Ultegra Chianrings

glasgowbhoy

Asked in workshop but not answers.

Will 6600 Ultegra chainrings fit onto my 6700 Ultegra ?
They seem a good price compared to 6700 chain rings

PeterBL

They will fit, but look really bad. Probably won't be as stiff as 6700 either.

glasgowbhoy

cheers, that's that sacked then

Sleeping_menace

FTR 6700 chainrings, the outer at least is NOT stif.. it's a piece of cheap stamped aluminum over plastic and has the structural rigidity of overcooked pasta.
Take one off the cranks and flex it in your hand if you don't believe me...
Cosmetics aside, pretty much any decent ring will improve your shifting over the stock outer, however Shimano designed them such to look like complete crap with any rings except the ones they come with.

tonye_n

Sleeping_menace wrote:

FTR 6700 chainrings, the outer at least is NOT stif.. it's a piece of cheap stamped aluminum over plastic and has the structural rigidity of overcooked pasta.
Take one off the cranks and flex it in your hand if you don't believe me...
Cosmetics aside, pretty much any decent ring will improve your shifting over the stock outer, however Shimano designed them such to look like complete crap with any rings except the ones they come with.

Eh?? WTF?!

desweller

Sleeping_menace wrote:

...it's a piece of cheap stamped aluminum over plastic...

I don't even know what this means, and I'm a manufacturing engineer...what are you trying to say here?

Sleeping_menace

what part of the statement is difficult to understand? Cheap? stamped aluminum? or plastic?

Look at the pic:


As I said, the outer ring is very thin, stamped aluminum ..over plastic.. a plastic ..'core' if you will. In your hands, the outer ring will flex terribly, and does so under load when being ridden under power.
Another pic of the alu/plastic chainring construction:


From a manufacturing standpoint, once dies are created, the time to stamp the aluminum is minimal, as is injection moulding the plastic form -- cheaper than CNC'ing a ring from solid aluminum.

desweller

I would have thought a normal chainring is stamped from a sheet and the ramps and teeth profiles etc. forged into it in the same operation. That's interesting, I'll look around for some more info.

Sleeping_menace

Most high quality rings are fully CNC machined, Very low end rings are often stamped (usually of steel), but Shimano are the first I know of wrapping a sheet aluminum stamping around a plastic core. For the amount of money being spent on Ultegra cranksets, it's a pretty appalling way for the outer ring to be constructed IMHO..
I know Shimano will put a spin on it, saying it's 'advanced manufacturing technique' or some other such rubbish, but the fact of the matter is that it's the cheapest possible way for the outer to have been constructed.

tonye_n

I usually don't bother to get involved when people post misleading comments such as the above.
However it does seem that the chap knows that he is telling half truths in order to give the wrong impression.
That (in the picture) is the "inner" sheet of a two part outer chainring. The chainring is made up of two plates mated together to form a hollow chainring.
And so the outer chainring uses hollow-tech system(same as shimano has been using on 105 - dura ace crankarms for some time now.
This makes for a lighter and stiffer chainring than just a single piece of aluminium (stamped or cold-forged). I think the outer plate of the Ultegra outer chainring is cold-forged but I am not sure. Ultegra sl was cold-forged.

When Shimano started using hollow crank arms this used much less metal(therefore lighter) than the old "c section" crank arm (still used on tiagra and below) and no one suggests that this makes for a less stiffer construction.

Sleeping_menace

The two piece ring, is, as I stated, plastic,or some variant thereof. The ring may indeed be hollow or not, probably is..but the fact remains that the outer is still a piece of stamped aluminum, bonded to the plastic inner.

Wherein you see half truths in what I'm saying, I'd be quite interested to know. I've got the cranks in front of me.. and the outer ring is constructed as I indicated. Its' also the most flexible outer ring I've run into. There's no rigidity there.

Where your machining costs are largely one time, when making stamping dies (proper quality steel die would last many many thousands of cycles stamping sheet aluminum) I stand by my comment that it'd be done as a cost cutting move, vs cnc machining the rings from aluminum stock.

From your stance, I'd be quite surprised if you're not running Shimano, and because of this, my comments hit a nerve -- fair enough. I was running them too. Had the crankset been decent, I'd have stayed with it but between the rings and overall construction of the crankset, it was just too flexy, yet didn't come in at any kind of aggressive low weight to offset this. Now these cranks sit as spares on a shelf and have been replaced after having been used for possibly a month. It's not often I bail on a part after such a short time,but there was just no redeem to be found. For the record, as you can see below, I did replace the outer ring briefly with a Rotor ring, and there was noticeably less flex than there had been with the original Shimano, so again, I stand by my comments.

desweller

I don't understand why a top end chain ring would be machined rather than cold-forged. Forging is a superior process in almost every respect.

cougie

http://www.bikeradar.com/gear/category/ ... t-09-34928

6700 chainrings look superficially at least the same as 6600 ?

tonye_n

The outer plate is cold forged. The inner plate(of the outer ring) is perhaps stamped alu, not sure. The inner plate is also attached to a composite material. They key is in the mating of both plates to form a stiff hallow chainring.

Unfortunately I can't afford Ultegra at the moment. I did some research when looking to replace my 7800 drivetrain.