How hot was the motor after the race? I ran a similar fdr on my sonic when i was running it blinky but with 45 degrees on the can. It came off at 160 after a 10 minute main which is still good and safe. That was also in mid 90 degree weather. And I was racing against boosted tekins and yes they were faster in the strait but not enough to pass me. That's on about a hundred foot strait.

SC10
Tekin RS ESC, Sensored-only mode
Tekin Redline 17.5
14deg can timing
25/75 gear ratio
CRC 65C 5600 mAh 2S LiPo
Good top-end but mediocre punch-accel
145-155F after 8 min A main


Arrma Fury
Castle MMP w/BEC
Orion 17.5
Stock timing
24/75 gear ratio
CRC 65C 5600 mAh 2S LiPo
Great accel, very torquey feeling, good top-end
140-145F after 8 min A main

I have the same truck and it was suggested by Casper to go 26/76 for 17.5 blinky. FDR around .

http://www.gearing.rcgearhead.com/Gearing/Browse If you put in the XXX-SCT at this link with say a Novak Ballistic 17.5 motor it will also tell you very near 7 for FDR....interestingly if you put in the Tekin Redline 17.5 it will say 8.34 FDR. I have no clue how that thing picks the FDR.

What do you mean by toasty? My finger cant distinguish between 130 and 160....all feels hot.
And going down on your spur will drop the gear ratio, putting more load on the motor. This would increase your temps.

try a 23t pinion and see if u like the torque and if u can live with the drop off of top end well at the same time you can advance the timing on the can accordingly, if it is too much of a drop try a 24t well at the same time do the same with the timing advance on the can again until the truck is performing according to the track layout. i use to tune the motor and gearing to temp but now i just do it to how it perform to the layout. if my truck is coming off the track kool (120-140) but is maxed out top end just almost at the end of straight and the bottom end is good enough to make the jumps all the way until the end of the race then there is really no need to gear up just for what, a few more feet of the straight and then have to swing a lil wider to make the jumps ...........naw i like good bottom end on a sc and enough top to stay with anybody not neccesarily pass em in the straight. if im geared like this i can beat em in the infield cause i can cut turns shorter and dnt need near as much run start on jumps to make em and im a lot faster out of corners man. i drive fairly aggressive

I've tried a higher ratio (smaller pinion) on the tekin redline 17.5 but then it gets really doggy on the straightaway. compared to my orion 17.5 the tekin is just way slower all around. one problem with these darn brushless motors is that they last too long so I don't have a reason to buy another one!! haha.

I will try advancing the timing some more as you suggest. :)

How old is the rotor in your Tekin? If you've over heated it a few times it will be down on bottom end but great on the top end. I fresh new rotor might solve your issue. If the rotor is fairly new then you havent found the sweet spot between motor and gearing. I'll See what the guys here are gearing their SC's and get back to you.:nod:

It's ~2 months old, raced ~7-8 times. The highest temp I ever had it was high 160s. You think I should get a new rotor/magnet?

It shouldnt need replacing if that's all you've run it and the temps are legit. If you get a chance take the rotor out at measure it. If it's 12.3mm that would explain your lack of punch.

can you explain what you mean by 12.3 mm? is that the rotor diameter i'm guessing? were those older rotors or something? I bought my motor only a few months ago. Are there different diameters?
thx dude!!

Different size rotors are tuning options. Take your rotor out and measure it with a set of calipers. 12.3 is more of an rpm rotor and 12.5 would be a little less rpm but more bottom end punch. If you bought the motor new only a few months ago it should have a 12.5mm rotor in it. Once you verify the rotor we can try to get to the bottom of your issue.

well right now my gearing is at 72/28. i have 30 degrees of can timing: stock from factory. im coming off the track at around 160 after a 6min run.

our track is indoor clay with a nice long hundred foot plus straight. i think it's 105ft. it gets to be at least 80 in the building during the day lately.

with the gearing i have now it can keep up on the straight, but i wont be passing anyone. it also jumps pretty good and if i line up i can clear most of the jumps.

i think i am going to call reedy and ask the tech what fdr the sonics should be geared for. i think it's the motor that determines the fdr.

160. i've been told this is a safe temp. the thing is i can smell my motor when it comes off the track. it is brand new 2 practice days, 1 race day old. bad motor? another reason to call reedy...

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what determines the fdr? the way the motor is made and the transmission ratio on your rc? im thinking thats it...

Hi Al. Final drive ratio is determined by the formula FDR = (S/P)*T where S is spur gear, P is pinion gear and T is internal ratio of the transmission. For the XXX cars it is 2.43, for Associated based cars it is 2.60.


Vehicle: Team Associated B4.1 Factory Team
Motor: Trinity/Epic Duo2
Motor Timing: 8
Gear: 31/69
FDR: 5.78
Track size: Medium/Large (~100' straight)

This setup is really good down the straight, but lacks the low end power that the Schuur Speed 17.5 has. The car is worn and the motor is old, but it is still within .4 seconds of my best lap with the X Factory X-6 Squared.


Vehicle: X Factory X-6 Squared (Associated transmission)
Motor: Schuur Speed 17.5
Motor Timing: 30
Gear: 33/72
FDR: 5.67
Track size: Medium/Large (~100' straight)

I don't want to change anything with this setup. If it weren't for other mechanical issues with my buggy I would have been solidly in the top half of the A main (after starting almost last in the B main). 3 stripped wheels and a broken CVD dog bone forced me to my backup car (B4.1 FT) for the A main, and then I broke that 2 minutes in. Bad night of RC even though my X was crazy good.


Vehicle: X Factory SCX-60CF (Associated transmission)
Motor: Tekin RS 17.5
Motor Timing: 12
Gear: 27/75
FDR: 7.22
Track size: Medium/Large (~100' straight)

With the Tekin motor I cannot gear it as high as I need to because of temperatures. At 27/75 I'm temping at ~140F, but at 28/75 or 27/72 I'm near 170F. This week I'll be trying out a new rotor (12.5mm stock legal high torque) which should give me more power with less timing, and with any luck it will be cool enough to add some gear. I'm getting killed on the straight but am making it all up in the infield (good enough for a podium finish my first run with a stock short course, anyway).

soooo after a few expensive lessons in gearing, i am here now:

losi xxx-sct - went from ball diff to gear diff
tekin rs blinky
tekin redline 17.5 w/ 12.5mm ht rotor
no can timing
76/28
thunder power g6 pro race 5300 65c 2s
sdrc raceway: med to high bite indoor off road clay track, long 90' - 100' straight
we just ran jbrl rd 6. :D

after 6 min run, motor is luke warm. esc is cold. i am thinking i can go up a pinion or two....or maybe add some timing. any suggestions anyone? should i gear up or add timing? she's a little slow on the straight, but the motor runs a lot nicer than the sonic.

I was at the track yesterday working on my SCX-60CF and actually geared down with added timing with good results. I'm now at 27/81 with 12 degrees of timing with the Tekin 17.5/12.5mm ht rotor. I'm sure some of it was chassis and some of it was more practice, but I shaved nearly 2 seconds off of my best times from Saturday.