zaje

Today I changed the old chainring and stumbled into orientation problem. I have Sora crankset with 46-36 chainrings, the new one is 50T; the old 46T chainring is flat but the new one is slightly concave. When I oriented it the way the numbers are on outside then the concave teeth part os oriented towards the small chainring and chain is rubbing against big ring, here you can see the ring combination 1:




Turned the big ring and installed the other way around (fig. 2) and now the chain is happy, but I have some doubts if this is really correct way how to install the big ring. I am not an expert but for me the teeth looks that they should be the other way around; maybe someone more knowledgable can verify that the big chainring is positioned correctly? If it indeed needs to be turned around, should use some washers to move small ring further away from big ring to avoid chain rub? Here are some pics with teeth:

Iride01 

I think you drew your illustration wrong. Or at least 1 is looking from the front of the bike and 2 looking from the rear of the bike.

For certain the big chain ring needs to have the ramp pins facing the small chain ring. The smaller ring I'd have to look at Shimano's tech doc website and pull up the crank specified by the numbers on the inside of the crank arm around the hole for the pedal spindle. Also you can probably put in the ring part numbers too and come up with the same info.

https://si.shimano.com/#/

If this doesn't automatically present in your preferred language, then look at the dropdown box in the upper right corner of the browser page. You might be able to pick a better suited language.


Welcome to BF!

zaje

Thanks for spotting mistake with drawing, corrected one is below. The old ring has the pin which was under the crankarm, the new one - no pin, this made me think of orientation.

Kontact 

That's the same illustration.

The chainring goes on as shown in the second photo. That should put the ring flaring to the outside for chain clearance and give you a recess for the chainring bolt heads to fit down into.

Iride01 

Check this link to the Service Instructions for several of their older cranks. Note what it says about ring orientation on the top right column.

https://si.shimano.com/en/pdfs/si/1H...0A-001-ENG.pdf

Though also check and be certain this SI is for your crank. And also be certain that you got a ring that Shimano says is compatible with that model of crank.

If the Tech doc site is difficult for you to wade through, then let us know the part numbers of the crank and the ring that you are having trouble with and I or another can check if it is considered compatible by Shimano.

FBinNY 

Orientation #2 is correct. They do this to improve clearance when riding the inner ring with the outer part of the cassette.

Note, that the ring sizes matter. If the inner ring is too large it will extend into the area where the gap is wider, an d allow the chain to jam between them.

zaje

Sora road crankset comes as 46-36 and 50-36 so I assume Sora 50T chainring is fine.

zaje

Thanks all, it looks that the chain rubbing told me that I am doing wrong and you confirmed that the ring is now correctly installed