Shimano R8100 chainrings - Brand new - £80

Spanking new rings. Removed as I’m running other rings. 50/34. Never had a chain around them.

£80

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I can drop these off within reasonable distance

Bump on these. EBay is a shit show. £70

I have no axe to grind with your ad, however factually, they're not both 8100 chainrings.

It might be an 8100 inner chainring i.e. Y0NG34000, but that's an FC-08 50t chainring i.e. Y0V398060.

The clue is the 11s stamped on the 50t. The 34t will have 12s stamped on it.

I'm not saying they aren't (or are) identical but technically they're not 8100 rings.

I'm saying that as someone with an FC-09 marked 11S but measured it to have a 12s chainline of 44.5 and a 148mm Q-factor, and identical tooth ramps etc of a 12s chainring. Where 11s cranks were all 43.5 and 146mm. So appears to be a FC-R9200 crank but stamped 11s for some reason. But Shimano haven't given out the specs of the FC08 or FC09 so who knows!
If you know more please let me know!

Simple answer is, you’re bang on and that’s why I had difficulty selling it on eBay.
I’ve measured this to be as you’ve said, 12s compatible, but it was hard selling it as such with the markings for 11s.

Now this was part of the recall for the 8000 era chainset. But the only returned the 8100 era stuff, which is 12s.

I worked as a service course mechanic a short while during the 11/12 speed transition, and we were advised by Shimano that they're interchangeable as there was no external difference in chain dimension externally between 11 and 12 speed. It was internally that it was different.

Which brings us to this chainring set, how do I advertise it, 11 or 12 speed compatible?

I’ve personally used these on both 11 and 12 speed groups and I’ve notes zero difference in shifting.

Offers? Just want these gone

Bump. £65

prov dibs for someone, do you know if they will work with 6800?

Ignore me, he has already bought a replacement crankset

These won’t work with anything apart from the 8100 series, but no rides their bikes so no worn out rings!

Ive put some 8100 rings on a duraace FC09 crank, no issues.

Be honest, say one is are marked as 11 speed, but informally it measures up the same as 12 speed chainrings.

Interesting about your service course experience.
How do you mean "external difference in chain dimension externally between 11 and 12 speed. It was internally that it was different."?
I've heard some stories of teams experiencing chain drops during the era of mixed groupset, but some others saying that was actually the first batch of 12 speed derailleurs etc being trouble.

Thanks. That’s good to know. Shimano nomenclature is a bit of a mess at the moment to be honest.
Shimano tech says fc09 are 11 speed replacements whereas the 9200 are 12 speed. I can see zero difference in design or fit.

My theory is with the looming recall a while ago, Shimano just redesigned it all the same and change model designation.

I could however, be totally wrong.

@Chak Hi, really sorry to bother you and interrupt the thread. I have a question about tyres if you have got a minute please mate?

I can't tell you specifically as even with a few of us taking a micrometer to the links, we only noticed narrower dimensions. Shimano techs told us that the outer link dimensions were never changed between 11 and 12 speed, so in theory, there's little to distinguish them; Shimano made the change to the inner dimensions of the chain in order to operate smoothly with the narrower 12 cassette sprockets.

Dropped chains during that era were no different to any other in my experience. The worst dropped chains were with Oval rings and mis-shifting was with oversized jockey wheels.

I'd like to say they're marked as 11 but they're 12, and to my limited experience with some measuring tools, they seem to be, but I really don't know.

Just say the word. What's up?

@chak you angel! I’m after a 35-40 /700 tubeless gravel tyre - have you got anything in your bike cave?!

Hmm, the bike cave and bikes have all been completely cleared out. Though I miiiiight have a Pirelli I’m unlikely to use.
How quickly do you need it?

wow, good on you for having a sort out. I’m in fairly desperate need. I am booked on a ferry that leaves on 17th

Let me have a look tomorrow. afternoonish. Earliest I can check I'm afraid. It might be in Storage.

think i have a spare WTB new cross boss 35mm if you are stuck

ah! amazing!

I’ve found a near new 38mm tyre. Vittoria Terreno dry

Totally forgot I still had these. £50

Just realised I still have these if anyone wants them. £45?