I put on the snow boots last weekend, (toyo garrit ht 17), wondering if there is any suggestion on best tire pressure for the snow tires.

BTW, just tried out the snow tire yesterday morning, it was freezing in the morning and black ice all over the place in the western tip of Mtl island. The DSC light comes on a few corners with cold hard surface. But for one icy corner, I can see the glassy reflection on the road surface, I could not even make a sharp 90' turn after a stop sign, a slow turn about >5 km, went over on coming traffic, thank god the kid right in front of my face was driving slow on ice and avoided the head on. The rear tugged in fine but the front could not get any grip. Be careful out there with the 8.

 

Snow tires should be inflated to 36 PSI cold. It's in the RX-8 Owner's Manual and I've confirmed this with the Tire Rack for my Dunlop Winter Sport M3s.

 

I also have garrit's and found that the rear wheels spin easily even with DSC on (just a little) but the summer treads did not. What's with that?

 

Gezzz, which part you not understand? 32 for summer tires, 36 for winter tires. Here, I'll quote from the from page 4-9 of the US Owner's Manual for yah:

"Use snow tires on all four wheels.
Don’t go faster than 120 km/h (75 mph).
Inflate snow tires 30 kPa (0.3 kgf/cm2,
4.3 psi) more than recommended on the
tire pressure label (driver’s door), but
never more than the maximum cold-tire
pressure shown on the tires."

Crystal clear now .

 

Yes, same here, wheel spin with the Toyo even gently release the clutch on dry road. No problem with OEM summer tire.

 

Wow, I thought lower tire pressure gives better grip. I might probably keep the tire pressure between 30 -32.

 

I would assume this is because of the trad pattern of the winter tires. Essentially, there is less rubber contacting the pavement because of the winter tread pattern that is designed to "bite" into the snow/ice. Think about it, ideal traction on dry pavement is achieved with a racing slick, or no tread at all. Simplistically, the more you add to the tread pattern, the less rubber will be contacting the road.

This is another case in which dry and wet/snowy/icy conditions need to be considered individually. On dry pavement, yes, the lower tire pressure gives better grip since the area of the contact patch is increased. You want as much rubber meeting the road as possible on dry pavement. However, in snowy/icy conditions you want just the opposite. The reason is that the tires need to "bite" into the snow and ice as much as possible. This requires that there is adequate pressure between the tire and the snow/ice. The smallerr the contact patch area, the greater the pressure since (pressure = force / area). Therefore, anything that decreases the size of the contact patch is beneficial for traction in snowy/icy conditions. This would include using a narrower tire and increasing inflation pressure. I hope this helps.

 

Thanks RX8_Buckeye, like you said, I need it check the pressure again. Probably try 34 and see if it drives better and not bouncing around.

 

also, about pressure. Remember your chemistry gas laws, as temperature increases, so does pressure. So in the summer, tires are inflated to 32psi, and probably increase to a higher running pressure (say hypothetically 37psi) well the snow tires dont really get as warm as the summers can, so to compensate they start at a higher pressure.

 

Reading the manual is always a good idea.
Some guys are even saying to adjust pressure for the smaller rims/tires. Is anyone doing this or is it not much of a concern. My tire guy didnt mention it, only to follow what the manual says for inflation.

 

I hope you dont go 130 on a slippery winter road.
Dont be gettin reckless on us now Mic, ya might end up lookin like Keith.