What we are saying is that you are obsessing about the rear axle width..... it is NOT that important and is so shockingly simple to adjust that you can test the results of a new axle width yourself in minutes.
Moving the seat and setting the pedals is work that 'should' be done in your 'workshop' before you go to the track.
Secondly, you are assuming that an axle setting that works for one lad who is tall, heavy and muscular should be the same for a 2 stone 'wimp'.
If you insist on worrying about the rear axle width, just TEST the settings for yourself. I'd recommend going about this in a logical way.
Obviously, safety is EVERYTHING so don't mount the hub so not ALL of it has axle inside it (I.e., don't put the hub off the end of the axle).
Then work out what the SAFE maximum width is (Put the hubs SAFELY at the end of the axle. Then work out the MINIMUM width and that will be controlled by how far you can move the engine-side wheel IN-ward. You now know the maximum and minimum. It's usual to set/measure/record your axle width based on the length of the axle which protrudes though the hub.
1) Divide the max and min in half and place the hubs at that position. Get the lad to do 10 laps taking his lap time. Call him in. Get him to describe the handling.
2) Move the hubs out to the MAXIMUM width and do another 10 laps taking his lap times. Get him to report to you CONCISELY how the chassis handling has changed.
3) Now move the hubs to the MINIMUM safe width. Do 10 laps, taking his lap time and call him in. Now get him to report on the changes in handling.
4) Now sit down with a tea/coke and work out what he has said from what it's done to the lap times. You'll then be able to tell EXACTLY what happens as you change the axle width!
This is PRECISELY how you test anything/everything in a kart and is the invaluable lesson for your karting/racing career.
It's just DAFT thinking that karts are a series of 'exact measurements' that are known by the excellent driver/mechanics that you can copy onto your chassis. If it was like that, then every kart would have IDENTICAL lap times as EVERYBODY would 'know' the 'perfect' settings.
The most important thing you'll note is that his lap times are NOT consistent simply because he's not had enough 'bum-in-=seat' time (unless he's the next Ayrton, of course). You'll see this because his lap times will fluctuate wildly. While they differ by more than 1 second per lap, there's not much you can 'tune' about the chassis as his DRVING is not of a high enough quality. At this stage, you should be learning how any 'change' affects the FEEL of the kart rather than its outright pace. When he can get his times to within (let's guess) 2 10ths of a second for each lap.... THEN you can start the constant work of 'tuning' the chassis.
That set of tests with the axle width WILL however give him the feeling (and you the knowledge) of how changing X makes the kart feel different in Y area of it's handling. Let's guess that he notices that a narrower rear INCREASES the rear grip..... BUT.... it makes the braking far less stable, then when you need to GET more grip and can afford less braking subtlety, you know EXACTLY how to change this to GET that result!
That works for EVERY thing that is adjustable on the kart. You need to FEEL and TIME how it changes the kart and then combine each change with other changes to get EXACTLY the handling you want. Just copying someone else's settings will NOT give you this!
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Having said that.... because your tyres LOOK good is NOT a test of whether they ARE good. Tyres go through heat cycles (cold-hot-cold) and each one changes the performance of the tyre. If the rear of you kart is 'loose' (that's an American term, please note, it's correctly called Oversteer over here....) then those rear tyres will be having GREATER heat cycle changes than the front tyres..... thus they will probably have 'gone off' faster and more than the fronts. Once he's driving consistently, then a new set of tyres is a MUST have as they have a greater effect on the handling than almost ANYTHING else. New tyres give you a 'datum' point from which you can start your testing.
Ian
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bambino set up help please by 'Dubzy1981' (21 Aug 2013 @ 22:17)
