Hi, new to forum, I live in an island in the middle of the indian ocean and have very limited bike spares, need some tech advice:
1) Is it normal for the teeth on a new triple chainset to have different profiles on the same chainring? Some teeth are pointed, some are shorter and squarer. This is a LASCO triple I'm looking at in a shop, need to clarify before I buy.
2) How can I tell if any new chainset I buy will match the spindle on my bike? The Chainset I currently have fitted is a SR SUNTOUR XR 120 - does that mean the square hole is 12mm wide?
Most new cranksets have ramped chainrings with oddly-shaped teeth to improve shifting.
There are some subtleties of matching square spindles and cranksets, but most of the time things play together fine. I'm not familiar enough with your Lasco or Suntour to know if they're exactly the same, but I'd bet they'll be close enough that the Lasco will fit on your BB like the Suntour. Maybe somebody else will have a better answer.
1) Yes, on every ring except the smallest. The teeth on the smallest chainring should look identical
2) The only way to find out is get the manufacturer spec for recommended BB spindle length and measure your current spindle length. There are also two different standards for square tapers, ISO and JIS, but chances are these are both JIS. I would anticipate buying a new BB for the new crank, and consider yourself lucky if you don't.