm.

45Nm is huge!! My last crankset (FSA) was only rated to 20Nm - I did 10Nm as it did not say anything in the instructions for the UN55 (and I have stripped BB crank threads many years ago), safe rather than strip the threads.

I will re-tighten though.

A quick google suggest about 34Nm upwards to 50Nm. I'd best dig out the 'big' torque wrench!

http://www.shimano.com/publish/content/ ... 0Specs.pdf

Thanks dude.

Yes it's huge. For that very reason I ditched the Allen-bolts and used the supplied ones with a socket instead. I would suggest that at those torques, either your Allen keys or the bolt will round off nicely.

On the plus-side, the regular bolts won't need adjusting much once they're on.

Kieran_Burns

My method is to tighten as much as is comfortable and then a 1/4 turn more. Quick and dirty I know but I've not stripped a thread yet and never had a crank come loose.

UndercoverElephant

Kieran_Burns wrote:

My method is to tighten as much as is comfortable and then a 1/4 turn more. Quick and dirty I know but I've not stripped a thread yet and never had a crank come loose.

Torque wrenches are cool and make you feel like a proper bike-mechanic: Accept no substitute.

davmaggs

rjsterry wrote:

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.

For me the bottom bracket was secure and wasn't the problem, the chainring bolts were good too. On the Sirrus there isn't a nut to hold the chainring/crank on to the bottom bracket. Instead it is a threaded bolt (with a big washer) that you tighten with an Allan key. That pushes the crank onto the spindle and snugg into the BB.

In my case this screw had undone a little, and the crank was able to slip down the square spindle of the bottom bracket a few mm. This meant that as I applied power to the pedal it caused the chainring twist a little, and then straighten again on the up stroke.

gtvlusso

And generally, you need 2 torque wrenches - 1 for small values on carbon frames and then one big fecker for bottom brackets! More tools is a good thing!

Hmm - crank bolts, rare to fing the old nut type....generally only the allen type bolts. Though there are some natty self extractor ones.

Kieran_Burns

UndercoverElephant wrote:

Kieran_Burns wrote:

My method is to tighten as much as is comfortable and then a 1/4 turn more. Quick and dirty I know but I've not stripped a thread yet and never had a crank come loose.

Torque wrenches are cool and make you feel like a proper bike-mechanic: Accept no substitute.

Ha.

Real men used:

mudcow007

UndercoverElephant wrote:

gtvlusso wrote:

I tightened them to a fair amount of torque - like 10Nm. Will check them though.

We have a winner, I seem to recall when I installed mine it required nearer 45 Nm.

Mr Lusso have you just openly admitted on this here forum that you have the arms of the snowman an arnt able to tighten more than 10Nm

*giggles*