.... or tell her you need a new frame as the geometry of the old one is hurting your back, pretend to be changing components over in the garage (more free time to yourself) ....when all along you have simply replaced the entire bike and got the odd spanner out and squirted oil on your fingers whilst tinkering with your new toy. Better still tell her you are merey spending money on spray paint as you fell off and damaged the paintwork on the frame ... then buy a can of spray paint and pretend you are creating a new look for your old bike but secretly throw it in a canal when she's not looking, or give it away to a friend several hundred miles away and unconnected to your woman's circle of friends (that'd possibly need to be on another planet as their underground networks are massive !) ... and then come in on the day of the new purchase looking slightly heady from the spray paint with the odd spot of paint on your hands and a few bits of bogus backing newspaper covered in the stuff grinning with satisfaction ... she'll think it is your ego puffed up from a good paint job and so you needn't hide the grin that the new dream machine has brought into your life ! .... or just buy new speakers for your stereo ..... and then try and convince yourself that you can feel the speed gain and smooth gear changing when you next get on your bike (requires almost the same leap of faith as simply fitting a new group set) Serious response to your original question:- If you change the cassette to a 10 speed you'll need a different chain size and the mech will need to move sufficiently to cover the 10 speed range (width of the cassette) or if the cassette is more compact you'll need to change the mech and the shifters as you'll need ones that move the cable and mech slightly less for each shift in gear .... appart from that you can mix and match the ratios to your hearts content on the cassette itself and for the chainset (within the range of what is available for the chainset .... with a small 30 tooth sprocket on the chainset at the front and 28 tooth selectable sprocket on the cassette at the back you have 30:28 which is approaching a 1:1 ratio for very very steep hills ... most riders will tell you this is uncool ... you may end up grinning however if you are able to climb to the top of a hill when they have had to dismount ... probably not necessary for winning triathlons though ?). The ratios overlap substantially between front chainset and rear cassette combinations .... especially when the cassette increases to a 10spd .... the reason riders want 10 and 11 spd cassettes is more for the "tooth at a time" fine adjustment whilst riding on the same front sprocket, to help maintain even cadence and even effort as the road conditions, wind etc vary slightly and to help maintain even effort as you accelerate. If you go for a triple chainset at the front you may need a new bottom bracket and front mech due to the extra width. This is only my understaning I have never done this myself! I am probably more of a novice cyclist than you are but this is my understanding and may help. Any good cycle shop will set you right though and shouldn'y let you buy components that don't marry up. I'd avoid e-bay for new components that i am fitting myself when I am still learning how things work and when the many many historical versions of the "same named" groups sets seem to get upgraded as often as Microsoft Windows! (i.e. Shimano 105's but which version, or what season etc). Good luck. S | 
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Simon Burgan 2
