Good day!

After months of trying to figure out what was causing a vibration in my vehicle, it was determined that the root cause was excessive road force on 3 of 4 of my new Hankook Summer performance tires from Tire Rack. These tires were initially road forced balanced at Tire Rack before being sent out. The vibration was also experienced on one of my Yokohama all season tires and we found that tire had excessive road force.

FYI...(Loaded Radial Runout) x (Tire Spring Rate) = Road Force Measurement

It was hard to believe that there was so much road force variation with those new tires and ranged from 35lbs to 15lbs and the one Yokohama tires has 15lbs road force whereas the rest of them are under 9lbs. My friend at the dealer told me that anything in the single digits would be better. Tire Rack replaced all 3 tires and I had them tested at the dealer and they are all under 10lbs of road force. I had them reinstalled, road force balanced, and now my ride is smooth once again.

I am guessing that all suspension mods that I have done this past year now make any tire imperfections much more noticeable. However, I would like to know more about what causes such high road force in tires! Is it manufacturing variation or could it be something is my suspension that is creating the issue??

Any insights??

Thanks

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2009 G8 GT -Sport and Premium Pkgs, Roto-Fab CAI, Cortex 93 Octane Tune, Billet Prototype Catch Can, BMR Front and Rear Sways, BMR RTAs, BMR Rear Cradle Bushings, BMR Steering Rack Bushing, GXP SW......and much more to come.

Sometimes it is a manufacturing defect. I work for Goodyear and I handmake most of the tires you guys ride on and they force test every tire that we make before leaving the plant. Also sometimes it is how the tire wears.

Milestone

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Thanks! Do you think that it could have something to do with my suspension that is causing the road force?

I know that I was getting more wear on the outside edges of the tires than the center...and that was when all tires were at 32lbs air pressure. I actually bumped the pressure to 35lbs prior to getting the replacement tires which seemed to help the vibration and I plan on using that pressure from now on to also help with the wear issues. I read that many Hankook owners are using 35-36 lbs of pressure. The max recommended pressure is something like 44lbs so I am not pushing the limits.

You must get some good discounts!

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2009 G8 GT -Sport and Premium Pkgs, Roto-Fab CAI, Cortex 93 Octane Tune, Billet Prototype Catch Can, BMR Front and Rear Sways, BMR RTAs, BMR Rear Cradle Bushings, BMR Steering Rack Bushing, GXP SW......and much more to come.

I get a free set of tires every year . Have you had an aligment since you changed your suspension??

Milestone

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That is great! Always nice to have fresh tires.

Yes, I had a 4 wheel alignment done after the LCA and Sway bar change end link change at the dealer.

Can you explain road force numbers a bit more?

Thanks

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2009 G8 GT -Sport and Premium Pkgs, Roto-Fab CAI, Cortex 93 Octane Tune, Billet Prototype Catch Can, BMR Front and Rear Sways, BMR RTAs, BMR Rear Cradle Bushings, BMR Steering Rack Bushing, GXP SW......and much more to come.

All tires vary in how true they spin so the road force balancer is able to separate the bad ones from the good ones. Sometimes the wheel is also a factor if it's not spinning true even if the tire is good.

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Bright Red 2008 G8 GT

Mods: DRCUSTOMPARTS Center Gauge Bezel
Superchips ECM/TCM Tune- Volant CAI
Solo Axlebacks - HID's
Holden V8 Badges
My Website

Fortunately, my Moda wheels were tested and not a factor in the vibration, according to the dealer.

The weird thing is that when I had my vehicle aligned by a small reputable alignment shop awhile back, he said my left rear camber was off a bit and he could not fix it unless he took the strut off and I would experience some slight difference in wear on that tire. When I had the vehicle aligned at the dealer, they said I did not have any camber issues on the left rear tire. Hmmm as I recall now, I think the who vibration issue occured AFTER getting the vehicle aligned by the dealer the first time. Hmm now I am wondering....could there be a glitch in their alignment system?

Could a potential camber issue cause a tire to develop high road force?

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2009 G8 GT -Sport and Premium Pkgs, Roto-Fab CAI, Cortex 93 Octane Tune, Billet Prototype Catch Can, BMR Front and Rear Sways, BMR RTAs, BMR Rear Cradle Bushings, BMR Steering Rack Bushing, GXP SW......and much more to come.

A camber issue will cause the tire to wear prematurely but won't cause it to develop a high road force number.

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Bright Red 2008 G8 GT

Mods: DRCUSTOMPARTS Center Gauge Bezel
Superchips ECM/TCM Tune- Volant CAI
Solo Axlebacks - HID's
Holden V8 Badges
My Website

So would having each of the 4 tires be worn on the outboard edge more than the center or inboard edge be a sign of low tire pressure?

The reason why I am asking is that the tires were set on 32lbs and I bumped it up to 35lbs in hopes to reduce that outboard wear. I like the way it rides after bumping up the pressure.

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2009 G8 GT -Sport and Premium Pkgs, Roto-Fab CAI, Cortex 93 Octane Tune, Billet Prototype Catch Can, BMR Front and Rear Sways, BMR RTAs, BMR Rear Cradle Bushings, BMR Steering Rack Bushing, GXP SW......and much more to come.

Low tire inflation will cause the inside and outside edges to wear. The wrong camber setting will cause the outside edges to wear.

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Bright Red 2008 G8 GT

Mods: DRCUSTOMPARTS Center Gauge Bezel
Superchips ECM/TCM Tune- Volant CAI
Solo Axlebacks - HID's
Holden V8 Badges
My Website

I work at 2 tire shops and 26lbs of road force is considered ok for car tires and 40lbs of road force is ok for LT tires (industry standard). From my experience, most name brand tires do pretty well in road forcing and have very few manufacturer defects. Import tires (which i would include hankook, even though hankook would be at the better end of imports) tend to not road force as well, and have more defects from the factory.

Also, they can try to "force match" the tire to the rim, which means clocking the tire on the wheel to make it pass road force. sometimes just the way the tire mounts to the rim can create high numbers of road force.

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2005 Grand Prix: SPO Spoiler, SE Front Extenion, Painted rear extension white, SPO Grills, Body Color painted Tails, 6000k HIDS
2006 Grand Prix: SPO Grills, Painted Body Color Tails, 10000k HIDs