my cateye enduro 2 seem to read pretty acurattly to me but recently someone in our club seemed to think the identical ride we had done was quite a bit longer.i spent a lot of time trying to set up mine before use but how can i check its ok? is there a way of checking settings??

Find a local roadie and get him/her to show you one of their time trial routes. That will have been measured to the metre.

Compare it to a GPS. Mine was (By chance) silly accurate last time I did this. Something like 0.1 of a mile over 50+ miles. 🙂

Inflate tyre to usual pressure. Take bike to long straight bit of level tarmac. Rotate wheel until valve at 6 o'clock, mark ground with chalk. Sit on bike and have someone push you forward in a perfectly straight line until the wheel has completed 10 revolutions. Mark ground, measure distance travelled, follow leaflet that came with computer and divide the answer by 10.

Find a measured half mile used by local traffic cops to calibrate their speedos / VASCAR and ride along to check accuracy. Bit tricky on motorways mind.

For long road rides the route plotting feature in Google maps is your friend if you don't have a GPS log.

And I have a standard calibration run for computers, exactly 2.5km between the junctions.