Danger when Rear derailleur doesn't match sprocket/chainring tolerance?

Looking for advice from our mechanically competent users.

I recently got a new wheel set, and put a new chainring set [cassette] on them, a Shimano 11/32, with my 50/34 crank set. My rear derailleur is a Shimano Ultegra RD-6800 SS (short cage). And I didn’t think before purchasing about the tolerance of the derailleur. But the short-cage is only rated to handle up to a 28T Low sprocket Max, and a Total Capacity of 33T.

Like I said, my largest sprocket is 32T, which is in fact larger than 28, and the Total Capacity, or differential, between the sprockets and chainrings is (34-11)+(50-34) = 37, which is again larger than 33.

How problematic is this? There’s not an ideal amount of clearance between the pulleys and sprockets when it’s in the 32. But it seems to run smoothly. Also in the 50 up front and 32 in back i can shorten the chain with my hands slightly, so it’s not like the system is being pulled fully taught. And I’ve been scouring the internet for something conclusive, the main issue I’ve read about is your derailleur not being able to shift to the largest sprocket, but it shifts just fine. But my local mechanic warned about cross training in the 50 up front and 32 in the rear and possibly snapping my rear derailleur. How real of a concern is this? Obviously i’m not planning on ever cross training, but if i were to accidentally let it happen it would suck for my derailleur to snap mid ride or mid race.

I chose this setup because I’m a heavier rider at 180lbs and do 24 hour races and want to be able to spin up hills without going into threshold or above while keeping a decent cadence. I also do a lot of riding through the Appalachians which pose a similar problem on very steep 20+ minute climbs.

I am planning to get a mid-cage or long-cage in the future, but wondering how urgent this is.

The best option without getting a new RD might be this:

You can extend the position of the RD lower and still get away with the short-cage.

  • I added the DM version to my new Domane with the R8000 group and the stock RD with an upgraded 11-32 cassette.
  • I didn’t even need to lengthen the chain, but you should verify for you needs if you head for the RoadLink.
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Did you get a new chain while you were at it? How was it sized? If its the old chain and sized for the 11-28, then there’s a chance if you try ti shift into the 50x32 the chain will be too short and rip the RD and hanger right off the bike and potentially jam into the chainstay destroying the frame. If you sized the chain for the 50x32 combo with a SS cage then the RD likely won’t be able to take up all the extra chain in the 34x11(and12/13) and there won’t be tension on those combos but nothing catastrophic will likely happen. You’ll also likely need to turn in the b-screw all the way to clear the 32t and/or get a longer b-screw depending on the bike. Occasionally a bike with a long enough rear hanger and/or long enough chainstays will work in all gears with a 50/34 11-32 with a SS cage.

did you even need the roadlink? the SS R8000 officially clears an 11-30 and shimano has long been conservative with max cog size and capacity.

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“Need”? Probably not.

But I already had the DM RoadLink on hand, and preferred that option vs potentially over-stressing the “wrong” RD with my 11-32 that officially exceeds the rating.

Others are likely doing it and getting away with it (as I have seen the conservative ratings in the past as well), but I had the option handy and wanted to see how it worked.

The chain was sized for a 52 up front and a 28 in back. Me being a dumb dumb i replaced the chain right before putting the 50/34 up front and 32/11 in the rear. But it still shifts. keeps tension in the 34/11 and isn’t fully taught in the 50/32.

Sounds like to avoid a possible catastrophic failure ruining my wheel/frame i should re fit a new chain. and to increase shift quality get the road link.

The chain length for a 52/28 is likely the same as a 50/32 since you’re increasing the diameter of one and decreasing the diameter of the other. If it can shift into the 50/32 and not fully extended then its sized correctly and you should be good to go since it also keeps tension in the 34/11

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thanks. That’s what i thought, but i really needed to hear it from someone else after images of my derailleur tearing off splattering me onto the road were in my head.