WizardOfBoz

I ordered an Ultegra R8000 Gruppo from ChainReaction (very positive experience - fast delivery and good price, btw) but in a hasty moment selected 50/34 chainrings where I probably want 52/36. Arggh!

I'm itching to put the bike (a 1999 Lemond Zurich, a made in the USA frame of Reynolds 853) together and ride it. If I do so, can I just replace both chainrings or do the different ring sizes use different cranks?

Alternately (if I wanted to preserve the R8000 chainrings as new), could I temporarily use a 9000 series dura ace crank? I realize that the chainring spacing is different with the newer (9100/R8000) shimano cranks, but is this a case of "Won't work", or a case of "Won't shift as well as its supposed to, but you can ride it for a few weeks" type of thing?

cpach

R8000 uses the same asymmetric 110 4 bolt pattern for all supported chainring combos: 50/34, 52/36, 46/36 and 53x39.

The 9000 crank will work fine also.

WizardOfBoz

So the different spacing between the R8000 and the 9000 won't matter initially?

I was able to get my preferred chainrings on order and will install those next weekend, but I'd like to get the bike rideable today and if the 9000 works, I'll be able to avoid using the other chainrings (50 and 34T) at all and can sell them as new on ebay.

I did find this thread which seems to say that the front chainring on the newer Shimanos is 0.4mm more inboard, and that the FD moves further inboard on its travel. I guess I'll give it a spin - literally.

cpach

It'll be fine. The FD is definitely adjustable enough to work for either. The newer chainings are designed to work better with disc brake bikes.

WizardOfBoz

Thanks!

How does the chainring affect the disc brake? How does this work? Thanks in advance.

cpach

It doesn't directly, but disc brake road frames are either 135mm quick release or 142mm thru axle for the most part now, which moves the chainline of the cassette outwards by 2.5mm. When combined with short road chainstays, this means that the angle of the chain when cross chained small/small can be such that it begins to get picked up the the shifting aids on the large chainring. Many current chainrings have been slightly redesigned so that they maintain the same Q factor as before, but work well on frames with 130mm rear dropouts and 135/142TA dropouts.

WizardOfBoz

Ah, clever. Thanks for the nice explanation. So it won't improve my caliper brake QR wheel road bike at al. And I can adjust the newer FD to accomodate the older Dura Ace until my 52 and 36T chainrings come in from eBay. One point that I think is not an issue (I hope) is that with non-disc brakes, the minimal change in inner chainring position won't negative affect my chainline.

It it will, and the FD R8000 works will the currently Dura-Ace crank I may just keep that crank. If not, then I'll sell the DA crank (used to be owned by National Downhill Champion Neko Mullaly) and the 50/34 chainrings I mistakenly ordered, and with the proepr 52/36 rings I'll be good to go.

I'm really enjoying putting the bike together. One glitch was that the front tubular brake nut wasn't long enough. I had a 12mm. So I'm off to the store to get a 20mm.

cpach

Sounds like a very nice build. Thankfully recessed nuts are pretty darn cheap. I'd keep the crank I liked the look of the best personally. Those 853 Lemonds are real gems.

WizardOfBoz

My local LBS gave me a couple of longer tubular nuts. A 20mm, and a 26mm. The 20mm has about 6mm engagement, which should be ok. So the brake is now mounted.

Regarding the 853 Lemond's, I agree: great material and built in the USA (in Wisconsin!) by Trek*. I was lucky to find one in my size.

I figure that I'll sell the older Dura Ace crank because it will generate more $$$. I've got the 52 and 36T chainrings for the Ultegra R8000 on order. Should be ride-able today with the DA crank, and finished within a week with the proper crank. Plus the new R8000 crank is hollow Al, which seems pretty cool.

*I like Trek, but figure that they owe Greg Lemond an apology. If I ever meet Greg and I'm on this bike, I'm going to steal a witty line from another cyclist, and I'll ask Greg write "I TOLD you so!" on this frame with a Sharpie.

Eggman84

I find the technical specs for the new FC-R8000 and R9100 cranskests interesting. Specifically, Shimano states " .. by the more extreme chainlines found on today's shorter chainstay frames, which when combined with greater cassette range and new rear spacing, totally changes the load the chain must manage for safety, To create a little more diagonal clearance the inner chainring has been offset .4mm inboard to the center of the bike."

If I read that correctly it says 0.4 mm, not 4 mm. They don't say anything about adjusting the outer chaninring, so that means they just increased the spacing between chainnrings, which is interesting because the chain just got narrower (for 11 speed). So doesn't this negate all that past verbage saying how critical it is that the space between chainrings be reduced when going to more cogs (speeds)?

As to what cpach says, if the OLD (over lock dimension) of the rear wheel increases to 135 mm (142 TA locates teh cassette the same as 135 QR) for road bikes with disk brakes, then the chainline of the cassette increases. So why would you reduce the front chainline while increasing the rear chainline. Just asking! Oh, and how long will Shimano support their current proprietary 110 BCD "standard" before their marketing department decides that a symmetric spider is better than an asymmetric spider (or some other bogus design feature). Just saying.

cpach

It's been decades since Shimano gave a crap about chainring cross compatibility or even frankly availability and I doubt they're going to start soon. They may follow the rest of the industry in having replaceable spiders/direct mount rings but I'll bet you that they won't be cross compatible with anything from another brand.

The chainring spacing is wider specifically to allow the chain to clear the big ring when cross chained. Not hard to visualize. You are correct in that the chain is at a greater angle when cross chained on the small ring, but I think poor chain line is better than ghost shifting; Di2 doesn't even let you shift into the small cross chained gears. The new chains are more flexible, and it's possible they sightly changed the chainring shaping to make this work better–also wouldn't be surprised if it's mostly similar. Regardless they work very well, so all's well I suppose.

WizardOfBoz

Interesting. So on my 61cm Lemond, a bike designed to be long (even on this frame, the rearwheel to seat-tube clearance is about 2cm!) and 130cm rear wheel width, that extra spacing might not be needed. Ah, well.

I will say that the FD on this R8000 group is like no other I've seen.

Eggman84

Very well said. Bottom line, no reason to get upset about it as their are lots of other crankset manufacturers if Shimano drives you crazy.

Thank you for taking the time to write-up the technical details. Have heard about the "ghost shifting" problem, particularly if their is a big difference in chainring sizes. Fortunately not an issue with the older 3x9 setups I run. I guess one reason SRAM is pushing 1x (that and to do something different than Shimano).

cpach

To be fair, 1x is really nice when you want to shift across the gearing range quickly under load at any time with excellent chain retention, and Sram was first to market with a really completive system for trail bikes which was really a killer product for them so it makes sense for them to capitalize on it. They're getting tons of OEM spec they wouldn't otherwise get because 1x is the right solution for some dropbar bikes.

Willmac426

I'm running the DA 9000 cranks. Sent myself the 8000 cam with my back. But I prefer the 9000 has great shifting never had issue.I've ran it mechanical eleven speed and also running it on my 11 speed 8050 ultegra Di2 setup right now never misses a beet

Mackers

squirtdad

My experience is follow the instructions, it is bit different, but when you get to the end the set up for final adjustment is really pretty neat how it works

choddo

Yeah, big improvement over the old ones and the cable routing is really neat.