crowep

Hi,

I've been riding about a year and purchased a Specialized Tarmac a few months ago. In the last week I have ordered - still waiting for delivery - a new set of Dura Ace wheels for it. A cycling buddy suggested I buy myself a second cassette to install on the new wheels so I will be able to (potentially) swap the wheels over without having to swap the cassette every time. Simple I thought until I realised there are different gear ratios on the cassettes! My groupset is Shimano 105 and I was thinking of staying with the 105 cassette but need to work out what my current ratios are before I buy the new cassette. First question is how do I work out what ratios I'm already using so I can buy the correct 105 cassette to mirror what I have today?

This prompted another thought, should I be considering a different set of ratios for the cycling I do. I cycle up and down the gorges of Sydney so it's reasonably hilly. I tend to go ok up the hills and never really feel the need for a lighter gear than my lightest today to get me up the worst climbs. Does this mean I'm running with the right combination of ratios and therefore should stick with them on the replacement cassette?

Many thanks in advance for any advice.

Cheers,
Paul

Retro Grouch 

You should have learned how to do this in kindergarten. Count the teeth on every cog on the cassette that you have now. Make sure that your new cassette has the same cogs.

joejack951

Since he knows it's a 105 cassette, he really only needs to count the smallest and largest cogs. I'm assuming 10 speed since the bike is new. Here are the available options:

https://www.universalcycles.com/shopp...58&category=40

Which Dura Ace wheels did you get though? Some of the pre-built Dura Ace wheels used freehubs with taller splines than normal. Those freehubs will only accept Dura Ace 7800 and Ultegra 6600 cassettes.

If what you have is working for you, stick with it. If you had some extra money to throw around, you could always buy a tighter and/or wider spaced cassette to have for extra flat or hilly rides. Then you'd just need to adjust your chain length to work with both cassettes (often doesn't require changing anything).

crowep

Hi, smallest is 12 and largest is 27! So that answers my question regarding which ratios to go for. It is a 10 speed. I bought a set of the Dura Ace 7850 CL's - I checked they work with the 105 cassette before I bought them. Whilst I'd like to try some other ratios to see what it feels like, I'm using all gears at the moment and never really feel I need an easier or harder gear - so presumably that means that what I've got is working.

HillRider

I don't think this is correct. 7800-series Dura Ace and 6600-series Ultegra wheel sets would accept only 10-speed cassettes since they had taller freehub splines than other 8/9/10-speed compatible hubs.

However I believe these wheels will accept ANY 10-speed Shimano cassette as all model 10-speed cassettes (including 105) have the deeper splines to fit them. Also, any 10-speed cassette will fit on any 8/9/10-speed hub with the former spline pattern.

joejack951

I should have used the term "wheelsets" and not "pre-built wheels". You did make an important distinction. I meant what you said

Perhaps I misread or misunderstood somewhere along the line. It was my understanding that only the 7800 and 6600 cassettes used the extended spline pattern. I thought that the 5600 and anything newer all reverted back to the short spline pattern thus making them incomcaptible with those short-lived 7800 and 6600 wheelsets. It would make more sense if what you said is true. Can anyone verify? The only 10 speed cassette I own is a 6600 with the tall spline pattern.

HillRider

I looked up Shimano's tech document for the CS-5600 (105 10-speed cassette) and found this note on the owner's instruction sheet:

Note
•A spacer is not needed when installing the CS-5600 to the
WH-7801, WH-6600, WH-R601, WH-R600, FH-7801.

The fact Shimano refers to installing it on the WH-7800 (Dura Ace wheel set) and WH-6600 (Ultergra wheel set) indicates it has the required deeper splines.

AFAIK, Shimano has reverted to shorter splines on the newer Dura Ace and Ultegra wheelsets and Dura Ace hubs freehub bodies which will again accept 8 and 9-speed cassettes.

joejack951

Cool, thanks for taking the time to look that up.