Can I exceed the capacity on my rear mech?

[Slioch]

I have the Shimano Ultegra 6800 groupset on my carbon, with the short cage rear mech. My current set-up is...
Front = 50 & 34
Rear = 11 to 28

So my used capacity is 33T.

According to the manufacturers blurb pasted below, total capacity is 33T, so I'm at the max.

It's new cassette time, and I'm playing with the idea of getting a 11 to 30, so I'll be exceeding the manufacturers max stated capacity and the max sprocket size by +2T.

Is pushing the boundaries a tiny wee bit do-able? Has anybody had any experience of doing this? Will the world come to an end?

My gut feel is that it will probably be ok, but would appreciate thoughts on here before parting with the readies.

Thanks

 

[si_c]

I reckon it'll be fine, just adjust the B screw to make sure the derailleur is low enough. Sometimes the jockey wheels rub on the cassette otherwise.

I've used a 36t on a 34t max capacity derailleur with no problems. The only side effect is that sometimes the shifts at the bottom of the block aren't quite as smooth, but the range is worth more to me.

Lots of people do what you are planning with no adverse side effects.

 

[Cycleops]

Give it a try, if it doesn't work you can use one these called a Wolftooth Roadlink.


These sell for premium but there are knock offs you can get for about a fiver. They just lower the mech so it sits away from the cassette.

 

[Drago]

In my experience one can usually go a tooth or two beyond the official limits without causing problems.

 

[Milkfloat]

A lot depends on the geometry of your bike, may get away with it. I have only had problems on one bike and I solved that by reversing the b limit screw.

 

[CXRAndy]

If your derailleur is a GS model upto 32t on the cass is standard. With a bit of careful setup 11-34 should work too. Cross chain would not be recommended

 

[themosquitoking]

I had a 30t cassette on a 105ss and it was fine.

 

[robgul]

Rule of thumb for me is 2 more teeth than Mr Shimano specifies for his kit - BUT work on the basis that chain on BIG RING should not go onto the lowest (biggest) 2 sprockets on the cassette ... but you shouldn't be doing that anyway!

As suggested putting the B-screw in the derailleur from the other side will give you a bit more gap between jockey wheel and largest sprocket ... and the derailleur extenders work a treat (£3 on ebay)

Rob

 

[fossyant]

Make sure the shifter can get in lowest two when in big ring without fowling or jamming (too short a chain) as you can bet your last dollar that may happen one day. Otherwise its a wolftooth

 

[Slioch]

Thanks for the responses folks. General consensus seems to be that it should be possible.

I'll be getting a new chain at the same time, so when I fit the new cassette I'll put the old chain back on to see how tight it is on the largest rings. If it looks a bit tight, I'll cut the new chain two links longer.

Not seen one of those wolfteeth thingies before. There's some clever bods out there.

 

[Slioch]

Quick update.
The 30T cassette duly arrived and has been fitted, and after a short ride seems to be fine with no issues. The only tweak I needed to make was a quarter turn on the "B" adjuster.
The length of the old chain was also fine, so no additional links needed to be added when I "cut" the new chain to size. Even cross-chaining (large front to large rear) is fine, though I hasten to add that I don't make a habit of doing this.
Just for the record, although my bike is Ultegra I bought a 105 cassette, which was half the price. A slight weight penalty, but I doubt I'll notice any difference

 

[T4tomo]

I bought a 105 cassette, which was half the price. A slight weight penalty, but I doubt I'll notice any difference

Your wallet will.

 

[ColinJ]

When I bodged the triple chainset onto my Campanolo-equipped CAAD5 I ran out of adjustment on the 'B-screw' (I think Campagnolo call it something else). There was some rumbling on the biggest couple of sprockets. I fixed the problem by cutting a strip of aluminium from an old Coke can and folding it twice to make a shim which I inserted between the end of the screw and the tab it normally pushes against.