Taxi on dirt, gravel etc..

Dear fellows,taxi on gravel with my istalled DC3 sometime is a pain, I understand that rolling on tarmac is one thing and that grass and gravel is another. Though, everytime I need to taxi on that kind of "pavement", the machine want a MP 40, even 45" to start and a good 30 - 35" to taxi. Isn't a little too much? My question is if there's a way to edit the airplane adesion. I feel it like rolling with almost no pressure in the tires.I've searched around but it seems that none have this problem.Thank you.