[Kevan]

Glue & true the stock tyres first, then you can 'treat' them with 3 in 1 oil very thinly smeared round the tread...leave for at least 3 hours to let the oil soften the outer layer of rubber.

Olbas Oil or Tea Tree Oil work even faster (honestly it works, it's the Eucalyptus oil) but the effect isn't as lasting as 3 in 1 oil.

After market tyres make a bigger improvement, NSR Supergrips or Thunderslot standard tyres are two good examples.