The outer edge of the wheel/tire will stick out 1/2" further than these:

17x11 50mm

If you drop a straight-edge down vertically from the widest part of the fender, the outer edge of the tire is just barely inside the straight-edge. The 36mm offset would move the outer edge about 1/2" further out, past the straight-edge. That means they would be outside the fender. To me, even my setup is pushing the limits of acceptability, but that was the only way I could get the 315 DR's in there, and the car is useless on the street without the DR's......

 

They look like *** IMHO...they stick out too far.

-Shawn

 

Anyone know the weight of the real ZR1s? And can you still get real ZR1s through GM or are they all knockoffs?

 

Thanks for the kind words.

 

Yes, nice... hehheh.... meanwhile back on the ranch....

So if they stick out 1/2 inch more does that mean you gain 1/2 inch of clearance on the inside?

The entire reason for this thread was I have a chance on a good deal for some AFS 36.5mm wheels. The way the AFS page reads it seems as if Firebirds/TA's have a wider rear and can thus handle the etrax half inch without sticking out. However, after seeing Injuneer's pics I don't see how this is even possible.

Plus I wasn't too keen on beating the inside fender at all. Could a small spacer be used instead? Maybe this way the wheels won't stick out a 1/2 inch and look as our colleuge put it "***" and then also give a tad more clearance on the inside?

Ideas?

 

the Pontiac's rear 1/4 panels do go out more than the Chevy's, so yes AFS is right.

And yes, running a 36mm offset (like the ZR1's) will serve the same (but more stable and no lug-thread loss) than having a 14mm spacer and 50mm offsets.

Here's some links to Pontiacs running the true ZR1 rims:
black 99 T/A: http://www.arches.uga.edu/~cagolden/pics.htm
white 98 T/A: http://ericcer.tripod.com/TA/ZR1_wheels.htm


The 17x11" ZR1 rims I have are more than 5 lbs lighter than the AFS 50mm equivalent (we've weighed them side by side). I imagine the 36mm rims would be similar.

Coincidentally, the AFS 17x9.5" rims and tire weigh the same amount as the ZR1 17x11" rims and tire! (yes, that's 10# of rotating weight on your drivetrain that disappears )

If you look at the second link I provided above, you can check out a small trick he did to widen the lower portion of the wheel well and inch or so to make it look more "normal". Even with the extra 1/4" or so, the Pontiac's lower wheel well still comes in a fair bit, exposing tread from the rear view (where a cop would sit ) The bulge out probably depends more on the tire width and model you choose than the rim. 295's or 305's would look more "normal" and provide less squirm on the 17x11's.

And yes... you won't have to "masage" the inside of the wheel wells as much since you are moving the wheel out 14mm. (if you do need to touch it up, make sure you put the rear seat in the upright position, and have a can of undercoating or POR-15 to cover up the "worked area").

I'll let you know what my chrome ZR1's look like once their mounted. (the current set I have is silver-paint, the chrome will arrive in a month or two)

 

P.S.
careful on taking that second post as gospel... some of his views are so far off base it's not even funny. lol... yeah, it's the channels of air that follow the grooves (not the stiff side walls and wide wheels that don't fit in the groves )

 

I belive the ZR1 rims were made by AFS, but to GM specs. I don't have any proof... except that my first set of ZR1's (that came off a 1-owner ZR1) weighed 20lbs and 22 lbs (9.5" and 11") and had NO "GM" stamp inside them. The casting instead had an "AFS" on them and the GM Part number (which matches the GMPartsDirect.com number). the chrome set I'm gettin has the same markings but the 11" rim weighs 23lbs (~1lb for chrome or scale differences?)

My friend's road-race C4 corvette uses AFS 17x11"s and his weigh about 5# (or more) above the GM units.

So it looks like either GM wasn't braggin about their custom rims (no stamp), doubtful, or they sub-contracted to a well known wheel producer to make wheels to their specs. My guess is that GM had AFS make an "A mold" quality wheel; while for durability/cost (due to the tight/costly tolerances GM probably demanded for ZR1 use) AFS sells their own heavier version. WHy it's heavier? I don't know... maybe they feel it may be used in 5000lbs trucks, abused over potholes or such in daily driving... or they dont' care about tolerances as much as GM did and just compensate with extra mass to make sure they don't have failures (few companies have the legal and financial abilities GM does in the event a product starts to fail and brings law suites, it's probably easier to just add some aluminum and avoid any possible issues).

Don't quote me on the conjecture, I don't know for sure. All I know is:
- the GM ZR1's do NOT have a GM stamp, but they DO have an AFS cast in
- the GM ZR1's are ~5# lighter than the AFS retail version
- the GM rims have smooth backings behind the spokes... some aftermarket ones have webbing back there
- the GM rims have GM part numbers cast into the back of the spokes.
- the GM ZR1's came in silver paint and chrome options
- GM ZR1's have the size cast into the spoke backings as well (I believe they say: 17.2 x 11 x 50 mm)

 

Steve, very informative post, thanx. So can you order the GM ZR1s through GMpartsdirect or a dealer or do you have to go through AFS and get the 5# heavier ones? The main reason I want to get ZR1s is the weight, and 22 pounds for 11" wide wheels in incredible.

 

Is the black car...

black 99 T/A: http://www.arches.uga.edu/~cagolden/pics.htm

36.5mm offset from AFS?

The second white car seems to stick out? If the pontiac has more width how is this possible?

Type of tires maybe?

Just a bit confused I guess and need clarification.

 

I'm confused, shouldn't that be the other way around? If the 36s stick out further, then putting a 14mm spacer would make them stick out even more right?

 

Whoops, my slip up. Should be the other way around:

And yes, running a 36mm offset (like the ZR1's) will serve the same (but more stable and no lug-thread loss) than having a 14mm spacer and 50mm offsets.

I'll fix it up top as well to elliminate confusion.

Also, I've been cruising the ZR1 forums and found that GM did not offer a chrome option for the ZR1 wheels... only silver paint (which explains why you can only get the painted ones from GM now).

HOWEVER... there were some dealerships in southern California that took the painted wheels, chromed them, and offered them as a dealer-option/upgrade so they are out there. Chrome should add less than 1# so the weight for a 17x11 should still be around 22 or 23lbs.

I have both a set of silver ZR1's from a 95 and a chrome set of ZR1s that came from arizona... and originally Cali. I'll see if I can get a photo showing the differences and what to look for if anyone wants it.

oh yeah, one more tid bit... if you do get some ZR1's, see if you can get the lug nut covers as well. Mine came with the wheels and I was shocked... they're not plastic... they're chrome-plated metal and SUPER light. I'm sure they're probably CNC'd aluminum... but they have this beige hue to them on the inside I'll have to get a hardness test on them to settle my curiousity...

 

test fit my ZR1's on the rear today... the 36mm offset with 17.2"x11" rims fits perfect... with GCS's at least. No need to trim the bump stop (from what I can tell... at full droop, and at static load). Only mounted the passenger side though... we'll see if the driver's side looks good in a few days.

I was worried that I may have to machine out the rear wheels a bit to make them fit the axles, but she fits on just nice. After that, I was worried that the wheels were reproductions... but the shape and text are identical to the set I KNOW are real... so I weighed them to make sure. Ok, they're ZR1's that have been chromed... so why the easy fit? Then it made sense... the hubs were still shiny.

Last May I replaced the axles when the posi blew up at the track and I managed to tweak the splines in the process. The new axles must have a smaller hub end... just like the LS1 cars do. I've never heard of the need to machine the hubs out until I talked to Jason at Bremerton, and later on the web when I specifically went looking for it. Seems the older 4th gen cars are the only ones mentioning this issue. (I guess this is similar to using LS1 or C5 wheels on LT1-era cars... they also need to be "clearanced" occasionally). Whatever the reason, LS1 cars, and LT1 cars with new axles, don't have any problems.

So I guess it's a good thing I put new axles in last year... might have cost a fair bit, but it saved me a small hassel now.

Now all I have to do is get these 315's (BFGoodrich g-Force TA KD) mounted and baanced... and be VERY careful with the 10-bolt.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

With 285 Eagle GSC's up front, and 245 Firehawk SZ50's out back... I finally have OVERsteer... a bit unnerving at first, especially on a grooved highway, but I'm kind of getting used to it. That said, I'll be very happy once the 315's are out back, and my 5-spoke chrome wheels actually match front to back. It's only for a short time anyway. . . but man it's impressive on how much these cars can be tuned simply with tire/wheel upgrades. Biggest asset of the 4th gen? big wheel wells.

Next project? LS1 brake upgrade. . . then a C5. These LT1 pads are ROASTED after a hard stop. No more ABS pulsing... the 285 GSC's are incredible for grip (compared to 245 Firehawks)! I can't wait to put 275 Eagle F1's up front in their place!

the BADBIRD is growing claws! <evil grin>

 

quick summary on the wheel weights I measured today:

GM 16" x 8", 55mm (chrome 5-spoke, '97 T/A 'vert): unknown
w/ Nitto 555R 245/45R16, past tread wear bars: 44 lbs

GM 17.2" x 9.5", 56mm (silver, '95 ZR1): 18.5 lbs
Goodyear Eagle F1 275/40ZR17 (new): 26 lbs
Combined: should be, ~46 lbs.

GM 17.2" x 11", 36mm (silver, '95 ZR1): 21 lbs

GM 17.2" x 11", 36mm (chromed, '94 ZR1): 23 lbs
w/ Goodyear Eagle GSC 315/35ZR17 (new): 50 lbs



I havn't weighed the new 285 GSC's that are on my chrome ZR1 front wheels yet... but maybe tomorrow.

So yeah, going from 245's to 315's is putting 12 lbs of weight in the back pair, and ~4 lbs up front. Compared to 4th gen 17" rims though... I'd bet I'm on par or less.

 

I used to have 36mm chrome ZR1s in the back with BFG drag 315s. I thought it looked great, had no problems with rubbing and I didn't have to cut or shave anything to make them fit. I also have 2" drop Jamex springs.