wheel run-out help

total rotating mass (hub, rotor, 5mm spacer, and wheel only) has an axial (side to side) run-out, measured with a dial indicator of .028in (28 thousandths). Measured on the outer edge of the 18" wheel next to tire bead. Is this within spec.? Alignment and RF balance done. steering wheel vibration at ~68 mph and again at ~120 mph.

are you saying the tires and wheels are perfect on the rf balancer

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My 996 Turbo reference gives a 0.7 mm number for both lateral and radial runout for "light alloy wheels". Assuming this is the same for the 996 NA "light alloy wheels" that's 0.0275" which puts your wheels out of "spec" by 0.0005". Even if you were measuring "just" 0.0275" I'd have to offer an opinion that 0.0275" (or 0.7mm) is pretty lousy and it is not surprising that the steering wheel vibrates. Are you sure there are no burrs on the spacer? They can get banged together and a burr can be raised. Be sure both spacer surfaces are smooth, the burr can be on the face and not on the edge, and parallel and the hub face is likewise smooth and free of any burrs or grit or something. Run your hand over the hub face, and the spacer faces, and the wheel were it presses up agains the spacer. Check the spacer centers properly on the hub and the wheel too without and with the spacer in place.

Wish I had known to ask for report, just know they said they balanced fine.

Thanks Mac. I've checked the surfaces and aligned the spacer. Need to pull the spacer and check at the rotor, then finally check at hub surface.

so with the balancing, they just balanced the tires, they didnt do any of the rf balancing indexing or check wheels or anything else. Thats normal unless you complain of a problem. Now you have a balance problem and you can have them analize all the wheels again and see if they are perfect or not. you can check anything else on the car you want to, but when you get back to the wheels, this is what the road force balancers are for

Have you tried switching wheels from side to side? If the run out moves with the wheel, you know it is a problem with the wheel, and not the spacer, hub, etc.

RF balance was done properly, just didn't ask for a report. Run-out is the same for both wheels, both sides of the vehicle. ~.028+/-.0005 Macster, what do you think I should see. less than .018 at the rim, assuming .002 max for hub and rotor assembly.

how are you measuring the runout?

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see original post. .018 at the rim is a calculation derived from Porsche posted max run-out of .002 for hub and rotor, projected to an 18" wheel. I will be checking actual values today. Mac at what point on the rotors and hubs should I position the dial indicator? Really just needed Porsche's max run out at the alloy wheel which Mac provided to determine if rotating mass exclusive of tire was in spec. vibration may be just the tire

what I meant, is what is the method you are using? how are you physically doing the measurement?

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Your question drove me to look at my factory manual reference and this is what it has to say: Maximum permissible radial runout and lateral runout of the light alloy wheels = 0.7 mm. Maximum permissible radial runout and lateral runout of the wheel with tyre = 1.25 mm. Values less than 1.0 mm better around 0.5 mm are desirable. Based on the above and assuming the same applies to the NA car's wheels you would want to see not 0.7mm or 0.0275" but instead 0.5mm or 0.0195" of runout at the wheel periphery. I've never checked the run out of either my Turbo's wheels or Boxster wheels so I do not know what they have but I have observed at various times various wheels of both cars spun by hand -- while on the lift and being checked for tire or wheel or rotor condition -- and as an ex-machinist I can spot run out a mile away and the wheels appeared to have negligible runout which based on my experience puts the run out down in the 0.005" range. Do all wheels manifest the same runout? If not then I would think you should at least have the run out the same as the wheel or wheels that have the least amount of run out. Is the run out symmetrical in that is the high spot matched by a low spot 180 degrees away? Or does the runout suggest the wheel has a potato chip shape? If the latter the wheel or wheels could be bent. With the dial indicator against the wheel can you see any signs of play if you grasp the wheel/tire and give it a wiggle like you were checking for bearing play? There should be some and you'll have to check all 4 wheels to find what the lowest amount is this being then what a "healthy" bearing would have, assuming at least one wheel bearing was good. Might mention the few times I've checked for play I have found very little play. I can't put an amount to the play but the amount of play was slight.

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Generally run out is checked for as far away from the center of rotation as possible, and of course you would like a machined surface. But unless you feel pulsing when braking I really doubt the rotors are running out. Most often if an otherwise good wheel -- good as in not bent -- is running out the problem lies at where it mounts to the hub or where the hub mounts to spindle. As the rotor is part of the hub and the braking is pulse free this suggests the wheel -- or the spacer -- is the culprit. And as you observe, the problem may lie with the tire, or tires. There have been a few cases where a tire balances good, even road force balances good, only to manifest balance symptoms when in use. The problem was traced to a bad tire, with bad belts, that under load and the stress of supporting the car during actual driving, that shift and the tire's balance and possibly even roundness changes.

Thanks Mac, been chasing the same issue for a few years over three sets of wheel and tires. RoW 030 sport with ~GT3 alignment. You ever delve into suspension harmonics? vibration noticeable at ~68, subsides then gets my full attention at ~118-120

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Hard to imagine 3 sets of wheels and tires all having a problem. Just thinking out loud but I assume all wheels were name brand wheels and ditto the tires? What has been the common denominator through your trials and tribulations? Suspension? Alignment? Wheel bearings? Spacers? I've never really had to deal with suspension issues other than relatively minor ones brought about by well, relatively minor mis-alignment issues. Some years ago when playing with tire inflation pressures over-inflation of not too many PSI -- just a few in fact -- I found can cause vibration in my Boxster that is indistinguishable from vibration that arises from tire imbalance. Never bothered to experiment with my Turbo. I set its tire pressures to just a few PSI under those given on the inside of the fuel door -- these are for a fully loaded car -- and the car steers, handles, and rides just fine and tire life is very good. Also, over the years even though new tires start out vibration free that as they wear vibration comes back but a rebalance cures this. The word I get is this behavior first appeared with Cayenne tires -- their size was blamed for their susceptibility to this -- but this vibration arising from tread wear has migrated down to the smaller tires so even my Boxster's 17" front tires can sometimes use a rebalance about half worn down. Regarding RoW 30 suspension: When I looked into having my Boxster's suspension refreshed and talked to the techs about this and brought up the idea of installing RoW into my Boxster my tech buddies talked me out of it. Both said while the RoW was an excellent suspension for track use they also said it was a bit stiff for street use. (Might add they talked me out of any suspension freshening as the car in spite of the miles still drove just fine -- both road tested the car at different times -- and said for now to leave well enough alone unless a shock developed a leak or some other suspension component developed sufficient wear or suffered an outright failure.) Now I hate to blame the RoW in your car's case, and I'm not going to, but I have to ask is it possible that just perhaps you are just mistaking the harsher ride and etc. produced by the RoW as something amiss with the tires/wheels? As an aside: I have not ridden in any Porsches with track suspension but I've ridden in other cars with track suspension, Corvettes and Camaros and such, and on the street the ride is atrocious. But I daresay bad enough tire imbalance would have to be pretty bad to be felt. Now on the track I'm sure the owners would note tire imbalance right away. Regarding alignment, have you tried a less aggressive alignment just to see if this affects the symptom? Without knowing the history of the car, are the alignment adjustments reasonable or does the tech find he has to adjust some settings all the way to the stop, so to speak, in order to bring the car into alignment? I bring this up as it is possible the car is "bent" and alignment is being used to "straighten" the car. Were I faced with what you are faced with -- and I hope I never am as these can be a real pain to trouble shoot -- I would start out at the bottom and ensure wheel bearings were good, the spindle hub run outs in spec, along with the rotors, spacers and then the wheels and the tires. You have to check and double check every step of the way to be sure you miss nothing. If there is a problem in this area, it might only be one bearing, spindle, hub or rotor. If you get sloppy and miss this... I could toss in that you must be sure all the suspension components are in good shape, with nothing bent, or broken, or worn out. You have to be sure everything is installed correctly and even that the right parts are installed. One other point and that is the axle half shafts. I was taught when removing a drive shaft or half shafts to always mark the assembly *before* disassembling so upon reassembly the driveshaft would be bolted up with the same relationship it had with the tranny and diff flanges. The same goes for the half shafts. A slightly out of position half shaft could manifest something maybe indistinguishable from tire imbalance. Long winded I know. Wish I could just say the problem is 'A' and be done with it -- though of course not before modestly accepting the accolades -- but I can't. Unless you have an 'aha' moment you are faced with a slog to sort this out, get to the bottom of it.

Thanks Mac. Doing the work instead of throwing parts at it , Damn it! I have to know! Bent? no damage report but bumper had been repainted before I got it. Been under it and looked but could never find even a hint of damage or repair. Think suspension height measurement locations would make squaring reference points? Agreed, RoW030 is not that pleasant on crappy streets.

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Sometimes throwing parts is acceptable. However, in this situation you can throw some very expensive parts at the symptom. If you throw the wrong parts...$$$. Like you I'd want to know so I would fix the car properly. Many older cars have repainted front bumpers. That in and of itself is not sufficient to suspect the car has suffered more severe damage. A newish looking headlight vs. one that has some discoloration, differences in the condition of the condensers, a new looking wheel compared to the other that has suffered the ravages of time and tire changes, these can suggest the car has been in an accident and the differences arose from repairs. (When my Turbo was repaired after a mule deer collision the factory condenser and radiator were a different color than the originals and the other side's hardware. I had the body shop paint the new ones to match the ones on other side.) But an accident bad enough to bend the car should have signs of severe damage and repair from under the car. That underbody anti-rock chip resistant paint may be missing in places, or it could be very fresh. One or more new plastic underbody panels. Bent jacking points. I'd point out the suspension/steering components could be different to, with some new and some old, but with the RoW... sometimes owners use an accident as an excuse or an "opportunity" to change suspension so one loses that "tell". Your alignment guy should spot any issues, but maybe you need to ask? He may not volunteer this. Ask him if he is having to use up too much adjustment to bring the car into alignment. Now some of this might arise from the different suspension. He may have to go to the rail to say bring the camber into spec. But the adjustment on each corner will be the same or nearly so. What I'm talking about is asymmetrical adjustments, with one corner having its adjuster in the middle of its travel or range while the other corner having one or more adjusters cranked all the way to their max (or min) setting. I'm not saying the car is bent only that that can be an explanation. But you have other things that can explain the car's behavior. The odds are it is one of those. It is your task to find which one. Oh reference points... that's tricky. There are many hard points that are to state the obvious critical they be in the right place, the right position, but many of these are only checkable by having the car partially torn down -- the wheels removed at least -- and the car placed on a special bench to which fixtures can be placed and the body's hard point locations checked for proper position. There are not many things you can do on your own. As I touched upon above the alignment guy can sometimes provide some enlightenment regarding the car's condition. (Again with my Turbo: Shortly after I bought it I took it to another dealer to have it aligned. The tech told me after he was done the car was one of the "straightest" he had come across. My point in relating this is the techs see a lot of cars, and get a feel for what's normal and what's not.) Is the car's ride height good? That is even? That is something you can check on your own.

Remove you spacers and try it again, that is, just drive it. Likely that has a lot to do with it.

unfortunately, need the spacers for clearance

I would drive the car at night in a quiet paved area close to a hard wall if possible. It's amazing what you can hear at night that you will never hear during the day. Try to make your wheel bearings make noise by driving in small circles. If you will observe your wheel/tire assembly spinning on a balancer, it's easy to see how much up & down or side to side movement it has, & therefore ride disturbance. If the tire/wheel passes you know to dig deeper, spacers ALWAYs mutiply any cumulative imperfections.

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So I don't see anywhere in this post about the wheels you are running. I take it they are not stock. Can you post details? Are you running hubcentrenic spacers? If so, are they metal or plastic. If your wheels are not stock, and they are two or three piece, I think you found your issue.

aftermarkets wheels at the moment, oe turbo twist and sport designs exhibit same issues. having spacers checked out, they are hub centric as a 5mm can be, with the locator screw. re-torqueing everything and looking for play with dial indicator. once I have a rotating mass base line, I will have a better idea what is going on. Like Mac stated, may not show up when unloaded.

FYI, Porsche worse case run-out for total rotating mass (hub+rotor=.002" at the hub which equates to .0045" @ perimeter, 18" alloy wheel =.0275) exclusive of the tire is calculated to be .032". With my 5mm spacer and all surfaces cleaned I am at .025". These are my aftermarkets wheels, not great but within spec., so I will assume my OEs will be better. We know where this leads, tires. For high speed driving, do I dare mention the "N"

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Not only what tire, but sizes & air pressures, & age of the tires.