Best pulley ratio for trail/ torque?

Im building a dynamark 16/42 i have a 19.5 horse brigs twin i want it to b a utv type mud mower like a trail buster it has a 4 speed in it im trying to get some advice on wat a good ratio is and if i want spd and torque or mainly torque if anyone has any advice that b awesome i also am building a speed mud mower for more ruppin through the mud with i was wondering if a double belt system is better or a single belt drive for this i have a few doners to choose from my power plant for that is a 15 horse single brigs

A 1:1 ratio is a good start for some good speed and good grunt. I run a 6" to 6" pulley and can pull most anything in first gear, and get a 15mph top speed.

Yeah I agree with RROD. A 1:1 is a good all round ratio, although I ran a 5" front pulley and 3 1/2" trans pulley for a while and clocked 22mph. It would still pull very strong in 1st gear. If you are going for torque, I suggest running big pulleys front and rear (at least 5"). You might find that you do not have the space for a huge pulley at the front but try and get the biggest possible one fitted in. Bigger pulleys = more surface area for the belt = less belt slippage = happy person

If your running stock clutch, dont go anything below a four inch rear pulley. Thats what i run on my craftsman and i experience minor belt slippage, but overall run a 1:1 ratio like RROD a and matthewD said.

Thanks for the advice everyone right now i have a 5" up front and a 4" in back i cant go any bigger up front do to stock clutch placement which i might change... This project is more of a mule or workhorse/recovery rig im building a speed mud racer too that will b for more speed

@thesmokeyredneck wrote:

Thanks for the advice everyone right now i have a 5" up front and a 4" in back i cant go any bigger up front do to stock clutch placement which i might change... This project is more of a mule or workhorse/recovery rig im building a speed mud racer too that will b for more speed  

5 to 4 should be fine for a workhorse.

You might find that 5:4 is a little bit quick for general jobs (pulling a trailer etc) but it is nice to have that extra speed sometimes!