Tight Chainring Clearance
 

Hey! I just picked up a new vintage bicycle and i'm cleaning it up at the moment. However I noticed that the inner chainring has very limited clearance and it looks like the frame's pretty banged up because of it. What could i possibly do to remedy this? Or is it normal?

Looks a bit too tight to be normal. Ideas: Original right hand crankset overtightened onto bb/not original right hand crankset/length of bb too short/small (inner) chainwheel warped. This looks too close for comfort. The chain is going to rub right against the right chainstay.

Well the chain shouldnt rub cause the chain isnt going to be sitting on the teeth in that area, but I agree its a bit too close, the teeth may rub the stay when you're hammering or climbing hard!

Any mis-shift could cause the chain to be sucked in between the small chainring and the chainstay.

I worked on the bike today but so far the chainring does not strike the chain stay at all but 3 of the 5 bolts do rub against it. Should I pull the crank and then thread it back on? The crank and the chainrings appear to be original based on the catalog scan and there is no warp in the rings.

Are you using an outer ring? If not, can you put this single there?

And removing and replacing the crankset will probably result in pushing it closer to the stay, not what you want.

I just got this bicycle sunday so i've been cleaning it any have yet to really ride it though I do believe I will make use of the outer chainring. Why would removing/putting it back in result in it being even closer?

You should check to see if the spindle is installed properly with the longer side on the drive side (most spindles are asymmetrical). You might end up having to get a longer spindle.

Use a shim on the drive side cup...I grab them off of Sturmey Archers AW's but most bike shops will have a proper shim.

I brought it to the LBS today and the two mechanics there said it should be fine. They said the bolts should continue rubbing the frame until the paint is gone and then there should be enough room and this shouldn't cause an frame damage. Oh I was also riding it pretty hard today and there wasn't any flex. Hopefully it will work itself out over time. Thanks! (Any more thoughts is appreciated though)

I second the suggestions already made. First check that the spindle is in right; and while you have it out, measure it. If it's in right, either put a 1 mm spacer under the fixed cup, or try a different spindle; someone here might have one to trade.

The 1-2mm spacer is easy, cheap, and painless...

:eek:

BF advice: Good
LBS advice: Bad

Haha yeah that's what im feeling. I'll check out some spacers or a new spindle. Actually, is there room for spacers? Sorry, if that's a dumb question. If so, could someone direct me to a compatible spacer. I believe it is a shimano 600 bb since most every other part on the bike including the cranks are shimano 600.

http://i294.photobucket.com/albums/m...bclearance.jpg

You can order a "Sprocket Spacing Washer" from Harris. It's part #16. If you have an old shop in town where the mechanics aren't idiots they'll likely have one just chilling in an old dusty box in the back...Your LBS mechanics advise is terrible and I'd never take my bike there.

Yes there is room...The washer goes on the fixed cup on the drive side.

Ugh. Shipping is 8.50. I'll have to post in the ISO thread. Should I probably not ride this until it's fixed or a little riding won't be too bad? Thanks guys!

There's your problem, dollars to doughnuts.

From your photo, I can see that the faces of the "bolts" (nuts, actually) are sticking up clear of the chainring instead of flush with its surface as they should be. The 5 mounting holes on a chainring are countersunk on the inboard side, to allow the nuts to nestle down into the chainring to prevent exactly your problem. I suspect that someone has flipped your inner ring over, perhaps to get a few more seasons' wear out of the teeth. Suggest you remove the inner ring and re-install it with the countersunk side inboard. You can do this without removing the crank -- usually you don't even have to remove the pedal. If you find that for some reason your chainring does not have countersunk holes on one side, get one that does.

(You don't want to remove the crank because each time you re-install it, you enlarge the mounting hole a tiny bit, making it drive farther inboard on the spindle.)

Putting a spacer under the fixed cup is not exactly easy and painless: the fixed cup is a bugger to get out usually. (Not for nothing are they called "fixed".) Before you start down that road, make sure there is at least 1-2 mm of the adjustable cup sticking out beyond the lock ring now. Otherwise after you've gone to all that trouble putting the spacer on the fixed side you'll find that the adjustable cup disappears all the way into the bottom bracket shell leaving no threads exposed to engage the lock ring. Grrrrrr! (In a properly spec'ed bottom bracket, the lock ring will already be flush with the adjustable cup as is. Unlikely will you have extra threads showing now.)

But get those chainring nuts flush first. They absolutely should not sit proud of the chainring.

Les

P.S. Why should only 3 of 5 nuts rub? Are you sure the ring isn't warped?

I agree with the suggestions in post #17.

The damage to the chainstay was caused by chain suck. It has nothing to do with missed shifts. It's caused by a worn out chainring. Perhaps the previous owner solved that problem by flipping the chainring around backwards.

^^ Bingo. We have a winner!

I declare myself the c&v mechanic numbskull of the week or maybe even the month. I actually took the chainrings off for cleaning and i put it back on wrong. The other chips were there prior to this aka the original post. I'll put the rings back on tomorrow and tell you how it goes. Hopefully I didn't permanently damage/weaken the frame. I rode about 25 total miles on it with bolts hitting the chain stay. I'll tell you guys how it goes tomorrow!

Usually, (not confessin' ta anythin', jus' sayin'....) knowing what to look for comes from having made the same mistake oneself.