PDA

View Full Version : Traction Roll Issue with 86mm RM


Blf
2016.11.15, 05:15 PM
Hey Guys, --- I love the darty feel of the short 86mm wheelbase to mix it up sometimes from the other classes and I've noticed I'm traction rolling pretty insane at certain times after straights into a hard turn.

Do I need to be looking at T plate and Rear Shock/DDS Springs?

http://i1052.photobucket.com/albums/s451/BLF38/3%20Rm_zpsquegyclc.jpg (http://s1052.photobucket.com/user/BLF38/media/3%20Rm_zpsquegyclc.jpg.html)

http://i1052.photobucket.com/albums/s451/BLF38/2%20RM_zpspjehz1y4.jpg (http://s1052.photobucket.com/user/BLF38/media/2%20RM_zpspjehz1y4.jpg.html)

cowboysir
2016.11.15, 05:25 PM
It's hard to say without specifics on your setup:

Front end I'd check whether the outside tire bead is secure, how smooth the suspension travel is and how stiff the spring rate is on the front.

Rear end I'd experiment with softer t-plates and damping characteristics on your disks

i'm sure I'm forgetting something....

mleemor60
2016.11.15, 06:50 PM
Based on the photo's I would guess that the front is too soft and the rear too stiff. Which tires are being used? Any evidence of front tire rub at full compression during turn in? Dif settings? There are more questions but these are good for a start.

TeeSquared
2016.11.15, 07:53 PM
To get the car to stop traction rolling:

Glue tire sidewalls - this makes an enormous difference. Be sure to only glue the sidewall to the rim and not to get glue too far up the sidewall. If you do, sand it down so it doesn't create a sharp edge as the rubber wears down. Thick CA works well but use it sparingly.

Stiff front end - on your short 86 MM wheelbase this should make the turn-in very sharp (perhaps darty) but it will help with weight transfer that often causes traction roll. A little toe in may help combat dartiness.

Rear end roll stiffness - you pretty much need to get this "just right" for the car to work well. If it's too soft the car tends to roll around the rear axle and makes it more prone to traction rolling, and if it's too stiff the rear end can loose grip and chatter around. This will be compounded by your rear motor set-up. Have you tried trimming the t-plate shim on the chassis? I've attached a picture showing what to trim (circled in red) and where to trim (black line). I found this helped my RM setup because I could still use a harder t-plate to get roll stiffness I needed while still having reasonable bound/rebound.

Harder front tires - try going one compound harder if the above doesn't work.

Cute car by the way, absolutely love it!! :D :D

TeeSquared
2016.11.15, 08:02 PM
Another issue I just remembered....that Stratos body has much wider rear track thank front, and the wheelbase is very short. Think "tricycle effect" in terms of how that's going to impact handling. No matter how well tuned you get that car, you may find yourself either having to back way off for fast corners, else run rock hard front tires so the front end always slides.

Mike Keely
2016.11.15, 09:16 PM
I would start with a softer T bar first. Round off the outside edge of the rear tires. Make sure that the rear tires are still taped well to the rims. If they are loose to the rims that will give you a very loose car in the rear end.

Hope this helps.

Blf
2016.11.16, 02:30 AM
Awesome info guys - that's what this board is great

The tricycle idea makes sense but will try all other suggestions

My brothers 86mm Lotus with 0 offset wheels on it at all 4 corners does it a bit on those sharp turns if you push too hard in corner.

Maybe the way I have the disc damper set up is too loose? It does feel like it's maybe too much side to side movement and potentially tucking under the body until it the outside tire lip grabs the inside of the body on full push at speed.

And that's the stiffest t bar I have - maybe stiffen up the plate Springs and front spring / harder tires will help

Oh btw, I'm using Marka V5 15 degree fronts and V1 10 rears - maybe I should try some 20 or 25 on front as last resort.

Blf
2016.11.16, 02:40 AM
Also, on hardest turns at the limit you do hear a little chatter/skipping as it fights - maybe a different issue but what causes cars, in any class or wheelbase to exhibit that characteristic?

TeeSquared
2016.11.16, 12:53 PM
Most rear motor cars suffer from rear end chatter or hopping. The motor behind the axle in combination with a springy T-plate makes for a set-up that's difficult to dampen. I think it's called axle wind-up or something like that. Since RM cars seem to like modest power levels, I run 30 degree Kyosho rears instead of the usual 20s I run on everything else. This slows the car down a bit but when the ties don't have so much grip, you don't get wind-up on the rear end that causes chatter.

If you absolutely cannot use harder rear tires, maybe try some throttle expo or train your throttle finger? RM cars are fast mid corner if you get the power delivery just so. If you hammer on it, they hop and chatter so although you can probably reduce that with tuning, it will require some adjustment in driving technique. I've never had an RM car you can lean on quite like a well set-up MM car.

bobbyz
2016.11.16, 06:36 PM
I tried adding a little weight to underside of the chassis on my MR02 86mm 934 Porsche. It did help give the car a more neutral feel, and carries speed around corners fairly well. I'm using softest Kyosho carbon fiber plate, and Narrow PN front with K20 Radial Wide tires on all 4 wheels, and Kyosho Xspeed motor. Kind of an odd setup, but wanted to see how well I could get it to handle. Adding weight allowed for some experimenting with location and amount in the channel on the underside of the chassis. (Be careful not to short out on the battery terminal!!) I just used some old nails cut with pliers and some clear tape. Easy to undo if you don't like the handling dynamic.

EMU
2016.11.30, 06:51 PM
Stratos has very little front wheel clearance. May need smaller diameter wheels. I used to use 18 or 19mm wheels. Relatively stiff front end with no shims under knuckle. I used reverse kingpin method, with stock arms.

Thinner tires will roll less, but will reduce steering. Try a slightly harder compound and see if you can make it work.

As far as damper springs, slightly harder to spring with mid to hard top shock and worn rear tires. Tighter diff setting than you would have an mm car set to.

Blf
2017.01.02, 01:07 AM
Hey guys - revisiting this I actually got it set to minimum traction rolling and have adjusted my driving style a bit too.

I'm running into an issue that may be just the nature of the body , but the car seems get into some insane flips/ crashes if you hit the sides of the rcp where all other cars seem to just stop or bump off without a hitch.

Is it the Stratos body type? I am using +1 offset fronts so maybe they are grabbing a tad but don't seem to be sticking out too much at all.

There's something I like about the "on the edge" feeling of the car compared to the F1, 98mm and 102mm chassis

EMU
2017.01.02, 05:08 PM
That's the nature of the stratos body. If you haven't done so already, change the first servo gear to a metal one. It will break.

The sides of the body scoop the car up when hitting the wall, then catch the front wheel and flips and tumbles soon follow. I raced it in a box stock class for a little while as a handicap for winning too many races. It is fast, but darty. Unsettled very easy, but can turn inside of almost any other car.

I used 0mm 18mm front wheels to try to prevent the wheels from grabbing the walls, it helped, but I would still get tires yanked off in collisions with the walls... Then I broke the servo gear...

Blf
2017.01.02, 10:55 PM
Makes sense but that's unfortunate - I really liked the body because it fits the front individual shocks I have on chassis.