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60 mph pronounced steering wheel shake left-right-left. 70 mph it progressively smoothed out. I took camera photos of the wheel weight locations after balancing. That culprit wheel was suppose to have (5) 1/4 oz adhesive backed weights on it. When compared against the photos I noticed there were only (4). Those photos saved me a ton of time and aggravation. Instead of taking wheels off for re-balance check, just stuck a new 1/4 oz weight where the missing one should have been. Problem solved. |
My wheels and tires have no more than .50 oz per wheel, 1 has no weights after road force. If tires and wheels are good then you should be ok. But remember you can balance an egg, and it will still vibe when rolling
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What tire pressure is everyone running?
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Street driving, 22 lbs.
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I have about 9000 miles on my car,I found sticky tires nitto nt05 245 wanting to grab everything was the cause. I will say tires are the problem remember the car is very light. you should leave the car up off the tires when not driving this will help.If I drive about 50 miles the car will drive better [less shake].Others have told me to use less of a performance tire but I can not bring myself to do so. Put a new set of tires and you will be amazed how much better the car will drive.At least that has been my experience.I have owned my 2013 backdraft for two years and put about 6500 miles.
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alignment
1 Attachment(s)
Shes now in shop getting alignment. Attachment 36716
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Wide tires on a light car with a manual rack and pinion steering is very susceptible to polar imbalance.
Imagine there is a heavy spot on the outside edge of a tire, and they try to fix the imbalance with a weight on the inside edge of the wheel, but opposite side. A static balance will look good, but as the wheel spins, the 2 heavy spots will try to move the wheel so that the 2 heavy spots are in plane and make the wheel wobble. At the perfect resonant frequency of the steering system, it will become a very obvious left right shake. ALSO, if the other wheel has a similar polar imbalance, when the wheels are synced, it'll be more pronounced, then you make a slight turn and they become antisynced and the 2 shakes will cancel. Most heavier cars with narrower tires and power steering are far less susceptible and most shops are not that picky about the polar balance. The only way to see the polar balance is with spin balancing. The old bubble thing won't show it. |
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When I drive along a smooth, straight road keeping a constant throttle and maintaining a constant speed (lets say 65 MPH), I have a wheel shake that comes and goes as I drive. Roughly speaking, its cycling every several seconds. I have 255/40s on the front and 315/35s on the rear (17" wheels). The diameters of these tires are 25.0" and 25.7" respectively, which comes out to a difference of 2.2" between the tire circumferences. What this means is that both front and rear will not remain constantly in synch when you travel in a straight line. Based on some rough calculations, after about 18 revolutions, the tires will be 180 degrees off from each other. Another 18 revolutions and they will be back to where they were with respect to each other 36 revolutions ago (again, approximate). So I'm thinking that there is some sort of harmonic going on where, depending on where the tires are with respect to each other, i am getting a pronounced shake or nothing at all since whatever imbalance there is is cancelling itself out. Hmmmmmm. |
Ill get it back tomorrow
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Two front wheels can cancel each other out, and so the steering wheel can shake at around 50-70 mph typical, and then cycle on/off. |
I agree with Gary. I think it is more likely the unbalanced tire(s) at the front is out of sync with your front suspension components at some speeds and the shake comes and goes as those two resonant frequency patterns come and go into phase with each other.
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Sean,
From your earlier posts (when you had 17" wheels) you've had this issue it appears back to 2017. That said this thread may be of help if it's your pin drive hubs causing the issue. http://www.clubcobra.com/forums/back...lly-fixed.html |
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Ed |
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I found that balancing the tires at your normal tire pressure made a difference. They usually run them up to 32psi when balancing and you run them at 22/24psi maybe?
Blas |
Got the Cobra back, they did an alignment and its much better. They checked everything bolt and nut on the car. Im going to look into that post where he upgraded the steering. I think they should have made a more robust steering system. I do relize the Billboards will effect the driving but i love the look of them. If i do the upgrade ill post some pics. SPM
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Vibration
Depends on the severity of the shake and vibration. I own #383 and the Cobra does not drive anything like my C7 Corvette or even my '65 Mustang. Wear of the tires on Cobra are good and in perfect road conditions, Cobra is smooth sailing. However in my opinion, the vibration and shake you may be experiencing is because you are in a short wheel base car with big wheels and tire. Lots of rubber on the ground and you are picking up road conditions. I would suggest having a reputable shop check out condition of the front end, steering, and look for tire wear issues. If a reputable shop states all looks good, then it really might be an over reacting.
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Help
2 Attachment(s)
[ATTACH]Attachment 36721[/ATTACH] Anyone know how to tighten this upper steering shaft. Its loose at the mount but i cant figure out how to get it tighten up. I cant get to it from underneath or inside the car. Theres got to be a way to tighten that mount Thanks SPM
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