Car v Bikes


The Setup

After 19 years or so, I finally redid my CBT, to work my way into getting big cruisers (at least a year before that happens).


If you have driven a car, the recommendation is to usually run a low RPMs. With my Ford Focus I usually have the car around 2000 RPM. And as a car driver, who also likes silence and despise loud noises, always get the amp with the bikes when they sound like they are pushing them to the limit.

During the CBT class, they told us that motorbikes do use higher revs than cars: O_o . That is my surprised face.

They gave as the reason the gyroscopic effect, with higher revs helping on keeping the bike stable. Though I have the suspicion that they mixed a bit the concepts. Certainly, like with push bikes, going at speed helps on the stability of the bike due to such effect.

I read a bit more (because I was curious). So it seems that the strokes (basically, the different phases on the revolution on the piston) on bikes are much smaller, therefore quicker. But also means that the Torque of each revolution is not as big as that of a car (they have bigger pistons). Power is, basically, torque by rpm. To deliver the same power, taking into account the smaller torque, would mean increasing the RPM. Bikes, due to their light weight, they have a power-weight ratio higher than cars, but linked to much smaller engines, they really don’t produce as much.

That goes to explain the higher revs they need to operate with.

Constraints create different effects.

The basis of the engine of a car and a bike are similar … combustion engine with fuel injection and pistons to provide the force. And yet, they need to behave differently in terms of RPM, due to the different characteristics of a car vs a bike.

Two similar ideas, two different approaches.

What about trucks? The engines are bigger, therefore the torque should be bigger. Which would be needed to move bigger loads. They don’t acquire as much speed, because the engine is setup specifically for weight performance, rather than speed.

If you have similar solutions, but their constrains or setup is different, more likely than not you should be taking different approaches and different decisions.

But my cruisers

One interesting fact about bikes, is that while most bikes are optimized to work on higher RPM, to provide enough power to compensate for the low torque, Cruisers are actually optimized to work at lower revs. As someone put it, is not about how quick you get somewhere, but about the style.

As an example, a Mutt Mongrel, a 125cc 4-stroke single cylinder, has a horsepower of 12hp, with a top speed of 70 mph. In contrast, a Sinnis Outlaw, another 125cc 4-stroke single cylinder, has 10 horsepower, with a top speed of 56mph.

With the same constrains, the objectives are different, so they have different setup.

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