I think they only go up to 16... Do you need DA in particular? (I have a phil on my 7600s)

i thought they did but it doesnt look like it.

yeah, 17t cogs are the way to go for most gear ratios, it seems.

I am very happy with 48x17, but want to go up a bit, which would lead to 48x16, which I want to avoid, so I am looking at going 49x17, then later to x16 since going up one chainring tooth is too tiny a difference. But since I don't skid 48x16 should be ok for me.

But I wonder if wear patches are only caused by skidding? Since I accererate from stops with the same crank position and same foot forward, doesn't this wear the tire out in patches too, although slower than skidding?

Said differently: Rear tires on all bikes wear much faster than front, primarily because they transfer power. If that power transfer is not even across the crank rotation, won't that cause uneven tire wear in patches?

Al

i've been on 48x15 and 49x15 for a while and both are nice. skip over 16...

I think you're looking at wearing your tires down from acceleration in extremely small rates as opposed to skidding. Some of the people that really seem to be concerned with this stuff, like mikearena who wore through his $35 tubular in one parking garage skid, acceleration doesn't even have a chance to play a role in this.

As far as your other questtion, the rule of odd numbers is good advice. 49 is a great number also cause it's only divisible by 7. And 49 x 14 is just huge for the street. I ride 49x 15 right now, but 49 x 16 and 49 x 17 are only slightly better as far as patches go.

Correct me if I'm wrong, but isn't the rule about switching feet (skidding with your opposite forward) to double your skid patches only practical if you have an odd number of patches from the chart?

Sure, but as a non-skidder I only wear tires out thru mileage. I really wonder (out of curiosity, not practical matters) if after 1500mi on a 48x16 if one would have a tire flat spot that varies around the circumference. I am not suggesting this would be bad, just a result.
I too have blown thru (not new) tires with a skid. Thats why I don't skid anymore, just a personal preference to save money on tires. But it is fun and I do it once in a while just to keep the technique up for emergency needs.
I only have 48t as it came with my cranks. Based on the chart I put together I decided on a 49t before I bought the cranks. Someday I'll need a new chainring and then I can get the 49.

Don't hurt my brain with the ambi question ;)

Al

dura ace stops at 16. those bastards.

I ran into that very problem when I ordered my RDs with the 48t ring and wanted to keep my ~75 gear inches. I ordered a Surly 17t cog and we'll have to see how it fares.

my surly 17t is fine.