17" Wheel backspace suggestions please

[Dual quad]

I'm thinking about some AR Torque Thrust II's for my newly 4/6 ECE droppped '72 SWB, but I need some suugestions on backspacing. I don't want to spend alot of cash and end up having to use spacers or have the wheels too sunken in the wheel housing. Here's what I'm looking at so far.

Front - 17X8 wheel (4" or 5" BS standard), 255/50-17 tire (27.0" tall)

Rear - 17X8 wheel (4" or 5" BS standard), 275/50-17 tire (27.8" tall)

AR also offers a 17X9.5 wheel with a standard BS of 5" that I could use on the rear, but I'm not sure how this would fit.

It may be that the standard backspacing doesn't work for our trucks and you need to custom order . Any suggestions on backspace are appreciated.

[lolife99]

Dual quad,... I have 17x8 and 17x9.5 wheels on my ECE 4.5/6 dropped "71 2wd Blazer. I am running 5" BS in the front and 4.5" BS on the back. (I think you could get away with a 5" BS on the rear also.) I have 255 and 275 tires you have listed above. (Nitto 450's,... from Discount Tire Direct)

[incoma]

I've also been inquiring about the proper backspacing. Everyone that I've messaged with says that 5" backspacing is ok and will work fine. I just traded some rims for some 15 X 8 ralley's. If my measurements are right, we could go with as much as 5.75" of b/s in the rear and still be ok (coil suspension). But unless you're going with some really wide tires, 5" b/s should do you fine. I believe TXfirefighter also had 17 X 8 with 5" b/s on the green stepside also.

[lolife99]

Here's a pic,...

[special70gmc]

17'' weld typhoons 8 lug 4.5 bs

[Tx Firefighter]

It was the truck I had before the green stepside, a 72 Cheyenne. You can see the green truck in the background of the picture actually. It's before I ever started working on it.

17x8 all around with 5" backspace. They cleared fine, but if I'd had my choice, I'd take 4.5 backspace with the 50 series tires you're going to be running. I thought they set a tiny bit too far under the fenderwells. The wheels were originally off of a 4/6 dropped 92 model truck is why they were 5" b.s. rather than the typical 4.5 b.s.



Here's a little 97 model truck I built about 5 years ago for a local kid. Sorry about the junky picture, it was before I had a digital camera. I dropped it 5 inches in the front and 6 in the rear. Anyway, the reason I'm posting the picture is that it has 17x8 wheels all around with 5" b.s. and the same size tires you're planning on. Nitto NT450 255/50/17 in front and 275/50/17 in rear. In my opinion, the sweetest tire combo for 17 inch wheels.

You can see my old 68 short bed in the back of the picture. It was the 1st vehicle I ever did a frame off resto of and the first whole vehicle my wife ever painted.

[68w/sbc406]

not to sound stupid............ does 5 inch BS push it out closer to the fender than 4.5, that sounds right to me, just making sure

[Tx Firefighter]

5 inch backspacing puts the wheel deeper under the fender than a 4 inch would. The more backspacing, the more inset it is.

[68w/sbc406]

oh kay, got it. like it is being measured from the back side, not the front lip

[67chevemall]

$0.02 Keep all the wheels the same.

[LONGHAIR]

67chevemall said:

$0.02 Keep all the wheels the same.

This really only matters if the tires are all the same too...or is that what you meant also?

[Dual quad]

Thanks alot for the feedback guys. Perry of PTS customs had also suggested a 17x8 with 4 1/2" BS front and a 17x9.5 with 5 1/2" BS rear, so it sounds like 4 1/2" BS with a 17x8 wheel is the way to go. Unfortunately, this is a custom wheel since American Racing only lists 4" & 5" BS as standard for the 17X8.

Although a 275 tire will fit an 8" wheel, the rear might look better filled out on a 9 1/2" wheel (Man'f recommends 7.5 to 9.5 width).

Now, if I use a 17x8 with 4 1/2" BS on the front, this means a posite offset of 3 1/2" from the mounting flange, right? (8" - 4 1/2"). So if I try to match this positive offset with a 9 1/2" rear wheel, the required backspacing should be 6", right? (9 1/2" - 3 1/2"). Am I making sense? Or just babbling? If the wheels are going to be customer order, I'd better get them right.

[lolife99]

Dual quad. I don't think you want a 6 inch backspace on the rear. For one,... go use a straight edge and a tape and see if you can clear a 6 inch bs. From the drum, back to the frame. I think the easiest way to measure for wheels is to take a " known wheel",... without the tire and mount it. Set the truck on jack stands to load the suspension. For example: Stock 8 inch rally wheel. 8" wheel w/4" backspace. Bolt that on and see which way you can move the numbers around. Also keep in mind that the truck has a "narrower" track witdth in the rear. (especially on lowered trucks) Outside of rear tires,...compared to outside of front tires, is a little narrower. Then figure that the backspace is measured from the BACK of the wheel mounting area to the back "edge" of the rim. (like laying a straight edge across the back of the rim and measuring down. Now the last thing that most people don't take into account,... is that an 8 inch rim will actually measure 9 inches! That is because the rim is sized from the "bead surface" of the wheel. (not rim lip to rim lip) Confused yet? Get a bare rim,...bolt it on,... and measure for any clearance problems. Too much money to mis-calculate! Sorry this was so long.

[bagged74]

these are 17x8s 4.5" BS and 17x9.5s 5" BS. Same tires you are asking about also.

[Dual quad]

Lolife, you are correct, too much money to mis-calculate! I'm going to take your advice re: the bare wheel and make some detailed measurements. Thanks for the insight.

I took your blazer pic, enlarged it, and modified the contrast and brightness to get a better look at the wheel/tire/body relationship. From what I can see, your setup looks pretty decent as is. If you were to do it again, would you change anything? BTW, that Blazer sure is sweet.

[lolife99]

No not really. The front is perfect in my opinon, for bagging. The front wheels are tucked in just right. For a static drop,... you could get away with a 4.5 BS on the front. (with an 8 inch wide wheel). I got lucky,...because I measured these wheels for my old '82 2wd Blazer. Just so happens they worked for my '71 also.

[Dual quad]

Just for reference, I called up Early Classics tech dept. today and asked what tire/wheel dimensions they recommend for a 4/6 drop. Here's the numbers they gave me. They also said that there would be no clearance issues in the front.

Front - 17X8 wheel with 4.5" BS, 255/60 tire (29" tall)

Rear - 17X9.5 wheel with 5" BS, 275/60 tire (30" tall)

These are the dimensions they used on their '68 SWB.

Now I've got some more thinkin' to do. Both these tires are about 2" taller than by using respective 50 series tires.

[BraveDave]

Originally Posted by Dual quad

Just for reference, I called up Early Classics tech dept. today and asked what tire/wheel dimensions they recommend for a 4/6 drop. Here's the numbers they gave me. They also said that there would be no clearance issues in the front.

Front - 17X8 wheel with 4.5" BS, 255/60 tire (29" tall)

Rear - 17X9.5 wheel with 5" BS, 275/60 tire (30" tall)

These are the dimensions they used on their '68 SWB.

Now I've got some more thinkin' to do. Both these tires are about 2" taller than by using respective 50 series tires.

i would go with a 5-inch backspace in the front. i had the smaller backspace at first and the tire rubbed on a hard turn.

rule of thumb - measure 10 times, buy once.

[5150]

What would be the problem with running 255's all the way around?

I know it's a stupid question, but enlighten me please.

[71/454]

I went to order 17x8 wheels from centreline asked for a 5 inch backspace and they said they would not warranty the wheel with a 5 inch backspace for my type of truck (71gm lowered 3 inches using spindles) just my 2 cents. Also I run 255/50s on the rear and is really short, runs out of gear when you get the speedo on the good side. Smitty

[Tx Firefighter]

That's crazy of them to say. 5 inch BS is the most common backspace on a 17x8 wheel. All the 4/6 dropped trucks from 88-98 used that backspacing.

The little blue truck I posted above has 5 inch BS and those are Centerline wheels on it. I've had several sets of them like that myself. I never ordered from Centerline though, always Summit.