Optima Mid one way diff?

[Wandy]

Can someone explain to me what one of these is? Were they fitted to Mids as standard or is it a Kyosho hop-up? Were they available front and rear?

[jerrywasaracecardriver]

One way diff is just a bearing that only allows the inner race to spin in one direction. What this does, is it allows the diff casing to transfer torq to the bearing when power is being applied. When off throttle, the one way bearing inner race then spinns faster than the diff housing, because the diff housing is being slowed down by the belt and rest of the drivetrain, allowing the front wheels to spin freely. So, basicly, any time the front wheels spin faster than the diff housing, they are spinning in the one way bearing. under acceleration when the front diff is actually trying to accelerate the front wheels, the bearing dosent spin its inner race. These were a hop up option. I have one from either gpm or mp, that fits inside a stock gear diff housing. On track this allows the front tires to have more traction when off throttl, because they dont have any breaking force. Not worth messing with unless you seriously race, are a glutton for punishment, or are practising to become a better driver.

[terry.sc]

These were available for the front as an Option House part. They weren't standard. When the car is running in a straight line all the wheels are rotating at the same speed so you get the extra traction of 4 wheel drive. When the car goes around the corner the front wheels run in a larger arc, so ideally need to turn faster than the rear wheels. using a one way allows the front wheels to turn faster than the rear wheels and you get the most grip in the corner. The downside is that the car is only running with 2 wheel drive until the rear wheels slip. An advantage of the one way is that if one front wheel lost traction the other wheel would still drive, unlike a front diff where if one wheel slips all drive is lost as all the power goes through the spinning wheel. In theory there would seem to be an advantage to using them both front and rear for forward drive but the problem is you would have no brakes at all.

With a one way fitted when the car brakes for a corner the one way disengages and you basically have a rear wheel drive car. You only have brakes on the rear wheels, which means the front wheels are just steering so you get more steering into the corner. If there isn't much grip it is very easy for the rear end to spin out just like a 2wd buggy. When you accelerate out of the corner as soon as the rear wheels start to spin the front one way re-engages and gives you 4 wheel drive again so you get better traction for acceleration.

The one way is a useful tuning option when racing, if the car understeers into the corners fitting the one way and adapting your driving to it can improve the handling - just remember to not be hard on the brakes.

[Wandy]

Hmm, interesting. Sounds like it's only a hop-up if it suits a particular track/driving style?

[terry.sc]

Yes, it was just a tuning aid, like the choice of ball diffs or gear diffs.