Pinion for XXX-T with P2K ?

[FilthyPierre]

Almost finished my new XXX-T (just waiting for some fine weather to paint the body), want to know what size pinion to start with. I'll be running a P2K with the standard 88-tooth standard spur of the XXX-T. I recall that when I built my XXX buggy, the Losi recommendation in the manual was too high and I burnt my comm on the first run.

Nairb, what combo do you run ? I know there's been talk at length on this subject but don't have a great deal of time to go back and search through the archives.

Any help appreciated. Thanks, FP.

[Railman]

Piere, My son with a XXXT & P2K, runs a 20 when he runs a 88 spur. If it's a smaller
track, maybe a 19.

[SirSpeedy]

Yep.

[athowells]

Railman is right.

P.S Send pictures of your XXX-T in.

[ 05-29-2001: Message edited by: athowells ]

[Nairb]

My track must be really small & tight, because I've been running 18/88 with my P2K & Chrome stock and last night my Chrome REALLY overheated. I'm gonna try 17 tomorrow and see if it helps. If it helps, I was truly overgeared; if it doesn't, I may have been undergeared, but that is very unlikely. I say start with a 18 or 19 and adjust it from there, if necessary.

BTW, most people run 22-23 pinions in their XXXs with stock motors, which is WAY off the 29 suggested by Losi.

One more thing... I had a BLAST pulling wheelies on the back straight last night when I raced mod truck with my new 11 double. SirSpeedy, that was even with composite outdrives! :eek: I'm gonna rebuild my diff with the steel ones today. BTW, I was geared at 15/88, and my mod motor stayed a lot cooler than my stock at 18/88.

[ 06-01-2001: Message edited by: Nairb ]

[very low budget racer]

Narib, what kind of motor? im looking for a nice mod, would a 12x3 pull wheelies in my XXXT with 16/88 or 12/88 gearing?

[FilthyPierre]

Thanks guys, I'll start out with a 20 on the standard 88 spur which is what Losi recommend in the XXX-T manual. I was just a bit nervous about doing that given that the 82/28 (7.116) combo they recommend for the buggy is too tall and caused my comm to burn and I didn't want a repeat of that. I now run 82/21 on the buggy (9.488). 88/20 on the truck is a final drive of 10.692, but I wasn't sure how this goes with the bigger wheels..... Nairb's 84/18 combo gives a final of 11.34, maybe I should drop one tooth on the pinion which would give (88/19) 11.254.

Out of interest Nairb, why do you run an 84 spur given that the kit-supplied unit is 88 ? Just personal preference ??

Thanks again,

Pierre

[Railman]

Piere, The most common reason for changing spurs is probably to hit that sweet spot in the gearing. However there is another reason that may be even more important; to move the motor forward, or back. Moving the motor forward (small spur) will centralize the weight more in the car which is both good & bad. With the motor forward, you can move the battery back some & still have the same balance front to rear. Being more centralized will allow the car to rotate through the turn easier, but wiil be slightly less stable in the rough. If you move the motor back (big spur), it will tend to swing the rear of the car through a turn, if driven agressivly. What's better depends on the track & your driving style. Hope this helps.

[Railman]

Nairb, Mod motors don't usualy get hot in the same way that a stocker does. There's just not much resistance in the wire to generate heat in the arm. The hot spot on mods is the end bell, & if overgeared it's easy to smoke springs. Just some thoughts.

[SirSpeedy]

Nairb's track is really tight.

I don't run a whole lot of stock, but at the WinterChamps I did, I ran 82/28 on the buggy, and 86/21 on the truck. That was on high-bite, blue groove, with the handout Peak Spitfire.

We were running about 10 laps in 5min.

It seems to me that Losi generates those suggested ratios with the large outdoor tracks in mind. There are far more out-door tracks than indoor.

See ya...

[FilthyPierre]

Railman, thanks, I never thought of the motor position. I'll see how mine goes. I might drop a couple teeth on the spur too.

[FilthyPierre]

Sir Speedy, ok understand about the larger tracks. Most of the ones I race on over here a smallish with lots o' fluff (low traction). So should I gear down or up for that? Currently 82/21 is what I run on the buggy.

The Aussie Losi importer has recently built a clay indoor track which is tiny, but good fun. At least I can run the taper pins that came with my kits. I haven't raced there yet but put in some track time with my buggy, I ran the same 82/21 combo I usually run on the fluffy track. Should I gear down or up for the clay i.e. higher traction ?

[SirSpeedy]

You would gear down(larger pinion) for low bite. Gearing down will also help to kill some wheel spin on low traction surfaces.

Always best to start small....ask about and see what they are running....

[Nairb]

Sorry, that 84 was a typo. I run an 88 tooth spur. I used to run an 84 (and 86) tooth spur because the 88 rubbed on my gear cover, but I fixed that and went back to 88.

VLBR, the mod I use is a Reedy TriSonic 11x2. It's very fast. The only way you'll be able to pull a wheelie is on a high-bite surface, and with high gearing (small pinion). Your 12x3 will probably be able to pull wheelies if it's a hand wound mod and if your gearing is substantially punchy. Experiment...

Pierre, I'd start with a 19 for sure. If your motor stays relatively cool after a race, go with a 20.

Railman, smoking springs...that would be nuts... Hopefully I won't find out about it. It's true though, mods always have higher efficiency than stocks, and that means less power converted to heat.