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]

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]

Rim size

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]

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]

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]

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]

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]

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

 

[TED]

Yes it can and it does ! It is capable to respond in 1 Millisecond Period wheather you believe it or not. Not my figures or thoughts but undisbuted FACT !

 

[Stella]

rims

Just to put my opinion on things. I don't believe that the suspension might work fully hitting a random pothole at 60. It might sense the hole withe the front susp. and adjust the rear? What I do know is it drives like a cadillac and has good performance to follow!Sorry to interupt the current discussion but with the rim sizes i read that a 19/10 w 79mm offset will not fit hits inner fender alot, theirs no way. Now does changing the offset to 65 bring the rim away from the car or put it into the car? thanks for the great conversations.

 

[Phrede]

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 ?

That is exactly what I am saying.

First, I do not believe that the system can react that quick. While the marketing people state that the system can read the changes in the road 1000 times a second there is much more that needs to happen to have the shock actually do something to effect any change. GM closely guards the actual response time of the magneto rheological dampers. I feel that 20-30 ms would be an exceptional response time for the shock based on my design work with similar technology.

After the mechanical shock wave hits the suspension the sensor reads the change and converts it into an electrical signal, that signal travels across the wire to the input module in control, once the input is scanned ( along with all of the other inputs) the data waits for it's share of the processors time when the algorithm determines how to react, this information is now sent to the output module where it waits on the scan time to output the correct electrical signal to the wiring where the signal travels to the shock. Now that the correction has reached the shock the fluid changes viscosity changing the dampening factor. This has no effect at all until after the suspension moves again (after the bump) ! A shock can have an infinite amount of dampening (blocked) or zero (non-existent) and it make NO difference in a static state.

Now, while all of this is happening with almost a decade old technology and computing power, this same shock wave travels at around 5500 meters / second approximately 2 meters to get to you where it is felt. That takes .36 ms or about 3 times quicker than the advertised READ time for the sensor! Just to be conservative, if you triple the mechanical propagation time for different materials etc. the shock wave will hit your butt at the same time as the computer will sense something happened.

That is the theory behind my claim. Anyone can prove this theory by adding 10psi to your tire pressure and go for a ride (Don't exceed the max tire rating for safety reasons). Did you feel a difference in the ride? Nothing can be corrected for instantaneously. Everything takes time, even with the fastest computer and technology.

If there were a system that could achieve this great feat in true real time we would not need any springs and would have solid tires.

I am not bad mouthing our suspension system. It is a great design and very good at doing what it is designed to do, albeit an expensive one.

 

[Phrede]

Just to put my opinion on things. I don't believe that the suspension might work fully hitting a random pothole at 60. It might sense the hole withe the front susp. and adjust the rear? What I do know is it drives like a cadillac and has good performance to follow!Sorry to interupt the current discussion but with the rim sizes i read that a 19/10 w 79mm offset will not fit hits inner fender alot, theirs no way. Now does changing the offset to 65 bring the rim away from the car or put it into the car? thanks for the great conversations.

Reducing the offset shifts the wheel to the outside of the car. I can't say if a 10" with a 65mm offset will fit or not. I do know that it will shift the outside lip of the rim .59" further out than a stock 8.5" with a 61mm offset. So the inside lip will move .91" towards the center of the car. Going from memory I don't think there is that much extra clearance on the inside. If you are OK with where the outside is I suggest you climb underneath and see if there is an additional inch.

Without doing my measurements again, I think to put on a 10" wheel you probably need an offset in the 40s.

I suggest laying a straight edge across your existing tire and measuring out the 9/16" to 5/8" to see where the new tire would be assuming that the profile is the same and the tire width increase proportionally. The measurement will not be exact but will be close.

I recommend you pick a tire before purchasing the wheels to make sure the size is available in that model tire.

To stay close to the rev/mile of stock ( less than 2% error) your choices are:

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[Phrede]

Yes it can and it does ! It is capable to respond in 1 Millisecond Period wheather you believe it or not. Not my figures or thoughts but undisbuted FACT !

And just what is the source of your facts?