Road Cycling - Equipment Capabilities???

Where can I find all this information my LBS seems to have regarding deraileur, crankset and cassette limitations/compatibility. Seems to me that there could be a spreadsheet out there that would show this.

My LBS(s) say my triple 52/42/30, 105 set-up won't support an 11/23 or a 12/27. But could accomidate a 53 or 54. Not that I don't believe them, but I'd like to see the matrix for myself.

I figure if I have enough chain to "cross gear" the 54-25 and the deraileur can take up enough for a grinding 30-12... I should be fine If I got an 11/23 cassette.

Enough numbers this early.

Any suggestions on where I can get my hands on this data?

Thanks

R

The Shimano website gives the spec and capacity for all their mechs.

Thanks - I'm looking at that now.
Now can someone help me with what I'm reading.
:rolleyes:

REAR DERAILEUR
Max Sprocket 27T
Min Sprocket 11T
Front Difference 14T
Total Capacity 29T

I am assuming that the largest sprocket on my cassette could be 27 and the smallest could be 11.
What't the Front Difference and total capacity?

FRONT DERAILEUR
Top Gear Teeth 52T
Capacity 22T (triple use)

Max capacity is 52? Not sure what the capacity of 22T means.

Looks like I'm stuck with 52 on the front...
But it seems I could swap out rear cassettes depending on the type of riding I'm doing.

Off for the weekend - have a good one!

R

Originally posted by Raedeke
Thanks - I'm looking at that now.
Now can someone help me with what I'm reading.
:rolleyes:

REAR DERAILEUR
Max Sprocket 27T
Min Sprocket 11T
Front Difference 14T
Total Capacity 29T


Front Difference is the difference between largest and smallest chainrings. The rear derailleur has a limited capacity to wind up the extra chain when you go to a smaller chainring. At 14T (would work for say a 53/39 double) this is likely a short cage derailleur, you need a long cage model to handle the chain.

Total capacity... dunno... it might be the largest cog that can be handled without massive interference between the jockey wheel and the cog. In that case, 27T would be the largest smooth shifting cog, 29T wouldn't shift well at all but would be possible.

The Front Der. capacity is likely the difference between large and small chainring sizes. A Ft. Der. designed for a wide range of gearing will have a longer cage and a different angle of motion than one designed for a narrow range of chainrings (like a road double).

Front Der capacity = difference between max & min rings

Rear Der capacity = (large sprocket - small sprocket) + (max chainring - min chain ring)
So for 53/39 & 12-27 you have:
Front capacity required = (53-39) = 14T
Rear capacity required = (27-12) + (53-39) = 29T

You can, however, run larger spreads than the capacity of the rear derailleur as long as you don't cross the chain (small-small or large-large), which is not a great thing to do anyway.

Your bike shop is full of hooey, and they are likely morons too. Shimano specs are always conservative anyway. When you are in the granny there is absolutely no need for the smaller cogs in the rear anyway...You can get the specs from Shimano, and Sheldon Brown at www.harriscyclery.com has a glossary of bike terms. What are you trying to do anyway? The rear will probably handle a 30,but there are no 9 speed cassettes with a 30 I know of anyway. There is little pont to bigger front unless you are going downhill all the time with a tailwind.

Originally posted by boudreaux
The rear will probably handle a 30,but there are no 9 speed cassettes with a 30 I know of anyway.

Don't forget MTB cassettes. Also, there are aftermarket touring cassettes which you may be able to build up with a 30.