Replaced tires with larger size, now cart bounces

[paulrickmakita]

My cart is a 2003 TXT with many miles on it, no lift. I replaced the OEM tires with the largest that would fit without a lift. Used 20 inch diameter on 10 inch rims. All was good then took it for a test ride. Now it bounces at higher speeds. Kind of a front/back bounce not side to side. When the road is very smooth it's fine, but with any bumps in the road it starts bouncing and slowing down is the best way to stop the bounce.

I'm suspecting the rear shocks but not sure how to tell. I think the springs are ok, but there too don't know what a sagging spring looks like. Mine seem not sagging based on what I see on other carts.

Any suggestions for this newbie appreciated.

[Cruise Master]

Is it possible your tires are out of round? Harmonics are built up the faster you go.

[StoveBolt]

What air pressure?

[BrewCityMusic]

I'm seconding "Bad Tire" or "Incorrect Pressure" first, also where is the governor set? With larger tires, if the governor is set *right* at the top end, it can kick in and out which will give a sort of "bounce" fore and aft as it engages and disengages ...

[paulrickmakita]

These are all great suggestions and questions. I took this long to reply as I did some experiments and have figured out the problem. But first I'll answer the questions:

-the tires are made by Wanda and private labeled to an eBay & online seller. The rims are also private labeled (cheap black steel rims, bought them as the nice machined aluminum rims are crazy price)

- I too thought about out of round tires and/or rims. I had this problem on a Carlisle tire that I bought for this cart some time ago and have lived with the bouncing from that till those tires wore out, what an annoyance. Oh, and those Carlisle tires were made from a very stiff rubber such that in cool weather they would retain a "flat" from sitting for even only a day until the cart had been run a half mile or so thus creating even more vibration. Don't get me going about how bad those Carlisle tires were :)

- Changing the tire pressure at first seemed to help, but then a day later I changed my mind and concluded that it did not.

Now to the problem and solution:
It turns out that these (cheap) steel rims do not have that nice detent where the lug nuts seat to the rim. The consequence is that the rims do not "self center" when the lug nuts are pulled tight. The solution is to hand tighten the lug nuts making several wiggle adjustments as they touch the rim thus allowing the rim to center before the lug nuts are pulled tight. Now they run true and the bouncing is all but gone.

Thanks to those who offered suggestions and questions.
ps: I have a rear suspension question that I'll start in another thread.
Paul

[Ezgas]

Fabulous diagnosis. Now I understand what was going on with mine.