guys,,, I am beginner in this hobby,, I just got my xray t3'11, and I am considering to get new brushless motor ..

what is the good one ?
but I saw in the motor there are a lot of differents turn,
it says,, 17.5, 21.5, 7.5, 3.5, what is that for ?
what is the different ?
and what is the good one for me ?

any suggestion I would be really appreciate it ,,

All motors vary a little from company to company but here it is from Novak...
21.5=1800kv
17.5=2200kv
13.5=3300kv
10.5=4200kv
8.5=5000kv
7.5=5800kv
6.5=6400kv
5.5=7400kv
4.5=9000kv
3.5=10500kv
The lower the turn or the higher the kv... the faster the motor

The higher the turn or the lower the kv... the more torque

Think of it as s.a.e. versus metric

if so, why do people run 17.5, 13.5 ?
why don't they get the faster one ?

Many motor purchasers are buying motors to run in local racing events that may "spec" which motor wind to use. If you are racing, the higher wind motors are more controllable; many top drivers cannot handle a 3.5T motor in a race.

Buy a motor based on what you plan to do with it. What are you planning to do with it.

A motor is a tuning device just like anything else on the car. A faster motor can actually be much slower in lap times than a slower more controlled motor. Remember that races are not won in the straight but in the turns. It makes no difference how fast a motor spins but how much power gets to the ground and is still controllable. I've seen many times that the slower motor turns the faster laps.

There are several classes based on the motor. 17.5 is considered the "stock" class and anything faster is open class or mod. Since you have an Xray you will be in a Touring Class. You may find a 13.5 class too. It all depends on what your track runs.

For bashing out on the street or parking lot you can use anything you want since you don't have to stay within the lanes and make prescribed turns. Remember that the faster you go the worse the wreck will be.

I am planning to race in the track ,,
but last time I heard someone suggested me to get the 3.5 one ..
but I don't even have the car yet ,,

and now I have xray,,, and I am planning to go to the track for race ...

what is the good one for me ?
cz I am still beginner ..

A 3.5 might be too powerful if your just starting out. It might look good going down the straight, but if you don't learn how control it, you'll end up spending a lot of $ on parts. Especially on an Xray. Check to see if your local track offers stock classes for a 21.5 or 17.5 motor. I would recommend either of those. Good luck!

Joven, I’m going to have to respectfully disagree. I don’t think some one starting out is going to look very good at all on the straight with a 3.5! (Hope you know I’m just funnin’ a little, suspect you agree)

Rendcool, even world class modified drivers generally don’t use a 3.5 for racing. Best to start with a 17.5 as others have mentioned and work your way up later after you gain some experience. Even a lot of experienced guys don’t go much faster, we have a lot of power available to us these days.

Something faster might be OK for just blasting up and down the street or around a big empty parking lot. But even then a 3.5 is a lot of motor, will generate a lot of heat, be very sensitive to correct gearing, will be hard on the driveline-differentials, and you won’t have much run time from a battery charge. Maybe a 6.5 to 10.5???

so 17.5 is good for me ?
or which one ?

I am just gonna run it in local track in florida ...

Here's a tip from an old time racer: go to the track and find out what they use there. That way you'll get the exact set up you need.