When searching tire tech always go to the tire mfg website.
Tire rack and Discount Tire (other tire chain stores) sells tires and may not print what "all" the tire mfg says which is the case with the 857 tires.
Part of the problem is euro size all position tires are for cars/trucks/vans and trailers which is something Americans can't seem to grasp.
Now lets look at what Kumho says about the 857 per their website.
*The Radial 857 is available in European-metric commercial sizes. The 857's primary application is to be mounted on a trailer. With its solid commercial construction, the 857 provides the durability and reliability you need from a trailer tire.*
SPECIAL FEATURES
*For commercial light truck, transporter, van and trailer.
*Deep zigzag grooves for increased mileage.
*Straight center groove and sipes on four ribs to improve ride and noise.*
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What Kumho says is quite clear. The 857's primary application is to be mounted on a trailer and "For commercial light truck, transporter, van and trailer".
The 857 is simply a multi position tire that according to those that use them (RV webs and non RV webs) work a whole lot better than the maypops the 857's replaced.