mrmb

Just under 2mm





My theory is that since it is a 36 tooth chainring and the crank has a BCD of 110mm, the distance from where the chain contacts the chainring to where the chainring contacts the crank is very short and as such the will be little to no flex of the chainring. Meaning I should be ok……at least I think I should be ok to run this. It is a Surly chrome moly frame, so hopefully not flexy. Also…fixed gear.

Would you run this?

jadmt

Looks like plenty. Much more than i have on my steel bike.

Joe Remi

It depends on how you feel about scratches in paint. I've run rings that close on a few steel frames and scratched every dang one of them..I imagine you will, too, grinding hard on a fixie up a hill.

Garthr

Sure, I would. I'd also use some sort of chain derailment/suck device ! My Bombadil has bowed stays like that and yes it's had some derails and scratching. At first I wanted to cover it back up, but then it happened again (laughing) .... so I left it alone. Spraying a little lube on it keeps it "freshly raw" , hah hah ! If I put anything on bike scratches when the crank is off, or anywhere on the frame, it's clear nail polish. Those tiny applicators are perfect for small spots.

delbiker1 

I would run it like that with no concern.

freeranger

Looks like I'm in the minority on this one. I wouldn't run it that close and risk scratching up that good looking paint. Why risk scratching it if you don't have to?

soyabean

You worry because you subconciously think a chain will be there, even though you know it won't.

A lot of the older Trek/Specialized bikes that used Sugino cranks had chainrains that hugged just as close to the frame. Ideally we want the least amount of crank width.

The only way that chainring can scratch the frame is if your bottom bracket cartridge is left shot to hell, in which case you have other problems to worry about.

Joe Remi

I think you're underestimating how much a steel frame can flex around the BB shell.

jadmt

what is the most actual flex you will get. stand with all your weight on each pedal when they are at the lowest point and see how close it will come. Mine is a crappy frame and it does not come close. Unless Mark Cavendish is going for the line than maybe...

Iride01 

I've had closer. A miss is as good as a mile.

And you don't have all the chain ring bolts installed. There looks to be a little gap between the spider and the ring.

Mr. 66

That is close, one could use a spacer at the bb fixed cup and gain a millimeter.

soyabean

And?

Will it get to the point where it will keep that way and the chainring gouge into the frame?

Sorry, I'm with everyone else on this. The setup is fine.

icemilkcoffee 

Unless you are this guy:

You are not going to flex that frame enough to make them touch.

maddog34

looks like it's too close... do this.. wrap your chainstay with three layers of masking tape at the possible contact point...... finish installing the chainring screws... go ride the bike on flattish terrain...look at the tape.

steel frames tend to flex more that most aluminum frames... Carbon frames can be too darn stiff, brilliantly perfect, or more flexy than steel... My Mitzutani SuperLite factory racer was nicknamed "The Flexy Flyer."... that thing's BB moved about an inch back and forth on steep climbs...19.5 lbs. of sheer terror. The 48t "low gear" chainring just barely kissed the chainstay fairly regularly.

79pmooney

Unless that frame is very flexy or you have a Nelson Vails build or are a strong but uneven pedaler, that clearance is plenty. I'd be quite happy with half that and have many miles with that half and less. Plus, if all goes to h*** and a hand basket, its an aluminum ring nicking a steel tube. It will take a while for more that paint to be damaged.

Again, unless that frame's a noodle (and you will know that first ride), you have plenty of clearance. Adding the additional suggested by some here is wearing a helmet in your car in addition to the shoulder harness and air bag.

Iride01 

Well despite airbags and shoulder harnesses, I think head trauma is one of if not the leading cause of death in automobile accidents.

caloso

Plenty. If you could put enough torque into the bike to cause that to rub, someone will be paid to maintain your bike.

icemilkcoffee 

Very easy way to test. push the front wheel into a wall corner. Put all your weight on the right pedal and bounce up and down and see if anything touches. I bet nothing touches. The chain stays will pretty much flex together with the BB.

Joe Remi

And I've had several bikes with that much clearance and I scraped the chainstay. I explained this.

tkamd73 

Looks like most of my bikes.
Tim

Troul 

could you use a narrower chain ( IE: 11sp chain on a 10sp gear set )
I know it will not impact the gap you have, but it might avoid some slap. I'd add 1mm or 2mm if possible.

Kapusta

Count me among those having a hard time seeing the frame flexing enough to move the stay over 2mm that close to the BB.

I’ve had really tight clearances in the past (I’d guess 2mm) and never had them gouge.

Russ Roth

But the helmet is required at the track, so's the roll bar.

OP, I'll chime in with the bulk of them, I've had the same amount of clearance and you're unlikely to damage anything. Probably means you have an optimal qfactor on the cranks for the frameset if they sit that close.

tFUnK

It's probably ok but as a bigger guy I wouldn't. Only the OP can gauge how flexy the frame is. It's true that the CS flexes with the BB but that amount of clearance doesn't leave a lot for comfort (eg, what if the chainring is really cheap with loose tolerance, or if the chainring is coated with grime or mud?).

zedda

So here the flex in the BB and the crankset won't hurt because it's in the up and down direction, however the flex of the frame while climbing might hurt?
I'm still somehow positive this is quite enough of a distance.