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Old 02-14-2008, 04:38 PM   #1
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Red face Rollout / Gearing?

I need some help learning all the aspecs of foam tires and brushless motors.
I understand that as my tires wear down I will gain torque but loose speed.So if I gear my 17.5 @ 3.8 fdr and put on new foam tires which puts my rollout at 51mm. The question is: as my tires get smaller, do I gear up to maintain my rollout? If so, this will change my fdr of 3.8. Shouln't I be concerned about burning up the motor? I guess as you gear the motor for more speed, the tires are giving you more torque. Is this true?
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Old 02-14-2008, 08:40 PM   #2
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Simply put, if 51mm rollout on new tires does not overheat your motor, then gearing taller as the tires get smaller to maintain that 51mm rollout will not cause the motor to run any hotter. FDR alone does not determine your motor temperature. It's a factor, but rollout provides a much more complete picture.

As the tires get smaller, the load the motor sees on the track diminishes. If you didn't change gearing to maintain the rollout, you'd typically see the motor running cooler and cooler as the tires got smaller. Changing the gear ratio to maintain the rollout as the tires wear keeps the load the motor sees the same, thus it will run at the same temperature as before.

The only time you can work by FDR alone is in a class where tire size stays constant, like rubber tire classes. If tire size changes due to wear as in foam tire racing, FDR doesn't give you the full picture.
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Old 02-14-2008, 09:19 PM   #3
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thanks, I thought I was on the right track. But I wanted to make sure before I fried something....
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Old 02-15-2008, 04:45 AM   #4
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yeah, what Trips said. When running foams don't even think of FDR, only rollouts. Check out www.gearchart.com and print up some rollout sheets so you can see when you need to gear up to compensate for tire wear.
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Old 02-15-2008, 06:50 AM   #5
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Already been there Matt. Thats an awsome site. Do you think 51mm is a good rollout for 17.5? Also, I think I'll start out running dblpink rear and pinkorange front, what do you think about that? Another question, do you by chance know what the diameter is on a new set of foams? I would like to buy all my gearing when I pick up my tires tomarrow.
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Old 02-15-2008, 07:25 AM   #6
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Originally Posted by Drifter73 View Post
Already been there Matt. Thats an awsome site. Do you think 51mm is a good rollout for 17.5? Also, I think I'll start out running dblpink rear and pinkorange front, what do you think about that? Another question, do you by chance know what the diameter is on a new set of foams? I would like to buy all my gearing when I pick up my tires tomarrow.
Talk with Todd Beardmore on the gearing for the 17.5, he's been running it in his TC the past couple weeks and it's pretty fast, I have no idea on what he's running though. Tire size out of the box depends on who's tires they are, the parma's I believe start out at 57mm, the jaco's were either 58 or 59, I don't remember.
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Old 02-15-2008, 08:13 AM   #7
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Thanks for the tire info Matt. I think I'll plug in 60mm for the chart. I did talk to Todd a little bit last Sunday, but it was still a little greek to me. I'm starting to absorb it now.
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Old 02-15-2008, 08:26 AM   #8
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Thanks for the tire info Matt. I think I'll plug in 60mm for the chart. I did talk to Todd a little bit last Sunday, but it was still a little greek to me. I'm starting to absorb it now.
come find me this weekend if you have any questions, rollout is easy when you get the hang of it. The PITA part for me is resetting ride height and droop as the tires wear
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Old 02-15-2008, 04:11 PM   #9
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come find me this weekend if you have any questions, rollout is easy when you get the hang of it. The PITA part for me is resetting ride height and droop as the tires wear


AMEN to that!!!
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Old 03-06-2009, 06:00 AM   #10
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hey guys, can anyone recommend a starting point for rollout on a tc with a 6.5 brushless and Lipo please ?
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