Front End Vibration with new PS2's
 

My Porsche dealer installed and road force balanced new PS2's (stock sizes) yesterday on my '03 996T. I have a major vibration coming through the steering wheel from 70 mph on up. The tech told me the tires are perfectly balanced with 40lbs of force and feels that once I heat cycle them a few times the belts will settle in and the vibration will go away. Does this sound correct? For what these things cost I expected them to be perfect out of the box. Thanks

I put the PS2s on my 996tt five months ago and have had absolutely no vibration issues. It sounds like whoever balanced them may have a balancing machine that needs to be calibrated. You may want to take the tires to another location and get them re-balanced.

You may need an alignment. It shouldnt vibrate.

Re: Front End Vibration with new PS2's
 

Did the mechanic tell you the "road force" measurement indicated 40lbs? If so, something is wrong with the wheel/tire combo showing that road force number. You will get a road force measurement for each wheel/tire assembly and you want the # to be as LOW as possible. Generally, anything over 24lbs of road force is unacceptable, and the machine will indicate a "FAILED" warning and tell the operator to check both the wheel and tire for excessive "run out". Either the wheel is bent or the tire is out of round. The "road force" measurement (in pounds) is the machine's way of measuring vibration which may be encountered under load/real driving conditions (it's not the force the machine places on the tire/wheel) -- even a balanced wheel/tire can exhibit excessive road force (vibration) if the assembly is not "true". Something does not compute here -- either the mechanic does not know how to operate the Hunter machine or you misunderstood what he told you?????

you may need your tires/wheels balanced or you may have herniated the side wall from hitting a pot hole, check the inner sidewall of your tires to see if there is a bulge.

Jack, I spoke with the tech and he said that each of the 4 tires measured around 40lbs of force. He said that since all 4 measured in the same range and since there was no evedince of anything bent that they considered this a normal measurement. While the tech agreed that 40lbs is in the high range he did not feel this was unacceptable given that all 4 tires measured similarly.

I'm sorry, but this is ABSOLUTE BS. 40 lbs of road force for a tire/ wheel assembly (mounted on a sports car) is way too high and you'd feel vibrations. However, I would be surprised if all 4 wheel/tires had the same exact road force measurement -- makes me think there's some operator error involved or the machine is out of calibration. I've had way too many tires/wheels balanced on a Hunter Road Force machine and don't believe I've ever seen all four wheel/tire assemblies with the same number of road force pounds. I'd get the tires/wheels rechecked by someone else. Just my 2 cents and probably worth less. ;)

They should be perfect.
Something is wrong.
Time to start all over again.

Having seen the new Hunter machines in action, I think Jack is right on in his assessment. I do not remember the numbers exactly but there are default limits depending on the "sensitivity" of the vehicle. I think the default limit for a light truck is about 40 lbs... a performance car should be in the middle 20s... the lower the better.

Jack is absoulty right 40 lbs. is way to much for a road force vibration balance, like "skaria" said it should be at least in the mid 20's or lower. But if there isn't operator error try turning the tire 180 degrees on the wheel and then balance again.

I am also w/ jack on this one. I'd also be scared if my belts "settled in" on a performance tire like this. He has no F'n clue what he is talking about. also ask him what speed he checked the wheels at. often a slightly out of round wheel or flattspotted tire will not show excessive force at speeds of 40 or so mph, but at 70-100 cause a noticible vibration. Since they don't spin them this fast they don't catch the occilations...

have them done right and then re-true the wheel with the highest force reading. That will probably settle them down.

dave w

My PS2's are smooth as silk. Have it checked out.

Finally have a resolution! The dealer was holding adamantly to the notion that 40lb of force was a valid number for this wheel/tire combo. When I suggested that I had gotten feedback that the tires should measure no more than 25 lbs, he told me that I was hearing this from persons who sit behind desks who are not out in the real world dealing with this on a daily basis like he is. I asked him to run the tires down to their sister dealership which also has a Hunter. After checking them again on the original machine and getting readings saying my front wheels were bent, they ran them on the other dealerships Hunter and they all balanced in the teens. The dealer is now arguing with the Hunter rep, with the rep now claiming there is nothing wrong with the Hunter. The good news is the car is completely vibration free and feels like new again! It makes me wonder how many guys are out there riding on tires that have been improperly balanced by this machine, still waiting for their belts to settle in. Thanks Jack and all who responded in helping me to resolve this issue.

Nothing like a happy ending.

We use GSP9700's and would N E V E R let a tire like this out with 40 lbs reading. That guy was a toolbox and needs more training. If anyone needs to know who has this machine in their area, try this:

http://209.176.154.132/pub/search/FindGSP9700.cfm