I am thinking of getting a bike, probably mountain as I want it to be sturdy enough to go over the odd bit of rough ground. What frame size am I looking for?I am 5ft 8in tall with an iside leg measurement of 31in.
As you are not going to be using it for mainly off road riding I would suggest that you try a 19"/20" frame size but with the main emphasis on getting the length between saddle and handlebars comfortable. It's cheap to raise or lower the saddle but getting the other measurement right can be time consuming and expensive.
When you have got your bike its important to get the saddle at the right height too. We were always told that you should be able to touch the floor with ball of your foot - both feet, when sitting on the saddle. This ensures that you get the maximum advantage from your leg effort when pushing the pedals. I see so many people these days with the saddle far too low with the result that their legs are in much too bent a position, with the result that they are not in a comfortable riding configuration.
From my dim and distant days of track-racing,the simplest method of getting the saddle-to-handlebars distance correct for yourself,was to place your elbow on the nose of the saddle,make a fist then put that arm so your fist touches the handlebar stem. Then slide the saddle back and forth until your middle knuckle just touches the stem.Tighten saddle bolts and away you go.
what's the jury's opinion on rear suspension on mountain bikes?
When I look at people pedalling them, a lot of the energy seems to be getting absorbed by the suspension unit, and most serious mountain bikers don't seem to have rear suspension. Are my thoughts correct?
Mountain Biking has evolved in several ways. In the 'cross country' side of the sport many riders still use what are referred to as 'hardtails' with front suspension only. Some use full suspension bikes but these usually have limited movement and/or lockable rear suspension so that energy isn't wasted bouncing the bike up and down instead of going forward. Downhill bikers use the full suspension, and usually quite long travel in it, as they don't do too much pedalling but do need to absorb the bumps that they are hitting at quite high speeds. The average fairly cheap full suspension bikes are really just fashion items and do use up a lot of energy when pedalling which isn't good as these are usually the heavier bikes anyway.