Backspacing, 5" or 42mm?
Thread Starter
Senior Member
Joined: 05-22-2009
Posts: 240
From: Rough & Ready, NE Calif
Backspacing, 5" or 42mm?
Just got off the phone w/ Summit Racing re: 6.5" x 16" chrome ralley rims. I'm confused now by the listing for backspacing. Their guy says that he shows 5" backspacing; I thought that the HHR used 42 mm. Just what is the deal on this???
Mo
Mo
Senior Member
Joined: 12-14-2007
Posts: 2,964
From: Toronto ON Canada
offset and backspacing are two different measurements. 42MM is the offset of the mounting surface from the centerline of the wheel. Sounds to me like he is measuring 5" from the back edge of the rim to the back of the spokes, which is the room for the brake calipers. Any backspacing measurement is approximate as it doesn't account for varying shape of the wheel or caliper size/location. Bottom line - youcant be sure it will fit until you try it.
Senior Member
Joined: 01-13-2008
Posts: 4,708
From: Washington State, where it rains
Backspacing measures from mounting surface to inside rim edge......offset measures from mounting surface to centerline of rim,,,simple math will tell if they will fit. Answer is 44mm offset. Which is maybe too much as stock is 42mm....meaning the wheel/tire will stick "inside" the wheel well farther..your better off going to a 35mm offset and get the wheel closer to the edge of the fender,so you would need an backspace of 4.75 with a 6.5 wide wheel...Soooooo..if you went with a 7" wide rim you would wind up with the correct offset. 7" wide divide by 2 is 3.5(centerline)...backspace is 5" so there is a diff of 1.5" which equals the space from mounting surface to wheel centerline..1.5" converts to 38 mm offset. Stock SS rims are 7" with a 42mm offset for comparrison.
Thread Starter
Senior Member
Joined: 05-22-2009
Posts: 240
From: Rough & Ready, NE Calif
IgottaWoody,
Thanks for the explanation; I now know everything I needed to know. After talking to Summit again, they absolutely assured me that that rim was built for the HHR...
Mo
Thanks for the explanation; I now know everything I needed to know. After talking to Summit again, they absolutely assured me that that rim was built for the HHR...
Mo
Joined: 07-29-2017
Posts: 1
From: Texas
G'ing up my "Onyx".
I have 20×8.5 rims that I'm wanting to sport on my 2010 hhr lt.the offset of the rim is 20mm.will this wheel fit with 225/35/20 tire or will I have rubbing issues cause of the offset.if so would spacers make a difference.
Senior Member
Joined: 09-16-2013
Posts: 1,408
From: Tampa, Florida
Not only rubbing you will have straight overlapping with the setup. Unless you get custom hub centric spacers, which are costly, then I'd say go with something that would fit without modding. And I don't think 225 would work with a 8,5 inch rim*