I run a 116 spur.....need a ball park pinion size. Dont know roll outs so if you can just give me a pinion # that would help. Thanks

People would need to know the length and type of track to help you.

ball park - 74

133' rl

first thing your gonna have to change that spur to something around 88-90, and run a 40-45 pinion

Ok.....I figured a 2.25inch tire. Which is not huge but not tiny either.
For a track that size and a 116 spur, you would need about a 50 or 51 tooth pinion. That would put you at around a 3.1 rollout.

Thanks everyone for their input. my motor wont slide back that far to put on a big pinion so I guess I will have to go down on spur size. measured my tires they are 2.18's all they way around.

use this formula to get your rollout down to a 3.1

tire size x pinion (how many teeth) x pie (3.14) divided by spur (how many teeth)

for instance
2.18 tire x 50 pinion x 3.14 divided by 116 spur = 2.95 rollout

what would a good starting point for rollout with a 13.5 be at a track that we run around a rollout of 2.55 with a 10.5 motor?

what would a good starting point for rollout with a 13.5 be at a track that we run around a rollout of 2.55 with a 10.5 motor?


I thought roll out was for the car gearing itself. Can you tell me how you found out your track had a 2.55 roll out, I am lost...... :confused:

rollout is the gearing for the car. It is actually the distance the car travels for every one revolution of the motor. I think 2.55 he was referring to was the ballpark rollout for a specific track and class. The rollout calculation above is very valuable to gear correctly when changing to a different spur or to compensate for tire wear.

I thought roll out was for the car gearing itself. Can you tell me how you found out your track had a 2.55 roll out, I am lost...... :confused:

These motors will take alot more gear. today I ran a 4.2 rollout on an asphalt track with 365 ft. run line. On a 10.5 I ran a 3.4 I believe it was. The motor came off the track at 140 deg with an 80 deg ambient temp. I tq'ed and won. I was running a 88t spur 55t pinion with a 2.15 tire size.
Go up about 4 teeth and check your motor temp when it gets to140 to 150 deg stop adding gear.dont worry I'v had mine up to 175 deg and it's still fast.

thanks guys I am new to this. Explaining like you did helped alot

I ran a 3.12 rollout last night on a 105' carpet track, granted I might not have had the best setup in the car but still from my old stock brushed track record of 71 flat, I pulled a 72 flat with a crash, I would have been good for atleast a lap or more if it wasnt for that crash. I do feel like I was over geared but more testing needs to be done since this is all new to us, the temp of the motor was 138 and that was after 8:26 seconds of the 150 lap main we do. any thoughts?

I must of built that stock motor. LOL :p

what would a good starting point for rollout with a 13.5 be at a track that we run around a rollout of 2.55 with a 10.5 motor?

I'd start about .50-.60 higher then 10.5. So in your case maybe a 3.05-3.15.

I'd start about .50-.60 higher then 10.5. So in your case maybe a 3.05-3.15.

same here!

Has anyone seen the motors get hot (around 175) from undergearing?

Thanks,
Chuck

No. If they're under geared, heat shouldn't be a problem. I'd say they'd get hot from over gearing, drawing too many amps.

Has anyone seen the motors get hot (around 175) from undergearing?

Thanks,
Chuck

Yes, Not so much on indoor tracks. Outdoor tracks it happens all the time. This past weekend I geared at a 4.12 roll and the motor came off at 155. The race before that I geared at 4.22 and the motor came off at 122 and was a tenth slower a lap.

So yes, I do think overgearing can keep the motor cooler and run slower.

13.5 stuff is all new to me , how hot is too hot ? Also track groove is 110 , ran about 3 teeth higher than a brushed stocker , should i go higher ? thanks :thumbsup:

Yes, much more then 3 teeth higher. Assuming you have a sintered rotor you might want to try ~2.90.

On our small track 120-130rl
13.5 2.77 roll out
10.5 2.40 roll out

thanks guys , appreciate any input .

I Am New To The Brushless Deal I Need Some Help. The Track We Run On Is 144ft. Driveline. I Have No Idea What Gear To Start Out With.I HAVE A 4300 WITH THE SINTERED ROTOR AND IT ALSO HAS CERAMIC BEARINGS IN IT BATTERIES ARE SMC 4200S My Tires Are 2.12 I Just Realy need Some Help It Would Be Greatly Appreciated Alot!! Thanks Jeremy