Chainring spacers in Ultegra cranksets?

[DMF]

Pulled apart my OEM FC-6500 crankset the other day. There are thin spacers between the spider and the inner chainring. I believe they were put there by Shimano, but these spacers don't show up on any exploded drawing.

I pulled apart another FC-6500 because the inner chainring had been assembled "backwards" - Shimano specs that the side with the lettering face the frame. There were no spacers in this assembly, but I also noticed that the cogs are offset slightly to one side of the ring. By flipping the chainring to the "backward" position, one moves the cogs toward the frame from the spider, just as the spacers do.

Anyone know anything about this?

Are the cogs directional?

 

[gclark8]

Shimano specs that the side with the lettering face the frame.

Show me where?

My understanding is, viewed from the drive side, all manufacturers marks face out and up.

 

[DMF]

From FC-6500 Service Instructions, re: double:

With the marked surface of the
smaller chainring facing away from
the crank arm, set the chainring so
that the ^ mark is lined up with the
crank arm position.

and re: triple:

For the FC-6503, the tooth
number marking on the largest
chainring should face outward,
and the markings on the
intermediate and smallest
chainrings should face inward.

There's also a picture showing the marks facing in.

Interestingly, there is also a ^ mark on flip side, where it shouldn't be needed.

 

[gclark8]

The little arrows or v marks are timing marks.

There should be a "Brand" on the outer face of the CR or the numbr of teeth stamped, "39", "53", "30", these face out.

 

[gclark8]

From: http://www.shimano.com.au/publish/c...r.0008.Schematic.0019.File.tmp/bb_6500_si.pdf Shimano may seem to be giving mixed messages, stay with the timing marks "IN".

Sugino and TA make it clearer and easier.

 

[DMF]

That's the exact document I lifted the quotes from! What in the doc give you the idea that the text on the inner ring(s) should be facing out?

There are timing marks on both sides of the smaller chainrings, so they don't tell you anything about facing.

 

[DMF]

Spacers are 0.2mm.

And they are between the spider and the outer ring, not the inner ring as I said first. (Not that it makes any difference, 'far as I can see.)

 

[gclark8]

That's the exact document I lifted the quotes from! What in the doc give you the idea that the text on the inner ring(s) should be facing out?

There are timing marks on both sides of the smaller chainrings, so they don't tell you anything about facing.

It is Standard Engineering Practice to have Manufactureres Marks Out, If you have timing marks both sides, look for aditional marks (tooth count) on one side. This is how TA and Sugino do it. There should also be receses in the face of the chainrings for the fixings on the inner side of the middle and inner rings.

 

[DMF]

SEP or not, I'm not going to argue with Shimano. They want them facing in, that's my SEP.

Look at the bleedin' picture, for goo'ness sake!

And good point. There are recesses for the chainring bolt retainers in the side with the manufacturer's mark and tooth count on it (the "marked surface"); no recesses on the other side. The retainers *must* go on the frame side of the crankset, therefor so must the "marked surface".

 

[DMF]

George, I received a brand new sealed-in-Japan Shimano crankset today. The marked surfaces of the two inner rings are facing the frame.

 

[gclark8]

OK, for genuine Shimano (6500) Cranksets, I will now "proceed with caution". Thanks for the info.

 

[DMF]

I replaced the shimmed (170mm) crankset with an unshimmed (175mm) one. Didnt' touch the derailleur adjustment. Brief test-ride and it felt fine, shifted smoothly. Then rode a century yesterday and at the first front upshift I threw the chain - the first time ever. I was careful to be gentle on the upshift thereafter and it didn't recur.

But maybe 0.2mm makes a difference after all!

 

[gclark8]

Did you use a torque wrench on the BB bolt?

 

[DMF]

Of course. 44 ft-lb on the BB shell, and 31 ft-lb on the crank arm retaining bolt.