Driving vibration RXV at speed

[Vulcaneer]

Two weeks later and the dealer finally got the axel bearings from Oklahoma. Apparently, EZGO withheld shipment, until they had a large enough parts order for one shipment. Dealer says...”That is the way they do it. Nothing I can do about it.” That sends me through the roof. And I remind the dealer that they are EZGO’s customer...and they need to act like it.

So two weeks later, and the cart is still apart. And whether or not these parts will in fact remedy the problem.

Total BS. Especially when the dealer has a major bearing supplier 20 minutes away. And there is nothing magic about standard ball bearings.

[cgtech]

Ezgo does not do what they stated. The reality is that dealer "sat on" your order until they had a large enough offer to get free shipping. The dealers can order any size order they choose, all the way down to one bolt. I always ask the customer if they can wait for a part on my next stock order, or if they would rather it arrive faster (but would incurr shipping charge). I think my approach is only fair, I'm not eating shipping charges, and I offer reasonable solutions. I have totally told customers who demanded that there was no reason for them to pay shipping that I had found no shipping service that offered to ship packages for free.


So the "total BS" part is true, but the blame is on the dealer.

[Vulcaneer]

CG...Your explanation makes sense. Being a warranty item, I am sure the dealer wants to cheap out where ever they can. They got their money. So screw the customer.

So now they have a VERY PO’d customer, for the cost of less than $50 dollars for a set of ball bearings 20 minutes down the road, or for about $12 to have them mailed from OK in about 4 days...which I would have thought reasonable.

Am confident that once this issue is behind us, I will not need their warranty service again. Or the dealer...for that matter. Had I known then what I know now, I would have done the job myself. I have snap ring pliers, slide hammer, floor jack, jackstands, impact & torque wrench, and a 20T press. Oh...And you tube.

[BobBoyce]

[Vulcaneer]

Latest news. Cart is back from dealer. Rear end noise is gone. The bouncing vibration at 3/4 throttle while cruising is better...but still slightly present. Hoping it stays that way. But concerned eventually it will progress to get worse over time, as it could affect tires, etc. But We’ll see.

Other causes I can think of...a possibility of AC motor being out of balance. Or Ring Gear out of balance. Both highly unlikely...but hey. Last possibility may be bad shock absorbers, that may allow normal shaking to be magnified through the frame.

[cgtech]

It's not the motor, the motor spins at 6k plus rpm (those motors run smooth past the 9k rpm area), any significant imbalance there would be something you wouldn't be a "I feel it driving down the road" thing. The imbalance is something thats spinning nearer to wheel rpm, not motor rpm. Any significant imbalance like you described but at 6k rpm would throw the cart sideways. I bet it's localized to the wheel areas, like out of round tire or rim. Possible you have a bent hub, or axle shaft also? I have totally seen machined aluminum rims that were just made horribly bad. If your cart has aluminum wheels with center caps, and you want to try investigation yourself, remove the center caps & try driving without them. I have seen lots of center caps that don't fit in the rim right, and don't allow it to bolt down flat to the hub.

[Vulcaneer]

You are correct. Not the motor. The shaking seems to be correlated (rotational and rhythmic) to wheel speed. All wheels/tires have been replaced. While shaking does seem somewhat better, it still is there. Suspect the longer it goes on, the result will be tires that develop wear patterns that then goes to further promote the shaking. Dealer is pretty much washing his hands...saying he has done everything possible...Differential axle bearings and new wheels.

My next steps are to check the shocks. And also to balance the new wheels/tires. At 19 mph the wheels may be rotating fast enough that bad balance could be an issue. At any rate, balancing wheels cannot hurt anything.

Cart was built April 12, 2019. And sat in a showroom for at least a month, before I bought it 5 weeks ago. So realistically had 3 months use. I suspect it had problems since it left the factory. How can a almost new cart need new diff bearings?

I do appreciate your thoughts and assistance.

[cgtech]

So, it hasn't been 100% confirmed (but I suspect based on tire pressure you posted) that these are stock 8" rim /18" tires? Right? You also said you spun them and they looked fine? That's wild, because I usually have to test through 12-16 stock tires & wheels to find 4 that act "truer" then the average. Yamaha unofficially "admitted it" when their order sheet included an extra charge for that on the dealer order sheet for pre-selected "best" stock 18" tires as a "box the dealer could check". Their newer carts all arrive with 10" rims now, and they're better. But their "65" profile means no easy speed gains for big fancy aluminum wheels. Those "take-off" tires/wheels are popular for dirt cheap upgrades on our used carts needing better speed & better tires. Most new cart buyers want fancy wheels, and those take-offs are great to have around. Maybe hit up the local Yamaha dealer for a set of 205/65-10 take-off tire & wheels. Big sidewall for suspension comfort, bigger diameter will gain speed. Minor trimming inside rear bumper might be needed tho (same thing all us RXV dealers do every day).

[Cobra,1]

Another vote for some sort of wheel related issue.
Out of balance wheel can show up at 10+ mph depending how out of balance it is. Out of round wheel/ tire can usually be felt once cart starts rolling.

Maybe find a shop that will speed balance the tire at speeds your cart runs at.
Also if your lucky you may have tire shop near by that also “shaves” - trues tires.
This is done with a machine similar to a speed balancer that rotates wheel slowly while a roller applies pressure to the tire simulating wheight of vehicle on tire at same time while a metal grinding wheel shaves off small amount of rubber from tires high spots.
A common practice done on road race cars and racing go carts.

This will give you a perfectly trued, matched set of wheels.😊

[Vulcaneer]

Have indicated the tires for roundness. While at 22PSI, they all are within .060” . So that appears to be a non-issue. All tires seem to be within reasonable static balance. But dynamic balance may help.

But I now have another theory. The RXV is a limited slip rear axle. Lots of things spinning around in the diff case. Spider gears, ring gear, pinion, axles, etc. I doubt that is an issue. BUT...what I DO think is an issue is that all those gears have backlash. When accelerating or decelerating the backlash is not a factor. Because acceleration puts forward motion torque load on the face of the gear teeth. And deceleration applies pressure to the back of the gears.

In accel or decel there is no shaking. Or when going uphill or down hill. ONLY while cruising at consistent speed on level streets. When cruising... the drivetrain is constantly adjusting (call it “shucking”) or searching for the correct speed between forward or rearward gear pressure. Likely in a cyclic pattern...if speed stays constant. And because of the looseness of the backlash...the cart shakes a bit.

So it does appear this is a condition that does affect limited slip differential carts. In my research, I have found this shaking to be rather common in RXV carts. To different degrees of severity.

I don’t know if other brands/models of golf cart have limited slip differentials. But I would bet, that if they do...there are elevated incidences of similar shaking conditions.

My theory. Then again...I could be full o sh...