backspacing???

[jerseyholsten]

i want to run 18's or 20's on my 72 stepside not sure if i can or what the backspacing would be i want to get these ordered so i get the truck mobile. please help
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[gcburdic]

ttt-anyone?

[jerseyholsten]

not sure what ttt is. would 4.5 in backspacin workm
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[nibs]

Originally Posted by jerseyholsten

not sure what ttt is. would 4.5 in backspacin workm
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ttt stands for "to the top"...

What you are asking from us is very vague. There are some other things you need to decide before you decide your backspacing. things like;
-Static Suspension or air? and how low are you?
-2wd or 4wd?
-wheel width

these kinds of things are important to figure out before you go out with throwing numbers around

[jerseyholsten]

its a 2 wheel drive goin to drop the back about 3 or 4 inches the front is already dropped not to worried about the width as long as i can get atleast about 255 or so on there
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[nibs]

well you kinda have to be concerned with the width as that will determine what backspacing will work. Im not sure if you are aware of how backspacing is measured but,

[jerseyholsten]

the rims i really want is coys or boss rims but all they offer is is 4.5 in or 5.25 in backspacing everything i have been able to find is for a fleetside nothin on a stepside. are they the same or differentm
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[nibs]

I want to say the same, but Ive never worked with a stepside. I cant imagine its any different

[jerseyholsten]

i have been looking for a couple weeks now and all i can find is for a fleet side so i thought if i stayed a little smaller i would be ok
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[nibs]

Coys offers this

18x8 with either 5" or 5.5" BS
20x8.5 with either 6" or 6.5" BS
20x10 with either 5.5" or 6" BS


If I were buying them, Id go with
20x8.5 with 6" BS in the front
20x10 with 5.5"BS

Should fit niceley

[CC69Rat]

The first thing you want to do is measure the width of the rear end housing. There were two widths available in these trucks. Yours being a 72, I'd say you have the later one.

I learned from another board member to just lay underneath the truck and measure from one backing plate to the other - side to side in the same place on both sides.

67-~69 - 55.5" wide.
late 69-70 is the transition -- could be either length
71+ - 57" wide.

This is all going to play a major part in getting your wheels correct.

For example (look in my 68 build thread) I have a 69 stepper with a 68 clip. It has the early rear end in it. I spent a BUNCH of time and effort doing research on this very question. I measured it 100 times, and I also have a Percy's wheelrite I used to measure it.

I looked high and low - East to West for good rust free step fenders. The last thing I want to do is cut the lips, or roll the edges, etc. All these things considered ..

Mine is dropped 6" in the rear and may go lower. My wheels are 20s, here are my specs.

Rear 20x8.5 - 4.75" Backspacing
255/45/20 Nitto 420S

Front 20x8.5 - 5.5" backspacing
255/40/20 Nitto 420S

* My truck has the 73-87 front K member swap. I am also running dropped spindles so I gained about .5" track width in the front with this conversion.

* I have heard of people running 285/35/22 in the rear on a 22x9. It will take a 5" Backspacking -- BUT -- This is on the early rear end. If you have the later rear end, you'd need to run a 5.75" backspacing to make this wheel sit this same way. Keith (search this site for 'Stella Mae' and you'll see the truck. That truck is incredible. He is running 22x9 5" BS on an early housing. 265/40/22. .. but it's bagged.)

First .. measure your rear end housing and let me know. I'll help you.

If you pay the shipping, you can borrow my wheelrite. No problem. Summit sells them, check it out.

Unless you want to cut the lips on your fenders, In my own opinion a 9" wheel is as big as you want to go. Some guys run 10's .. but if you want any kind of tire bead (tire is wider than the wheel) .. a 9 is as big as I'd go.

Example
20x9 - 5" BS EARLY rear end housing.
20x9 - 5.75" BS LATE rear end housing. (the extra width of the rear end housing)

In 71 when they went to disk brakes, GM widened the rear end housing to accomodate the added track width up front.

The narrower rear end housings are desirable for this reason. You just loose .75" of wheel "lip" if you have the wider one. .. just makes your rear wheels appear more narrow because your housing is so wide.

My wheels are the same width, but I used the backspacing the make them fit and appear wider in the rear. I MIGHT put my 255/45 on the front and go 265/50 Not sure. My rear wheels are tight but my truck is lower than yours. I could air this one out right now and not rub anywhere. .. but I have a Big block too so I wanted a little 'wiggle' room.

Hope this helps
Later.

[lolife99]

Originally Posted by CC69Rat

The first thing you want to do is measure the width of the rear end housing. There were two widths available in these trucks. Yours being a 72, I'd say you have the later one.

I learned from another board member to just lay underneath the truck and measure from one backing plate to the other - side to side in the same place on both sides.

67-~69 - 55.5" wide.
late 69-70 is the transition -- could be either length
71+ - 57" wide.

This is all going to play a major part in getting your wheels correct.

For example (look in my 68 build thread) I have a 69 stepper with a 68 clip. It has the early rear end in it. I spent a BUNCH of time and effort doing research on this very question. I measured it 100 times, and I also have a Percy's wheelrite I used to measure it.

I looked high and low - East to West for good rust free step fenders. The last thing I want to do is cut the lips, or roll the edges, etc. All these things considered ..

Mine is dropped 6" in the rear and may go lower. My wheels are 20s, here are my specs.

Rear 20x8.5 - 4.75" Backspacing
255/45/20 Nitto 420S

Front 20x8.5 - 5.5" backspacing
255/40/20 Nitto 420S

* My truck has the 73-87 front K member swap. I am also running dropped spindles so I gained about .5" track width in the front with this conversion.

* I have heard of people running 285/35/22 in the rear on a 22x9. It will take a 5" Backspacking -- BUT -- This is on the early rear end. If you have the later rear end, you'd need to run a 5.75" backspacing to make this wheel sit this same way. Keith (search this site for 'Stella Mae' and you'll see the truck. That truck is incredible. He is running 22x9 5" BS on an early housing. 265/40/22. .. but it's bagged.)

First .. measure your rear end housing and let me know. I'll help you.

If you pay the shipping, you can borrow my wheelrite. No problem. Summit sells them, check it out.

Unless you want to cut the lips on your fenders, In my own opinion a 9" wheel is as big as you want to go. Some guys run 10's .. but if you want any kind of tire bead (tire is wider than the wheel) .. a 9 is as big as I'd go.

Example
20x9 - 5" BS EARLY rear end housing.
20x9 - 5.75" BS LATE rear end housing. (the extra width of the rear end housing)

In 71 when they went to disk brakes, GM widened the rear end housing to accomodate the added track width up front.

The narrower rear end housings are desirable for this reason. You just loose .75" of wheel "lip" if you have the wider one. .. just makes your rear wheels appear more narrow because your housing is so wide.

My wheels are the same width, but I used the backspacing the make them fit and appear wider in the rear. I MIGHT put my 255/45 on the front and go 265/50 Not sure. My rear wheels are tight but my truck is lower than yours. I could air this one out right now and not rub anywhere. .. but I have a Big block too so I wanted a little 'wiggle' room.

Hope this helps
Later.

Excellent info!^^^
I will add,... I know there is a difference between the fleetside beds and the stepside beds.
You have alot more room to stuff a tire under a fleetside bed.

Measure, measure, measure.

[CC69Rat]

Oh, Coys offers a 20x8.5 5.25 BS. That's what I would put on the front. The key is the rear as stated above. .. just my .02

[CC69Rat]

Here's the MAN right here ^^

He helped me out a ton. We'll get it man.. just get a width measurement of the housing when you can and post it up. ..

Are you looking at wheels pre-made? Or Billets, etc. ? Keith, don't they make a 338 with 5.83" BS? It might work for this truck (assuming 57" housing)

[lolife99]

Originally Posted by CC69Rat

Here's the MAN right here ^^

He helped me out a ton. We'll get it man.. just get a width measurement of the housing when you can and post it up. ..

Are you looking at wheels pre-made? Or Billets, etc. ?

Keith, don't they make a 338 with 5.83" BS?

It might work for this truck (assuming 57" housing)

Here's the Boss 338 specs.
http://www.bossmotorsports.com/wheel...d=1920&cat=466
5.24" BS on the 20x8.5's and 6.23" BS on the 20x10's.

They make other backspacings,... but not in the 5x5 bolt pattern.

[jerseyholsten]

it is 57 in wide

[jerseyholsten]

i was lookin at the boss 338 gun metal finish the ones they said would fit 4.6 backspacing on the front and 4.5 on the back with 235/60/18 and 255/55/18 but would like 20's

[CC69Rat]

Without seeing the truck, I'm thinking you'll want:

20x8.5 up front. 5.25" BS
18" wouldn't change the BS in my opinion. Your call.

Most run 255/40/20 on the front but using a 4.5" drop. I wouldn't run this tire unless you go that low. With maybe 2.5" spindles only, .. you could run a 255/50 up front (?) Do you know how much your truck was dropped in the front as it is now? How was it lowered? Springs cut?

The back is going to be a little challenging.

I would suggest a 20x8.5 in the rear too (not just because that's what I did) .. 5.5" BS
It really depends on how low you go now. Ex. 6" drop, I'm running 255/45/20 and it's tight but clears without cutting my fenders. IF you want to cut the lips you can get by with more. I basically took my 20x8.5" 4.75 BS and added .75" to accomodate your axle width. (5.5" BS)

This will put the wheels almost flush with the fenders, but just 'tucked' a little. If you later decided to go lower .. you could, no prob.

4.5" front and 6" rear drop looks GOOD ! It's never low enough !!

Good luck man

[jerseyholsten]

i believe the springs are cut in the front but im going to order new springs and spindles the back needs to come down alot to be even with the front. thanks a lot for the info you guys know way more than i do about these truck i have always played with muscle cars but i love these trucks

[CC69Rat]

Some Stella lovin for you ..

http://67-72chevytrucks.com/vboard/s...d.php?t=414742

[jerseyholsten]

thanks so much i will give it a try and hopefully get some pics posted when i get it done. cleveland tn is not that far from where im at.

[CC69Rat]

Yeah man! Get all your stuff together and I'll even bring the ole GMC up and help you get 'er on the ground!

My name is Chad, I'll help you all I can. Welcome to the forum by the way. This will become an addiction for you soon. Hahaha ..
Later.

[jerseyholsten]

alright i will thanks chad and believe it or not my name is chad as well have a good one and thanks again