I can understand horespower/torque limits on these but everyone always says to never run a tire larger than 33" with a 2D. Your site says 32". I would like to know why:

If people run 33"x15" paddle tires, they got to hook up way better than a 35" 12.50 dirt tire. So why is the dirt tire bad if it will never load like the paddle?

If your R&P is 5.14, and a 35" tire is only 6% larger than a 33", would it not be like running a 4.83 R&P with a 33" tire (load-wise)?

Would not the gear ratio be a factor in tire size?

Is it because of the tire weight and momentum increases the load on the gears by an inordinate amount though it is only 6% larger and a few pounds heavier?

Honestly, I would just like a clear explaination on this.

Thanks,
mike

These are great questions.
I have been pondering how to make this a easy answer with out getting to long winded.
so here it goes:

Overall mass (weight) does play into the dynamic effect in vehicle performance, and drive line loads.
BUT,
Even more prominent is tire diameter.
The larger the tire (O.D.) the more mechanical advantage it has over the ring and pinion and related components (C.V.'s, Axles,Hub's).
It becomes even more pronounced on a power load reversal.
Power load reversals are initiated on "off-throttle" conditions.
lifting off the throttle in rough terrain and utilizing the engine for its compression braking is just as bad or worse than landing with the throttle wide open.
In a power load reversal all driving members become driven members.
It is responsible for 50% to 60% of all ring& pinion related failures.

It is important to know that most sand tires are not the size they claim to be and when measuring the height you don't include the paddle.

Thank you for the question

Interesting...... So a v8 with lots of engine braking is going to load the components harder than a freer wheeling turbo v6 or Subie. That is something Grant mentioned to me when building the car. Enging braking is a lot different

My question: paddles are considerably lighter that a dirt tire so what about a 33in dirt tire?

Thanks for the reply. I see your point. The lower the r&p ratio the smaller the pinon gets. On reverse loading (engine braking) the larger tire will throw a lot at the ring gear which in turn will dump on the pinon. That sounds reasonable.

I wonder if there is a gear and r&p combination that would be stronger than some others? I'm thinking like a 3.88 r&p with the lowest possible ratio gear clusters. Have you guys looked at the possible combinations from this perspective?

Regards,
mike

My buddy has a new Gen 5 funco witha a subi and a 2D. 37 in tires I belive. I think they put in a 6.66 ring & pinion, no problems so far.

i have a 2200lb car 5 seat 6.0 ls2 500hp at the crank. i run extreme 35x14 tires at 15lbs of air. extreme 35x14 is a narrower and same height tire as a sandblaster 33su. with 15lbs of air my car slides in the corners nice and has minimal square inches of paddles in the sand, i like the all around look and feel of the car and dont want to change. what are the worse things i can do as a driver to blow my trans? what can i do to save it but still have fun?