Towing: 35i vs 35d

[JCL]

Thought it may help to use a truer analogy.

Originally Posted by seattle

Another analogy, better one.
Let's say you have a skinny fast guy on a 8-speed bike. Fast pedaling = more work done = high horsepower. He can pedal and go fast all day in any gear with relative ease. Sounds good, right?

Now, let's hook a small trailer with to that bike and load 200lbs on it.
Will the skinny fast guy be able to pull the trailer? Yes, he will switch to lower gears. Coming up to a hill, change to even lower gear and just pedal fast (high RPM). Will sweat a lot and need lots of Gatorade.

Let's say this skinny guy can push 300lbs with his legs in the gim, and pedal 300 times a minute. That's X5 35i with 300 hp /300lbf torque rating. A very good athlete compared to others, no doubt about it.

Then you have another guy, who can't pedal as fast, but got muscular legs that can overcome more resistance (torque). This guy can pedal "only" 265 times per minute, but can press 425 lbs at the gym. 35d rating.

Skinny guy on an eight speed bike. He can pedal up to 7000, but develops peak torque at 1300. He can leg press 300 in the gym. Divide cadence by 50 to make it more believable.

Another guy, on a six speed bike. He can pedal up to 5000, but develops peak torque at 1700. He can leg press 425 at the gym.

The two of them are put on identical weight bikes with trailers that can carry variable weights. They are asked to ride up the same hill, to see what is the maximum total weight they can get to the top in one minute, using whatever gear they like. The skinny guy gets 300 lbs to the top. The other guy gets 265 lbs to the top. They are equally tired and sweaty. That is a better analogy for power, and it matches the engine ratings.

And the difference continues with more weight, ie larger trailers. Heavy guy is proportionally slower.