I'm not so convinced that's its a rear tire issue; it would be nice if you told us your complete setup....

Tires:
F-43mm 2x Pink
R-45mm Magenta

Front end
3.5mm ride height
.20 springs(30k diff fluid)
3 shims behind wheel(wider front track)
.5-1.0 camber
3.25 caster
5 reactive caster
front upper arms moved in 2mm(longer upper link)
.5 toe out

Pod
3.5mm ride height
Blue side springs-no preload
Gold center spring
25wt in both side and center shock

Rear end
172mm wide
3.5mm ride height

746grams
ssx esc - no timing
x12 motor
4600 reedy

Years ago, our 12Ls used to do something like that because they were dragging on the track. You can try raising the front and rear ride height to see if it improves. Other options include stiffer center spring, stiffer side springs, or increase cross damper oil weight.

Things to check:
- Make sure main chassis is level and not higher toward the rear.
- If the rear pod droop is less than 1mm, try increasing it to 1 to 1.5 mm.
- Make sure diff/spur gear is tight; you should not be getting slip anywhere on the track, but make sure the differential action is free. Too much drag in the differential action can cause the problem you describe.
- It sounds like maybe the front tires are really digging in...43mm 2x pink fronts create a lot of bite. If you don't already you should try putting CA on your front tire sidewalls to limit front tire outside edge rollover in the corners. Also make sure the edges have a small radius on them, not a sharp corner.
- When you check camber, push out gently on the top of the tire to make sure you are getting an accurate reading. This takes out any play in the suspension. You may want to try 1 to 1 1/4 degrees of camber to smooth out the front end through the corner.

Andrew,
your set up looks normal. You may want to try pink rears instead of magenta for low grip and yellow rears instead of grey once the grip comes up.

You may also want to try removing the shims behind the front wheels and spacing out the lower a-arm instead. Shimming the wheel makes the jacking effect due to caster more pronouced which can lift the inside causing snap oversteer you describe. Widening the car at the lower a-arm doesn't do that. You may have to place shims between the front wheel and nut to take up the slack.



Good luck,
Etienne

Guys, thank you very much for your help and advice. I'll be sure to write these suggestions down to try out at the track.

A side note, per a 12r5.1, when assembling the upper arms and attaching the ball ends. If the upper ball end is at an angle, is that effectively changing the caster?

I included a screen shot below to better explain.

http://i674.photobucket.com/albums/v...at110446PM.png

Here the upper ball end is essentially flat with the steering block, if it were tilted for/aft, would that be effecting the travel thus inducing/reducing caster?

The ball end itself will not change the amount of caster you have, the clips that you put in between the upper arm and caster block does that (ones that clip onto the upper hinge pins).

I think the upper ball ends ideally should just be positioned parallel to the top of the ball that is inside it (i.e. perpendicular to the kingpin angle if viewed form the side). If not it might hinder the arm movement.

Heres another question.

On my 5.1, the balls are pretty tight inside the eyelets, are they removable once snapped in? Will replacing with the coated steel balls from AE relieve the problem? Any other tips on freeing them up?

Thanks for that. Regarding the eyelets, I use the CRC ball end 'popper' and pop them in and out till they're free.

CRC:
http://www.teamcrc.com/crc/modules.p...prodID=7718876

Left hander-rc has a few:
http://www.lefthander-rc.com/catalog/index.php?cPath=48

There's a few things you can do...

A. Pop them in and out several times with the pivot ball tool
B. With a kingpin in the pivot ball in the arm/eyelet, squeeze the arm/eyelet with a pair of pliers. It seems to set the ball and free it up.
C. If it is not a new front end, clean everything with a q-tip and motor spray.

I have tried every type of pivot ball for the AE and CRC front end, and the easiest no hassle way has alays been the plastic balls. They always seem to be smoother, and in the AE they lasted forever for me.

RC12 5/5.1R

what's the part number for the full front end kit?

asc4686

tweak
 

Sounds to me the problem is not the tyres ,would try all pivots and balls and make sure you have nothing binding then check the tweak.
Gold springs on sides and shock. And 020 on front.

Hi guys!
I have one question for the experts in this category, I'm "rookie"
In two weeks I have a race, in asphalt track, with very low grip and dirty, wide lane.No way to tread the track,forbids the organization
I have an Xray XII T-bar and it's very difficult to drive.
I tried many combinations of setups, bodies,tires and compounds but any works well,at the middle-finish the corner when I touch smoothly the throttle, have oversteer.
my question is, if you're in the same situation,(not worth staying at home ... :blush:) what extreme setup would you used?
I hope you can help me,please:cry:
Thanks

(sorry for my english if I haven't been able to explain)

Well if you aren't allowed to treat the track...there isn't much you can do. I would ask to see if you can at least clean the track, a leaf blower will work well to get rid a lot of the pebbles and dust, using a hose or pressure sprayer would be even better. After that use the softest rear tires you can get...whites are usually the softest. Unfortunately while they will provide better grip it may not be enough and they wear out fast.

Use a hard front tire like purple or black. You might even try a red or orange. Max out your caster, on bad asphalt I often run 8'. Check the edges of your chassis plate to see if it is scratched or beveled from touching down or dragging. Heavier fluid in the damper will help if it is.