noglider 

I am installing a lightly used crankset I bought from a gracious BF member. (Thanks! \[wave\]) It has three chainrings. The big one was placed incorrectly on the crank: the pin that prevents the chain from wedging between the ring and the arm wasn't against the arm. No biggy, easy to fix. But is there a correct orientation for the middle chainring? I don't see any signs of it.

Thanks.

Wheels Of Steel

Middle chainrings sometimes come with nubs jutting inboard towards the bottom bracket axle. This nub should be aligned in a similar fashion to the outer, that is in line with the crank arm. If there is no nub orient the chainring however you like.

fietsbob

Logically (to my wee Mind), the big ring pickup pin would be a bit ahead of the one on the middle..
by an amount reasonable for the sideway flexibility of the chain.

Campag has their logo imprint on the outside as a Guide.. ('Race Triple')

a hidden bolt 5 would have the pin behind the arm 180 out from one with the arm at 6:00 and the 5th bolt at 12:00.

noglider 

Thanks. No nub here, but I just realize that I could flip or flop the middle ring. How do I know which way is right?

fietsbob

Quote:

How do I know which way is right?

Counter bore around holes. in aluminum rings lets the sleeve nut stick out much less on the inside..

Look at a New Bike that is fresh out of the factory carton, on the sales floor of your LBS.

Al1943

What is the brand name?

On Shimano chainrings the lettering faces to the right on the big ring and to the left (toward the frame) on the middle and small ring.

On manny other brands they all face to the right.

As for rotational orientation, the numbers or lettering should be in alignment.

FBinNY 

Some chainrings are totally neutral, ie no forward or back, no inside/outside. But most have an orientation. The most obvious is the counterbore for the chainring bolt. If there's no counterbore (ring is the meat of a 3-ring sandwich) you might check of offset symmetry, and gauge by distance to the outer ring. Lastly is tooth profile. If the teeth aren't symmetrical, then the ring is mounted so the steep side is forward at the top, to hold the chain, and the sloped side to the back.

Once you have the inside/outside figured, then it's a question of timing. Besides the tab, they may have a dot, X, or diamond (Campagnolo) to line up with the crank. If there's no timing mark, you can do it the old fashioned way and look for best timing. Loop a length of chain around the outer ring, and lead it through the gate and down to the middle ring. Mount the middle so the flex of chain lines up is best lined up to engage. Repeat this method to phase the inner to the middle.

HillRider

Al is correct for Shimano chainrings. The tooth count number and Shimano name and model number face inward for the middle and granny ring. The middle ring has a small triangle engraved on the inward facing sides next to one of the fixing bolt holes and this triangle should align with the crank arm. Here is Shimano's Tech document for the FC-5703 (105 triple crank) and it shows how the middle ring is oriented:

https://techdocs.shimano.com/media/te...9830702207.pdf

Granny rings are "flat" (no pins, ramps, etc.) so their rotational orientation is not important.

SquireBlack 

What the document says is that for the [l]middle chainring of a triple , the triangle (which is by a bolt hole) goes diametrically opposite the crank arm. For the [l] Inner chainring of a double , the triangle is between bolt holes, and does align with the crank.

Inner chainrings are flat, but that does not mean that their rotational orientation is not important. You still want to have the teeth positioned so that the chain can engage the middle and inner at the same time, during the shift. If your inner ring has 30 teeth, and there are 5 bolt holes, then the teeth are in the same relative position to all of the 5 holes (since 5 is a factor of 30), and the rotational position is indeed irrelevant. However, Shimano makes 30 T granny rings in at least 5 variants (30A thru 30E), which differ in how the teeth are arranged with respect to the bolt holes. Each of these is designed to work with some specific middle ring (39D, 42B, etc)

Whether any of this matters if you are not racing in the Giro is another matter. Some of us have been using “double clangers” with flat rings since the 1970s.

HillRider

Thank you for the clarification after 6-1/2 years.

You are correct, for a Shimano triple crank the triangle on the middle ring is aligned 180º from the driveside crank arm and on a double it is aligned with that arm.

noglider 

I started this thread long ago, and I don't remember the equipment I was dealing with. I don't remember the problem or the solution. But I guess I'm glad to learn a little upon its resurrection.

vane171

I may need some info from here when assembling the triple crank I bought on eBay since it was shipped with the big and middle rings off to make it a more compact parcel. I don't think I will have problem figuring the inner & outer sides of the middle ring because the side facing out is black, but rotational position might be different mater. But I didn't get that far...

The funny thing is, I tried to slip the middle ring on and couldn't figure out if it goes on by threading it on the crank arm and over the spider, or if it should go on over the small ring. I tested the screws on the small ring if the seller removed the small ring to take the middle one off and then re-attached it back, but in that case, he wouldn't tighten the screws on the small ring to the full as they seem to be tightened. He might even have left the small ring off in that case. I only had one try from each side for a bit and put it off for the time being. I would prefer not to remove the small ring since it is really tightened down, maybe I will swallow my pride and send a message to the seller asking how he took it off

It reminds me of one of those jokes (in reverse) when somebody sticks his head in the railing and is not able to get it out again.