Gearing questions for my Xray .....

[Floyd]

Ok , I picked up a Trinity Revenge of the Monster Stock Pro motor ( same thing as the RotMS but retooled for higher RPMs and more torque ) . Now Im at a point of not knowing what gearing I should go with . The X-Ray I picked up was from the guy that runs the local race track and he ran in the modified class so the car has a 94 tooth spur in it . Should I change the spur to a smaller one or just go ahead and leave that HUGE 94 tooth one in it . I figured I would pick up a 22 , 24 ,and 26 tooth pinion to start with but am at a loss to know what the heck Im actualy doing with the gearing . Any and all help , suggetions , flaming , etc. etc. would be most appreciated .[]

[stulec52]

what I would do is ask what the guys at your club run for gearings as every track is different.

Maybe even start 1 tooth smaller on the pinion.

you can also go to : http://www.teamxray.com/xforum/

click on T1, and setups

and also : http://www.gearchart.com/index.cfm

and build your own gear chart !

Best bet though is to go ask the fast guys at your local club.

also remember, bigger the pinion the taller the ratio (i.e. faster overall top speed, less accelaration) and Bigger the spur gear the smaller the ratio ( i.e. faster accelaration, lower top speed)

[Floyd]

Well , as far as the one tooth smaller pinion , X-Rays dont come with any so there is realy no "stock" gearing to judge by . Ill have a look and see what I can find on the X-Ray site and see if there is anything relevent in the setups part .

I havent realy met anyone else from the club yet , they only run in the fall and threw the winter so the only one I have met so far is the guy I bought the car from and he only runs in the mod class . Which is kind of why I was woundering about the spur , if he was running 94 tooth spur with a 19 turn mod motor ( not sure which one exactly or the pinion he ran ) would that same spur be ok with the stock class motor I mentioned above .

Oh well ,thanks Stu []

[HunterZero]

A lot of racers at the club I visit go by roll out instead of gear ratio, which is the distance the car travels for every rotation at the motor.

To work out roll out, you need to know the tire diameter in mm (usually 62mm to 64mm), the number of teeth on the pinion and spur, and the internal ratio of the gearbox.

roll out = (pi * diameter in mm) / ((spur / pinion) * internal ratio)

The roll out to go for depends on the track, but for stock a rollout of between 20 to 30 is normal. Start at about 24-25 and pinion up/down from there depending on the track.

- James

[stulec52]

only need to bother will roll out if you are using foam tyres.

Rubber tyres stay pretty much the same diameter, foam tyres are something you can true through many sizes, and also they wear down, both do affect the overall ratio.

"Well , as far as the one tooth smaller pinion , X-Rays dont come with any so there is realy no "stock" gearing to judge by ."

and you misunderstood me here. What I mean is ask which pinion and spur the local fast guys are running with the same motor you intend to run, then use that same spur but fit the pinion with 1 less tooth as a start point.