rclab1

Hello all, am still trying to figure out why I still have steering wheel shake at 55mph-60mph (someone said its a sweet spot for trouble in our SC430).

I replaced my front rotors and brake pads (brand new) thinking that would be the cause since my old ones would shake my steering wheel and brake pedal when applying (depressing) my brakes.

since the new front rotors and brake pads were installed, I only get steering wheel shake when I'm cruising at 55mph-60mph......does anyone know the cause.

am thinking my tires are out of balance? anything else I should have the dealer look at?

help.....

thanks....

rominl

iTrader: (4)

did you try to do road force balancing on the wheels? it sounds like a wheel balancing issue here

rclab1

what is "Road Force Balancing?" .....is that the same as going for a normal balancing at the dealership?

rominl

iTrader: (4)

umm, it's also wheel balancing, but it's a special type, which usually are more accurate and reduce the chances of vibrations

rclab1

does Firestone or the dealership do this service? where? .....thanks

Pearlpower

iTrader: (2)

These care much like most with performance low profile tires are sensitive to wheel shake at those speeds and more so as the miles pile on as the suspension components become looser such as ball joints, etc...
Road Force Balance is a machine from Hunter. Generally more expensive to balance your wheels on these machines but sometimes to only way to rid of vibration.

What is Road Force Measurement?
couresy of Hunter Engineering
Road Force Measurement

Road Force Measurement? is new to the automotive service industry. This new measurement identifies tire and wheel uniformity, which has been measured for years in assembly plants and manufacturing facilities. Road Force can be used to solve uniformity related tire and wheel vibrations. Tire/wheel assembly uniformity can only be measured under load.

The load roller on the GSP9700 performs a computer simulated "road test". It measures the tire/wheel assembly to determine how "round" the assembly is when rolling under a load. If a tire were not exposed to the road surface, then balance would be more than sufficient. However, not all tires roll round under a load. For example, an egg-shaped tire/wheel assembly can be balanced about its axis, but an egg-shaped tire-wheel loaded against a surface would not give a smooth ride.

To understand the effects of radial force variation on vibration, a model of a tire can be used. The sidewall and footprint can be understood as a collection of springs between the rim and the tire contact patch. If the "springs" are not of uniform stiffness, a varied force is exerted on the axle and causes it to move up and down as the tire rotates and flexes. This movement creates a vibration in the vehicle unrelated to balance.

The GSP9700 load roller applies a force of up to 1400 pounds against the rotating tire/wheel assembly as it performs the Road Force Measurement?. The GSP9700 measures loaded radial runout of the tire/wheel assembly within 0.002". It plots data points as the component is rotated and calculates the radial first harmonic of the tire/wheel assembly and the first harmonic of wheel runout. The peak-to-peak value (Total Indicated Runout) and second, third and fourth harmonics of Road Force are also calculated and used for diagnostics. These measurements are all displayed on other screens.

The measurements of loaded radial runout are converted to Road Force Measurement in pounds, kilograms or Newtons using the following equation:

rclab1

where can I have RoadForce Balancing done at? any chain automotive places or do you know any of hand? ....thank you....

rominl

iTrader: (4)

just talk to different alignment shops and see which one has the correct equipments to perform it

sjpobox

Hello, make sure they check for bent wheels as well. if i had to diagnose your concern I would say the inner lip is bent. coupes, is300 anything with a low profile tire increases your chances of bends. I do suggest not using momo wheels, they bend really easy.

Just go somewhere you trust. I would say your dealer since they would stand by there work.

tennistodd

Greetings everyone...I have had this same issue for a while now. I had put 19 inch wheels on my car ,19x8 front and 19x9.5 rear, and they could never get them balanced. I had Road Force balancing done 3 or 4 times and they still vibrated only at 55 to 60 mph. I got so tired of it I put my factory wheels with runflats back on and I have not had one vibration. I guess I will stick with the factory rims until I sell my 19's and find some 20's I like.

rclab1

I do not have aftermarket wheels, my wheels are OEM, and I have non run flats on my car....... does Lexus dealership do the "road force balancing?"

Pearlpower

iTrader: (2)

There is no way we are going to know this information. You will need to search for yourself.
Here you go
http://www.gsp9700.com/pub/search/findgsp9700.cfm

I do know the tire person I go to has the machine as well as some local Lexus dealers but that is up to the individual dealership.

KevsSC

I just put 19" wheels on and I get the same vibration at that speed. My wheels are brand spankin new. Everything is balanced too.

talwang

iTrader: (4)

Did you use hub centric rings?

1NEAT_SC

I had a similar problem with another vehicle (not Lexus) and I switched rims (front to rear) and found the vibration was hardly noticable. Evidently one of front wheels was totally out of balance and couldn't be balanced. Just a thought before you get into $$

lar