Please help stop an expensive mistake - rims on '63 5 lug swap

[J1MMY]

I apologise up front for being a bore but the availability of wheels over here is limited and you'd find the price of them hair raising.

I am looking at buying 8x18 4.75 backspace for the front and either the same for the rear or 9x18 5.25" backspace. The truck is lowered 5.5" at the front and 6" at the back. I have measured up and mocked up and am pretty sure that the fronts will tuck in the arches (rolling the lips will help too) but I am unsure about the rear, particularly the 9's.

If anyone has fitted this combo (or part of it) on a fleetside, or is aware of such a combo on a 5 stud converted truck please do chime in. I've gone through as many wheel/tyre and static drop threads as I can.

Thank you.

[joedoh]

backspace is measured from the back of the wheel to the mounting surface. so if we take an 8" wheel and subtract 4.75 backspace, we are left with 3.25" "frontspace", which is how much the wheel sticks out past the mounting surface. doing the same math for the 9" minus 5.25, we get 3.75" frontspace.

to figure out if it fits your truck, jack the truck (under the axle) up so it is level, take off the rear wheels, tie a bolt to a string and tape it up high inside your fender so it hangs down and measure from the brake hub to the string. this measurement is the max frontspace you can have. measure BOTH SIDES because the panhard bar can pull the rearend off center.

one more thing though, the lips of the wheel are not included in the width measurement and add usually 1/2" to the front and back of the wheel. add 1/2" to the measurements above, so 3.75" frontspace for the 8" wide wheel and 4.25" frontspace for the 9" wheel. tire bulge can add a little too!

[LVPhotos]

18x9.5 and 18x8 with 4.5" back space each and 295 45 rear 245 45 front.

[dwcardfan]

I have 8x18 with 4.5 inch backspace front. Rear is 9.5x18 with 5.5 backspace. It is lowered 3" front and 5" back. Hope that helps. It has a 1972 rear end. Which is 1.75" wider.

[63 & 64 Bowties]

Since wheels are so expensive in the UK, one thing you may look at, do a search for Percy Wheelrite. It's a tool to measure fitment on wheels/tires combos. It's pricey in my opinion (about $77 US) but it gets good reviews, and the only sure way to know if something will fit as far as I know.

[duallyjams]

http://67-72chevytrucks.com/vboard/s...ight=18+wheels
http://67-72chevytrucks.com/vboard/s...ight=18+wheels
http://67-72chevytrucks.com/vboard/s...d.php?t=673354

[joedoh]

Originally Posted by 63 & 64 Bowties

Since wheels are so expensive in the UK, one thing you may look at, do a search for Percy Wheelrite. It's a tool to measure fitment on wheels/tires combos. It's pricey in my opinion (about $77 US) but it gets good reviews, and the only sure way to know if something will fit as far as I know.

80 bucks? shipped overseas? and the reviews arent that great. for what its worth I gave him an example on how to do the exact same thing with a string and a nut (use a metric nut even, UK guys!) and gave him the math to figure out the perfect backspace.


wheel fitment isnt about a singular measurement either, wheel width and backspace are interrelated, so a 18x8 with 4.5 backspace that tucks inside the fender only translates to a 18x8.5 IF you calculate the frontspace, first.

8+1 (for lips) = 9 - 4.5 backspace = 4.5 frontspace.

so a 8.5 wide wheel would need 4.5 frontspace, solving for backspace needed would be

8.5+1=9.5-4.5 frontspace = 5 backspace.

and you can do it for any width. the backspace is only the relationship between the rim edge and the frame, which isnt the limiting factor until you get to widths over about 10". frontspace is what you need to compare wheels to each other and once you get the formula down you can almost do it in your head.

let me know if you also need the formula to convert backspace to offset, that is where the discipline of adding the inch for the lips really matters.

[ptc]

You have to take into consideration what rear end is in the the truck and front end. (if not stock).

Like joedoh stated lust hang a string down from inside of both the front and rear fenders and get a measurement of your OVERALL width. This will be your MAX width with tire bulge and everything considered.

For the rear; deduct the total rear end width. (from drum face to face) whatever is left over is what you have to work with.

Example: 80" overall width - 68" rear end = 12"/2 = 6" on each side of the drum face. An 8" rim with a 4" backspace would leave about 2" between rim and fender. assuming about 1.5" of tire bulge and you would have .5" of gap between fender and tire face.

Do the same exercise for the front.

string and nuts cost about $1.00 US

[J1MMY]

Thank you for all the input - the pics and accompanying info have been extremely helpful and I have spent some time measuring, measuring and measuring some more.

As it happens I had a rare stroke of luck today and scored some refurbished van Ralleys with trim rings and centres at a snip of a price. I am going to run these but will report back on my eventual wheel choice so that others using the search might find the info useful.