I'll just lay down the senario first, and you guys tell me what you think. First off, my problem:

I'm driving on the freeway, and when I go over 60-65mph, the car starts riding really rough, as if I'm driving over a bunch of 1 inch tall speed bumps and at the same time, it starts to pull to the left. Its really unstable feeling, like I'm about to just shoot into the center divider or something. I wouldn't want to drive next to me if I were another car.

Now the senario I think led to this. My car is stupid low to the ground now, so I had to raise it up as high as I could stand doing, on my lame B&G coilovers. There should be a smaller thinner spring above the main coil on the coilovers, but its completely pinched down and not providing any cushy help. So the ride is stiff like crazy. I'm driving to a gas station and have to make a U-turn, and some lady is "being nice" and decides to just sit there and look at me instead of just making her left turn and getting out of my way. Finally I just get annoyed and dump the clutch and bust a quick 180º sliding across a couple lanes, and I shoot down the street. I pulled into a gas station, and figured if I wanted any extra clearance on my bumper, I'd need to fill up the tires quite a bit more. They only had 25 psi on a tire with max pressure 50 psi. So I filled them to like 40, and jumped in the car, noticing that extra 1/2 inch really did help when I pull out of the driveway. Before this I'd scrape literally 50 times per drive, just quick little dips in the road would bring my splitter to the floor and scrape right through the mounting hardware daily.

Now that's all I did right there, that I can associate with any of this. Before this, the tires were flatter, and didn't have these problems at all. So I'm driving on the freeway, and notice that just out my passenger window I hear a hissing sound for about 3-4 seconds. I'm thinking its my tire I just filled up, but the tire was fine? So after I heard that noise, which I'm not even positive came from my car (but I think it did) when I'm going over 65 my car starts damn near bouncing in the front like I'm riding on the little bumpy section on the shoulder that wakes you up if you drift off while driving. You know what I mean? Like brain shaking vibration in the car, ONLY THERE'S NO BUMPS??????? And my car starts pulling to the side like I'm caught in a tractor beam or something. Its quite freaky, and I'm trying to get this car ready to sell.

I've pulled the wheels, checked the bearings, which are fine, axle nuts on tight, coilovers tight, brake knuckle is on tight, control arms tight, sway tight, strut bar tight??? What the hell else do I check? What would make a hissing noise? You think there's any chance I blew my pressure in the passenger coilover??? Would that translate into my described issue?

 

It sounds like you have a bent rim. Low tire pressure can mean a bent rim easily. When was the last time you had them balanced? You should look into balancing your tires. When they're being balanced the service tech can tell you if they are warped, bent or not. The hissing may have been any number of things including shocks, A/C over pressurization, patch of small rocks, rubbing or even another car..

 

Rims fine. The day before I was driving 85 on the same roads with no prob. Plus it rides great under 65. It does however catch every tiny line in the road and moves with it.

 

They're probly bent as you were driving with 25PSI. Hyundai recommends 32PSI on the 15" rims. They rate smaller rims with lighter PSI as they absorb better with less risk of bending the rim. At 25 PSI you wouldn't feel a bent rim. You'd be riding light on tread. 25PSI with just about any rim would bend it on a speed bump. Don't you have 17"s?

 

yup 17s. So should I let some air out or what?

 

no, if the rim is bent then you'll need a new rim or maybe they will be able to repair them. Try getting them balanced first though.

 

Ehh If the rims are decent at all that wouldnt have bent them. And Chris doesnt hit speed bumps at a speed to bend a rim at all.

 

my friend had the same problem with his celica, he said it was something about the vertical balance in the wheel...do you have hub spacers? You might have wheels that are centered offspace from the hub. also check your shocks again...those are prolly havin problems....

you should look underneath the wheel well of the tire in question, if there is oil leaking from the shocks, then you need new ones (pair) if not, then check how the rim settles on the hub.

 

25PSI on a 17" rim is practically flat. It wouldn't take much to bend any rim at 25PSI on a 17".

 

Why do larger rims need higher pressure (as long as the tire is not narrower)? Presure is per area (pounds per SQUARE INCH), so the fact that there is less air-volume should not matter..

Maybe 40psi is a little high, try taking some air out and try it again.