Barry2 

Bike is currently using an RD-R8050-SS
52-36=16 (Front)
11-30=19 (Rear)
= 35 Capacity & 30T rear max


Where I'd like to be
50-34=16 (Front)
11-32=21 (Rear)
= 37 Capacity & 32T rear max

Is there a way to get there from here, the light at the end of the tunnel seems dim.

I know it's beyond spec's, but if you've done it, it it work?
I suspect the +2T on the rear cog max spec is achievable.
It's the +4T over the max (33T) capacity that really concerns me.
Although the bike came +2T over the capacity as standard? weird


Thanks

Barry

dmanthree

Is the current unit a long cage model?

Bosco13

I went +2T on an older Ultegra RD. I did have to fiddle fart with the b-screw and replace it with another longer screw. Shifts just fine.

dsbrantjr

If your chain is correctly sized to clear the big chainring/big cog combination, the capacity will only come into play in the small chainring and smaller cogs combinations, resulting in a slack chain where you really shouldn't be anyway.

Koyote

You can try it and see if I the b-screw adjustment allows it. If not, just buy a GS derailleur.

Barry2 

That is an awesome observation.
Di2 in Full-Syncro wont even allow that combination (Little Front, Little Rear). It breaks the cross-chaining rules and the universe explodes.

I didn't even consider the Di2 aspect (I'm new to Di2 as in <24 hours)
Now I need to go and check if Di2 will even allow me to program the combination I'm looking for or if it simply rejects it.

Thanks

Barry

Barry2 

The E-Tube Di2 configuration software will not permit the selection of a 11-32 cassette for the SS rear derailleur.
Not that the derailleur hardware would know if you lied and installed one.

Only issue I can see, being the details in the Full Syncro-shift configuration page would be incorrect.
You'd have to calculate and configure your own large ring / small ring shift point ratios.

I'm not willing to chance the purchase of a cassette, so that's the end of that.

Barry

jimincalif

yes, I’ve done this too, running a 12-30 10 speed cassette on my older bike with a short cage Ultegra. I still have the standard b-screw but it’s maxed out. Shifts fine.

70sSanO

But you can still go to a 50/34 and keep the 11-30?

John

Edit Added: I don’t know enough about Di2. What little I read about Synchro shifting is the front derailleur will automatically shift at 15t(?) and adjust the rear to keep the cadence smooth.

If on the 11-30 it shifts the front at 15t and then drops the rear to 21t, is there an issue if it really happens at the 16t to 22t on the 11-32? Just wondering.

cxwrench

You didn't pay attention to the OP's post. Current derailleur is SS.

dmanthree

Saw that, but didn't know what it meant. I recently bought one and there was no suffix on the part name.

Dante49

If you insist you can but be sure the chain is on the longer side. Otherwise you may risk rip the RD off the moment you go from big (rear) small (front) to big/big. It may seems fine on a bike stand but sometimes when your FD shifts from small to big, the chain momentarily ride on the chainring. THAT'S when things go poo-poo.

Iride01 

How new is this thing? Can you return it? The proper solution will be to have a RD-R8050-GS medium cage Di2 DR.

If you can't return the bike, then buy a RD-R8050-GS and hope you can sell the -SS version on eBay or elsewhere to recover some of your expense. Consider the money you cannot recover as part of your education fees.

Though if I was in your situation, I might would just try and see if it'll handle an 11-32. Though I bet if you try just the crank change you'll find the 50/34 from 52/36 enough of a difference. Unless you are where hills are really steep and really long climbing.

Barry2 

Yes the GS would increase the rear Sprocket capacity from 30T (SS) to 34T (GS)
and the Capacity from 35T (SS) to 39T (GS)

But is that one expensive RD !

I'm going to move my 50/34 Stages PM to this bike and call it good.
I'll lose two teeth in the rear, if I can't hack it I'll take up knitting.

Barry

Iride01 

Yes it is expensive. Although I didn't directly state so, I was implying that if the bike is new enough to be returned, you should do so. Then purchase a bike with the GS version of the Di2 RD. Of course it very well may not be offered for that model line of bike. So you might have to look at another model or even another brand.

My Tarmac came with a GS version Di2 rear DR. I'm sure plenty of other road bikes do too.

Your issue is all about taking up the chain slack when going from the big's to the small's. Not an easy thing to hack. Wolf tooth and other hanger extenders are only aimed at cog clearance. About all you can hope for is that on your bike an 11-34 will work well enough for you.

If you need a lower ratio you could go to a smaller than 50/34 on the front. But I'll never like going down the backside of a hill on a 50/34 much less anything smaller.

Barry2