Help me spec an offset for new wheels?

[Satatic]

I am going to get 20x10 wheels and 305/25/20 tires for my 68 camaro (on the rear) but after measuring out the wheel wells and axle everything else just confuses me. I made a ms paint drawing with my measurements on it.
https://static1.pt-content.com/images/pt/2009/09/rearwell-1.jpg

The inside measurements are inside wheel well lip to spring. I would like to have the wheels closer to the spring because i fear that the tire could rub where the back part of the wheel well arc curves inward. I do not have rolled lips because of the aluminum trim.

The axle is not welded to the spring perches yet so i think the measurements should both be 5 5/32 to split the difference. And then use the smaller of the wheel well depths. Also there will be a disk brake on there so that puts 1/4 inch onto the axle flange.


For the front i have not taken any measurements yet but i want 18x8 with 245/40?/18. Its pretty stock up front the only thing I did was remove the stock disk/hub and install drum brake hubs onto the disk brake spindles. That made the wheel go in further I think, or out farther i cant remember which one. I will measure that sometime soon.

Well thanks hope to get some help i havnt had any bites on other forums yet.

[ProdigyCustoms]

Looks like you put in some shallow mini tubs? How wide is the rear axle flange to axle flange with or without the brake rotors (let me know)

[Satatic]

I am not sure what you mean. The tubs are actually a tiny bit wider than the measurement, i just measured to the spring. w/ offset shackles.

[ProdigyCustoms]

Normailly we see 14 1/2" clearance on Mini Tubs. 13 7/16 seems shallow, but I have seen them installed taht shallow.

Anyway, based on the width of the rear, I can help with backspacing.

[Satatic]

It is 14 1/2 deep. The measurement is to the springs. My axle is 60" outside to outside with no rotors.

[ProdigyCustoms]

11" wheel with a 7" BS and a 305 tire.

[Satatic]

The wheels I am getting only come in 20x10 so 6 inch?

[ProdigyCustoms]

What wheel are you looking at? What tire size combo you running. Can they weld the center in where you want it or is it a limited selection of BS. 6 1/4 may be more safe since 20s can be tall. Depends on the tire size. You just want to protect your front space. Keep you outer wheel profile where you want it so the wheels are not to sucked in (my pet peeve) or to far out is obviously a huge issue.

[Satatic]

http://www.bossmotorsports.com/custom_chrome_wheels.cfm?id=408 in black

[Satatic]

I saw this in the tech spec section is that close?
20x10 Super Finish Black 5 on 4.75 20 mm 6.225

[ProdigyCustoms]

Perfect!

[Satatic]

What do you think about the front?

[Satatic]

Looks like there is only one option for the front
18x8 Super Finish Black 5 on 4.75 +2 mm 4.517

Will that work too?

[ProdigyCustoms]

Those wont work. You will rub the outer fender.

You need at least 4.75 for the front, 4.875 is even a better fit.

[Satatic]

I mentioned that i have the drum brake hub on disk spindle up front does that change any measurements? I have 5 7/16 from the outside of the rotor to the outside edge of the fender, Where there is kind of a square edge. I am not sure that is the best place to hang a string from.

[ProdigyCustoms]

You still need that extra 1/4".

[Satatic]

My friend was saying when we were looking at the wheels that they are custom and come in any dimensions i want. I just figured he was mistaken when i saw the specs on the boss website. So i will run the numbers by him and see if maybe they do also do them custom.

[ProdigyCustoms]

Good luck, If you need anymore help, let me know

[camaro2nv]

Those wheels are cast and fitment is very limited.

[Satatic]

Maybe i could get 1/4 inch milled off the back side :lmao: but seriously?

[camaro2nv]

Depending on how thick the pad is, yes you can. Do you like the wheels that much?

[Vegas69]

And will they still clear your brakes after the milling....

[ProdigyCustoms]

Most cast wheels cannot stand to have anything milled off. The lug holes will most likely get to shallow.They are already cast, I would not want to risk it. I am not saying it would be a problem, but I would never authorize it

[ProdigyCustoms]

OK, I admit it, i just looked at the wheels for the first time.

NO WAY you can mill a 1/4" off that wheel.

[Satatic]

Depending on how thick the pad is, yes you can. Do you like the wheels that much?

Well I do like them. The other part is $ and since my friends shop is the dealer than that hopefully means even less $

[JRouche]

Those are some sharp looking wheels. And I ran into the same issue you are hitting right now. I was shopping high and low for wheels. Many of the wheels I loved were cast. Which I dont have an issue with, but the back spacing I needed just wasnt available. So I HAD to go with a billet wheel where they can custom weld the center in. The cost is around 200 buck a wheel more for the wheels I was looking at. But really... Im glad I went that direction. Now I have piece of mind and can sleep at night knowing I wont be scrubbing the fenders. Or worse yet, hit a dip on a sharp turn and curl in the rear of the fender!!!! Really bad.

And really, if you wanted to keep within a strict budget a 7" wheel with proper back spacing would look great too. Dunno if you would have a better back spacing with their 7" wheels but something to think about.

The diff between a 7 and 8 inch rim with different tires can be almost un-noticeable. For example, get a tire with a wide sectional width for the wheel used. The tire is what hits the road and for the most part is whats seen. Yeah, but you dont want too much, that fat tire bulge is silly looking too. JR

[Satatic]

Hey look what I found http://www.camaros.net/forums/showthread.php?t=159541

[MonzaRacer]

Well if your dead set on the wheels change your front bolt pattern to 5 on 4.5 as they have a 4.989 backspace, by Franks opinion that would probably fit perfect, I dont understand why you shouldnt be able to custom order the larger bolt pattern but who knows till you call Boss. Depends, which would be cheaper, redrill/replace your hubs and rotors and rotors.

[Satatic]

Hey now thats thinking!

[Satatic]

https://www.made4uproducts.com/cart/proddetail.php?prod=80-21392 I ordered this in anticipation. I believe I should be able to slide it over my lugs and mark out the 4.5" lug holes. I think the back side of the hub the lugs may end up slightly in the contour. Will just have to grind a little, if there are no objections?

[Satatic]

Ok update i tried to get the front wheels in the 5x4.5 but the guy at the warehouse said no we just did a 69 camaro with these and if they dont work send them back. So i got all my wheels in the 5x4.75 and here is whats up. The front w/rotor the edge of the wheel lip is even with the inside edge of the fender. No good. The rear w/rotor, the edge of the lip has 1/4 inch clearance to the inside edge of the quarter lip, at least 2 inches clearance to the spring.
The specs are
20x10 5x4.75 +20mm offset
18x8 5x4.75 +2mm offset

So my plan now is to send them back and get
20x10 5x4.5 +35mm offset
18x8 5x4.5 +14mm offset

and drill my hubs and axles to match.

[Vegas69]

You should of took the advice of the veterans around here the first time around......

[Satatic]

That advice would have had me spending Gs on wheels. I would rather spend 700 and a couple days scratching my head.

[Vegas69]

I'm not talking about buying forged wheels, it's backspacing.

[buickfunnycar.com]

I don't like this new plan...

[Satatic]

How come you dont like it?

[MonzaRacer]

Hey if your ok changing the wheel bolt pattern to get the offset whats wrong, and after it all fits if you have 2 piece hub/rotor talk to tobin at Kore3 they might be able to make a new hub with only one bolt pattern.
But if the numbers fit what Frank says will work, go for it.
I dont know if I would use 5 x4.5 on both axles if oyu can get proper offset with stock bolt pattern and just change up front.
We used to get solid pipe plugs, drill and tap hubs and install them, then let local welder to some tack welding on plugs then move to bare spot and redrill and use either new screw in lugs from moroso and use local friends lathe to smooth the face after cutting majority of plug off first. This re-strenghtens the hub where as if its got 2 sets of holes it allows cracking.
We had a guy bounce frontend of drag car and bust old drum hubs that had been redrilled, in lieu if fixing his suspension so it didnt pull a 5ft hop and bounce HARD we did this and after he took it off road and started turning corners he hasnt cracked a single one yet and hehad a big set of roadrace wilwood brakes all along. Never could figure out why he would pay us to make hubs when he could have bought a set from wilwood.