swapping rear cassette, maximum teeth for road bike

[HLaB]

I've gone 28-11 not a huge difference but will just give me a little more both ways. How many extra links would you guess I'd need to add?

You will probably get away without adding any and 3 teeth will actually make a surprising difference!

Depends how your chain is set up in the first place; I changed from a 25t cassette to a 26t kept the same lbs chain length and fooked my deraileur

 

[BimblingBee]

Depends how your chain is set up in the first place; I changed from a 25t cassette to a 26t kept the same lbs chain length and fooked my deraileur

How did that happen? Surely you tested it before riding?

 

[gbs]

SRAM and Campag now offer 30T 10 speed cassettes but check for compatibility of the total no of sprockets and the rear mech length.

 

[HLaB]

How did that happen? Surely you tested it before riding?

The original lbs chain length had worked fine for two 25 t cassettes (thousands of miles) but failed after a couple of rides with a 26t cassette.
Tested it in the stand and one or two short rides but on the first longer (circa 30mile) and pacier ride
The curious thing is the jockey cage snapped but the hanger which is supposed to break didn't!
Now I'm particular about calculating chain length when I make any change.

 

[slowmotion]

I've gone 28-11 not a huge difference but will just give me a little more both ways. How many extra links would you guess I'd need to add?

The chain length calculator will tell you. I went from a 30/27 lowest gear to a 28/28 and the chain length stayed the same. Strictly speaking, it shouldn't work with my Shimano 105, according to Shimano's teeth calculations, but it does.

Here's a chain calculator...

http://www.epicidiot.com/sports/chain_length_calculator.htm

 

[pac-man]

regarding the reach of the original rear mech.... and its ability to take up the slack of the chain at both extremities, with this kind of upgrade...
ie. long/ short or med caged mech. would this be needed to be taken into account?

 

[BimblingBee]

The original lbs chain length had worked fine for two 25 t cassettes (thousands of miles) but failed after a couple of rides with a 26t cassette.
Tested it in the stand and one or two short rides but on the first longer (circa 30mile) and pacier ride
The curious thing is the jockey cage snapped but the hanger which is supposed to break didn't!
Now I'm particular about calculating chain length when I make any change.

The hanger is primarily there to protect the frame not mech. Sound like you were very lucky, I've seen frames snap due to chains being to short!

 

[BimblingBee]

regarding the reach of the original rear mech.... and its ability to take up the slack of the chain at both extremities, with this kind of upgrade...
ie. long/ short or med caged mech. would this be needed to be taken into account?

Yes, but in reality you'd try your current mech and go from there. It's in the specs how much slack they take up but they are generally quite forgiving...

 

[jifdave]

well it went on no trouble, stupidly i didnt take pictures beforehand, i'm hoping one of the gents in the triban owners club will be able to take a pic and show me so i can compare the difference....

 

[JoeyB]

My LBS said I could go to 12-30 on my Ultegra 6700 rear mech but I would need a new chain. I think later groupsets can deal with the bigger numbers.