87350IROC

iTrader: (2)

Hi,

I'm planning to pickup a set of Boyd PT-10 18x10" wheels for my Camaro. This will be with 285/35/18 Nitto NT-05 tires on each corner. Car is used as a weekend cruiser, track days, and for open road racing.

I know plenty of people use 9.5" wide wheels with 275's with no issues. Can a 10" front wheel with 285's be used with no issue? I am not concerned with very minor rubbing at full steering lock.

For the rears I know i will have to whack in the sheet metal that is already very close to the stock wheels towards the front of the wheel wells. Will I have to do any additional modifications to fit?

Wheels must fully tuck on front and rear. Currently the fronts are 0.3" further out due to the Wilwood brakes. This almost makes the fronts flush with the front fender. It looks fine, but I am not willing to go any further out. The stock rear wheels tuck to far in. I am willing to go out probably 0.5-0.75" in the rears. The car is fairly low, so I will need to take that into consideration as well.

Here is a bad photoshop showing the proposed wheels on my car and my current ride height.

Guest

There's another thread here, a guy did 18x10.5" at all 4 corners, with big front brakes, but no real mods. Mostly just getting the spacer thicknesses exactly right.

87350IROC

iTrader: (2)

Interesting. I will be specing mine so a spacer is not required. I could not find this thread, do you happen to have a link?

Guest

As I remember, and not well at that, it was on the second page of someone else's thread. I think the guy doing the 10.5s was Big Mike, or something like that. I think he was doing an orange-red Camaro, and the wheels were C5 'vette rears? They just barely cleared his struts, which I think were yellow, so Koni or Bilstein. And in those pics, I recall the wheels were bare, no tires yet.

//<86TA>\\

iTrader: (14)

yeah, probably a little minor work int he rear, but you can fit 18x10.5's on the front, you have to keep them as close to the strut as you can though. the wheels will rub the a-arms in the back, so keep that in mind. you would want to add some material to the steering stops to prevent this.

the tie rod should fit right into the 18" wheel.

BIGMODS uses 18x10.5 and 285's ion the front, and anther buy here does, but i forget his name. He has a red iroc thats just completely badass

Im pretty sure his front wheels are flush or just a tad under the fenders.

I dont know if i would want to drive 10.5" front wheels on the street for long though, im sure its a workout.

Im interested in what you come up with for wheels specs, i plan to do some sheetmetal work and use 18x10.5 or 11's in the front of my 92 at some point.

//<86TA>\\

iTrader: (14)

good info here, and there are pics of bigmods stuff and others.

https://www.thirdgen.org/forums/whee...ont-wheel.html

87350IROC

iTrader: (2)

Thanks 86,

I finally worked some calculations and this is what I'm thinking

Fronts
18x10 with 6.5" backspace

Rears
18x10 with 6 3/8" backspace

In general I like the the wheels to be just a little tucked into the fenders. The stock front IROCs look great once pushed out by my brake kit. The stock front IROCs are 16x8 with a 4.5" backspace, hence 18x10 with 6.5" backspace for the same outside appearance.

For the rears, with the stock IROCs I think they tuck into the fenders to far. I think a 3/4" out would look good. The stock rears seem to be 5.1" backspace. Hence going to a 10" wheel I calculated I would need a 6 3/8" backspace. 5.1+2-0.75 = 6.35 ~ 6.38

Does this look like good math?

I need to do some more on-car measuring to make sure everything looks good. I'm going to put the front IROC wheels on the rear to see how that looks with them sticking out a little further.

Do you think 6.5" backspace front and 6.38" backspace rear will fit with minor messaging? I don't think I'm willing to cut the rear bump stops like many of done to fit 11" wheels. I think typically the 11" wheels have a 7" backspace. Most of the 11" wide wheels stick out from the fenders a touch further than I would prefer.

Finally, i have built a template that i will temporarily attach to the back of my stock iroc wheels and tires to simulate the extra backspacing. Hopefully this will work out so I will know for sure what gets in the way, and what doesn't.

Thanks,

John

fireturd350

iTrader: (8)

Sounds like a lot of backspacing to me. Most people run 15x10s with only 5.5".

//<86TA>\\

iTrader: (14)

and they stick out....

you rear BS looks good, my typical setup on the rear would be 6.5" of bs, that keeps them tucked in, you could push them out another 1/2" and the tire will be about flush, at least on a firebird, i assume the camaro's are the same.

front sounds about right (brake upgrade noted), it will defiantly not stick out, and thats less than what i've seen for front BS on the wider 11 and 10.5" wheels. I htink you are good, but you can always measure back from your current wheels, at various places, and see where the new wheel would be. if you are using "front" wheels, you should have to measure back 2".

backspacing is usually just 1/2 increments from aftermarket outfits.

87350IROC

iTrader: (2)

Yup. But that is with the tires sticking out of the fenders. Not the look I am going for.

87350IROC

iTrader: (2)

Yeah, I was just looking for a sanity check. I built a 26" MDF ring that I'm going to tape to the inside of the stock wheels to simulate the extra width. That should be pretty telling for fitment.

Regarding the backspacing, Boyd builds to 1/8" increments.

//<86TA>\\

iTrader: (14)

well there you go!

are these going to be track only-ish wheels or ?

SKELITOR117

iTrader: (3)

I wouldn't put anything bigger than 9" in the front if I were you. i got 10s in the rear and 8s in the front.

87350IROC

iTrader: (2)

Not really. The car is still primarily a weekend street car, but does see several track days per year and will continue to. I am also getting into open road racing this year. Should be a good time. Typically I time out tires before I wear them out, so I keep using softer and softer tires until I finally find some that I can wear out. With the kind of driving I do, using R-compounds on the street would probably not be an issue. I finally timed out my last set, Goodyear GS-D3's and don't really want to put money back into the 16's if you know what I mean. Also tire selection improves in the 18" sizes.

87350IROC

iTrader: (2)

With a statement like that I would expect to see some evidence or at least theory why you think that?

SKELITOR117

iTrader: (3)

Well the front wheels dont get any power, so you dont need worry about traction loss due to power coming from the engine. So you dont need to have fat tires in the front, 8 inches should be fine for guidence, + fatter tires = more expensive. Tires that are too wide in the front can effect handling, that's why when you look at the statistics on performance cars, wheels are almost always fatter in the rear (specifically if it is 4WD or RWD). That is my theory at least. I do not have the hard core scientific data that some of you might like.

SKELITOR117

iTrader: (3)

I used to live in Snohomish by the way. That is a beautiful area of Washington, with some great driving roads

87350IROC

iTrader: (2)

Yes that is true. However most modern sports cars also have a much better weight distribution than our cars thus meaning less weight on the front wheels. Plus my car handles very neutral right now. If I went with a fatter rear tire it would induce understeer at the limit. I would prefer to remain more neutral. Cost doesn't really bother me as the difference between a 245/40/18 and 285/35/18 is negligible especially considering the low rate at which i put miles on my car. These tires will probably last me 5 years.

SKELITOR117

iTrader: (3)

There we go then.

Guest

When I buy wheels to replace my stock 15x7s, I'm not going to settle for less than 10.5"s up front, since they will tuck. The front is the heavy end, thus it needs the most contact patch, for cornering especially.

keeslinger31

Really you need the same size tires on front and back for track racing/ for the street I like my c6 wheels #1 they're sezy #2 they are 19x10 and 18x8.5 So it understeers around those stoplight corners with ease SO street wider in the back and skinny in the front because offset is so cool and same size front to back for track racing granted its all opinion

87350IROC

iTrader: (2)

Ok guys, I picked up a BMW 18x9.5 +25mm wheel to do some test fitting. Why? because they claimed it was 10" wide and it was cheap. Oh well, it was still very useful.

In short, the rears fit with very minor relocating of the front of the inner wheel well. I was able to do this in about 2mins with a rubber mallet. The fronts will work with slightly reduced turning radius.

Now the pictures. I took a ton.

Here are the rears. There are no issues with the bump stops, with the 18's and the lowered stance the bump stop fits well inside the wheel.


Now since the wheels were only 9.5" wide I had to do some fiddling. This picture shows the wheels with a 3/8" spacer. This puts the outside edge of the wheel where my proposed 18x10 Boyds will be.


And from the front of the car. Tucks nice.


And the view from the top.


Now here is with the spacer removed, the inside edge of the wheel will be 1/8" more towards the center of the car than this picture shows.

87350IROC

iTrader: (2)

Now for the fronts. The fronts in this fitment can work with a slightly reduced turning radius. I would need to add about 3/8" to the steering stops on my Spohn a-arms. Without it, the wheel would hit the back of the a-arm at full lock. As is well documented, the tie rod fits inside the 18" along with the brake line bracket on my Koni struts. With the slightly reduced turning radius, I expect very little rubbing at full lock. Finally with this backspace (6.5") the wheel comes VERY close to the strut body. I will have about 0.15-0.20" of clearance. I am not sure if I am comfortable with that little clearance. Thoughts?

I am considering reducing the back space by 1/8" on the fronts to give me a little more strut and a-arm clearance. I am also considering 9.5" fronts to make life easier. Boyd does not advertise 1/2" widths, but I will find out tomorrow.




Strut body clearance.


Strut bracket fitting inside wheel.


Tie rod clearance.


Full right.


Full left.

itsMikey

looks good dude

//<86TA>\\

iTrader: (14)

i would go for a tad less BS in the front, keep in mind tirebulge and deflection when turning hard.

other than that, looks good!

87350IROC

iTrader: (2)

Thanks.

Yeah there a few things I need to consider as well. Ever since I revamped my suspension and brakes my passenger side front tire sits about 1/2" further out than my driver side. I suspect this is caused by either the Spohn k-member or a-arms. The passenger side tire already sits about flush with the fender and the drivers side is tucked 1/2". Fortunately, my Spohn a-arms are adjustable. So my plan is to see if I can shorten my passenger side and lengthen my drivers side so the tires sit in the same place. Then I will be able to reduce the backspace on the wheels while still keeping them inside the fenders. I should be able to decrease the backspace by about 1/4". So that would be 6.25" backspace overall. That would also help out the rim/strut clearance and the rim/a-arm clearance. I think I will also decrease the rear backspace by another 1/8" to match the fronts at 6.25". I don't want the rears to have a smaller lip than the fronts. That will also allow me to rotate fronts to backs.

87350IROC

iTrader: (2)

I did some checking and decided to go with 9.5" fronts. I just don't want to sacrifice steering angle. I have to go full lock twice just to get out of my driveway. If it wasn't for my driveway, I would definatley go for the 10's.

By the way, I suspect I could run 10.5 rears with VERY VERY little work. I just don't want that big of a stagger.

Final specs.

Fronts 18x9.5 5 7/8" backspace with a 275/35/18 tire
Rears 18x10 6.25" backspace with a 285/35/18 tire

I will be ordering today.

406TPI

iTrader: (1)

Have you got your wheels yet? I heard the Boyds had a long lead time right now.

Lonnie P

Keep in mind the design of the wheel center.

Is the Boyd thicker in the center to allow the wheel center to clear the bearing dust cover? If not you may have to run a spacer to obtain the correct center thickness & alter your wheel offset to get it back where you want it.

87350IROC

iTrader: (2)

Nope not yet. Yes it seems they are running a bit behind. I was supposed to get my wheels by Sept 1.

87350IROC

iTrader: (2)

The wheels are padded up to account for my Wilwood brakes. The pad size is 1.25" IIRC. I suspect they will fit fine. If not, I'm sure i can run a low profile dust cap to gain some clearance.

That is a good thought though. My impression is that Boyd would have thought of that already as these are spec'd for a Chevy fitment. Who knows. It is worth a look.

hellz_wings

iTrader: (2)

Curious to know about fitment as well.. I was thinking about having custom wheels made that are 10" wide IROC gold replicas (the 85-87 style) and 18" in diameter, with 285 rear and 275 front tires. Similar to what you are going to be using. Also, wouldn't the correct tire height be 40 since a 16" wheel is 50, 17 is 45, and 18 is 40? I could be wrong though, this just seems like a logical pattern?

87350IROC

iTrader: (2)

I originally considered doing 18x9.5-10 IROCs. But by the time I bought 18x8 chrome replicas, had the chrome stipped, widened, prepped, powder coated, I'd be in them well over $2k.

As for tire height, you have to remember that is highly dependent on tire width. With a wider tire, 285 vs 245, you need a lower percentage of sidewall to remain a similar height.

A 285/35/18 will read 0.8% slower while a 285/40/18 would read 5.2% slower than stock.

Lonnie P

I mentioned this because I put a set of American Racing Rebels on my car & had to do a lot of work to get the centers to fit. Had to flatten the dust covers, grind the spindle tips down etc to get everything to fit. I also have different brakes that push the wheel 3/8" outward.

Seems like many wheel designs are now tailored to front wheel drive or cars with unit bearings (such as the 4th Gen Camaro & C5/C6 vettes).

Hope everything works out for you. Post some pics when you get them.

Lonnie P

x

87350IROC

iTrader: (2)

Yeah, while my wheels are pushed out 3/8" due to the brake kit. The center hub section of the wheel will also be padded up 0.5" over a normal Boyd wheel because the Wilwood calipers stick out further than most brakes.

Were you able to find lower profile bearing dust caps, or do you have to modify your originals?

fast377

iTrader: (4)

10.5 rears would have fit fine. I run 19x11+55 rears and they fit perfect...but with no room to spare (I'm pretty low, and I'm running a 295/30/19 tire and a 4th gen rear). See pic below.

I'm also running a big brake kit, and it pushed my wheels out as well. My alignment guy was able to get everything sorted out. My fronts (19x9+44 with a 2" spacer) now sit just tucked in the fenders. The only thing that stopped me from running 10s in the front, are my coilovers.

87350IROC

iTrader: (2)

Agreed completely. But I wouldn't go 10.5" rears unless I could fit 10" fronts which is not possible with my requirements. The last thing I need is to introduce a bunch of understeer.


I'm not sure what your point here is? LonnieP and I were talking about bearing dust cap fitment.

Lonnie P

Your extra wheel thickness probably took care of any clearance issues.

I just flattened the center caps slightly until they touched the spindle.
Then removed them & used an anvil & solid bar to make them flat on the end.

I then ground the end of the spindle flat down to the point of where it was close to the spindle nut, removing the unused portion that stuck out.

Afterwards & put a piece of clay on the spindle & installed the center cap to verify the clearance.

Another clearance item was the end of the hub (around the dust shield), it actually contacted the back of the wheel. I had to run a small spacer (factory rear spacer, approx 1/8" thick) to keep the wheel from bottoming out on the hub.

I really want to go to an 18x10 wheel on all 4 corners. Currently I have a 17x9 5.95" BS wheel which is very close to my tie rod. The strut as you showed, is the limiting factor on ax 18" wheel. I want bigger tires, but do not want them to stick out.

87350IROC

iTrader: (2)

Well Genuine Boyds is out of business. Sounds like the two Coddington brothers have split. I spoke with Chris Coddington and he said he may still be able to make the wheels. We'll see.

In the mean time I have been looking at options from other companies. I think my alternate front runners are from iSS forged.

I am now also considering a gold center. I think it could look pretty good with my paint color. To see if i liked it I sprayed the center of my bmw gold. I think it came out pretty nice. Still not sure if I'm going to go this route.

87350IROC

iTrader: (2)

And here is a rough photoshop.

406TPI

iTrader: (1)

That gold looks sharp!

DBLTKE

iTrader: (1)

That looks more like bronze, but even gold would look out of place. I think that car needs silver, or polished. No chrome though.

Awesome-X

Lovin the gold center! I think it makes it look even better!

startat2

iTrader: (2)

Why not just use those BMW wheels? I think they look pretty nice!

87350IROC

iTrader: (2)

Yeah the actual color is aged bronze/brass, or something like that. Just a can I had laying around. Yeah I am not a chrome guy. My centers will either be brushed or a lighter gold with polished lips.

87350IROC

iTrader: (2)

Yeah I agree they look pretty nice, but under the paint, the wheels are chrome, which I don't want. But more importantly the BMW bolt spacing is 0.7mm smaller than GM. I am not willing to run wheels that don't fit quite right.

//<86TA>\\

iTrader: (14)

i like the gold

87350IROC

iTrader: (2)

Well I think I have finally picked out a wheel now that Boyd has gone out of business. The ISS Forged FM-8. I have been goofing around with some photoshops and have come to two conclusions, the stock 25.7" tires don't fill out the fenders quite right and with a slightly taller tire, the car would really need 19"s.

Camaro with 18" FM-8's and stock sized tires (25.7"). Look how much gap there is on the left and right side of the rear tire.


Here is the same picture with 19" FM-8's and 26.6" tires. I think it looks better.


And here is a better photo showing the 19" FM-8's and 26.6" tires.


My question is, has any ever run 26.6" tires with the car well lowered. Any rubbing issues? I will create another thread to address this issue particularly.

87350IROC

iTrader: (2)

fast377,

Now that I am considering 19's, what size tires are you using?

Thanks