4" backspace vs 4.5" backspace
 

Hey guys! Been a year for me to post or so. I am ordering up some rims and tires for my supercharged 71. I have been reading old threads for days and I am confused. I want my rear wheel to be flush with the rear fender. I attached my red vette (ignore wheels, wrong size and came on it with spacers). The blue one with polished aluminum has COY's with 4" backspace. The blue one with grey centers has Boss 338's with 4.5" backspace. You can see in the picture the 4" backspace is flush with the fender. I really like that look.

Right now, it appears I am ordering those coys in polished (even though its a 2 month wait). I like grey centers but I want a polished lip (not machined clearcoated). The ONLY wheels I can find that are polished lip are the Boss 338 but they only come with a 4.5 offset. The Torq-Thrust M looks like it has a polished lip also. But anyways, I am looking at 18x8's all the way around, 255/45 up rear and 245/45 front, 0 offset.. backspace to be determined. Someone told me I could get 4.5 and just put in a spacer but I dont want to do that, I do like the big deep lip on the 4" backspaced rim.

Any advice on this 4 vs 4.5 you could offer would be much appreciated.

do it right and get the 4'' backspace wheels:

http://i128.photobucket.com/albums/p...ps59a0093d.jpg

4 1/2" BS with 8" wheels will tuck the wheels in too far. The fronts will rub on the frame when turned at full lock.

Search for the following on google:

Rocket "booster" wheel

and

Ridler 695 series

Both are classic 5-spoke designs

vetfever

I'd go with these; you can get any backspace you want.

American Racing Classic Torq Thrust II

I wish they had those when I was looking at wheels last year, although I doubt I would have paid the money for those

I tried some 7" 74 Chevelle rally wheels on my 69. They are 15x7with 4.25" backspacing and come within a quarter inch of the lower spring in the rear. I guess that would be why C3's in 7 and 8 inch came with 4 inch backspacing. They might also come through the top of the inside fender well on a hard curve which is pretty close to the back of your head....
:cheers:

If you're considering going in that direction check out
Vintage Wheel Works and Team III E/T Classics

I have 4" back space and they still werent to my liking as far as stance....put 1" adapter front and 1.25" in rear

Also lowered front 1.75" and rear 1"

To me stance makes it or breaks it

that rear tire sticks out way to far

Still think so?

nope, must be the camera angle :thumbs:

good! your vette has a nice stance :thumbs:

Thanks. it looks just like yours :D

Thanks for all the replies! I agree 4" backspace. American Racing wants 350ish for a 4" backspace wheel. Vintage wheel works are awesome looking wheels but $400 a wheel.. I emailed boss this morning asking if they could make the boss 338 with 4" backspace and if so how much. So far the fully polished coy's are winning but will take months to arrive. Any of you running a 9.5" wheel on the rear? I see some people are but I keep wondering what kind of offset they have and if they had to make modifications. I'll probably end up sticking to 18x8 all the way around.

I'd hoped that Coys could be made available sooner but guess not. Except for the arrival delays, they are a good product at a fair price.

I spent an inordinate amount of time measuring and double checking my car before pulling the trigger. Realizing each car will have minor variances, I made the choice to stuff as much rear tire as possible without exaggerating the tire past the fender line. The drivers side is subtle enough that I'm pleased with the result.

See the small white tag in the following pic. Shows the wheel data:

http://i259.photobucket.com/albums/h...7T2/Coys04.jpg

Once the 285/40 tires were mounted, the drivers side shows more than the pass. I attribute that to the factory dimensions of how the rear axle is mounted:

http://i259.photobucket.com/albums/h...-2009_009a.jpg

http://i259.photobucket.com/albums/h...-2009_010a.jpg

I also had concerns about clearing the standard length VB&P rear spring. Once settled, it's not an issue. Drivers side:

http://i259.photobucket.com/albums/h..._2-09_105a.jpg

Pass side:

http://i259.photobucket.com/albums/h..._2-09_106a.jpg

http://i259.photobucket.com/albums/h...MG_7023a-1.jpg

On purpose, there are no mods made to the frame or body. No adapters used either.

Rest assured that if you choose to stay with 8" wide and 4" bs at each corner, you should be safe from any interference issues. Afterall, those are factory dimensions.

Good luck.

MY NUMBER ONE design/engineering requirement is that the wheel centerline remain as per stock, so if you have say an 8" wheel, and it was stock, like on my '72.....the width increased by 1.5" when I went to '89+ C4 wheels.....the overall tire DIAMETER remained the same as was stock tires.....

NOW, that divides out to 3/4" increase in width per side, and so to move the ebrake from behind the tire.....relocate that bracket, I find I have almost no more room to be against the sway bar.....
I limited the steering radius in front to keep tires from rubbing frame....added a bolt/nut/washer/spacer to the lower rear rub pad on the A arms....

but the salient point IS, to keep the same wheel/tire center line or you will be straining the rear suspension, and front also, anything from bearings on to bushings.....not such an issue with a solid axle say link in an old GOAT, truck some such.....in the REAR that is.....

:thumbs:

Thanks Dustup7T2. So you fit the coys with 18x9.5 5.5 offset with no modification? I have stock leaf springs (for now). Do you have a shot of your car from the rear (whole picture?). I was ruling 9.5's out as I thought I would have to buy offset trailing arms. Kinda sucks having to order this stuff online and HOPING it fits :) I see you're in NY.. I am by Ithaca.. not sure how far away you are.

You're welcome, a-c-Matt. Though I haven't yet visited the fine state of NY, I'm a little further west of you, very near the Rocky Mountains of Colorado.

Thanks for the questions. Having struggled myself to find a working solution, I feel your anticipation locating the right combination of parts to suit your vision.

Bear in mind too: your mileage may vary. Meaning: what works for one may not work for all due to manufacturing variances (but it's close enough so that you shouldn't have to come back and punch me...very hard).

Check it out:

http://i259.photobucket.com/albums/h...0_5-27018a.jpg

I DO have offset trailing arms. I have stated this before and frankly, they did not offer any more clearance than OEM units. Mounting a 285mm wide tire on a wheel with 5.5in of bs, clearance with the car's frame and body turned out to be the main concern.

The primary clearance benefit realized of the offset TA's was having the e-brake cable relocated over the top of the arm (note in following pics), as opposed to the OEM cable tab location on the tire side of the arm. Otherwise, having new bushings and wheel bearings were the biggest plus. The e-brake cable should run across the top with these wider tires to avoid interference problems.

In actual operation, I have kept an eye on where the tire makes contact with the frame or body. See the following,(drivers first):

http://i259.photobucket.com/albums/h..._1-23_104a.jpg

Pass side:

http://i259.photobucket.com/albums/h..._1-23_102a.jpg

The next shots show the rub on the inside of the tire's tread. These contacts are not a constant; they only occur when I hit a bump at speed so it's a momentary "kiss".

http://i259.photobucket.com/albums/h..._2-09_101a.jpg

http://i259.photobucket.com/albums/h..._2-09_102a.jpg

I suppose if I always carried a heavy load (full-size kegs of brew, truck-load of ammo, a fat chick, etc) tire rub might be a bigger problem but with a bucket of chicken wings, 12-pack (hey, I share), golf clubs, and the iPod, it's a non-issue.

Put another way, after 4 years, I wore this set of tires out from cruising around, auto-crossing, and a few knarly burn-outs. Tire interference never materialized as a problem.

I hope this helps and keep us posted on what you end up doing. Remember, we love pictures so you gotta show us.

Again, good luck. :thumbs:

That is a killer stance, beautiful!