Talisman51

Despite deep topic history on this, I am still lookin for feedback on stuffin my 65 wheel wells with rally wheels and rubber.

After researching all the archives and the various factory GM rally specs, I am thinking of going with Wheel Vintiques 15x6 rallys with the 4.0 backspace.

Ok....I arrived at the 4.0 based on published GM specs and my actual backspace measurement on my original 65-66 JK steel wheels (3.687). Yes...I understand that backspace is not solely a function of wheel width and offset, but also of lip geometry. Based on my steel wheels, I have measured lip heights of roughly .5 inches. I backed into lip height given a published width of 5.5 and offset of .44 with the following calc:
Measured Backspace = Width/2 + offset + Lip height
3.690 = 5.5/2 + .44 + Lip
resulting in a Lip Height = .5

So if...factory KOs are .5 wider (15x6) than steel (15x5.5) and have the same offset, this would result in a backspace of 3.690 + .25 = 3.940 or roughly 4 inches. Can anybody verify this backspace on their factory or repro knock offs? Given factory fitment of KOs, I assume a steel rally of the same dimension would clear equally well....right?

For tires, Duke and others seem very high on the Pirelli P4000s in the 215/70x15 size.

Your feedback is appreciated as always..

JimV

dmentzer

I just put a set of Wheel Vintiques rallys on my 66. I used the 15x6x3.5 which is the factory measurement. They fit perfectly and look good. They are a good wheel and what I like, is that they are made in the USA.

66since71

My parts book (Chevrolet P&A 30B) shows the 5.5" wheel (65-66) as 7/16" offset and the 6" wheel (67) as 1/8" offset. Seems to confirm dmentzer's numbers. My book is not so clear on aluminum wheel offsets, though..

By the way, if you are having them custom made for your 65/66, 15x7 with 0 offset (4.0 BS) will fit pretty nicely.

I also like the P-4000's. Bought mine in the 225/65 size though (7" rims)

Talisman51

Yes..the factory DCs (15x6) show a offset of 1/8. Given this the backspace computes as follows:
Backspace = width/2 + offset + lip
3.560 = 6/2 + 1/8 + approx 1/2

The 65-66 Steel wheel (15x5.5) with its larger 7/16 offset has a deeper backspace.
3 11/16 =5.5/2 + 7/16 + 1/2

The 65-66 KO (15x6) with its 7/16 offset computes to
3 15/16 =6/2 + 7/16 + 1/2 (assumed value?)

Can anybody measure their actual backspace on their 65-66 Knock offs to verify the roughtly 4 inch backspace?

Talisman51

Sent you a PM as well Would love some details on your clearances using the 15x7 4.0 backspace WVI wheels and pirelli's.

Also, did ya ever look at or try the factory FW 15x7 wheels. With there .30 positive offset they move the wheel in about 1/4 inch away from the fender compared to the WVI 15x7 with the zero offset and 4.0 backspace. Of course this might cause spring and e-brake issues....

66since71

Got your PM, replied.. for the rest of the forum..

Size is 225/65. Is special spec for Jaguar and available only in P-4000s.

Ran the factory FW wheels for quite a while, with 1/4" spacers. Details in the PM.. Made may mods over the years for really big tires, but with modest tires (like 215/70 or 225/65), I think only tying back the parking brake cable, and shimming the front bump stops is necessary (details also in PM)

Harry

SWCDuke

The actual offset of the '67 6" Rally wheels is .060" (about 1/16"), and this is also the offset of the KO wheels including the adapter and the '67 bolt-on aluminum wheels, and 215/70s will work with these wheels on most C2s with reasonable production body tolerance. The '63 to '66 5.5" steel wheel offset is 0.44".

The only "problem" is that the tire might rub on the steering gear carriage bolts heads at full lock, which is not a real issue because you only use full lock at parking lot speed.

Duke

JohnZ

The Kelsey-Hayes drawings show the 15x5.5 steel wheel with 0.44" positive offset, and the 15x6 "DC" wheel with 0.06" positive offset.

Talisman51

Thanks for confirming the offsets. What I missed in my computation for the KO backspace was the adapter....duh! Sounds like the adapter subtracts about 1/2 inch from the effective backspace of the knock off....yielding a 3 1/2 backspace (same at DC).

But...has anybody measured the actual backspace on the 65-66 KO? (without the adapter obviously...)

Still considering fitment issues between these wheels:
1. Wheel Vintiques 15 x 6 3.5 BS
2. Wheel Vintiquies 15 x 6 4.0 BS
3. Wheel Vintiques 15 x 7 4.0 BS

all with 215/70 rubber....

Thanks

dmentzer

As I said before, I have the 15x6x3.5 wheels. Also have the 215/70 tires with no fit or rub problems.

Talisman51

Yep....thanks for filling in the tire size.

Still would like to hear from anybody who may have experience with option two and three....

63 340HP

I have a little different 15x7x4.29 backspaced Rally by US Wheel on my 63. The extra backspace (over the 4-inch BS rim) helps to keep wide tires under stock fenders as the drum brake cars have a slightly narrower track (corrected per SWCDuke's valued input in the below post, thanks).

The concern is body alignment on the chassis. Not all C2 bodies are aligned on the chassis centerline, and with the 7-inch rim the clearance under the rear fender flange is not much more than 1/4-inch (where the difference between a 4-inch and 4.29-inch backspacing can make a tire hitting the fender lip flange ... fit).

Body alignment plays a part in what fits, as does suspension alignment (proper rear camber and toe-in), and the length of the rear spring end bolts that adjust the rear ride height (some locate the spring and spring cushion washers too close to the tire & rim).

If you want to fit a 7-inch rim and a tire in the 225 width, it's wise to buy one rim and tire and test fit it on the car at each corner. A tire shop that will help you is a great asset. With the changes most of these 40-year old cars have lived through, and the wear in the bushings that try to hold everything in alignment plus or minus 1/4-inch of movement over time can trip up the best of plans (and if Murphy is an optomist, it will trip up any "solid" advice on what hit's or fit's other than the wheel currently on the car).

Good Luck! A handling improvement from a modern H or V-rated performance tire, over standard WSW pizza cutters, is worth the effort.

SWCDuke

It's just the opposite. Drum brake C2s have about 0.6" narrower track than disk brake versions. Check any reliable specifications source.

Duke

Talisman51

Hmmm...never heard of US Wheel....another one to check out!

66427-450

if you wanty want 7" rallys..... check out 68 7" wheels for the rear, and Z-28/monte 7" wheels for the front. i used to run that combo when i autocrossed. seemed the best combo for clearance....if i remember correctly.

Talisman51

The 68 7"rs would be roughly equivalent on BS, but the 1.5 additional width would ALL be outboard into the fender. That coupled with wider than stock (215s) tires sounds and looks like trouble for the old original fender lips....

The Montes are effectively +.61 on the inboard side and + .89 on the outside.

JoesC5

I have a pair of original DC rallys 15 X 6' on the rear of my 56 ( I added the four "nubs" to secure the stock original wheel covers. Measuring from the lip to the back of the spider, I get 3.75" back spacing. The original 15 X 5.5" wheels that GM put on my 64 measure 3.62". These are actual measurements, not "specs". Since your 65 has disc brakes which sets the wheel about 3/8" out vs the drum brakes on my 64, you should have no clearance problems with the 4" back spacing on the wheels you are considering.

Talisman51

I also measured 3.62 on my 15 x 5.5s. The e-brake bracket would be the only issue on the back. Based on the spec, I thought the DC should be more like 3.5 instead of 3.75.

The calc is..
Backspace = Width/2 + offset + flange
3.56 = 6/2 + .06 + .5

Surprised to hear measures 3.75 actual...