would all pulleys have to be the same

[etap]

I have a zero turn,and i had to replace the center pulley,because i bent the pulley taking off blade. It was 4.75 and i replaced with 5 inch but the two pulleys outside are 4.75. Thx

[piston slapper]

If the belt works...should be ok...though the center blade will spin a tad slower..
Might be an issue in thick grass..

[dutch1]

Ya beat me to the gravy, Slapper--I was doing a bit of figgerin with my sharp pencil.

I just picked out a Toro Z 60' that just claims a blade tip speed of 18,500 ft/min=222,000 in/min. Assuming a 20" blade, that yields a spindle speed of about 700rpm. Replacing the 4.75 diameter with a 5" pulley will reduce the spindle speed to about 630rpm or a blade tip speed 197820 in/min or 1648 ft/min. In other words, about a 10% loss of rpm/blade tip speed.

Like you say Slapper, it may be an issue in tall/thick grass(quality of cut) but it also may negatively effect deck clearing capabilities. How much of an effect, I can't predict.

[birddseedd]

I always go to the local industrial supply shop for my bearings and pulleys. much cheaper than what youll get at the mower shop and higher quality.