jseremba

9.5 x 17
Hello everybody,

I am just about to get the car on the road. I was looking at tires. And I realized that this car does not have original wheels. The wheels are 9.5 x 17. The car is an 85 it should have 16 inch wheels. I saw an article about wheels and offset and thought I should ask if anybody knows anything about these wheels and what tires, size, should go on this car.

hcbph

Don't know if this will help your or not: https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm

I went with 18's on my 86 due to tire availability of the 16's that came on them originally and 17's which are getting harder to find every day. One thing to consider though is as you go larger diameter in the rims if you want to keep the same O.D., you'll have shorter sidewalls.
I wanted something with the same width and O.D. as the oems and found that 18x9.5 40 backspace rims with 255x40zr18 tires fit just like the originals on mine. I only street drive my car (no track) so that's all I can speak to - they fit and handle great.

jseremba

The word offset is what started this thread. Does anyone know where I can find the offset of my wheels. And, do I have to do anything because of the offset i.e. more toe, caster, camber. Or can I just buy tires and slap them on.
I disliked the 84 Corvette because only BF Goodrich had the correct tire size and they cost 185 each.
Thank you

WVZR-1

'90 wheel and best I recall all of the information is 'cast' into the division bar that separate the 'windows' on the back-side. I don't recall the offset being on a division bar but the offset is 56. To use these on an '87 and earlier most use a 19mm(3/4") adapter style spacer. On the division bar rotation, wheel manufacturer and code. The wheel in your snapshot is a RH rotation.. A set of these for a car would require 2 cast left and 2 cast right on the back-side. There could also be a 3 letter code but I believe that some GM SPO catalogs have errors regarding rotation for a '90.

Tire - 275/40-17 Very easy find nearly everywhere.

***I checked an eBay wheel and off-set is noted on the division bar. There's also likely an 8 digit part # cast on the division bar also.

Here's a left on eBay with images of the division bar

https://www.ebay.com/itm/Corvette-Or....c100005.m1851

ghoastrider1

those cracks in one of the wheels pictured? If so...thats a scary wheel to mount on a 150 mph car and one that corners like a go car.?
?

MatthewMiller

Everything in this post is spot on. The only thing I'd change is that instead of using a 3/4" adapter, I'd swap to longer ARP wheel studs and use 3/4" or 1" spacers instead. An adapter bolts to the hub using the original studs, and then has its own studs for the wheels. A spacer is just a "shim" that slips over the wheel studs, and the wheels go on the same studs (which is why the studs need to be longer). A spacer has much less chance to be off-center, and much less opportunities for stress risers and breakage. If you go with adapters instead of spacers, I'd especially consider the 1" option because the extra "meat" in its body will make it stronger. But either option is well proven over time.

On 3/4" vs 1" spacing, the 3/4" option will put the wheels right where there original factory wheels sat in the fender wells. You have plenty of room for another 1/4" outward spacing, and IMO that looks a little better on a C4. So 1" works well too. It's mostly just a matter of what you like.

jseremba

First, thank you.

So what I am getting is I need to buy longer studs and a 1 inch spacer so that I can use these wheels on this car, correct?
Does anyone know how I order the stud and spacers. I am on Guam. Everything is a little more challenging here. Thank you

WVZR-1

I'm not familiar with a stud that would allow you to use a 1" spacer. I use a 16mm pass-through hub-centric spacer and wheels that require similar exposed threads. Those wheel studs at the time '03 or '04 were very inexpensive. GM # was 22551491 and likely still available but expensive. For a driver I don't see issues with the adapter style if they're done on billet stock. Around here guys that use these generally pin the stud in the adapter so they can't spin. I believe that most/many on here would agree there's few reasons to avoid a quality adapter style. That's why I mentioned 'most' in my original post.

Maybe Mathew is familiar with a stud of sufficient length but I doubt it.

MatthewMiller

ARP makes wheel studs for "late model GM cars" with M12x1.5 threads in several lengths: #100-7713 is 3.25" long, #100-7725 is 2.5" long, and #100-7726 is 2" long. You'd want at least 1" longer that your stock studs. Then you need a spacer with 5x120.65mm (5x4-3/4") holes to slip over those studs. It could either be 34/" or 1", depending on how far out you want to set the wheels under the fenders. Those may be a little harder to find, because in those thicknesses everyone wants to sell you an adapter instead.

jseremba

First let me say, HOLY ****.

I never thought that this would generate such an interesting thread. You people are amazing.
So what I need to do is measure my studs and add an inch to the length, purchase a spacer and then install 275/40-17 on my rims.
Question one of the threads talked about left hand and right hand. Am I going to need to look on the rims for something that tells me right or left. And pardon my ignorance does it matter? I mean it is the rim not the tire.

Thank you for your help and patience.

WVZR-1

There's way more to consider - WAY MORE!!!!

The expense of 'just studs' is very likely equal to (or just less than) the price of the adapter per wheel. Now you need to add the price of the spacer of choice! Using a pass-through and longer stud install can be very challenging. On the rear of my later I was able to install 68mm studs by only grinding a chamfer on each stud head. I doubt a 3.25 could be done similarly even on a later.

On an 'EARLY car I believe there's way more challenge for stud replacement. I've never done an earlier rear. You have 'shoe in rotor' for e-brake and stud replacement I'd think is a 'TASK' I'd consider nothing until you determine if you're up to the expense and also the difficulty. Do you have an FSM for your car?

I doubt rear studs can be done inexpensively and I doubt no one that's done the job would like to tackle it again unless necessary.

You need to have someone with an early car 'shoe in rotor' explain how difficult the task is for replacing a rear stud. A stud twice as long I'd think a real challenge!!

Anyone that's done a rear hub & bearing can likely explain 'degree of difficulty'!!!


***The wheel in your snapshot is a 'right' and mounted correctly on the car. Has nothing to do with tire or factually fit BUT with them mounted in other than the correct orientation you'll likely get quizzed frequently.

jseremba

Well you have hit the nail on the head sort of speak. This is a brake in the hub car.

So really stupid question.. The rims are on the car. What is wrong with just putting new tires on the road.
What problems does it cause.

Thank you

And the spacers cost any where from 100 to 600 per set. Holy Cow.

WVZR-1

Do you know for a 'fact' that there already isn't an adapter on the hubs? The wheel in your snapshot seems to be reasonably positioned in the wheel-house!! OR SO IT APPEARS FROM UP HERE IN THE WILD & WONDERFUL WV HILLS!! Pull the wheel/tire and do another snapshot!!

MatthewMiller

I'm going to defer to WVZR-1 on this. I hadn't considered the challenges of installing the studs on an early C4. When I've replaced mine, it's always with the bearing/hub off the car. It's not that hard to remove them, but in the rear it's a lot more work than just bolting adapters on. So yeah, adapters are probably the way to go for most people.

As for left and right wheels, any wheel will roll just fine on either side of the car. It's just that most C4 wheels are directional in design (appearance). So as WVZR-1 said, it would look funny. To answer your question about "what's wrong with just putting tires on the road," the question is how far in the wheel and tire sits. Those wheels have 7.45" backspacing, and that may be so much that you end up with rubbing on the suspension or the inner fender liner, especially in front with the steering turned to full lock. OTOH, everything may fit as it sits - it's going to be close. But even if it all physically fits, the wheels and tires will be set far in towards the center of the car, with big gaps to the fenders. IOW, the track width of the car will be reduced, but the fenders will be just as wide as ever. At that point, the biggest issue is that it would look kind of funny. A secondary issue is that you've technically decreased cornering grip by increasing lateral weight transfer, although unless you're autocrossing or doing track events you probably wouldn't notice it.

jseremba

WVZR-1

Interesting that you should say that. Because the rims come on and off easy. I am thinking that with everything we are talking about, the rims on the wrong hub should be difficult to remove and install. I will check tomorrow.

Thank you

Then off to the Philippines for a week

ghoastrider1

WVZR1 knows his tuff on this subject and I respect his knowledge in this subject. In other woeds, listen to what he says. best of luck.

jseremba

I am not planning on not listening to your or his advice. It is funny he mentioned the possibility of the hubs already being changed. Is the lug nut spacing on the 16 inch wheel the same as the lug nut spacing on the seventeen. Because the wheels go on the hub. I found spacers on ebay 3/4 of an inch to two inches. I plan on using the 3/4 of an inch.
I was just wondering "if the wheels fit on the car. what is wrong with just buying new tires and not using a spacer." Just for informational purposes.

Thank you all for your help. Believe me this project would have been in the crusher if it were not for you all's help.

MatthewMiller

You're missing the point of what adapters or spacers do. All C4s have the same bolt pattern - adapters don't change that. All that adapters or spacers do is move the wheel toward the outside edge of the fenders (i.e. they subtract offset). We have no doubt that the wheels/tires physically fit without spacers or hubs. Without spacers or adapters, though, they may hit the inside of the fender liners or some part of the suspension at certain points of suspension travel and/or at full steering lock up front. Even if they don't rub anywhere they will look kind of goofy.

What WVZR1 is saying is to check to verify that you don't already have spacers or adapters on the hubs. That's because in the picture you posted, the wheels appear to be set out where they should be - as if there were already adapters on the car. But from that angle it's really hard to tell. He just doesn't want you to buy parts you already have. If you're not sure what to look for, take the wheel and post of pic of the hub and we can tell you.

jseremba

I think I sent this reply. So sorry for the duplication.

Thank you all for clarifying the reason for the spacer. I know the car does not have a spacer on it because I took off the rotors to change the calipers. If this is a 1990 wheel and it should have the spacer. Then it gets a spacer. Someone mentioned that the wheel may have a crack in it. I will look for that. But, this cars 150 mph days are over.

Thank you all.

BLKMAMBA

this may help as well

http://mirrockcorvette.com/c4-parts-guide/wheels/