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View Full Version : Oversteer left, but understeer right


helee4
2006.07.05, 01:00 PM
Hello,
I have been trying to figure what causes this problem but no luck. Car seems to be oversteering or spin-out to the left, and understeering turning right. I tried the following still no luck:
- different combination of tires
- changed steering knuckle
- swapping from bearing to bushing/bushing back to bearing
- fully locked/unlocked diff,
- different set of H-plate
- Removed main and lateral suspension (only using H-plate)
- All tires seems to be laying flat no obvious wobble.

The turning radius seems to be the same when car was going slow, then become oversteering/understeering when driving faster.


Thanks in advance!

Spoon
2006.07.05, 01:16 PM
If both front wheels are spinning smoothly and nothing is cracked, it sounds like you may have tweak. Search for tweak in the forums and you'll come up with a lot of answers.

SuperFly
2006.07.05, 02:46 PM
I didn't see in your list whether or not you checked for binding or other unwanted contact between the motor pod and the body, or the motor wires. I've used overly heavy wires to the motor that caused unbalanced movement of the rear end.

builthatch
2006.07.05, 03:01 PM
I didn't see in your list whether or not you checked for binding or other unwanted contact between the motor pod and the body, or the motor wires. I've used overly heavy wires to the motor that caused unbalanced movement of the rear end.

kyosho .2mm shims are ideal for situations like this...you can place one .2mm shim between the hplate and motor mount hole for the screw on the side that the car is spinning out, if i recall and am visualizing correctly. this shim will equalize the condition where the rear pod is twisted, usually from a tweaked hplate. motor mounts with four holes for hplate screws are nice because you can choose which hole to use for the shim- the closer holes with a shim will give a more pronounced correction that using one of the outer holes.

helee4
2006.07.05, 04:31 PM
Thanks, builthatch! This is something I didn't thought of, but it does make sense though. I would never imagine my alloy motor pod can be twisted, but through 3 years of abuses, it is likely to happen.

Do you think the racer chasis can be slightly twisted? Or the alloy motor pod is not so balaced.... I will try out the shim tonight!

builthatch
2006.07.05, 05:10 PM
Thanks, builthatch! This is something I didn't thought of, but it does make sense though. I would never imagine my alloy motor pod can be twisted, but through 3 years of abuses, it is likely to happen.

Do you think the racer chasis can be slightly twisted? Or the alloy motor pod is not so balaced.... I will try out the shim tonight!

most detected tweak is from motor wires, alloy motor mount not pressed in and tight against back flat part of h-plate when screwed down, or tweaked hplate...you might want to check the little "bar" underneath the small part of the hplate on the chassis side and make sure it's flat against the chassis. sometimes plastic can be pulled up from screwing/unscrewing front hplate screws and this can lift that little bar up, which can in turn cause tweak because the small part of the hplate is not parallel with the bottom of the chassis.

fastrthanyou
2006.07.20, 06:07 PM
Check your caster in the front end, dial in your anti-dive geometry and calculate the spin factor and g-forces. do a skid pad test to dial in your toe-out and set the negitve and positive camber, plumb bob the front knuckles and machine .009877 off the left side tire and .009666 off the right side rear tire. cut about .076 off the bottom of the body. And if all this doesn't work scrap the peice of crap and buy a new one.

locwan
2006.07.26, 10:32 AM
There is another important aspect which could be overlooked sometimes. Check that the front suspension is smooth and the kingpins is not rusted or bent, especially if you use the stock ones.

Since your car understeers turning right, do check that the left suspension is providing smooth damping and nothing is abstructing its travel. If the suspension is notchy, you car will have lost the damping effect of the suspension and will behave like you've got ultra hard suspensions / no damping, resulting in understeer through the turns.