dcteague

I recently purchased a nused bike and want to change my chainring/cassette combo. I'd like to go to a 50/34 chainring with a 11/30 cassette - 11 speed from the current 10 speed cassette which is 12/28. My rear hub can accept the 11 speed cog setup if I remove a spacer, but I'm unsure if my crank setup will accept the changes I want to make. The cranks are Ultegra 6700, combined with a Di2 electric front/rear. Anyone have recommendations on what would need to be changed? I'm assuming I'll need to reset the electronics. I researched some info and it appears the rear derailleur is a potential problem - probably needing to upgrade to the 6870 and then everything else is compatible but I'm finding some risks due to firmware upgrades that might have made that a problem.


Interested in the easiest route to get to the 11 speed setup and a chainring/cassette combo that's pretty close to what I'm going after. I'm a bit new to the mechanical items so probably making some errors here somewhere so any help is appreciated.

delbiker1 

If I read your post correctly, and If your crank set is 6700 with 130 BCD, and probably 53-39 rings, the 50/34 chain rings will not fit. You need the 6750 crank set with 110 BCD. You can get a 50T ring for the 6700, but not a 34T, 38T being the smallest that will work and they are only non OEM. Also, I know nothing about Di2, but Shimano changed cable pull from 10 speed to 11 speed and the STI levers will not match up with the DR's or the brake calipers. I also think it is quite likely going from 10 speed to 11 speed Di2 will not be compatible,

It seems to me, even if you could somehow make it work, the cost would be considerable. If I misinterpreted your post, or am mistaken in my post, I apologize.

CliffordK

I've had pretty good luck mixing and matching with front chainrings. As long as the shifters have multiple clicks.

Your biggest issue probably will be whether you get full sprocket to sprocket cross chaining in the rear.

Your 6700 rings are probably 5 bolt, while the 6800 and 8000 rings are 4 bolt. But, you should be able to purchase 5 bolt, 11 speed off-brand rings in 130bcd or 110 bcd.

dcteague

Thanks - I figured the crankset would be a problem but had read the Di2 could handle the switch if I upgraded the rear derailleur. Its a rim brake system so that's not an issue, but will need to validate the cable issue. Looks like more research or a potential variation using a 50/38 and different rear cassette combo. I'll have to play around with ratios to see if it'll make a meaningful difference if I'm limited on the chainring sizes.

dcteague

Yes, the 6700 is 5-bolt. Thanks for the info. Starting to think this may not be as feasible as I had hoped.

CliffordK

I'd just try it. You'll likely be just fine.

SoSmellyAir

If I am reading this correctly, one aspect of what you are asking is if your 10 speed crank set and chain rings will work with an otherwise 11 speed drive train, right? If so, the answer is yes.

Technical FAQ: 10- and 11-speed drivetrain component compatibility | VeloNews.com

I recently installed Shimano 105 (5750) 10 speed chain rings onto an 11 speed drive train, and it works just fine after I adjusted the Shimano FD-5800 front derailleur.

All Silver Chain Rings on Black Crank Arms - Bike Forums

From what I have read, the Di2 front derailleur adjustment is even simpler. But like delbiker1 said, if your existing crankset is 130 BCD, it is too large for a 34T chain ring.

dcteague

After going for a good 40 mile ride yesterday I think I'm fine leaving my cassette as a 10 speed, but want to change the cog sizes a bit, and found an 11/32 which I think I can get to work if I change the cage on the rear derailleur over to the GS size from a 6800. The ratio of gearing on my old bike using the 50/34 compact crankset was 1.21 at the lowest ratio gear, up to a 4.55 ratio at the top gear. Keeping the 53/39 crankset and using a 11/32 rear cassette gives me 1.22 at the low end and 4.82 at the top. The drivetrain capacity moves from 33 to a 35. If I'm reading all the specs on the cage for the GS, it can handle up to 41 with the largest cog at 32, so all good there. Since I'm leaving the chainrings alone, I'm thinking this should be easy to swap out without having to make any major adjustments. I'll probably try to change the cassette without any cage adjustments first to see if there's enough room, and then change the cage if the original is too small.

Anyone see a reason this wouldn't work? I've seen the cage swap performed and it seemed to work fine after reading thru it a bit. I'm giving it a shot and see what happens - it all seems to make sense on paper at least.

Iride01 

Chances of success for changing the cassette depend mostly on what exact model and version of your rear DR are.

Not saying it's not likely to be successful, but it might not work.

If your current DR is a Ultegra 6700 SS or GS, by spec, the max tooth on your rear can only be 28 teeth.
https://si.shimano.com/api/publish/s...0B-003-ENG.pdf

You can sometimes exceed that, and maybe just add a longer DR hangar. However those sometimes cost as much as just getting another DR that will give you the ability to run those larger cogs.

If your current crank is a FC-6700, then you probably aren't going to find rings to make it a 50/34. BCD is 130mm on that spider.
https://si.shimano.com/api/publish/s...0A-002-ENG.pdf

However you might just shop for a 50/34 hollowtech crank of any tier Shimano and easily replace the entire crank. Assuming of course your current crank is a Ultegra 6700 or other Shimano hollowtech. Should be less than $100 for new and less for used if you find someone that is realistic in the asking price.

6800 is a 11 speed DR. Why not a FC-4700 GS?

SoSmellyAir

It should shift OK but leave you with even bigger gaps between cogs; whether that works for you or not depends on your fitness and the terrain. Do you really need the 52:11 (= 4.82) top gear ratio? You had previously considered a 50:11 (= 4.55) top gear ratio, which is already pretty high:

Are you doing some mad descents? If not, would a 12T smallest cog be sufficient? A 52:12 top gear ratio is 4:33, only a little bit lower than your existing 53:12 top gear ratio of 4.42.

At the low end, you have been getting by on 39:28 (= 1.39); do you really need to go as low as 39:32 (= 1.22)? Or maybe 38:30 (= 1.27) is sufficient?

Perhaps 52/38 (or 50/38, depending on where you want the top end to be) chain rings with a 12-30 cassette (Shimano Ultegra CS-6700 10-Speed Cassette Excel Sports | Shop Online From Boulder Colorado) would work just as well for you. This requires new chain rings but your existing (Shimano?) rear derailleur would likely work because 30T is only two teeth over (Shimano) specifications.

But if you really need a super low range, note that SRAM has a 12-32 10 speed cassette:

SRAM Pg-10700 Speed Cassette | Jenson USA

SoSmellyAir

Good idea to buy and install a new Shimano 50/34 crankset which would work well with OP's existing 12-28 cassette, but don't see any Shimano crankset (either 10 or 11 speed) for < $100 new. Still a good idea though even at about $160 for Shimano 105.

Iride01 

I find listing for new Shimano cranks for less than 100 bucks at plenty of places. Don't just look on ebay or Amazon, you probably won't find a deal there.

However the current state of anything bicycle parts has left much of the 10 and 11 speed inventory pretty scarce. Not just for cranks either.

However if you are expecting to find Ultegra cranks for less than $100, then I agree you won't find those. But Tiagra and other 10 speed Shimano Hollowtech are often less than 100 dollars if they can be found in stock.

SoSmellyAir

My bad, I did not know that the tiers below 105 are still Hollowtech.

Iride01 

hmm, you might have me on the term Hollowtech II. Maybe I should have said Shimano 2 piece road cranks, which TMK, use the same shaft diameter as hollowtech II and are compatible with BB's for hollowtech II cranks..

dcteague

What I'm doing seems feasible based on the various components I'm mixing. I'm using a 6770 Di2 RD but changing only the cage using the GS size from a 6800 ($25 so a pretty low-cost modification compared to a new Di2 RD) - this should in theory allow the cassette to go up to a 32t with a max capacity of 37t. If I just change the cassette to either a 12/32 or 11/32, keeping my chainrings as-is, I'm within both of these parameters. I know the cage swap is using the cage from a different RD, but from what I've read and seen it works. I have no intention of changing the current 53/39 chainring setup and if the calculators I used to compare gear ratios are correct, it should be good to go. Only way to find out is to give it a try and see what happens. I'll report back either way. I will likely change a couple cogs but the starting point is a 11/32.

dcteague

I'm mainly trying to work with what I have. My old bike has an 11/28 cassette and 50/34 chainring. My new bike is 53/39, with a 12/28. At this point, I'm just wanting to change the cassette out to something with more like a 12/32 but couldn't find one, but found the 11/32. The increased cog in the rear is the problem, but the GS cage should allow that to work. I just need to play around with the cog sizing if the GS cage will work. I really don't want to change the chainrings if I don't have to - and the options are really limited at the 130 sized crank.

Iride01 

I entirely forgot you were talking Di2 by the time I responded.

So what the heck is it you want to do? Make your 10 speed Di2 bike 11 speed? That'll require some voodoo I think.

SoSmellyAir

In my (albeit limited) experience, mixing and matching cogs from different cassettes to customize the gear ratio is hit and miss with respect to downshifting onto adjacent, next largest cog from a different cassette if the Hyperglide shift ramps are not lined up.

No, OP already has Ultegra RD-6770 Di2, which is a 10 speed Shimano Di2 rear derailleur. Yes, I had to look that up; I too thought Di2 came after the introduction of 11 speeds.

dcteague

No, I just want to change the gearing to a broader range with more hill climbing gears. The rear cassette is the primary focus, but obviously that's not as simple as changing things given the RD limitations, and the crankset being a 130 only seems to offer a 38 as the lowest available. That doesn't really help me much.

I know building legs up for hills is one method, but would prefer to save energy when I'm doing century rides, so having a good range is preferred for now.

dcteague

I wish it had, that would certainly simplify things. Now that I've seen a few options that look like they may be feasible, I'm fine sticking to a 10 speed cassette but I'll know more once I test things. I'll start with just putting the larger cassette on with the existing RD, and if I need a little room because of the largest cog, I'll change the cage which is supposed to move the top jockey wheel down a little to clear the 32t cog, but also give a little more range between low/high gearing (presumably due to the chain tension range it adds).

Iride01 

This thing currently has a Shimano 2 piece crank doesn't it? If so, then I think the best you can really do is get a 2 piece Shimano crank with 50/34 rings on it. Won't give you much more but it will make it easier till you get stronger legs. Try to get a 10 speed, but maybe a 11 speed crank will work just the same. Not certain what the spacing difference of the rings is.

You might be able to try a 10 speed 11-30 cassette. But I'd try to borrow one and see before buying. You are competent, capable and confident you can do the work yourself aren't you? You'll need the Shimano lockring tool or generic equivalent. You'll also need to have another chain and know how to properly size it to your new set of cogs and rings. But a larger 30 tooth gear on the rear will be out of spec and you might trash your DR and wheel while on a ride one day. But this might be a case where a hanger extender might be a good idea. But your shifting may or may not suffer in the smaller tooth cogs.

I had issues trying to find a 11 speed chain a few weeks ago. However now some have gotten them in stock.

dcteague

The cranks I have are using a 130mmx5 bolt pattern, and this won't accept anything lower than a 38t small ring. In order to go to a 50/34 I'd have to change the entire crank out to a compact, and then the cost goes up considerably, so I'm trying to avoid that. I have both a 11/32 and 12/30 on the way, so I can see which of these will work. I originally inteded to swap the 11t to a 12t anyway, which would give me a 12/32 if it fits, if not, I'll try the cage swap. If that fails, I'll probably just go with a 12/30 and deal with it.

Iride01 

What are significant costs to you? A Shimano FC-4700 should be in the $100 to $120 range. And other older 10 speed NOS Shimano even less.... unless you insist on 105, Ultegra or DuraAce.

https://www.universalcycles.com/shop...9&category=688

But there is the lack of inventory everywhere. Up until I rode Mount Evans a little over a week ago I would have been happy to give you my 50/34 105 5800 crank, but I think I'll keep it now. It was useful for giving me the ratios I needed for the long climb. I put the 52/36 back on as soon as I got back home.

With the newer Shimano Cranks, don't have to swap the entire crank, 50/34 rings will happily fit on the same spider that 53/39 rings fit on. But the price of Shimano rings alone for the newer style cranks is almost as much as the entire crankset.

You might could look for 9 speed or 11 speed Shimano 2 piece cranks. Lower versions of them are inexpensive too... if you can find them in stock. I just am not certain myself what the ring spacing on them will be for your 10 speed rear and how well it's chain will shift on that front with the existing front DR expecting a 10 speed set or rings between it.

So maybe with some patience by mid summer 2022 you'll find something. Or find that your leg muscles are in better shape and wonder why the fuss. <grin>

dcteague

My tolerance for the cost of this is more my wife's tolerance than mine. Having said that I am hoping to be reasonable with these mods. I'm looking at new cranks but can't yet justify the cost if I can get the cassette and cage approach to work. I'm going to see what happens with this approach and then I'll revisit things if it doesn't. At that point, I'll definitely start to look for a new crank setup. I just don't want to have to also replace my Di2, that'll really start to rack up costs fast.

SoSmellyAir

A new 50/34 crank, while slightly more expensive than a 10 speed cassette plus a derailleur cage, is a better solution overall because it (1) allows you to retain the use of your existing 12-28 cassette (IMHO the best compromise between cadence and range) and (2) opens up the possibility of using other cassettes in the future without needing a frankenstein combo cassette (which is more expensive and shifts less well) to accommodate your 53/39 chainrings.