Originally Posted by
alcjphil
There seems to be a lot of confusion about what exactly the OP was measuring. Everyone here wants to be helpful, so if the OP could explain exactly what they were measuring all the rest of us could offer better advice
No, the OP measured 24.3mm the only place close to this on a modern bike (the OP's model was introduced in 1998ish) is the stem/handlebar diameter interface.
It can't be the steerer, as by 1998 everything (MTB) was 1 1/8" (with the exception of a very few DH bikes), for the stem/handlebar, it's too early for 31.8mm or 35mm.
It can't be the brake lever/shifter mounting point, as these are 22.2mm
The OP does need to re-measure as they appear to have under/miss read the caliper (hope this was what they were using) or just take the handlebar / stem apart, (as the exact size should be stamped/laser etched/printed on both these parts), although, given we know what bike the OP has there are no real alternatives for the correct reading to be 25.4mm, also, given that the OP used a mix of metric and SAE sizes, that further indicates a measuring and possibly conversion issue.