Lowering the tyre pressures does 2 things...
1st It allows the tyre to flex more, thus generating more heat and a larger contact patch on the road. The reason you will get more milage from a rear running a lower pressure is a direct result of the above, with the grip gained from the extra heat and the larger contact patch the tyre will spin up a lot less and put the power down on the road better, less spin means less wear on the tyre...simple
2nd This is the iffy one, due to increased running temperature it can cause the tyre to overheat which can in some cases cause failiure of the tyre if it is used mainly for straight line work...ie motorways
With that in mind GB is correct, modern tyres on SPORTS bikes will perform better running somewhere around 32/34 front and 36/38 rear depending on load and type of riding you do.
Tyre manufactures reccomend 36 front 42 rear on most modern bikes because the testing they do indicates that for 90% of appliacations it is the best pressures to run. Its not just worked out on pressure, but the volume of air in the tyre and wheel. They recommend the pressure that their tests show will give best life/grip/RELIABILTY/fell for the majority of bikers and bikes.
The only way to know if a lower pressure works for you is to try it and see what you think, if you dont like it adjust it a couple of psi at a time till you are happy with it.
Oh just another quick pointer, those of you with larger type bike(tourers) may find that adjusting the pressures away from recomended pressures will affect stability in a straight line due to the load on the tyre so beware.
Gav
