Ultegra 6870 - easier climbing gears upgrade

a148pro

Sorry for asking this, its a bit tricky, and I'm just not technically minded

I have an old ultegra di2 groupset on my road bike. The derailleur has 6870 on it. It doesn't say if its short cage (SS) or long cage (GS) but I found a thread online suggesting the difference between the two is the distance between the two cogs on the derailleur (5.8 CM v. 8.3 CM).

Mine is 5.8 cm so I assume I've a short cage. When I got the bike second hand my LBS told me the largest cassette I could put on it was 28. This matches Shimano spec for the short cage.

I'm running 50 - 34 and an 11 - 28. Basically, I'd like more gears for climbing, I tend to grind it up steep climbs as opposed to spinning.

So what are my options?

1. Get a 6870 long cage derailleur. This is expensive (over €200 new) and will only increase the capacity to 32 per Shimano.

Will 32 even make that much of a difference?

2. Get the 8000 series long cage derailleur, but will this be compatible with the rest of my group set? Its only €60 for some reason I can't understand - is it just that they don't make 6870s any more so they've gone up in price? Would extend capacity to 34. Some suggestion online I'd need to update the di2 firmware to do this.

3. There's a product called a wolf tooth roadlink (€30) which can apparently increase the capacity even further. I'm just not clear if I can use it with my existing derailleur. There's at least one review on amazon suggesting you can run it on a short cage derailleur and run a 34 cassette. This would be a pretty good improvement for €30 plus labour. But my reading of some other stuff suggests the range of the short cage derailleur is more limited.

Anyone any experience doing this successfully on a shortcage 6870 derailleur?
Anyone know what the range would be if I got the long cage 6870 and the wolftooth? Could I go even bigger than 34?


Some links covering the wolftooth:

https://biketestreviews.com/wolftooth-roadlink/

https://www.wolftoothcomponents.com/pages/roadlink-tech-page

hesker

absoluteBLACK oval chainrings 46-30 will give you a lot easier climbing with basically just the loss of the top gear selection.

Not sure how well they work with di2 as the rings are positioned a couple of mm inboard. But I’m sure google has the answer. Cheapest I’ve seen for the set is €165.

Much more choice with the 8000-GS which can go to a 36 unofficially and to a 40 or 41 when matched with a 46-34.

Have been looking into this for someone who is running 8000 mechanical. There’s loads of info online as big interest in the gravel community

hesker

Ok I checked for the hell of it.

People with 6870 short cage saying online they can get 32T to work. That's a decent improvement on 28 but possibly won't get all you need.

Adding a wolf tooth is probably the next cheapest option. Not sure how much bigger you can get with one of these.

Daroxtar

There's a big difference between 28 and 32.
I use a 32 for big days on the mountains but it's more of a security blanket for tired legs. It's nice to be able to spin and get a bit back if I'm halfway up Sleive Mann with 120km already done. Unless the road is pitching well up above 15% then a 32 should be plenty.

a148pro

hesker wrote: »

absoluteBLACK oval chainrings 46-30 will give you a lot easier climbing with basically just the loss of the top gear selection.

Not sure how well they work with di2 as the rings are positioned a couple of mm inboard. But I’m sure google has the answer. Cheapest I’ve seen for the set is €165.

Oval rings are a curve ball for me (ba-dum!). Do they expand the effective range even more because of their shape? As in do they feel like an even lighter gear notwithstanding their number of teeth?

To be honest I'd be a small bit worried about spinning out on a 46, I don't go fast on descents but have effectively spun out a 48 ring on my other bike before, so not too comfortable dropping below 50 on a road bike. But in general can I keep my derailleur and 28 cassette but just make it a lot easier to climb by reducing the size of the front rings?

hesker wrote: »

Much more choice with the 8000-GS which can go to a 36 unofficially and to a 40 or 41 when matched with a 46-34.

Will they be consistent with the rest of my di2 stuff though? Anyone any practical advice about doing this?

hesker wrote: »

Ok I checked for the hell of it.

People with 6870 short cage saying online they can get 32T to work. That's a decent improvement on 28 but possibly won't get all you need.

Adding a wolf tooth is probably the next cheapest option. Not sure how much bigger you can get with one of these.

I'm just a small but reluctant to rely on random comments on the internet in case whomever posted it has it wrong, or has a high tolerance for the concept of something "working" when its less than optimum. Anyone any concrete experience of doing this or using the wolftooth?

I could probably borrow a cassette off a mate and bring it to LBS, pay them to fit it and they'll probably have a good idea of what I'd get away with

Daroxtar wrote: »

There's a big difference between 28 and 32.
I use a 32 for big days on the mountains but it's more of a security blanket for tired legs. It's nice to be able to spin and get a bit back if I'm halfway up Sleive Mann with 120km already done. Unless the road is pitching well up above 15% then a 32 should be plenty.

Yeah I've 32 32 on the other bike, I find myself picking it when I'm tired, even though its a lot heavier. I'd go higher again to be honest, hence the interest in the wolftooth. I presume its a question of fitness - tour lads will tear up hills in gearing harsher than mine.

a148pro

a148pro wrote: »

Yeah I've 32 32 on the other bike, I find myself picking it when I'm tired, even though its a lot heavier. I'd go higher again to be honest, hence the interest in the wolftooth. I presume its a question of fitness - tour lads will tear up hills in gearing harsher than mine.

It's a combination of fitness and overall weight. If you weight 60kg and are really fit you could probably get up everything on a 23t

a148pro

Alas I fail that test on both points!

Mefistofelino

Shimano tend to be very conservative on their specifications. If they say a max of 28T, you can usually stretch 30 or even 32T out of it (assuming correctly adjusted, chain lengthened etc). the 32T long cage will get to 34 (at least)

The Wolftooth is only half of a solution - it will provide you with the additional clearance you need to get past the larger sprockets but it does not add to the chain capacity of the mech so you may end up in a situation where the small chainring / sprocket combination results the cage being unable to keep tension on the chain OR for large chainring / large sprocket, the cage is pulled forward into an almost horizontal position.

I'd seen a thread somewhere before (possibly Weightweenies) where someone had transplanted a longer cage onto a standard Di2 mech

a148pro

I suppose the other thing I need to ask is can I stick any old, say, 11 - 36 cassette on or does it have to be ultegra, and if so do ultegra even make a larger cassette that is compatible with 6800 di2?

There's no point in my going to hassle of getting long cage derailleur and or the wolf thing if I can't get a compatible cassette? There is, of course, a second hand derailleur one for sale up the road from me now so I could get that done but is there any point if the wolf thing will get me to 32 and maybe beyond as it is?

EDIT looks like the larges ultegra cassette is 11 - 34, but I assume a cassette is a cassette and once the derailleur and chain have the capacity it will work? I've read online of 40 and 42 being possible at a push

Mefistofelino

Shimano make GRX gravel chainsets in 46/30, which would be more-or-less the equivalent of putting a 32 on the back of your current set-up. The gravel chainsets are centered a little further out from the BB than the road equivalent (about 2.5mm) which means they sell you a GRX-specific front mech. However, there are threads where people are running Ultegra Di2 road mechs on GRX chainsets quite happily

https://forums.thepaceline.net/showthread.php?t=241232e

hesker

Mefistofelino wrote: »

I'd seen a thread somewhere before (possibly Weightweenies) where someone had transplanted a longer cage onto a standard Di2 mech

I’ve read a few discussions on this. At least in relation to 8000 series it’s not that simple. The body of the derailleur is also different and you can’t just stick in the longer cage. I’ll try to dig out the thread.

Peterx

I had an Ultegra Di2 mech on a CX bike and also wanted more gears for climbing. It takes an 11-30T cassette no issues and does take an 11-32T but I was never happy with it, I couldn't get the mental image of a Di2 Ultegra mech wrapping itself into the spokes out of my head.

I got an XT mech (expensive in fairness) and it swapped in easily. I think it works fine with double ring on the front but I am on single ring so haven't checked that.

38t front and 11-40T back on it now and can get up most things I need to. Spins out easily enough obviously on tarmac descents.

If your set up is 10 spd I believe you can't put an 11spd mech on as Shimano have it set to not work.

a148pro

Peterx wrote: »

I couldn't get the mental image of a Di2 Ultegra mech wrapping itself into the spokes out of my head.

This is precisely the image I have - I think it may be unrealistic, seems if it doesn't work you may just have trouble getting into the gears at either end, but I've heard that crunch on cheaper bikes in the past and don't really want to hear it on di2

at1withmyself

a148pro wrote: »

Sorry for asking this, its a bit tricky, and I'm just not technically minded

2. Get the 8000 series long cage derailleur, but will this be compatible with the rest of my group set? Its only €60 for some reason I can't understand - is it just that they don't make 6870s any more so they've gone up in price? Would extend capacity to 34. Some suggestion online I'd need to update the di2 firmware to do this.

Hey - just a watch out on your cost comparison there, I think your comparing an R8000 mechanical rear mech as the R8000 Di2 rear mech is closer to 200€

a148pro

Must be thanks

Whatwicklow

I had a 11/36 mtb cassette with a 6800 (mechanical) ultegra with no issues. Where are you based, I have a few 10 speed 11/36 you could try here if you wanted

a148pro

Whatwicklow wrote: »

I had a 11/36 mtb cassette with a 6800 (mechanical) ultegra with no issues. Where are you based, I have a few 10 speed 11/36 you could try here if you wanted

That's sound of you thanks but i've two mates running ultegra with wide gearing and not getting out a whole amount so should be grand to borrow one of theirs. Plus the lbs knows what he's at so I reckon he'll be able to tell from looking at it once he fits the long cage. Going to try and ride a mates 34 34 up a hill to see how easy I want to make it. Also I now have some pretty reliable articles online suggesting 36 is possible on the long cage. Eg:-

https://www.velonews.com/gear/technical-faq-big-can-go-shimano-rear-derailleur/

I'm 11 speed though amn't I? Your offer worries me, as in I've 11 rings on my existing cassette, so I assume I'm 11 speed or am I missing something?