Wheel Chocks 2 Pack Heavy Duty Rubber Chocks Black Wheel Wedge with Eyebolt, 7.8" Length x 3.5" Width x 3.9" Height

Q: Will these work with a 30 inch tire?

These chicks are way too flat for my 25" tires. Your 30s or larger would work . Honestly , keep looking

Q: Will these work for a large Class C?

Of course, this one can meet your needs, and there is no problem with the usability and functionality of this one. But as a professional seller, we recommend B085Q2X5CZ and B07VHGRCYH or B085Q3QBKR, They will be more suitable for your vehicle use. You can check our related products