I did some searches and saw lots of threads but still have questions about my commuter bike:
mountain bike, bought new in 1993, used offroad lightly/moderately for a few years and then put away for a decade or so.
I pulled it out in early 2006 or so and started using it for commuting. The first thing I did there was swap the fat knobbies for 1" slick tires; by summer 2007 I realized the original 7-spd gearing was way too low for street. The original chain was also pretty worn by then, so I took the bike in for a tune up and got a new drivetrain:
we swapped the gearing from the original 46/36/26 crank up front to 46/35/24. The original cassette was a wide-spaced 13-30t Shimano Hyperglide "G", which I switched to a close spaced 13-23t. We used a new chain, of course...just a basic OEM brand.
I mostly live in the middle ring as my commute is only 7 miles and mostly stop and go, with tons of traffic lights, stop signs, traffic and peds to go around, etc. I have little chances to use the big ring and I do need to save my knees (I'm 44) so I started using the granny ring twice a day to cross a bridge over the East River. I had been using the 36x30 before but wanted a closer spaced cassette for the street....So we kept the 24t granny and swapped the rear for a narrow Shimano Hyperglide "I-L", 13-23.
After a few months riding (all new chain, chainrings, cassette), mostly commutes and one or two metric centuries, possibly 500 miles, tops, I decided in the fall of 2007 I still wanted higher gears. I bought a backup wheelset and put a 12-21 Hyperglide cassette on there and have been using that ever since.
Fast forward to the present: about a month or so ago I started having skipping when I stood up to honk (starting off at lights, accelerating past cars, etc.) in the 35x12. Then it started getting worse, and then started happening in the 46x12 too.
I measured the chain from 2007 and sure enough it is stretched at least 1/8" over. I slapped a new SRAM chain on two days ago and cleaned everything off. To my eye the cassettes didn't look bad, but yesterday on its first run, the new chain was slipping like crazy...I understand that the cog teeth could be worn to the old chain. But today I threw the original 13-23 cassette I got in 2007 on and while it is not as bad, it still slips unless I keep it on the big ring. The 46t seems to work fine with all the cogs, even the 13t. The middle ring works ok with the largest cogs (21t, 23t), but starts to slip even in the middle of the cassette. The granny ring is very slippy unless I am calmly climbing in the 21 or 23. Anything jerky or intense on the pedals and it skips.
My questions:
*I understand how the 12-21 cassette I used from late 07 to early 09 - probably about 2000 miles - could have worn from the old chain. But would the original new 13-23 cassette also be too worn for a new chain? As I mentioned, it has maybe 500 miles or less on it, albeit with a different chain, but one that started out new together.
*would the fact that it is a SRAM chain on a Shimano Hyperglide cassette matter?
*Would the length of the chain have anything to do with this? I was wondering if shortening it would make a difference. I should point out I had no skipping issues until a month or so ago, so I guess that isn't likely. btw, I shortened the new chain I just put on to match the new chain installed in 2007...no idea whether the shop used my old original chain with the 13-30 cassette as a guide or resized big/big, etc.
*Finally, while I have no problem spending the money on a new cassette, I hate to do that if it isn't the real problem...is it possible I just made bad gearing choices here? Maybe I just don't need a granny on this bike, and should just live with the bigger chainrings and get larger cogs?
any sane replies are welcome