Hello, I am about to buy some bushings from mazda, I have a choice between UHMW, urethane, and rubber that is 40% stiffer than stock. I'm pretty sure I am just going to go with the rubber that is 40% stiffer than stock, unless that is what one of the ones above is in the kits. The kids just say uhmw or urethane, but you can buy them individually and that is where their description is 40% stiffer than stock.

If someone could help clear some of that up, it would really help me out a lot.

Thanks
~Tweak

 

opps, sorry miss spell/type. The kits say, not the kids say.

 

UHMW (Ultra High Molecular Weight) is a thermoplastic, which is self-lubricating. It has a hardness between 60-70 Shore D; as shown on the Shore Hardness Chart below. It has a hardness similar to delrin, which is very close to a solid (aluminum) mount.

Polyurethane can be tweaked to adjust the hardness between 45 Shore A and 60 Shore D.

Most OEM bushings/ mounts are around 60 Shore A. Unless you can find the exact hardness of the urethane being used, I would go for the Mazda Motorsports mounts. Being "40% stiffer then stock," the hardness has to be around 80-85 Shore A. Unless you have a great tolerance for NVH in a street car, get the Mazdaspeed mounts.

 

UHMW is like a plastic cutting board, and the rubber ones are probably the softest (not to say that they're soft), with the urethane in the middle somewhere.

I've got the stiffer rubber all through my drivetrain and the increase in stiffness is noticable but it's still very civil. I've got urethane in the front suspension and it's not bad at all. You should be fine either way, but I'd stay away from hard plastics on a street driven car.

 

Thank you. I went with all 40% stiffer.