Winter Tires on, Steering Shake
11-18-2009, 02:49 PM
#16
Race Director
Macster,
The dial gauge tells the truth...
With the wheel lugs removed I was able to vertically move the winter wheels on the hub a total of 20 thousandths of an inch. To me this means that if you just put the rims on the hub and let gravity do its thing, the rims will be offset from the hub centerline by at least 10 thousandths.
To see if I could fix the problem I placed a small flat jack underneath the tire so that I could raise and lower the wheel relative to the hub. At the same time I had a dial gauge fixed to the hub that would measure the tire position relative to the hub. After moving it up and down a bit I determined that if I raised the wheel 9 thousandths that I would hit the centerline. After finding center, I slowly tightened the lugs and rechecked the dial gauge.
It seems to have fixed the problem. If the rims were manufactuered as well as the OEM Porsche wheels I wouldn't have had this problem. Thats what I get for choosing the cheapo winter rims from Tire Rack.
The dial gauge tells the truth...
With the wheel lugs removed I was able to vertically move the winter wheels on the hub a total of 20 thousandths of an inch. To me this means that if you just put the rims on the hub and let gravity do its thing, the rims will be offset from the hub centerline by at least 10 thousandths.
To see if I could fix the problem I placed a small flat jack underneath the tire so that I could raise and lower the wheel relative to the hub. At the same time I had a dial gauge fixed to the hub that would measure the tire position relative to the hub. After moving it up and down a bit I determined that if I raised the wheel 9 thousandths that I would hit the centerline. After finding center, I slowly tightened the lugs and rechecked the dial gauge.
It seems to have fixed the problem. If the rims were manufactuered as well as the OEM Porsche wheels I wouldn't have had this problem. Thats what I get for choosing the cheapo winter rims from Tire Rack.
Those don't sound like cheapo rims so much as defective rims. I can't imagine wheels that do not center properly using the mechanism in place for this already being sold at any price.
If someone were willing to live with the vibration the vibration could result in -- worst case -- lug bolts/nuts loosening and the wheel coming off.
Even if the wheel remained on the wear and tear to the suspension and steering and drivetrain components would be a deal breaker. With tire/wheel vibration car control compromised and it makes the effectiveness of the tires even less.
You might consider contacting where you bought the tires/wheels and see if there is an alternative wheel choice that accepts the same tire size but doesn't have what I would have to consider a serious defect.
Mention reporting the wheel situation to the NHTSA (National Highway Traffic Safety Adminstration).
Link:
http://www.nhtsa.dot.gov/
Link to report a vehicle safety defect:
http://www-odi.nhtsa.dot.gov/ivoq/index.cfm
Sincerely,
Macster.
11-18-2009, 03:43 PM
#17
Former Vendor
How old are the wheels? How many times have they been put on/taken off? If new, PM me your order number.
Which wheels are they?
Sorry for the trouble on this...
11-18-2009, 11:15 PM
#18
Burning Brakes
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I purchased this set of Sport Edition Cup 4 rims with Pirelli SnowSport 240's used (had about 4k on them). I purchased them from a pretty reputable guy (http://www.lnengineering.com/) and they came to me in what appeared to be perfect condition. I had them checked and re-balanced after I received them at my Porsche dealership, they looked great on the balancing machine. When they put them on the car however the shake was still there. So, (as mentioned previously in this post) I thought I'd order a couple more front tires (SnowSport 240's) from tirerack to see if that would fix the problem (we were thinking it was tread separation). Same problem existed after the new tires were installed and balanced.
If you go to TireRack.com and put in a model year such as 2003 it will give a recommended wheel and tire package using the Sport Edition Cup 4 rims. If you then do the same thing, but for a 2005 (my model), you'll see that the front rim dimensions are the same for 2005 and 2003 (17x7.5). What changes between 2003 and 2005 for the front's are the tire's. Bolt patterns (5-130) are the same for front/rear 2003/2005. So as far as using the right rims for my car it appears they are compatible. The only dimension I can't extract is the inner diameter on the rims where they mate with the hub guides (the three protrutions on the hub which center the rim on the tire prior to inserting lugs). If that dimension is different somehow (can't tell from specs on TireRack), that would explain the issue.
Given the condition (no scratches), I'm guessing the rims haven't been removed and put on that many times. There's no doubt though that when you first place the rims on the hub, there is at least 10 thousandth's worth of slop between the hub mounting guides and the rim. I can't imagine Porsche changing a dimension between the 2003 to 2005 models by 10 thousandth's, especially for something like the hub where they would probably use similar wheels from earlier models.
Don't get me wrong, I'm not slamming TireRack, my experience has been excellent so far (I just purchased a couple more winter tires from there recently). I'm mostly curious to figure out what happened.
Special thanks to Macster for helping me to diagnose!
Daemon,
No worries and thanks for the help.
I'm curious if on your test fitments for these rims what kind of slop, if any, is acceptable (slop between hub guides and rims). If you look at the OE Porsche rims, they fit so tightly to the hub mounting guides they can almost hold themselves on without the lugs. You know for sure when you install the OE porsche rims that they are centered on the hub...
If you go to TireRack.com and put in a model year such as 2003 it will give a recommended wheel and tire package using the Sport Edition Cup 4 rims. If you then do the same thing, but for a 2005 (my model), you'll see that the front rim dimensions are the same for 2005 and 2003 (17x7.5). What changes between 2003 and 2005 for the front's are the tire's. Bolt patterns (5-130) are the same for front/rear 2003/2005. So as far as using the right rims for my car it appears they are compatible. The only dimension I can't extract is the inner diameter on the rims where they mate with the hub guides (the three protrutions on the hub which center the rim on the tire prior to inserting lugs). If that dimension is different somehow (can't tell from specs on TireRack), that would explain the issue.
Given the condition (no scratches), I'm guessing the rims haven't been removed and put on that many times. There's no doubt though that when you first place the rims on the hub, there is at least 10 thousandth's worth of slop between the hub mounting guides and the rim. I can't imagine Porsche changing a dimension between the 2003 to 2005 models by 10 thousandth's, especially for something like the hub where they would probably use similar wheels from earlier models.
Don't get me wrong, I'm not slamming TireRack, my experience has been excellent so far (I just purchased a couple more winter tires from there recently). I'm mostly curious to figure out what happened.
Special thanks to Macster for helping me to diagnose!
Daemon,
No worries and thanks for the help.
I'm curious if on your test fitments for these rims what kind of slop, if any, is acceptable (slop between hub guides and rims). If you look at the OE Porsche rims, they fit so tightly to the hub mounting guides they can almost hold themselves on without the lugs. You know for sure when you install the OE porsche rims that they are centered on the hub...
12-13-2009, 03:49 PM
#19
Type_LT,
I was linked to this thread by Macster because I was having the EXACT same issue with Sport Edition Cup 4 rims. It vibrates like crazy at 60 MPH, then once I speed up to 70 MPH and slow back down to 60 MPH, the vibration is gone.
I had a feeling it had something to do with the bore of the wheel not being perfectly matched to the hub size, and your findings confirm that. I will go and check for this on my wheels as well, as I'm sure that's the problem. I had the tires rebalanced on a Hunter 9700 and all of them balanced out perfectly, which tells me it is a wheel problem, not a tire problem.
I will call TireRack on Monday and probably just return the wheels and mount the snows on my OEM wheels.
- Anthony
I was linked to this thread by Macster because I was having the EXACT same issue with Sport Edition Cup 4 rims. It vibrates like crazy at 60 MPH, then once I speed up to 70 MPH and slow back down to 60 MPH, the vibration is gone.
I had a feeling it had something to do with the bore of the wheel not being perfectly matched to the hub size, and your findings confirm that. I will go and check for this on my wheels as well, as I'm sure that's the problem. I had the tires rebalanced on a Hunter 9700 and all of them balanced out perfectly, which tells me it is a wheel problem, not a tire problem.
I will call TireRack on Monday and probably just return the wheels and mount the snows on my OEM wheels.
- Anthony
12-13-2009, 08:28 PM
#20
Rennlist Member
Interesting read. I nearly purchased these wheels in 17" format with snow tires, but instead decided to just do with tires and use my existing pristine 18" wheels. My thought is, a replacement OEM Porsche wheel is less than $200, which is less than buying newer wheels which may not have the same quality as Porsche wheels.
12-14-2009, 11:38 AM
#21
Burning Brakes
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adg44,
Thats different that if you slow down from 70 mph to 60 mph that the vibration mostly goes away. My only thought is that speeding up to 70 then back down to 60 you're giving the suspension a chance to stop vibrating at that resonant mode then when you're back down to 60 it's stiffness can cope with the wheel offset.
Hopefully Tirerack will give you another set to try. I just don't think they would let this problem slide by since the manufacturing fix is relatively simple. It could just be a bad lot we happened upon. The fact remains however that we've both noticed our OEM porsche wheels fit snugly against the hub (mine so much so that they can sit on the hub without lugs) and the sport design's don't.
Thats different that if you slow down from 70 mph to 60 mph that the vibration mostly goes away. My only thought is that speeding up to 70 then back down to 60 you're giving the suspension a chance to stop vibrating at that resonant mode then when you're back down to 60 it's stiffness can cope with the wheel offset.
Hopefully Tirerack will give you another set to try. I just don't think they would let this problem slide by since the manufacturing fix is relatively simple. It could just be a bad lot we happened upon. The fact remains however that we've both noticed our OEM porsche wheels fit snugly against the hub (mine so much so that they can sit on the hub without lugs) and the sport design's don't.
12-14-2009, 06:27 PM
#23
Rennlist Member
12-14-2009, 06:32 PM
#24
Nah, it's not a suspension problem, it's an issue with the wheels. Driving at 60 MPH again today causes the wheel to vibrate, then other times be totally fine, then vibrate again. Sometimes speeding up and then slowing down helps it, othertimes it doesn't. This is the sign of a wheel that is not perfect centered on the hub (as seen in the photos above).
TireRack is taking the wheels back and I'm going to just mount the snows on my factory wheels.
TireRack is taking the wheels back and I'm going to just mount the snows on my factory wheels.
12-15-2009, 10:04 AM
#25
Burning Brakes
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adg44, I believe the "coming and going" effect is because the front wheels, both being off center, sometimes sync up with each other to produce smoothness or awful vibration.
You'll be rolling smooth again with the factory wheels, I'm thinking of looking for some stock 17" rims on rennlist or ebay myself.
You'll be rolling smooth again with the factory wheels, I'm thinking of looking for some stock 17" rims on rennlist or ebay myself.
12-15-2009, 11:41 AM
#26
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TireRack is taking the wheels back and I'm going to just mount the snows on my factory wheels.
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03-18-2020, 09:44 AM
#27
Balancing Porsche wheels.
If you have vibration about 60 + mph, there is a good chance it is wheel balance.
Some times fashion can be more important than function. we do kind of understand that.
When balancing a wheel the very best way to do it is to dynamically balance it. ie weights on the out board edge of the rim, counterbalanced by weights on the inboard edge of the rim.
However with some wheels if you put balance weights on the outside of you wheel it looks rubbish, so clever balancing machines these days can still balance your wheels while hiding the weights on the inside of the wheel. I have come across wheels that this doesn't work on. If the structure of the wheel is such that the out board balance weights can not be adhered to the rim some distance out board of the centre of the rim then it will not work.
There is an answer, ask you wheel balancer to static balance your wheels and just have one set of weights near the centre of the wheel. It isn't as good as dynamic balancing. But it is better than out of balance.
just as a note, Pirelli now make the correct 16" P7 tyres for these cars https://www.longstonetyres.co.uk/cla...rsche/911.html which i would encourage you to go for. Worth noting Porsche themselves have tested them and given them the N homologation
If you have vibration about 60 + mph, there is a good chance it is wheel balance.
Some times fashion can be more important than function. we do kind of understand that.
When balancing a wheel the very best way to do it is to dynamically balance it. ie weights on the out board edge of the rim, counterbalanced by weights on the inboard edge of the rim.
However with some wheels if you put balance weights on the outside of you wheel it looks rubbish, so clever balancing machines these days can still balance your wheels while hiding the weights on the inside of the wheel. I have come across wheels that this doesn't work on. If the structure of the wheel is such that the out board balance weights can not be adhered to the rim some distance out board of the centre of the rim then it will not work.
There is an answer, ask you wheel balancer to static balance your wheels and just have one set of weights near the centre of the wheel. It isn't as good as dynamic balancing. But it is better than out of balance.
just as a note, Pirelli now make the correct 16" P7 tyres for these cars https://www.longstonetyres.co.uk/cla...rsche/911.html which i would encourage you to go for. Worth noting Porsche themselves have tested them and given them the N homologation
