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I was practicing with a fellow racer the other day. We both have Pro 3 HD and our set-ups APPEAR to be exactly the same. The only noticeable difference I could see is that he was running an 80 tooth spur and I had a 110tooth spur. He really seemed faster than me. Could the spur size cause that? BTW-it was a asphalt track about 330 ft run line.

Thanks,
AL
 

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This has been gone over in length on in the general thread.

To me...A small spur gives you more top end speed, and a big spur gives you more out of the corner. This is just how I feel about it, and others will disagree. To me a ratio is not a ratio, but again others will dis-agree. Try running the small spur and see for yourself.

Joel White
 

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Joel pretty much hit it.....you will get 1000 different opinions on this, but like Joel, I agree that smaller gives you more top end speed.

Since you are specifically talking about Easley, which is where I race every weekend, I can tell you that most everyone there is running between an 80-96 spur gear. I am running a 90 right now, but have been running 88 for a good while.

At Easley, I think a smaller spur gets you more speed down the straights, but you give up just a bit getting up off the corners. It seems to me that a smaller spur spools the motor up better and helps keep the momentum going, which at Easley, is pretty much what it is all about anyway. But, as with most anything, your mileage may vary!
 

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I was practicing with a fellow racer the other day. We both have Pro 3 HD and our set-ups APPEAR to be exactly the same. The only noticeable difference I could see is that he was running an 80 tooth spur and I had a 110tooth spur. He really seemed faster than me. Could the spur size cause that? BTW-it was a asphalt track about 330 ft run line.

Thanks,
AL
One major change it has is the bigger the spur you run, the further forward in the pod your motor is, which makes the car have more forward bite(tighter off). This is a pretty big change in a well-handling car.

Of course, if you're running on cap tires, chances are it always comes down to tires, tires, tires, tires, tires......
 

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I got an opinion from a guy who used to think a ratio was just a ratio, until he tried the same ratio with a smaller spur and apparently gained noticeable speed.

I like running a smaller spur just because I have enough room to hold my motor down by using both screws on the bottom end, thus lowering the weight of the motor 1/8th of an inch.
 

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mathematically and from an engineering standpoint a ratio is a ratio. The only thing that changes by going to a larger spur is the motor is closer to pivot point which changes the way the car reacts. Dont get sucked into the idea that you can get more off the corner or at the end of the straight by changing the spur gear.....1.6:1 is 1.6:1 reguardless of how you get there. What changes in the way the chassis reacts to that big weight you keep moving back and forth. Adapt your setup to suit your spur gear...and remember not all motors are created the same.
 

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the fulcrums are what change ex.the distance from the center of the motor shaft to the edge of the pinoin.then the bigger the spur gets the easier to turn the tire,but this requires a bigger pinoin and thus you loose output due to the longer "arm" of the pinoin.but in reality the differences in torque output are very small.remember be a sheep do what the others are doing to see if it helps,i dont a spur change will pic you up a tenth though.
 

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mathematically and from an engineering standpoint a ratio is a ratio. The only thing that changes by going to a larger spur is the motor is closer to pivot point which changes the way the car reacts. Dont get sucked into the idea that you can get more off the corner or at the end of the straight by changing the spur gear.....1.6:1 is 1.6:1 reguardless of how you get there. What changes in the way the chassis reacts to that big weight you keep moving back and forth. Adapt your setup to suit your spur gear...and remember not all motors are created the same.
One major change it has is the bigger the spur you run, the further forward in the pod your motor is, which makes the car have more forward bite(tighter off). This is a pretty big change in a well-handling car.

Of course, if you're running on cap tires, chances are it always comes down to tires, tires, tires, tires, tires......
these 2 post say everything !!:thumbsup::thumbsup:
 

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One other thing that changes is that as the gears get bigger the forces pushing the gears apart get smaller. so you have less loss to friction. If you think of a small pinion say 10 T with a big spur there is a decent amount of force trying to push the gears apart. this is much less of an issue with the large pinions we are running now with brushless motors. The inertia of the large pinion gears has to have some effect as well since inertia has a radius squared in it.

So there are a bunch of tradeoffs in efficiency of the gears, inertia and chassis setup when running smaller or larger spurs. I am running a battle axe which has a limited amount of motor movement, so I have to run what gears fit and cant really experiment with the big spurs.

John
 

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Of course, if you're running on cap tires, chances are it always comes down to tires, tires, tires, tires, tires......
when it comes to cap tires....this is the most important advice you will ever get!
 
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