Bike gears vs Vehicle gears?

[OneTime]

Im trying to understand how vehicle gears work. I have a LC 80 with a 3FE engine and am considering regearing and new tires. I am limited in vehicle knowledge, but do ride bikes and understand bike gearing.

I related going with a bigger tire like stock 31" to a 33" like a 26" bike tire vs a 29er. I understand the large tire moves farther distance with each revolution, thus requiring less rpm than an 26" tire. I assume the same principle ablies to trucks.

I currently have 4.11 gears and am think of going to 4.56 or 4.88. Help me understand. Is the change in gears like a change in the rear cassette? Would it be like dropping to a smaller rear gear and making it harder to pedal but getting more torque and going faster, or is it like shifting up a gear and making it easier to pedal and not going a far with each revolution.

Or is it more related to shifting the gear in the cranks either up or down?

 

[jcbrandon]

...I currently have 4.11 gears and am think of going to 4.56 or 4.88. ...is it like shifting up a gear and making it easier to pedal and not going a far with each revolution...

This is correct.

 

[OneTime]

So it will make my rpms higher. Why then do you regear for bigger tires? Is it because you engine is working to hard a stock ratio to turn the bigger tires? If its is like going up a gear and making the pedaling easier. How does regearing give you more "grunt"?

 

[haven]

Regearing restores the power you lose when you add the taller tires. Using your bicycle analogy, when you shift from the small chainring to the large one in front, you can keep the same cadence by shifting to a larger cog in the rear.

 

[OneTime]

Ok let me see if I get it. Going to a bigger tire is like shifting to a bigger chain ring. And regearing is like shifting the rear cog to a higher gear thus making the engine work less to rotate the tires?

So going to 4.56 gears might by like pedaling im the middle of the cog and 4.88 would be like pedaling in the highest gear.

 

[jesusgatos]

Putting large tires on a vehicle with stock gearing will lower the RPM's that your engine will run at any given speed. In some instances that might be desirable, but more often, you'll want to re-gear to get the engine back into the meat of the powerband. In bike terms it would be like this: 42/12 = 3.5:1. If you put a 49 tooth sprocket up front and wanted to maintain a 3.5: gear ratio, you'd have to go to a 14T rear sprocket. Make sense?

 

[OneTime]

Jesusgatos It should make since to me, but I am not much af a numbers guy with my bike.

I understand why my truck runs lower rpm on flats with the larger diameter wheels, like a 29er. In the vehicle world, when some one says "taller gears" can you compare that to a larger "taller" rear cog?

I see see how that helps on climbs and hills. I can also see why it would make the engine rev higher at highway speeds on flats. Like riding in your granny gear so so speak.