Harrison Cobra Rear Wheel offset

hp1050 · #1 (**permalink**) 07-12-2012, 11:15 PM

I have a Harrison Cobra with the Skyline R32 rear end I want to order a new set of 18 x 10 rear wheels just as a sanity check the offset is 130mm? and the PCD is 5 x 114.3?

The car is in QLD and I am in Melb so I can't measure it up any help would be appreciated. Thanks

PS: Tried to ring Warrick and the phone is disconnected?? Is he still in the same shop?

07cob · #2 (**permalink**) 07-13-2012, 01:34 AM

hp1050

130mm sounds about right for the distance from the bolt up face to the outer edge of the rim. I had mine made up to 125mm for this measurement. Difference can be accounted for in that my rims are 16" and the tyre bulges about 5-10mm from the outer edge of the rim. Your 18"s will have much less bulge, probably about 0-5mm.

As I understand it, OFFSET is the distance from the centreline fo the wheel to the outer or inner face of the wheel. This will be different depending on the width of the wheel. I stopped using the term with wheel manufacturers as each seems to have a different interpretation.

Cheers

Geof

400TT · #3 (**permalink**) 07-13-2012, 02:51 AM

What you guys are describing is "wheel backspace".

See if you can give Warwick a call to confirm.

Warwick is contactable on mobile only these days. The number is on his web site: Cobra Kits: Home

Rog246 · #4 (**permalink**) 07-13-2012, 03:01 AM

Hey HP
PM me and I'll send you some wheel offset charts, as well as what Warwick advised for mine, with 9's on the front & 10.5's on the rear

Rog

Merv and Sharon · #5 (**permalink**) 07-13-2012, 04:02 AM

I used Dragway wheels on my Harrison. I used the diagram on their website to do all the measurements. The wheels fit perfectly. Call Dragway they have all the measurements for Harrison's. If not I can send you my measurements.

07cob · #6 (**permalink**) 07-13-2012, 04:39 PM

Quote:

Originally Posted by 400TT

What you guys are describing is "wheel backspace".

... or frontspace in this case, Craig??

Merv and Sharon · #7 (**permalink**) 07-13-2012, 11:52 PM

If you go to Classic Wheels and then Offset Chart you get a useful diagram with the necessary measurements.

I am no expert and I had an unfortunate experience with another set of wheels after using measurements that I derived from other owners of Harrisons. They all vary in the way that the chassis sits on the frame (L-R) and the type of suspension fitted (typically R32 or R33) and also with how the suspension is set up.

On the chart (above, but I will send this by email) measure all four wheels carefully with a ruler and straight edge and determine the required measurements that keep the eventual tyre (your 18"s) within the 'guard edge and not hitting any suspension or brake components on the inside. Take your time with this step as it is the most important. Then talk to Dragway or another provider.

For my 17"x 8" rims, I eventually used a front space of 78mm on the Front and for the 17' x 9.5" on the Rear, 94mm. Fit is perfect, even with my larger AP calipers and disks. You can determine backspace as well using the diagram for a known rim width.

Not sure what bolt pattern that you have but they may vary from front to rear on some Harrisons (GM/Ford/Nissan).

400TT · #8 (**permalink**) 07-14-2012, 07:18 AM

Quote:

Originally Posted by 07cob

... or frontspace in this case, Craig??

Sorry did not read the post clearly. Yes it is frontspace, the remainder is backspace.

Offset is is the relationship of the bolt up face to the centreline of the wheel.

Good advice from Merv. Warwick should by able to give you his recommnedations. I would contact Warwick first and then confirm the measurements yourself taking into account your wheel alignment and suspension travel.