Symox

I've been thinking of swapping the first position 12 tooth cog on my 105 10-speed cassette with an 11 tooth one. Is there a certain model I should look for? I can't seem to find one specifically for the 105.

Thanks

caloso

https://www.jensonusa.com/Shimano-10...Speed-Cassette

70sSanO

I find eBay to be a good source.

https://www.ebay.com/itm/Shimano-10-...sAAOSwKtlWm8ZB

And don't forget the lockring...
https://www.ebay.com/itm/Shimano-XT-M8000-11-Speed-Cassette-Lockring-for-11t-Cog/402510777175?epid=1265996529&hash=item5db7830b57:geYAAOSwZYFfk08z

Or just buy a new 11-XX 10 speed cassette, as noted above, for a little more.

John

Symox

Do I need a new lockring? I would assume it would be identical

Eggman84

You could swap the 12T cog with an 11T cog but there are two technical considerations. First, I assume your current 2nd position cog is 13T, so going to an 11T 1st position cog will mean you have a LARGE step between the 1st and 2nd cogs (its 8% now, would be 18% after the swap). Second, Shimano designs their cogs to be matched with the adjoining cogs to optimize shifting; meaning if you change to an 11T cog, the shift to the 13T cog (and visa versa) wont be very smooth.

You can buy loose 1st position 10 speed cogs from many vendors. For instance Universal Cycles sells loose 10 speed cogs, see https://www.universalcycles.com/shop...&category=1569. The parts list for Shimano 105 Cassette 10 speed cassettes (CS-5600) can be found at https://si.shimano.com/api/publish/s...5600-2455C.pdf.

Davet

The lockrings for the 11t cog are different, they’re smaller in outside diameter than the lockring for the 12t cog. Using a 12t lockring with an 11t cog won’t allow the chain to fully engage on the cog.

70sSanO

I checked 11t and 12t Sunrace lockrings and the 11t is smaller.

One more thing I just remembered. At one time there used to be a difference in ramps between 1t difference and 2t difference cogs. I once did a 1st & 2nd position cog swap, 13/15 to 12/14. The problem on the 14t cog was it only had one ramp. It seemed to hesitate when shifting. The 2 tooth change cog had 2 ramps. I have no clue if that is still done or not, but I thought I would mention it.

John

dsbrantjr

IIRC they are not, the 11T is smaller to avoid interference with the chain side plates.

KCT1986

Another issue with replacing a 12T with 11T is that many of the 11T cogs have a built-in spacer that is that is thicker than the normal amount needed to properly space the cogs. The added thickness is added to strengthen the cog since the 11T cog's "valley" in the gear is so close to the center of the cog. Because of the added thickness in the 11T cog, the matching 2nd cog (usually 12T or 13T) has a recessed area to take up the additional amount while maintaining proper spacing.

Note the recessed area in the pic.



A 13T second position cog that is meant for a 12T first position may not have the recessed area since it is not needed. The 12T first position cog would be just thick enough to maintain proper spacing since it doesn't need the added strength needed in the 11T cog.

So, a 11T cog, with the added thickness, used with a 13T second position cog without the recessed area will sit further out & not have the proper spacing.

caloso

You're going to need a new cassette eventually. Just buy a new 11-28 cassette for $40 and avoid the hassle.

Symox

After everyone's reply, I think you are right.

Thanks everyone

Symox

Took the advice, went to ebay and bought a used 11-25 105 Cassette.

I swapped out the last three rings/spider with my 12-27 so now I have a 11-27 cassette

It works great and I love the extra range

Thanks everyone for the great advice - much appreciated

Symox

Found a used dura ace 11-28 for cheap. Omg it’s light and shifts even nicer. Plus the 28 coupled with my triple’s 30 chainring means if I can’t climb it I’m not trying

trailangel

Why you buying used cassettes? Waste of time.

Symox

Used cassette because not everyone is made of money.

Got a great deal on a lightly dura ace cassette. I never would by it at full price, I couldn't justify it.

70sSanO

It does depend on the cassette and condition.

A few years back, my brother found a very slightly used XTR M950 12-32 8 speed cassette at a really good price.

John