what is overdrive?

[Itchy]

Babyyam's other half described it at squires last week I glazed over and understood up to well over drive is.... , and I keep reading about it for in various adverts looking at hacks.

so what is over drive?.

Ta
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[Method]

From what i can remember...

Overdrive is where the gearbox is turning the rear wheel faster than the engine is turning.

Therefore 1st-3rd gear are say turning slower than the engine, 4th gear the rear wheel is being turned at the same speed as the engine, and 5th gear is overdrive - where the rear wheel is turning faster than the engine.


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[veeeffarr]

Isn't it a low RPM, high speed cruising gear that sacrifices power for fuel economy?

[T1z3R]

https://en.wikipedia.org/wiki/Overdrive_(mechanics)
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[feef]

[Method]

[Method]

[Kickstart]

Hi

Wear will depend on lots of things other than just engine speed. Running the engine at too low a speed will have just as nasty effects as revving it too hard.

As to efficiency, lots of odd factors. For a basic example, no point running higher gearing if that just means larger throttle openings to maintain speed and straying into the area where the mixture is richened up for acceleration.

Quite common for cars to be tweaked to do well on the standard 90 kmh fuel consumption figures, but in doing so land up rather worse in real life (when people just land up sitting a gear or 2 lower to get adequate performance on tap when required).

All the best

Keith
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[johnsilva]

[veeeffarr]

[flat spot]

[craigs23]

It's kinda like Warp Speed I think. Or is that Hyperspace? Both pretty nippy, that's for sure.

[lumphammer]

As has been said was an extra "gear" for cruising purposes fitted to cars with only four forward gears (those were the days ). Now almost all cars have five forward gears so no longer needed.

ex- Vitesse owner (1600 one of course)

[lilredmachine]

The new Vette Z06 has an overdrive in 6th, 1-5th get it to 200mph, and sixth gets it 26mpg on the highway. The 700R4 box in the Camaro we had contained an overdrive as 5th, 30mpg wasn't bad out of a 5.7 V8. Essentially it's a hugely long gear, the Camaro would pull 1500-1800 rpm between 70 and 80 mph on the motorway.
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[finpos]

As indicated, 3 meanings:

1. technical - the output of the drivetrain is spinning faster than the input.
2. legal - as applied to cars with poor fuel consumption, so they can meet mandated requirements (seems prevelent in US)
3. british car industry bodge - Can't build a decent gearbox? slam an unreliable auxilliary gearbox onto the back of the standard one, and turn it into a marketing feature

finpos.

[colin1]

does anyone know of any bikes with an overdrive top gear ?
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[Itchy]

[feef]

[yambabe]