Crank touching Chainstay under load

[tippers_kiwi]

Hoping someone can help on this one. I have a Genesis Day One which I converted to Fixed back in April. I have the Miche Advanced 172.5 Cranks which under normal use or when I am climbing out of the saddle seem to clear the chainstay OK but when I am seated and put a bit of extra push through the non-drive side crank the drive side rubs against the chain stay.

I had noticed this when I first converted it and I took to the back of the crank with a Dremel which seemed to rectify the issue but this weekend it was back and I am not too keen to start removing more metal (I hadn't removed very much anyway). I have some helicopter tape on the chainstay and the contact is not enough to get through the tape, it has just left a light gouge in it so it's really only just touching.

My thinking is to go to a 170 or even shorter crank, would this resolve the issue? Any other possible fixes I should consider?

[Torslanda]

Get a longer bottom bracket. You don't mention if the cranks are evenly spaced. They should be.

[zigzag]

Take a piece of wood/dowel place it right on the spot where there is rubbing and pound it with a hammer few times, you only need about 1-2mm extra clearance by the sound of it

[tippers_kiwi]

Thanks Torsland, I'll measure that spacing. I hadn't thought about the BB option, I guess that would also mean spacers on the hub to keep the chain line. Will take a look.

Thanks for the idea Zig Zag, I'm not confident enough in my hammer finessing skills to have a go at that yet I reckon, but I'll defo keep that in mind when nothing else works.

[LittleWheelsandBig]

Have a good look at how cranks fail at the pedal eye. Then compare the amount of metal at the sides of the pedal eye with the amount at the end of the pedal eye. Then file some more metal until you've got sufficient clearance.

A 1mm spacer under the fixed cup is very quick and barely affects chainline.

[Chris N]

I'd be concerned that you fixed the issue then it came back.  What changed?

[Oaky]

I'd be concerned that you fixed the issue then it came back.  What changed?

... further to this - have you noticed any oddness in chain tension lately?  I had a BB where the bearings failed (the original one on the day one, as it happens) one symptom was that occasionally when I checked the chain tension, it was tighter (much tighter) than the last time I'd tensioned it.  The other symptom was that occasionally, the BB spindle would go off-axis - it never caused my crank to contact the chainstay, but I iguess it could easily do so.

It's a long shot, though, my failed BB was considerably older than yours is.

[mrcharly-YHT]

If you get the matching BB,
http://www.wiggle.co.uk/miche-primato-track-bottom-bracket/

Then it can be adjusted for chainline.

I reckon you should replace your BB and do this to adjust it so that the cranks don't hit the chainstay.

[tippers_kiwi]

After the Flatlands where I had a lot of different noises coming from the drivetrain (some I suspect due to the amount of rain washing away lube etc.) I stripped it all down and rebuilt. All the noises are gone but that rub has come back, I suspect it might have been there all along just not quite as bad.

Interesting point you make Oaky, I do have a spot where the chain is slacker, I suspected that was to the relatively common not 100% round chain ring and the fact it is difficult to get them 100% centred. I hadn't noticed anything particularly noisy or loose when I cleaned up and regreased the BB and the cranks definitely don't have any play once installed.

I guess spacers are the starting point for now...

[tippers_kiwi]

If you get the matching BB,
http://www.wiggle.co.uk/miche-primato-track-bottom-bracket/

Then it can be adjusted for chainline.

I reckon you should replace your BB and do this to adjust it so that the cranks don't hit the chainstay.

This is the BB that came with the bike in the 110.5mm

FSA Square Taper BB

I suspect that this gives the same adjustability as the Miche one as in I just put spacers on the drive side to move it out. I guess I need to check how close the Non Drive side crank comes before doing this as well.

[Torslanda]

I have seen a BB like that seize the bearing and begin to unscrew on the left hand side. By degrees the BB worked its way to the left until it locked up on the RH stay.

[Tim Hall]

Have a good look at how cranks fail at the pedal eye. Then compare the amount of metal at the sides of the pedal eye with the amount at the end of the pedal eye. Then file some more metal until you've got sufficient clearance.

A 1mm spacer under the fixed cup is very quick and barely affects chainline.

This (the spacer thing) is what I did when I had similar issues on my Dave Yates.  I got a lad at work to turn a few at around 1mm, and have some left. I can stick one in the post if you want, and if I can find them.

What's the chainline like at present?

[Kim]

+1 for BB spacer.  They're not expensive.

[Biggsy]

I'd be concerned that you fixed the issue then it came back.  What changed?

Assuming square taper and if crank was removed and refitted, it could just be the crank moving up the taper after initial (re)fitting.  It's only a worry if it repeats, which it might if the bolt is retightened repeatedly or if the crank hole is knackered.

[matthew]

Have a good look at the chain stay, I just tried to salvage a donated bike where the chain ring was rubbing the chain stay only to find the chain stay was badly damaged at the bridge and the rear end was therefore bent resulting in the rubbing.

[tippers_kiwi]

Thanks to all for the input on this one. I managed to get my hands on a 1mm spacer and popped it on the Fixed cup and yesterday's 300k was completed without a single click!

I had wound the fixed cup out and the other side in but I didn't feel comfortable that it would stay put and it bothered my OCD side when I looked down and saw the gap. The spacer sorted all of that and as LWaB mentioned, not any material change to the chain line, if anything it seems to run slightly quieter....maybe I need to do a proper measure up to see just where it is.