CTS-V Wheels/Tires - A perfect match for the G8

[hulkss]

I've been pondering summer wheels/tires for some time now and I finally made a decision with the help of other posts and this cool tire data calculator: Tire Data Calculator Link (http://bndtechsource.ucoz.com/index/tire_data_calculator/0-20)

I wanted wheels and tires that fit without rolling fenders, provided improved handling performance, better launch acceleration for my cammed motor, and ride comfort not worse than the stock sport 19" wheels. I entered the data for the stock set-up and then for the way cool looking Factory CTS-V wheels others have posted about.

Besides dimensions and other cool stuff, the calculator determines a tire suspension comfort value which is related to the as mounted tire radial stiffness. Radial stiffness is important for more than just comfort, it interacts strongly with suspension tuning and handling.

Wow! The CTS-V staggered combo (Continental ExtremeContact DW values used) is perfectly matched front to rear and is just slightly softer than the stock tires (see attachments below). These should really work great on the car with more rubber on both front and rear. A thin 3 mm spacer is needed up front for a perfect match to the suspension and preservation of the stock steering scrub radius.

MoonPie Car Pic Deleted, New ones below

[dilligafdave]

I completely agree. Just picked up my set on ebay. Though they are used and have a few marks, I think I got a good deal at 2000 with factory ps2s with 7/32 tread left. Can't wait to clean them up and put them on.

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[MoonPie]

Not a good pic, that was with Goodyear Eagle GT's 245/40/19 on rears and Eagle RSA on fronts with no front Pontiac center caps. Here's one with with the Continental 285/35/19 EC DWS on the rears and the Eagle GT 245/40/19 moved to the front with Pontiac center caps, dirty.
http://i950.photobucket.com/albums/ad341/VMIMoonPie/cf610f93.jpg

Here's a night pic cleaned up, I'll have mad time to really clean her up this weekend and I'll throw up some better pics.
http://i950.photobucket.com/albums/ad341/VMIMoonPie/98f0b1e8.jpg

You can't tell, but the rears fill out the wheel well nicely in person and the stance is much more aggressive, especially in person. It's true because it's science.

[MoonPie]

If that is an accurate calculator, I'm going to be changing the front 245/40/19 to 255/40/19, I haven't yet because the comparer on rimsntires.com said the front would be slightly taller, this has them perfectly even, .3 higher in the rear. The one on rimsntires.com has a 255/40/19 as 4 mm taller than a 285/35/19 in the rear, I know that isn't noticeable but I would know there's a difference and would rather have that difference be in favor of the rear tires, this one shows the rears as .3 mm taller, I'll take it!

[hulkss]

Purchased some tires today to go with the wheels. 255/40-19 fronts and 285/35-19 rears.
The new Bridgestone Potenza S-04: Tire Link (http://www.bridgestonetire.com/ProductPrint/Other/2369)

http://www.bridgestonetire.com/images/Tires/Full-60/PotenzaS04.png

New S-04 Image: Super Pic Link (http://www.tirerack.com/tires/BigPic.jsp?sidewall=Blackwall&tireMake=Bridgestone&tireModel=Potenza+S-04+Pole+Position&partnum=44YR9S04PPXL&vehicleSearch=true&fromCompare1=yes&autoMake=Pontiac&autoYear=2009&autoModel=G8%20GT&autoModClar=)

[dilligafdave]

Got mine put on today.
http://184.72.239.143/mu/aefc714c-d4b6-d582.jpg

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[warbird]

Did you use spacers on the fronts?

[dilligafdave]

I did not use spacers. I am thinking about it since they are cheap and seeing if there is a difference in the feel. Still debating.

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[warbird]

If you dont get any rub I wouldnt worry about. Drive it much yet?

[dilligafdave]

No rub with the car down. Tire rubbed when it was in the air though. Been driving a bit but a little cold to push them hard.

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[hulkss]

Ok, now for some tougher questions :uhm:

With these larger wheels/tires should we use the wheel lug nut torque recommended for the CTS-V and Camaro which is 140 ft-lb (stock G8 is 125 ft-lb)?

The recommended cold tire pressure for the CTS-V tires (by Cadillac) is 32 psi all around. Is that is the proper pressure to use? What about the G8 TPMS? The systems is set for 39 psi in the rear tires.

[dilligafdave]

Im not sure on the lugnut torque...

As far as tpms I think the G8 system goes off under 32 psi.

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[hulkss]

As far as tpms I think the G8 system goes off under 32 psi.

If that's true, I'll have to put a set of sensors in a home made pvc pipe canister with valve stem like below.
Then pump up the canister to 39 psi. I might have to make four of them first to register a new set of sensors to the car, then put 'em all in one.

http://i199.photobucket.com/albums/aa125/HarrisburgJoe/Img_0002.jpg

[DRCUSTOMPARTS]

You should use the recommended tire pressure and lugnut torque specs for the G8 not for the car the wheels came from.

[hulkss]

You should use the recommended tire pressure and lugnut torque specs for the G8 not for the car the wheels came from.

The CTS-V sedan weighs just a little more than the G8. These are much different tires and rim widths than the stock G8. I am probably going to use the Cadillac recommended tire pressures (32 psi). The Camaro and CTS-V have the same hubs and studs so I will also probably use their recommended lug nut torque values. The bigger tires put more force, overturning moment, and torque into the wheel mounting interface. Greater mounting preload may be required and the wheels are also designed for it.

[warbird]

Plus the 39 psi for rears is for maximum load rating, I believe the manual says 36 for normal duty

[hulkss]

Plus the 39 psi for rears is for maximum load rating, I believe the manual says 36 for normal duty

Yes, and the manual also says 33 psi front and rear for P245/45R18 96V tires with up to 573 pounds of occupants and cargo. I did not notice that before. Thanks.

My 19" stock tires are a 94 (1477 lbs) load rating. The new tires are 100 (1764 lbs) front and 99 (1709 lbs) rear.

[DRCUSTOMPARTS]

If you install aftermarket wheels and tires on a G8 you use the recommended pressure for that car, not for any other car, regardless of the size of the wheels and tires.

[warbird]

I'm planning on using G8 specs when I mount mine, been known to snow in NW Ohio during March so probably still be a few week yet before i put mine on. I did order spacers just in case. Will probably see how tight front is after mounting and if it seems risky put the spacers on.

[MoonPie]

I used the PSI specs for the G8, 36 cold up front and 39 cold in the rear, haven't had any issues. I also used the G8 torque specs with CTS-V lugs.

[hulkss]

Man, this tire pressure stuff is complicated.

First find the load range of your tire. It will be standard load (SL) or extra load (XL) which is also called reinforced. Then look at one of the attached tables to see your tires load capacity at different inflation pressures.

The CTS-V front tire is a 96 SL @ 32 psi = 1411 lbs
The CTS-V rear tire is a 99 SL @ 32 psi = 1543 lbs

The G8 GT & GXP front tire is a 94 SL @ 36 psi = 1477 lbs
The G8 GT & GXP rear tire is a 94 SL a 39 psi = 1565 lbs (estimated)

My new front tires will be 100 XL @ 33 psi = 1466 lbs
My new rear tires will be 99 SL @ 32 psi = 1543 lbs

So I feel good with the 33 & 32 psi which will yield more ride comfort and handle full vehicle load.

[DRCUSTOMPARTS]

You're better off running 35 pounds in the tires then the TMPS alarm won't go off. Adding a few pounds to the tires won't change the ride quality.

[hulkss]

You're better off running 35 pounds in the tires then the TMPS alarm won't go off. Adding a few pounds to the tires won't change the ride quality.

You may be right. The numbers that I used above are basically the minimum pressures that should work well for the car (the maximum tire pressure is molded into the side wall). When tire pressure is increased you are increasing the spring rate of the tire which can dramatically affect handling. Tire pressure is a way of tuning the car for handling. If you drive hard at the tire's limits you can really tell the difference in the inflation pressures and will gravitate toward higher than minimum inflation pressures.

[SRG963]

Ok, now for some tougher questions :uhm:

With these larger wheels/tires should we use the wheel lug nut torque recommended for the CTS-V and Camaro which is 140 ft-lb (stock G8 is 125 ft-lb)?

The recommended cold tire pressure for the CTS-V tires (by Cadillac) is 32 psi all around. Is that is the proper pressure to use? What about the G8 TPMS? The systems is set for 39 psi in the rear tires.

I like my pressures balanced, call me crazy. I run 33 cold and 38/39 warm. I've found out star torquing the wheels to 90 ft/lb then 125 ft/lb works well.

[hulkss]

I tested the TPMS today. When the systems reads 31 psi or less the rear alarm goes on. When the system reads 28 psi or less the front alarm goes on. Cadillac recommends 32 front and rear so I'll leave the TPM sensors in the wheels and run 34 psi all around. Just picked up this Accutire MS-4355B pressure gauge. Nice product.

http://ecx.images-amazon.com/images/I/41rgm1l0bjL._SL500_AA300_.jpg

[warbird]

Was planing on mounting mine this weekend, now weather says possible snow and temps below freezing:snow:

[texn884]

Crazy Paul suggested 125 ft/lb but all the tire places want to put them at 140 ft/lb that is to high of torque.

I have Nitrogen in my new set of tires and the tire pressure is 36 cold and they will get up to 40-41 hot but average 39 all the way around when hot for my Potenzas.

[hulkss]

Crazy Paul suggested 125 ft/lb but all the tire places want to put them at 140 ft/lb that is to high of torque.

Cadillac issued a TSB on CTS-V wheel torque and recommends increasing to 158 ft-lbs for customers who experience wheel "clicking" sounds.

[warbird]

Cadillac issued a TSB on CTS-V wheel torque and recommends increasing to 158 ft-lbs for customers who experience wheel "clicking" sounds.

Anybody have more info on TSB?

[dilligafdave]

TSB INFO HERE (http://www.cadillacforums.com/forums/cadillac-cts-v-series-forum-2009/165703-service-procedure-wheel-clicking-official-tsb-4.html#post1961588)

[MoonPie]

I'm getting a clicking too, very rarely though, I'm going to get them torqued to 158, see if that helps.

[DRCUSTOMPARTS]

Don't break the wheels studs with all that torque.

[warbird]

Are the hub side of everyones rims flat or do the have deep grooves in them? My GXP's have grooves, my CTS V's flat.

[hulkss]

I would try the cleaning process of the TSB and 140 ft-lbs first. The TSB is from 2009 models (the first with G8 style hubs) and the owners manuals for the current model CTS-V still say 140 ft-lbs.

[hulkss]

Just picked up my newly mounted Bridgestone S-04 tires. The stock 245 wide 19 inch wheel/tire assemblies weighed 58 lbs each. The new CTS-V wheels and tires weigh 54 lbs in front (255 wide) and 59 lbs in the rear (285 wide). I'm happy. Dramatically more rubber on the road and less weight. Each wheel/tire assembly required less than an ounce of weight to balance. Weather here sux, I'll install them in a few weeks. Got a set of black 2" long spline drive lug nuts to hold them on the car.

[LDM]

Has anyone run a 245/40-19 front, 275/35-19 rear setup on these rims? Can anyone foresee any problems with doing this? The reason I ask is because I'd like to get the new Michelin Pilot Super Sports that come out next month but they won't be offering the 255/40-19 & 285/35-19 sizes that most seem to be using; at least Tire Rack doesn't list it. I know the contact patch won't be as wide, but I'm used to 245s all around so I'm not concerned about that.

[hulkss]

You will have shorter side walls and less tread width but no "problems". The result will be less grip, a slightly harsher ride, and a smaller tire appearance. Use the calculator I referenced earlier in this thread to compare the "comfort" number. Consider the brand new Bridgestone S-04's. I have not driven mine yet (Minnesota winter), however, I just spoke to a guy who tried them in a tire comparison test drive in Phoenix (he owns a local chain of tire stores). He claims the S-04s were better that the new Michelins. In addition, the S-04s have a tread life rating of 280 which is double the stock RE05 which was 140 (the new Michelin may be rated 300).

[20lbbooster]

I wonder if they changed the design on the ctsv wheels. My graphite ones have holes drilled on the hub. According to the stamp on the wheel they were made in Oct 2010.
http://i678.photobucket.com/albums/vv144/20lbbooster/photo3-2.jpg

[hulkss]

This wheel is from March 2009, looks the same to me.

http://i158.photobucket.com/albums/t115/one1wang/CTS-V%20wheels/DSC01755.jpg

[20lbbooster]

This wheel is from March 2009, looks the same to me.

http://i158.photobucket.com/albums/t115/one1wang/CTS-V%20wheels/DSC01755.jpg

Yeah, yours look the same as mine. Someone else told me that their ctsv wheels had a flat, solid hub. I wonder why the difference? BTW, you have any actual pictures of the centercap covers that you ordered? I checked out that site...will e ordering a set.

[hulkss]

..... you have any actual pictures of the centercap covers that you ordered?
My center cap overlays were just shipped a few days ago. That photo of a polished wheel with holes in the mounting face is from another post. I'll post a photo if mine are different.

BTW, I bough some of these lug nuts off ebay:

http://d5otzd52uv6zz.cloudfront.net/8ebd35f5-83e7-44b4-8f98-24bc1b3f0db7-420.jpg

Edit: I ended up using the stock lug nuts and black plastic covers.

[warbird]

Yeah, yours look the same as mine. Someone else told me that their ctsv wheels had a flat, solid hub. I wonder why the difference? BTW, you have any actual pictures of the centercap covers that you ordered? I checked out that site...will e ordering a set.

That was me. The GXP's have grooves where each V is. Thought it might have something to do with the torque issue. Mine have been setting in the corner of the garage cause its too damn cold to mount them, looked at them earlier today and they have the holes as well (same as pic above) so I guess thats not the issue with TSB. Still seems odd the GXP's are grooved and Ive never had a clicking noise from them.

[Napalm]

Where are you guys getting your CTS V rims? I'm torn between that and those BE by Breyton rims that tire rack now carries.

both are really light compared to the sport 19 rims and wider.