: Proper Offset for a 10.5" Rear Wheel...



thebigjimsho
06-03-11, 11:10 AM
Does anyone who has custom rear rims know what their offset is? I'm looking at the TSW Nurburgring and know the 18x9.5" wheel has been successfully used F + R. But if I can get a 10.5" wheel and 305 road course slick back there, I'd be stoked.

Even if I did something like a 275/35 18 all around, I'd still like to run staggered wheels, if I could...

gnxs
06-03-11, 11:42 AM
Does anyone who has custom rear rims know what their offset is? I'm looking at the TSW Nurburgring and know the 18x9.5" wheel has been successfully used F + R. But if I can get a 10.5" wheel and 305 road course slick back there, I'd be stoked.

Even if I did something like a 275/35 18 all around, I'd still like to run staggered wheels, if I could...
I think a 10.5 inch wheel with +44mm offset would be equivalent to the factory sedan rear wheel (9.5 +56mm offset I believe). However, if you're going to put a wider tire on (305, 315), then you might want something closer to a +40mm offset to allow a little more clearance (.2") in the wheelwell.

My $0.02.

TMC CL65
06-03-11, 11:59 AM
Maybe this offset calculator will help (although always a little skeptical on actual fitment):

http://www.1010tires.com/wheeloffsetcalculator.asp

Tom

musclesbmf
06-03-11, 02:28 PM
Offset would need to be no less than 54... That is putting the wheel 15mm more outward. you need to measure the face of the stock wheel to the edge of the fender and see what the distance is. I bet it is less than 15mm.
A 44mm offset will make the well come out 1 inch, so basically your wheel would protrude outside the fender.

Mark

thebigjimsho
06-03-11, 02:37 PM
Thanks, guise.

The 18 x 10.5 TSW isn't even close in offset so that's out. I think I'm just going to do 18 x 9.5" since it can be rotated and it's been done by at least 2 here...

musclesbmf
06-03-11, 03:40 PM
On the 9.5, if the offset is 43 or 44, you would be sitting about flush with the fender I believe.

gnxs
06-03-11, 04:11 PM
Offset would need to be no less than 54... That is putting the wheel 15mm more outward. you need to measure the face of the stock wheel to the edge of the fender and see what the distance is. I bet it is less than 15mm.
A 44mm offset will make the well come out 1 inch, so basically your wheel would protrude outside the fender.

Mark
He's talking about a 10.5 wheel vs. the factory 9.5. If he bought a 10.5 inch wheel with a +56mm offset, the backspacing would be .5" deeper and would very likely rub somewhere in the wheelwell (assuming no wheel spacer). I believe you'll have to make the sacrifice of moving the lip of the wheel outboard a bit to fit an inch wider wheel under there.

musclesbmf
06-03-11, 04:21 PM
He's talking about a 10.5 wheel vs. the factory 9.5. If he bought a 10.5 inch wheel with a +56mm offset, the backspacing would be .5" deeper and would very likely rub somewhere in the wheelwell (assuming no wheel spacer). I believe you'll have to make the sacrifice of moving the lip of the wheel outboard a bit to fit an inch wider wheel under there.

I know what he is referring to, and I know what I'm talking about (not being rude). There is approx 12 - 15 mm of space between the wheel face and the outside of the fender. That is basically half an inch. So the wheel can only be a half inch wider on the outside, and thus a half inch wider on the inside. To accomplish this, you leave the offset to factory (because we are equally splitting the 1 inch to inside and outside).

Trust me on this. I just went from 10" coupe wheels to 11" aftermarket and I think I added 1 or 2 mm to the offset to get flush. you can check my pics for reference, or also use that nifty calculator that was posted above. Results are accurate.

Mark

gnxs
06-03-11, 04:35 PM
I know what he is referring to, and I know what I'm talking about (not being rude). There is approx 12 - 15 mm of space between the wheel face and the outside of the fender. That is basically half an inch. So the wheel can only be a half inch wider on the outside, and thus a half inch wider on the inside. To accomplish this, you leave the offset to factory (because we are equally splitting the 1 inch to inside and outside).

Trust me on this. I just went from 10" coupe wheels to 11" aftermarket and I think I added 1 or 2 mm to the offset to get flush. you can check my pics for reference, or also use that nifty calculator that was posted above. Results are accurate.

Mark
You're noting how the wheel fits in relation to the fender and I'm merely noting ralates to the fit of the factory wheel (regardless of the fender). I use this calculator when sizing wheels for a few cars (including my CTS-V Sedan) and it's worked well for me so far:

http://www.rimsntires.com/specs.jsp

Seems we're both saying the same thing only you're focusing on how it sits in relation to the body and I'm focusing on whether the wheel (with a wider tire) will rub on the inside. Is anything on my previous post, that you quoted, inaccurate?

musclesbmf
06-03-11, 05:01 PM
I see what you are saying... Rubbing on the inside would not be an issue for sure. It wouldn't look too pleasing sitting outside the fender about an inch though :-)
good stuff!!

Caddy Wagon
06-03-11, 05:54 PM
TSW Nurburgring comes in a 10.5 wide with a 65mm offset. That would push the wheel outward an extra 4mm over a stock 9.5" 56mm offset sedan/wagon wheel. I know at least one car running the 20x10.5 rears in that wheel.

Razorecko
06-06-11, 08:39 AM
Yea I was looking at these wheels prior also. Great price for a lightweight wheel. Though never was sure if the rear 18x10.5 would go with a 65et

thebigjimsho
06-06-11, 01:22 PM
I'm going to give a hard look to the 10.5" wheel and see if I should try or not. Maybe I could work a deal for a single wheel to test fit first...

BLitzkrieg
06-06-11, 01:25 PM
I have the 20X10 35mm offset coming tomorrow. If they don't work I will RMA them and swap for the 20x10.5 65mm. I will post up the results along with where I got them from cheap.

thebigjimsho
06-06-11, 05:19 PM
TSW Nurburgring comes in a 10.5 wide with a 65mm offset. That would push the wheel outward an extra 4mm over a stock 9.5" 56mm offset sedan/wagon wheel. I know at least one car running the 20x10.5 rears in that wheel.
The C5 Z06 18x10.5" wheel has a 58mm offset. But that needs a small spacer to clear inside, right? If that's the case, a 65mm offset sits the wheel closer to the inner wheelwell. So I'd guess this also needs a spacer, albeit bigger...

BLitzkrieg
06-06-11, 05:23 PM
Keep in mind there is 1" more in radius clearance. I used a 1" wide tape measure and managed to make is all the way around between the stock wheel and inner components so I have higher hopes then the wheels I an getting tomorrow.

thebigjimsho
06-06-11, 07:10 PM
The C5 Z06 18x10.5" wheel has a 58mm offset. But that needs a small spacer to clear inside, right? If that's the case, a 65mm offset sits the wheel closer to the inner wheelwell. So I'd guess this also needs a spacer, albeit bigger...


Keep in mind there is 1" more in radius clearance. I used a 1" wide tape measure and managed to make is all the way around between the stock wheel and inner components so I have higher hopes then the wheels I an getting tomorrow.
But I'm talking about the Z06 wheel, which is already 10.5". If that needs a small spacer, surely the TSW will need a larger spacer with its greater positive offset...

BLitzkrieg
06-06-11, 08:30 PM
Possibly but I'm talking about a 20" wheel and not an 18".

thebigjimsho
06-06-11, 10:51 PM
Possibly but I'm talking about a 20" wheel and not an 18".
That really shouldn't make a difference. The tire/wheel width and diameter should all be the same whether an 18" or 20" wheel...

Caddy Wagon
06-07-11, 12:23 AM
That really shouldn't make a difference. The tire/wheel width and diameter should all be the same whether an 18" or 20" wheel...

The difference will be the a-arm clearance. If you run a 20" wheel vs an 18" wheel, the wheel will probably clear the lower a-arm with a 20 and rub with an 18.