Grip setup for Rally VXL

[EsaHoo]

Trying to find out setup for grip driving for Traxxas Rally VXL standard configuration.
From the box, the car is spinning all the time, which may be its purpose, but I cannot handle it.

As proposed in manual, I have changed front and rear differential oil to 10k. I have 2 degrees camber, as well as 2 degrees toe-in both in front and rear. Now the handling seems to be fairly balanced, when cornering, I can control understeer with throttle. The car will accelerate to straight line quite easily.

The main problem left is when lifting the throttle (even without braking), the car will spin out very easily. I tried to loosen the slipper clutch 1,25 - 1,5 turns hoping to have less braking power in rear, but that did not help me noticeably. Maybe I have to loosen it even more. Even just turning the car too much with high speed (without changing the throttle), sends it to spinning out (rear of the car gets loose).

Perhaps I need center differential? What benefit it could have?
Or maybe this car is purposely heavyweight in rear and I must sell it and try something else?

[turok]

make a wing. or use tires with more grip. but then the car will not slip it will be flipping all over the place. i use tires with less grip and i get a better response from it.

[EsaHoo]

Thank you for a good hint!
I try to add a wing. I think I can make one by myself, but anybody knowing if there are aftermarket bodies with this size available with wing?

[prototyp]

Suspension setup. Tires. Aero.

Mechanical grip is first. Little changes to toe have a huge effect on how the car responds. You're at 2º, maybe work toward zero toe up front and a tiny bit toe-in rear. Camber's a little less critical, and your 2º sounds about right (just a little seems to be better than / \ ). Ride height matters as speed goes up, and keep in mind that as you change the preload, to change the height, you also change the camber (handy for tuning best camber setup easily tho).

The standard Rally tires are very erratic... they don't slip or grip particularly predictably. Spin city. If you really want stick, dig right into the many options of 1/10 touring tires - some specifically tuned for optimal grip at specific surface temperatures.

Aero starts to play a big part in stability over about 15 or 20 mph. Splitter and underfloor make good experimentation projects. It's not so much a downforce thing as it is counteracting the natural lift tendency of the car shape. The open underside further slows the air under the car and it piles up in the body. A wing will help a little but considering the surface area of aero under the car vs a narrow strip across the back I'd focus there. I'm about ready to hack my Rally body and open up some DTM style venting:

[EsaHoo]

Thank you!

The manual told me to have more toe-in in front for straight line stability and more toe-in in rear to prevent spin-out.
I try to reduce my 2 degrees as you advice and see what happens.

The underside aero looks and sounds really interesting! Are there more details, links?

[prototyp]

There really isn't one perfect setting... different surfaces, speeds, driving activities, different driver 'style'... Point is that toe has a big impact on handling and the best way to get is to move it around and get a feel for it. Make gradual changes, a little at a time, and see where you end up. Of course it's helpful if you're running a consistent course at consistent speeds so you can focus on how the changes effect the handling.

[RobF353]

Hey proto, do you have any pics of the under side of your car with the underfloor installed.

Im thinking of doing that to mine and just wanted some ideas.

Also, would the T-Bone Racing skid plate work well?

[E-PoweredRC]

those things love to slid we have them at work for rentals and on the carpet track they act more like drift cars. they seem fast if they would handle better,.

[aggie rustler]

I have just the opposite too much grip and traction rolling with relatively sticky VTA tires. Since the last race, I have installed the stiffer springs #7342 (4.3 rate) and dialed out most camber (0 in front and -1 in back). I will be playing with weight a little tonight like running with both batteries and/r adding lead to give it a little more mass down low. Any other suggestions?

RobF353 - you might benefit from the stiffer springs too. When entering a turn and letting off the throttle (drag brake) shifts the weight of the car forward and this results in loss of traction at the rear (spin). The stiffer spring essentially counters this shift forward enough to keep rear traction.

[EsaHoo]

This is a kind of answer I am looking for! Thank you!
The stiffer springs is really a good idea.
Wish I can also get more grip... working on it...

For your question, there is a good basic information about suspension tuning. I have tried to learn it, but it would be really valuable to get real life experiences. Which is why I was originally asking my question about grip setup for Rally.

http://www.rc-truckncar-tuning.com/r...on-tuning.html

[EsaHoo]

My setup now is: toe-in 1.25/2.0, camber 2.0/2.0. I have stiffened slipper clutch back to std, there was no point to loosen it, I think.

The front and rear differentials are lubricated with 10k diff oil, which helps grip driving, because it prevents wheel spinning, I think.

I changed stiffer springs in front: 4.3. I tried stiffer springs also rear, but it went worse for my goal, grip driving. So there is now std springs 2.89 in rear. I tried softer springs 2.2 in rear, but unfortunately they are longer springs: rear was up, front down and it got worse again.

I added a wing. I have had dual batteries in parallel all the time, which probably makes low C.G, which probably helps a lot (perhaps those suffering of flipping). I have Seben racing high grip / high speed tires (not big difference between these in traction, I think):
http://www.mods4cars.com/sms/shop/in...de=view&id=153 and
http://www.mods4cars.com/sms/shop/in...de=view&id=558


Now the handling is very balanced, spinout happens sometimes, but it has decreased dramatically. Next I try higher viscosity shock oil. In front first (with different spring weights).

[EsaHoo]

Increasing shock viscocity in front helped a lot with stiffer springs.
Here is now so far the best grip setup for me. There is no spinout tendency anymore. There is slight understeer, which can be controlled with throttle: lift throttle and car turn nicely around corner.
toe-in 0/2 (front/rear), camber 2/2, springs 4.3/2.89, shock oil 80k/60k, differentials 10k/10k, ride height about 2 turns/1 turns. Dual 2s batteries in parallel, high grip tires, wing.

[Paul_jarvis]

I just switched to X Patterns for my first grip run since a rebuild.... absolutely awesome! Corners at high speed without spinning out, speed runs without wobbles. Occasional flips but far less than stock. Dropped the body 2 holes front and rear also, made a difference I think. Tyres rub at full compression but on tarmac, thats not too much of an issue for me.

[BigFlash]

One trick i do with my hpi tires is spray them with simple green. let it soak in for a little and then wipe off the excess. Once they dry after wiping they'll be softer and have more grip.

[prototyp]

Just started working with the stiffer road springs. I bought one set of the 4.3, and one of the 3.4. The 4 up front is great, very crisp, but the 3's in back seem to have snappy oversteer as the rear unloads into corners... Sounds like the stock "soft" 2.89s in back may be a better pairing, or perhaps the 3.4 with stiffer damping (60wt all around currently).

Also picked up a Duratrax camber gauge and my cambers are all exactly 2.0.

[MD6]

Here are some ideas that have worked for me. I run HPI X-Patterns in the parking lot. I run the sixty weight oil in the front and 50 weight oil in the back. I like the Traxxas black springs in the front and brown springs in the rear. But, the biggest improvement came with the installation of the the Hot Racing sway bar set. The car drives more like a traditional touring car. I've seen other people with their own sway bar sets.

[fraggs]

This makes interesting reading and has helped a lot but I am having trouble with grip on a wooden (very worn in places and varnished in others) floor, running a standard Ken Block VXL Rally apart from twin servo steering setup.
I could be mainly down to the tyre choice thinking mini pins (yellow) would be a good choice but very interested in any recommendations.
Liking the idea of the under tray fitted in the pics above

[efarrell]

I just switched to X Patterns for my first grip run since a rebuild.... absolutely awesome! Corners at high speed without spinning out, speed runs without wobbles. Occasional flips but far less than stock. Dropped the body 2 holes front and rear also, made a difference I think. Tyres rub at full compression but on tarmac, thats not too much of an issue for me.

Which x patterns.... Is it the set u can get at tower for$39.....by any chance

[prototyp]

Only Paul can tell us which HPI X Patterns he's running.

The only set of X pats at Tower I can see for around $39 are the #4702 pre-mounted D Compound tires on split-spoke wheels. Those will work well for general road use. Maybe not grippy enough for competition.

Fwiw, I've gotten a solid half year of street and dirt running out of my D compounds (#4470, tires only). I'll probably order some belted Pro (#4495) next.

[MD6]

Since we've moved inside to race on carpet. I have gone to the following setup which is working well.
Hot Racing silver sway bars - front & rear.
24mm Tamiya type "A" tires -front and rear.
100 wt. shock oil - front and rear.
Traxxas black springs - rear.
Proline body.

[tirado_881]

what i did to my car is i bought a new rear body post cut it in half and used it as my front body post so i could eliminate almost all the gap to the road. i have about 1/4 inch between the body and the road. stock i can fit half my hand under the front of my KB and with the setup i have now with just changing the body posts i can barely fit the tips of my fingers. it is a great setup for smooth surfaces and i literally can go full throttle no problems. i also have the xpattern tires on my KB.

[MD6]

tirado_881 - What kind of surface are you running on and what x-patterns are you running?

[arcaptainic]

tirado_881

I like your thinking but doesn't the tires rub on the body with the body adjusted down so low?

[Finalist1971]

I see all the comments about camber set at 2.0. Is it safe to assume that is negative 2.0?

[MD6]

I would assume so also. There are very few cars that use positive camber. I use negative camber on this car.