Good BL System

Originally Posted by Andrew32

ok thanks for the info guys!!

another Q, would the MM and 8xl be so much powr that i need stronger diffs?

i forgot to sayi dont want a system thatll rip my stock maxx in one run

but dont worry, im going t odo a complete 3.3 conversion

Don't be surprised when your diffs prove to be the weak link in the drive train, even 3.3 diffs won't last. At least shim them properly and put the diffs in some cheapie metal diff cases so they can't twist under accel. That might make them last a little longer.

OS 18TM was enough to shred my 2.5 rear diff repeatedly and the 8xl should deliver more torque than that. The difference in the 3.3 diff was 2 extra screws in the stock plastic diff case so it had 4 vs the 2 screws the 2.5 stock diff case had. Was some better, but not strong enough, it can still twist enough to let R&P strip.

[ClodMaxx]

diffs are the red headed stepchild of these trucks. it just seems strange that a stock diff is such an extremely weak link. i'm very interested to see how the new maxx diffs hold up to extreme power and abuse (i'll personally be torturing them with my LMT) that traxxas says they can take. i'm not holding my breath...

after LONG LONG intese thinking, i have decided to go with the MM and 8xl motor. going to run EP 4200 7cell for a while then ill take the dive into lipo after i pay my car off, only 6 months left


what gearing should i use. the gear calc says o use a 18 pinion and 66 spur to achieve 45. is that gearing to low? cuz ikbow he hv systems require like a 12pinion 72 spur.

[suicideneil]

Not too low, maybe a little high infact. The 8xl will run a little hotter than the 9xl, so gearing down a touch is advisable- aim for more like 40mph; going faster than that will be hard to control. Easy way to know if you are over/under geared:

Hot motor + cool esc/batteries = under geared. (not enough load on motor, so it over revs)
Cool motor + hot esc/batteries = over geared. (too much load on esc to supply amps, causes it to heat up & thermal/fail)

Generally speaking anyway. You will want a fan on the MM and run a ubec to power the tx & servos (disable built in bec via programming or remove red wire from rx lead to esc).

cool i guess gearing will just have to be a combo of the gearing calc and tem checking.

so i went to the CC part of the forum and people are saying NOT to run 14cells on the MM controllers cuz they are frying. Is this true?

[mmdooley]

Hey, I am running an 8xl with a quark, (But the MM should be fine) I assume you will be running a strobe with a 51 tooth spur? If so start your gearing at 14/51 and go up on the pinion to tweak it.

[suicideneil]

Well, the older MMs could do upto 14 cells/5s with no problems really. Newer MMs use different parts internally (fets) and the voltage limit has been lowered so that 12 cells/4s is the maximum. The Quark125b is a solid controller and good for more voltage, but sooner or later the heat spreader inside seperates from the fets, and it causes thermal shut downs, even though the outside of the case is cool (heat cannot travel between fets & case, so fets overheat). It is said to be the smoothest esc available at the moment though, which is a big plus for racing.

[highflier]

Correction to above post 12 cells and 3s max lipos.