Egg Shaped Tires or Driving Down a Washboard...that's what it feels like...Why?

Speedvision

Hello All. Great forum. Enjoying my 2008 PQ Precedent. Just put an Allsports A-arm lift, HD rear leaf springs and some mud grip tires to complete the package.

Cart was programmed to setting 3, no regen from the guy I purchased it from.

Anyway, after I got the cart (bone stock, brad new US Batteries and cables), I noticed a "washboard or tires out of round" feeling and I chalked it up to the stock tires being out of round after sitting for several months before I bought it. Now that I put new wheels/tires on, the feeling still exists. Accelerates smooth, good power, but once I'm up to speed (at any reasonable speed, really) it starts to "washboard" at about 120 Hz or so.

I would expect the motor to vary a bit when the speed setting is achieved or a bit of a wobble or a bounce due from cheap knobby tires, but this feels more like the motor could be pulsating causing this feeling, it simply too consistent to be tires.

Is this normal? If not, what should I hunt down first? Thanks!

BGW

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Speedvision

Anything?

TheWiltz

Just a shot in the dark, buy how about putting it on jack stands, remove the wheels, then running the motor. If it still wobbles then you know it isn't the tires.

Speedvision

Thanks for the reply. Since the "pulsating/washboard" feeling is identical between the stock and brand new wheels/tires that's out. I see no way it can be anything but the drive system, so I'm wondering if this feeling is normal or if something in the drive system is going or gone - mechanically or electrically.

When driving on a flat surface the "washboard" feeling is very consistent and you can also hear it...

TheWiltz

i dont have a CC but i would bet that is not normal. I would try to determine if it is an electrical pulsation or mechanical wobble.

try hooking a DMM to you motor studs while driving. then to your controller, then to the batteries... if its electrical it should show somewhere on the DMM as a voltage surge or drop. (im just giving you things i would try)

to see if it is mechanical VERY CAREFULLY tow your cart with something. if you get the wobble then you know it is mechanical. Bent wheel, bent axle, worn bearring, worn differential gears... (or it could be from the front end)

good luck

jjs650

It kinda sounds like a possible bent drive axle shaft.

May be worth checking while on jack stands.

Down South

Did you change the tire rims? If not, could be a bent rim. Put the rear of the cart on jack stands. Have someone give the gas and see if you have a wobble. Could be a bent axle.

Speedvision

Thanks for the replies, guys. I did confirm that the axles are straight. Rims run true, so that's not the issue. Remember, this issue is identical between the stock wheels/tires and the new 23" mud grip tires.

Wish I could edit the first post, the washboard feeling is not 120 Hz (120 times per second) it's more like 2 Hz. Been racking my brain on how to explain what it feels like and the only think I can of is like putting a small kid on your knee and bouncing them. Not real fast, just steady. There is a bit of a whine/hum from the rear end and the sound emulates the bounce. Feels like a bounce, but it could be a surge from the motor/driveline.

Is there anything is the power system that could cause the motor to pulse consistently creating this lack of smoothness?

Speedvision

Thanks for the replies, guys. I did confirm that the axles are straight. Rims run true, so that's not the issue. Remember, this issue is identical between the stock wheels/tires and the new 23" mud grip tires.

Wish I could edit the first post, the washboard feeling is not 120 Hz (120 times per second) it's more like 2 Hz.

Been racking my brain on how to explain what it feels like and the only think I can of is like putting a small kid on your knee and bouncing them. Not real fast, just steady. There is a bit of a whine/hum from the rear end and the sound emulates the bounce. Feels like a bounce, but it could be a surge from the motor/driveline. It's just not smooth.

Is there anything is the power system that could cause the motor to pulse consistently creating this lack of smoothness?

TheWiltz

You need to hook up a volt meter and see if you see surges on it.

I know nothing about regen, but could it be turning on and off?