Backspacing?

When the weather cools down some I going to start working on back-halving my car with a 4 link setup. I'm tired of playing with the stock suspension and putting money into it. Right now I'm in the planning stages on figuring out what the length of the new axle will be. What is the norm for back spacing on the rear wheels?

I got your wheels Grandpa !

Mine are 4 " in my 4 link car.

Doug I believe the general consensus is that the shorter the axles the lower the rotating weight and total weight of the rearend as well. That being said I think the most common backspacing will be in the 3.5- 5.5 range. If you go with 3.5 and leave an extra couple of inches on each side to the frame rails then you have the option of going to a bigger wheel tire combo later by increasing the back spacing.

I think a lot of guys opt for the big Chevy bolt pattern as well. That way the wheels resale value may be higher.

dkp

How big of a wheel/tire?

Thanks guys! I figured that most would go for the shorter axle for weight purposes and most of the wheels I've seen intended for this are in the 3-5" range on the backspacing.

John, I haven't made up my mind yet, but might be 15x33's. The wheels my Grandson is taking about are 15x14 with 5.25 backspacing.

Here's what I've drawn up so far, just need to verify the tires will have enough clearance from the fender lip. I'll definitely be ordering gun drilled axles to cut down the weight.

Screen Shot

take into consideration the driveline angles changing if you sit those tall tires up into the tubs to keep the rear ride height the same as it is now.

Keep the backspacing in the whole or halfs. Just easier to pick up a new set of wheels that way. Make sure you check for what Fabio mentions too. I have some 32x14.5 ET Drags on mine and the trans needed to be jacked up about 2.5" in the rear and the motor plate had to get dropped a bunch to get the driveline to line up... Consider removing the trans tunnel if necessary. When I bought my car the tunnel was gone and I hated it but now that the driveline is all lined up it is nice. I don't think the tunnel and powerglide would've not interfered with each other.

I'm about as low as I can go in the rear in regards to ride height. If I drop the rear anymore the tires will get up into the quarters right under the quarter windows. As a result I need to use shorter lower arms up front as well as a 2.25" offset front wheel to get the front tires to tuck in nicely. If not the rear trackwidth is narrower than the front and that looks like crap to me.

I'd also stretch the wheel openings before you do anything just so you can locate the tire/wheels in there better during mockup and assembly.

10-4! I've been working on that drawing too, to work out the details. I usually don't do anything until I completely draw it out and confirm it will work.

Doug my rims are 15x15 and I have 7 1/2 offset. I believe in keeping it close to keep from putting undue stress on the axles and bearings...


Randy

the Coug wrote:Doug my rims are 15x15 and I have 7 1/2 offset. I believe in keeping it close to keep from putting undue stress on the axles and bearings...


Randy

I agree Randy. Not so much as the load on bearings and axles the way I think about it. But that is something to consider. I feel if the axle pad is a close the center of the wheel as possible, then there is lesser degree of possible oscillation when a rotating load is applied. I've seen slow motion video of cars where it appears that could be happening. I'm definitely no Engineer to say that happens for sure, but it sure seems feasible. I guess the Engineers at work all these years have been rubbing off on me, or maybe I just think about shit to much. .

Where in the world did you find a .dwg or.dxf of a Fox Mustang?

I didn't find it, I drew it based on my car . I get bored real easy when I have nothing to work on in the shop, so I draw! Drafting is the only subject I made straight A's in back in school . I wish we had computers back then Oh shit, I just told on myself .

Doug Rahn wrote:I didn't find it, I drew it based on my car . I get bored real easy when I have nothing to work on in the shop, so I draw! Drafting is the only subject I made straight A's in back in school . I wish we had computers back then Oh shit, I just told on myself .

That's because you're older then dirt !!! BUT, I'm liking the way the "revision" looks...

Doug, what drawing program do you have? Thanks Brian

It's called AutoSketch 9 by Autodesk, easy to use 2D program I've been using for years. I just started to learn their free Beta version of Autodesk 123D. Here's my first attempt with that program, a Yellow Top Optima battery. It took a while but I'll get use to it.

Doug Rahn wrote:

the Coug wrote:Doug my rims are 15x15 and I have 7 1/2 offset. I believe in keeping it close to keep from putting undue stress on the axles and bearings...


Randy

I agree Randy. Not so much as the load on bearings and axles the way I think about it. But that is something to consider. I feel if the axle pad is a close the center of the wheel as possible, then there is lesser degree of possible oscillation when a rotating load is applied. I've seen slow motion video of cars where it appears that could be happening. I'm definitely no Engineer to say that happens for sure, but it sure seems feasible. I guess the Engineers at work all these years have been rubbing off on me, or maybe I just think about shit to much. .

Doug I know mine is not a mustang but when I built my rearend for the Ranger I set it up for a 5.5 back spacing I am running 12x15 welds rims with 31x10,5Ws my rearend from outside of axle to outside of axle is 47''. I wanted my axles to be as close to the center of the wheel as I could get them. I know some say it don't matter on the back spacing but back in my early 20s I had a 82 Dodge D150 I had 12'' wide rims 3.5 bs on it that I had bought for my 69 mustang to put slicks on it sold the car and kept the wheels.Long story short I put them on my truck we went down to Daytons FL I burnt up both front wheel bearings and 1 axle bearing before I got back home.So I think when a wheel with the less of back spacing plays havit on the bearings. I know on a race car/truck they not going to take the beating of hitting bumps like on a dayly driver would but they do take a beating on lanchesplus more load on the wheel studs.

the smaller the back spacing, the easier it is to get the tires on and off. The hub to the center is way oversold. The Prostockers have experimented with all kinds of back spacing and none have found an advantage.

Good point Curt. I have to deflate the tires to get them on and off my car.

I would go 3.5". Used wheels all day everyday. plus if you ever decide on beadlocks you can not beadlock a 7.5" bs.

whatbumper wrote:I would go 3.5". Used wheels all day everyday. plus if you ever decide on beadlocks you can not beadlock a 7.5" bs.

Why?

jbozzelle wrote:

whatbumper wrote:I would go 3.5". Used wheels all day everyday. plus if you ever decide on beadlocks you can not beadlock a 7.5" bs.

Why?

it is how the inside of the wheel is made. most wheels you can't get the tire on and off the wheel because of this. there are very few wheels that will take a double beadlock with that much backspace.

http://www.cwibeadlock.com/TechSpecs.htm

Thanks

Thanks. The smaller back spacing is definitely something I'm keeping it mine for ease of removal and installation. That's the main reason I alswys like to draw this stuff out before I build it. Before it's all said and done, I'll probably make 20 revisions to my drawings before I even fire up the plasma cutter and welder. It doesn't cost me anything to draw it.