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Old Jan 19, 2013, 12:36 PM
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St. Louis, Mo.
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HPI Sprint 2 Sport; Pinion gear change for quicker acceleration

I got a HPI Srint 2 Sport for Christmas and am looking for a little more speed without going BL yet. With the 15t motor it is pretty quick already, but I am considering changing the pinion gear for quicker acceleration, not top end speed.
Do I go up a tooth or down a tooth? I have been told both and am confused as to which way to go. Where do I find this gear once I know which way to go?
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Old Jan 19, 2013, 05:18 PM
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As per your other thread...

Smaller pinion or bigger spur = faster acceleration
Bigger pinion or smaller spur = faster top speed.
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Old Jan 19, 2013, 10:45 PM
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As per your other thread...

Smaller pinion or bigger spur = faster acceleration
Bigger pinion or smaller spur = faster top speed.
Thanks. Thought I would try different sites and get as many options as possible. You caught me.
Where can I get a smaller pinion gear for the Sprint 2?
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Old Jan 20, 2013, 07:03 PM
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It's a 48 pitch pinion, you can get them from pretty much any hobby store. You just need to know how many teeth your current one has to make sure it it isn't too drastic of a change.
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Old Jan 20, 2013, 11:15 PM
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It's a 23 tooth pinion on a 15t motor. Any suggestions as how much to gear down?
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Old Jan 21, 2013, 07:28 PM
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http://www.hpiracing.com/manuals/pdf/704.pdf

Look at page 8 of your manual it will show you the recommended pinions for your car. You want to be close to the gear ratio. Looks like you can go up to 24 to 25 with a 81 tooth spur you may get better results with a 64 pitch gears. That is what we use to race. That is indoor on carpet.
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Old Jan 22, 2013, 03:52 PM
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Looking at that chart, I currently have a 90 t spur with a 23t pinion (8.33).
If I keep the spur as I have intended to do, I could go up to 27t pinion(7.10), or
a 28t pinion (6.85). The chart shows recommended gearing for a 15t motor is 7.0. Would a 28t pinion give me good top end? I was looking to improve on better acceleration and was looking to gear down from the 23 pinion to maybe 22 or 21. If you race these, I'm sure you know best as I am just starting out. Appreciate your input as what I should do.
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Old Jan 22, 2013, 10:12 PM
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With your motor according to your manual 7 is the magic number that is where your motor will run the best. you will get more top end with a higher pinion gear.
According to the chart 27 or 28 is good for that motor. If your on a short track with a no long straits then you may not need a lot of top end speed. Your pretty low at 23 try a 22 or 21 but watch your motor temps. If it is to hot to touch your working the motor to hard. As a disclaimer I did race these it has been awhile mostly oval was my game. The biggest difference between the two I had no gear box's to contend with. I had an HPI Hara edition a real finicky car.

Hear is a 64 pitch chart remember the 7 gear ratio you have more options going that route. You would have seven options of gears and still be close to the ratio that is recommended for the motor.
http://www.rctek.com/pdf/gearing_cha...h_electric.pdf
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Old Jan 27, 2013, 04:52 PM
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I bought a package of 5 pinion gears from A Main Hobbies 17,18,19,20,21. I tried gearing down gears yesterday. It comes with a 23 t pinion. I tried a 21 tooth pinion and was not thrilled with the results. I then went with the 20 tooth. Didn't notice much if any difference. So then I went with the 19 tooth. Still not all that much different. There I stopped for the day. I will try the 18 tooth next good day I can get it out, raining today. I went with a 15T motor on my Ruckus from a 20T motor it came with. I went from the stock 18 tooth pinion to a 17 tooth and what a difference. I just may do the same on this Camaro since it is also a 15T motor.
Looking for quick acceleration, not necessarily topend. Let you know how this turns out. I am interested in what effect the 27T pinion gear will bring as it is what is listed on the chart as the most effective for this motor. $5.00 spent may be worth it to satisify my curiosity for this gear.
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Old Jan 27, 2013, 05:08 PM
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Originally Posted by rwek View Post
I am interested in what effect the 27T pinion gear will bring as it is what is listed on the chart as the most effective for this motor. $5.00 spent may be worth it to satisify my curiosity for this gear.
That's the Spirit!.
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Old Feb 01, 2013, 05:06 PM
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Well I never did run it with the 18 tooth pinion gear. I went to my LHS and bought a 27 T pinion gear as the chart in the manual showed for this motor. Ran it just about half hour ago and holy cow. It took off. WOW. This is what I was looking for.
I can't wait to get it out on a parking lot where I have a lot of room. Man what a difference. For those of you that have this car and still running the stock motor and nimh batteries, I strongly urge you to change the pinion gear to a 27 T as the chart suggests. You will not be disappointed. I thought I could get more speed without going BL. This saves quite a bit of cash instead of buying a BL setup. The chart states to get as close to 7.0 as possible. With the 27 T pinion it is at 7.10. With a 28 T pinion it is at 6.94. Don't know what that one will do, but I may try it also just to see the difference. What's $5.00 just to see. That's what I did on the 27 T. & it was money well spent.
By the way, I was curious how warm the motor would get with this gear. After runninig it about 10 minutes the motor didn't even feel warm, granted it is around
25 degrees ouside right now. Overall I am very pleased.
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Old Feb 01, 2013, 08:49 PM
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Originally Posted by rwek View Post
Well I never did run it with the 18 tooth pinion gear. I went to my LHS and bought a 27 T pinion gear as the chart in the manual showed for this motor. Ran it just about half hour ago and holy cow. It took off. WOW. This is what I was looking for.
I can't wait to get it out on a parking lot where I have a lot of room. Man what a difference. For those of you that have this car and still running the stock motor and nimh batteries, I strongly urge you to change the pinion gear to a 27 T as the chart suggests. You will not be disappointed. I thought I could get more speed without going BL. This saves quite a bit of cash instead of buying a BL setup. The chart states to get as close to 7.0 as possible. With the 27 T pinion it is at 7.10. With a 28 T pinion it is at 6.94. Don't know what that one will do, but I may try it also just to see the difference. What's $5.00 just to see. That's what I did on the 27 T. & it was money well spent.
By the way, I was curious how warm the motor would get with this gear. After runninig it about 10 minutes the motor didn't even feel warm, granted it is around
25 degrees ouside right now. Overall I am very pleased.
Good deal I'm glad to hear your having success. The right gear makes all the difference.
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Old Feb 01, 2013, 10:09 PM
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It was a fun process though but in the end I found what works. And cheaply at that.
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