Some Examples to expand on that theory:

Bridgestone Blizzak DM-V
Size: 255/55R18
Sidewall Style: Blackwall
Serv. Desc: 109RLoad Index 109 = 2271lbs (1030kg) per tire
Speed Rating "R" = 106mph (170kph)
Load Range: XLMax Load = 2,271 lbs
Max psi = 50 psi

Michelin Latitude Alpin
Size: 255/55R18
N1(Porsche)
Sidewall Style: Blackwall
Serv. Desc: 109VLoad Index 109 = 2271lbs (1030kg) per tire
Speed Rating "V" = 149mph (240kph)
Load Range: XLMax Load = 2,271 lbs
Max psi = 50 psi

Bridgestone Blizzak LM-60 RFT
Size: 255/55R18
Run Flat, OE Vehicle Use Only
Sidewall Style: Blackwall
Serv. Desc: 109HLoad Index 109 = 2271lbs (1030kg) per tire
Speed Rating "H" = 130mph (210kph)
Load Range: XLMax Load = 2,271 lbs
Max psi = 50 psi

Michelin Latitude X-Ice Xi2
Size: 255/55R18
LRR: Green XLow Rolling Resistance Tire Technology
Sidewall Style: Blackwall
Serv. Desc: 109TLoad Index 109 = 2271lbs (1030kg) per tire
Speed Rating "T" = 118mph (190kph)
Load Range: XLMax Load = 2,271 lbs
Max psi = 50 psi

Notice how some winter tires are rated R, T, H, or V.

I'll stick to my V (N1) Porsche tires.