Factory rim spec

[Stella]

Anybody out there know the real factory rim specs for the xlr and the v? I've read 18/8.5 w45mm offset,18/8 w45 then 51mm offset. Then when you take a tape lip to lip the stock rim is 9" wide. Looking to put rims on taking measurements,want to put a rim and tire that fills the wheel wells and has a nice dish to it. Would like to go with a 18/9.5 w56 and 19/10 w65. I know offsets are a tricky thing but see alot of pics on forum of c6 wheels on xlr's look great wondering if anyone can help? Appreciated thanks.

[Phrede]

Originally Posted by Stella

Anybody out there know the real factory rim specs for the xlr and the v? I've read 18/8.5 w45mm offset,18/8 w45 then 51mm offset. Then when you take a tape lip to lip the stock rim is 9" wide. Looking to put rims on taking measurements,want to put a rim and tire that fills the wheel wells and has a nice dish to it. Would like to go with a 18/9.5 w56 and 19/10 w65. I know offsets are a tricky thing but see alot of pics on forum of c6 wheels on xlr's look great wondering if anyone can help? Appreciated thanks.

I recently went down this road. My stock (XLR-V) size is 19 X8.5 with a 61mm offset. I tried to fit a 10" width with a 79mm offset and can say for sure it will not fit. This wheel wou8ld have put the outer lip very close to the stock position about 1/2" inside the fender. a 9.5" w/ 56mm will be .7" further out than stock and a 10" w/ 65mm will be .59" further out than stock. The 65mm offset does not sound right for a C6 wheel. They usually are offered with a 40, 56 or 79 mm offset. If you are wanting the look of rubber outside the fender than maybe a 10" will work, otherwise it will not.

I had many problems with the wheels I purchased and ended up staying with stock and paying $200+ to ship the ones I ordered back. The quality of the Factory Reproduction wheels were poor and they had so much run out they could not be balanced.

My reason for wanting to change was to get better tire fitment and selection of good non-runflat tires. In the middle of all of this Bridgestone came out with Potenza S04s in a 255/45-19. I am happy with these tires on my stock rims.

HTH

[Stella]

I appreciate your response but kind of confusing. Will the 19/10 work? I found a place that has 65mm offset will that work better for me. I have no problem with 9.5 but I would like to put the fattest tire on the rear without sticking out of the fenders. Really like how tight D3 does it, maybe not that extreme.

[Phrede]

Originally Posted by Stella

I appreciate your response but kind of confusing. Will the 19/10 work? I found a place that has 65mm offset will that work better for me. I have no problem with 9.5 but I would like to put the fattest tire on the rear without sticking out of the fenders. Really like how tight D3 does it, maybe not that extreme.

Everything depends on the offset along with the width. If you do not want it to stick outside the fender a 10" wheel will not work. I suggest you also research what tire sizes are available in the tire model you want. or..... what tire models are available in your size wheel you are using while not changing the revs per mile too much.

If you look at a stock setup using a 255/45-19 there is only about 1/2" clearance on the inside and a little less on the outside to the fender. This tire fits on an 8.5" wheel.

[Stella]

Thanks phrede for your help. I hear yah on the clearance on the stock rim but if you put a tape on the rim from lip to lip it reads 9". I have a reg xlr want to put 19/9.5 probably? Also I thought you could recalibrate your speedo with a tech 2? I don't know just thought it was possible.

[TED]

YES a 10 inch wheel Will work and clear the fenderwell I have 285/30 ZR20 on the rear and they are awesome I dont know the offset of the wheel as they were installed by LUND Cadillac I do know they are MAYA wheels and are definitly 10 inch Good Luck

[Phrede]

Originally Posted by Stella

Thanks phrede for your help. I hear yah on the clearance on the stock rim but if you put a tape on the rim from lip to lip it reads 9". I have a reg xlr want to put 19/9.5 probably? Also I thought you could recalibrate your speedo with a tech 2? I don't know just thought it was possible.

Are you measuring the lip inside dimension or outside?
Wheels are measured from the inside of the lip or tire mounting position.

A new tire size could probably be reprogrammed using a Tech 2. There is way more going on than just the speedo. Don't forget that there is a suspension travel sensor at each wheel. The height of the tire comes into play many places. I know that some dealers, who have this expensive Tech 2, will not do this and will have nothing to do with non-stock size tires. YMMV

There is also a concern with getting aftermarket wheels to run true. Don't expect a low end wheel to be as good as the OEM in this regard. I found that there is a lot of confusion around our wheels being lug concentric or hub concentric. IMHO I believe them to be lug concentric just as a C6 'vette is. The hubs have the same GM part number after all.
This comes into play when balancing a new tire/wheel assembly. Many tire stores do not have the lug adapter to do lug locating on the balancing machine and will use the cone locator. A high quality wheel will have the center bore run true with the BHC and this is not an issue. Less expensive wheels, not so much. Remember to snug the lugs with the wheel off the ground to locate the wheel properly.

If you are wanting to keep your rubber inside the fender I would suggest staying with the 255/45-19 on all 4 corners. If you need more performance go to a softer compound. That is not a wimpy size after all.

The difference from an 8.5" and a 9.5" rim will probable not matter since the tire width is the same.

You may want to consider putting stock XLR-V wheels on your XLR. They are available without breaking the bank and will get you the 19" look with the proper offset.

HTH

[Phrede]

Originally Posted by TED

YES a 10 inch wheel Will work and clear the fenderwell I have 285/30 ZR20 on the rear and they are awesome I dont know the offset of the wheel as they were installed by LUND Cadillac I do know they are MAYA wheels and are definitly 10 inch Good Luck

The offset is extremely important. How about a picture to show how far outside the fender the rubber is? Also, your 285/30 will fit a 9.5" wheel.

If the interior clearance of the tire is maintained, there is not a lot of extra there at full suspension travel, all of the additional 30mm of section width must go to the outside. A stock tire has about 1/2" from the outer edge of the tire to the fender so the tire has to go outside the fender lip.

I also prefer not to lose the ride quality between a 45 and 30 series profile or the additional risk of road hazards. It's nice to be able to do a full rotation by not having a staggered setup.

To each their own.

[TED]

Yes offset is the key here I know mine to be 10" by a small sticker i can see from the outside that states 20"x10" Plus with the lower side wall and the way our suspensions work they go up into the fender well on an angle NOT streight up and down And yes Cheap wheels are just that CHEAP why any one would put those on a car like this is beyond me. And since i was not willing to give up the handeling performance of this car (one reason why i bought it ) The lower profile works perfect. And with the magnetic ride control the diference between sidewalls (and ride )is not affected near as much as a ( Regular ) car. This system has incredible variations to compensate for this. And beleive me the handleing is NOTICEBLY different But being a part time racer (not this car ) i just might notice these things a little more Being able to rotate them all is great Since i cant do it on my VIPER either I do it on my sons neon

[TED]

That was 20 x 10 wheels not 10" offset I dont know what the offset is Next time i have one off i can measure it

[Phrede]

I just realized that I have been posting the incorrect size I have. Brain cramp, sorry. Mine are 255/40-19 not 255/45.

I don't know that I agree with the statement that the magnetic shocks will compensate for the firmer ride for a lower series tire profile. The way I understand it the change in dampening is based on the suspension position (load) along with road speed and some other factors. The reaction time to any road imperfections transferred to the chassis would be so fast that the shocks could not react in time.

I know that others have tried 10" width and had to replace the plastic inner fender liners. I do not know what offset they had. I tried 10" rims with a 79mm offset and the tire/wheel could not be bolted on as the tires were hitting on the inner side with the suspension in it's normal static position. It was not close. I chose a 79mm offset because that put the outer lip of the wheel and tire within .040" of the stock position.

[TED]

These shocks react in MILLISECONDS and are far more advanced then you i think you realize. Many high end exotics now use a variation of this ground breaking technology.

[Phrede]

Originally Posted by TED

These shocks react in MILLISECONDS and are far more advanced then you i think you realize. Many high end exotics now use a variation of this ground breaking technology.

Milliseconds or even microseconds are not quick enough. If you hit a single bump on the road the event has passed before the shocks can react and is ignored by the system. If there are a few bumps at an irregular time pattern these are also ignored. This is because the shocks are reacting to the event itself starting with information from the suspension sensors. When the sensors change, initiating action by the system, the results of the bump have already been transferred to the chassis. The system is not, and can not be, predictive of road conditions.

All other things being equal, a taller profile tire will ride better because it absorbs more of these bumps before it gets transferred on to the suspension. This side wall flex is the same reason why cornering performance is less with the taller profile. This same concept is evident when people get a better ride after changing from the stiff walled run flats.

The magnetic shock system does work well with changing individual suspension loads due to cornering, braking or acceleration that have a much longer time span. The system is also useful for a fairly constant frequency rough surface such as a gravel road. There is also a benefit of having a firmer or softer preload on the system which can give a firmer or softer overall ride. This is what the system was designed for.

I don't see many gravel roads at speed with my XLR.

Advanced technology can help in many ways augmenting and solving problems in complex mechanical systems, but sometimes a pure mechanical solution is best.

Everything is always a compromise.

[TED]

So you are saying a system that can change its dampenig up to 1,000 times a second is not fast enough to change in the course of and even through 1 bump Really ?

[BusaMan]

Originally Posted by TED

So you are saying a system that can change its dampenig up to 1,000 times a second is not fast enough to change in the course of and even through 1 bump Really ?

I'm fascinated by this discussion. Can this magnetic suspension system really make a dampening change in a millisecond? If so, it would be making a change for every inch traveled at 60 mph. If one is hitting a pothole, I would hope it would be at a slower speed than that. FWIW