Wheel backspace for stock 69 C10 Shortbed Stepside

[C4UC101969]

Guys, need some help with figuring out backspace without taking the wheels off. I have full stock 69 Chevy C10 shortbed stepside and want to order some detroit steel smoothies 20"x8 and 20"x9 and trying to figure what is the backspace on the stock set up, Mobsteel guys said its 4" all around, but I just want ya'll input on this.

[71sierragrande]

Those rallies are not stock, but they're probably 15x8 with 4" b.s. Take a look at the wheel arch in relation to the outside of the tire, the fronts should stick out more. Your new 20x9 with 4" b.s. in the rear will be kicked out one inch further to the outside than it is now, which is a good thing imo, and should damn near even them up. But your pic it looks like rears are out further, which may be an optical illusion.

Edit: Ah, the step side bed is throwing me off. I believe the fleet is wider so everything I just said may be bullcrap
Edit #2: Yes, I just did a search on it. At least one person says the stepper is over an inch narrower each side(2+inches total). So keep that in mind.

[Mike C]

Typically zero offset works best on these trucks. On a 7" rim, that is 4" back space. 4.5" on an 8" rim and 5" on a 9" rim.

I have zero offset rims, 17x8 on the front of my 69 short step and 17x9 rear. I have a wider 71-72 rear axle though. The bedside is awful close on the stock length 69 setup.

Rim width is measured between the beads and not outside to outside. So a typical 7" wide rim is 8" in width outside to outside, so 4" then is the distance to center from the outside.

[C4UC101969]

Originally Posted by 71sierragrande

Those rallies are not stock, but they're probably 15x8 with 4" b.s. Take a look at the wheel arch in relation to the outside of the tire, the fronts should stick out more. Your new 20x9 with 4" b.s. in the rear will be kicked out one inch further to the outside than it is now, which is a good thing imo, and should damn near even them up. But your pic it looks like rears are out further, which may be an optical illusion.

Edit: Ah, the step side bed is throwing me off. I believe the fleet is wider so everything I just said may be bullcrap
Edit #2: Yes, I just did a search on it. At least one person says the stepper is over an inch narrower each side(2+inches total). So keep that in mind.

Thank you, yes it is narrower than the fleetside. I will keep this in mind.

[C4UC101969]

Originally Posted by Mike C

Typically zero offset works best on these trucks. On a 7" rim, that is 4" back space. 4.5" on an 8" rim and 5" on a 9" rim.

I have zero offset rims, 17x8 on the front of my 69 short step and 17x9 rear. I have a wider 71-72 rear axle though. The bedside is awful close on the stock length 69 setup.

Rim width is measured between the beads and not outside to outside. So a typical 7" wide rim is 8" in width outside to outside, so 4" then is the distance to center from the outside.

Yeah that is what I have also found out through some research that I should strive for a 0 offset, thank you for your input on this.

[Mike C]

It is the 67-69 axle housings that are 3/4” narrower on each side than the 70-72 housings. It has nothing to do with fleetside/stepside. But there is less room in a stepside wheelwell for backspacing mistakes with wide tires.

Most 1970 housings are the wider but have 6 lug axles still. But it is a transition year so the tape measure is your friend.

[C4UC101969]

Originally Posted by Mike C

It is the 67-69 axle housings that are 3/4” narrower on each side than the 70-72 housings. It has nothing to do with fleetside/stepside. But there is less room in a stepside wheelwell for backspacing mistakes with wide tires.

Most 1970 housings are the wider but have 6 lug axles still. But it is a transition year so the tape measure is your friend.

Thank you, I've realized that the tape measurement at this moment is my best friend if I want to fit some nice and wide tires on the back without any issues, appreciate your effort with this one......

[geezer#99]

Did ya know they make some nice little toys to help you measure and fit your wheels/tires.
Like this.
https://www.summitracing.com/int/par...1201/overview/

[C4UC101969]

Originally Posted by geezer#99

Did ya know they make some nice little toys to help you measure and fit your wheels/tires.
Like this.
https://www.summitracing.com/int/par...1201/overview/

Thanks, yeah I've come across it from searching through older posts. The only thing is I have a six bolt and they only offer it for 4 and 5 bolt, and judging from the comments on their website it is not of the best quality and I am guessing I can just pay that to a local shop to get me the same measurements

[Mike C]

Converting to 5 lug the best thing you can do IMO to be able to buy nice looking affordable wheels. And getting away from 15" rims if you want to maximize stance. And we know that it's ALL about stance!

Back of my truck with 275 55 17

[C4UC101969]

Originally Posted by Mike C

Converting to 5 lug the best thing you can do IMO to be able to buy nice looking affordable wheels. And getting away from 15" rims if you want to maximize stance. And we know that it's ALL about stance!

Back of my truck with 275 55 17

That looks good, what is the width of your rims and the offset and the backspace, you got stock sized axles or did any mods to them except the 5 bolt conversion?

[Mike C]

17x9 zero offset (5" backspace) 1971-72 complete housing that I swapped my existing posi into.

[michael bustamante]

heres something to concider also, I took my bed off my 67 stepside last year and upon looking, noticed my passenger side wheel was closer to my frame than my left side, I measured and sure enough, my frame is not perfectly centered back there, I brought this up to the forum here and they said thats normal..... i`ve since noticed that two other shortbed frames are built the same way.

[C4UC101969]

I did some measuring and figuring out and I am thinking of going with 8x20" on front with 4.5" backspace and 0 offset and for back 10x20" with 5" backspace and also a 0 offset, what ya'll thinking of that in terms of fitment and the look, stance etc.

[Mike C]

I'm sure you know that 5" backspace is NOT zero offset on a 10" rim. It is -12mm or 1/2" less than zero offset. Zero on the 10 is 5.5" Your 5" selection is a good choice with the shorter 69 axle housing.

What size tire do you plan to run? Wider than 9" rim on a stepside is pushing it, but 20's and the more square sidewall of the lower profile tire will probably be ok. Pushing the lip of that 10" rim closer to the fender is probably going to result in a rub on the outside.

Rims are such a personal choice but I'm just not a fan of 20's and trying to keep within the 27-29" height range that works best for these trucks.

You can probably go to 28" in the front and 30" in the rear and still not have issues, but the front will start to contact the inner fenderwells and may rub on the frame at steering lock.

Any 18" wheels you like? That would be where I would look first.

Is your truck a coil spring rear? If so, an adjustable track bar can be used to center the axle on the frame. My truck is a leaf spring truck.

[C4UC101969]

Originally Posted by Mike C

I'm sure you know that 5" backspace is NOT zero offset on a 10" rim. It is -12mm or 1/2" less than zero offset. Zero on the 10 is 5.5" Your 5" selection is a good choice with the shorter 69 axle housing.

What size tire do you plan to run? Wider than 9" rim on a stepside is pushing it, but 20's and the more square sidewall of the lower profile tire will probably be ok. Pushing the lip of that 10" rim closer to the fender is probably going to result in a rub on the outside.

Rims are such a personal choice but I'm just not a fan of 20's and trying to keep within the 27-29" height range that works best for these trucks.

You can probably go to 28" in the front and 30" in the rear and still not have issues, but the front will start to contact the inner fenderwells and may rub on the frame at steering lock.

Any 18" wheels you like? That would be where I would look first.

Is your truck a coil spring rear? If so, an adjustable track bar can be used to center the axle on the frame. My truck is a leaf spring truck.

I haven't yet thought of the tire size as I am still trying to figure out the rim size, i figured that it is easier to get the right set of tires after I get the right rims.

You said it right rims is a such personal preference, I am not a big fan of 18" or smaller wheels hence looking for a bit bigger than 18" size.

In the rear I have coils.

So you really think that 10" in the rear might be rubbing on the outside wall, even with low profile tires?

[Mike C]

It might. You really need to find someone running the combo you want to go with. Personally, I would figure out what size tire you want to run first. The tire determines the ultimate fitment. Then you size the wheel appropriately for the tire using a rim neither too wide nor too narrow.

Figure a section width of 285 is max on a stepside that's dropped 6"? Depending on how low you want to go really. If you don't go really low then you can go a lot wider (the guys that run 295 50 15's for instance. Usually on a 10" rim with 4" back space. Or less.) The 295 is only 26.5" tall so it can stick out to the edge of the fender and not rub because the truck bottoms out first. But if you run tall tires and you drop 6" or more then it can and most likely will rub.

I spent a long term searching for threads before pulling the trigger on a set of wheels. That and using my tape measure to make sure everything would fit.

[slowcpe]

Originally Posted by Mike C

Any 18" wheels you like? That would be where I would look first.

18s are really limited in tire sizes for these trucks. Its hard to find a tire wider than 255 if you want to stay in the 28-30" range. I've got 18" Ridlers on my '72 and it needs new tires and I want something wider than the 255/55/18 it currently has out back.

I just ordered a set of 20x8.5 w/4.75" BS fronts and 20x10 w/5.5" BS rears for my '67 stepside. I'm either going with a 295 or 315 out back but going to get my wheels on first and measure. I'm prepared to cut my bedsides, run a narrower rear end and roll the fender lip if need be.

Here's my '67 with 18s. Fronts are 18x8 0 Offset, and 18x9.5 +6 rear. Rear tire is a 255/55/18.

[C4UC101969]

Originally Posted by slowcpe

18s are really limited in tire sizes for these trucks. Its hard to find a tire wider than 255 if you want to stay in the 28-30" range. I've got 18" Ridlers on my '72 and it needs new tires and I want something wider than the 255/55/18 it currently has out back.

I just ordered a set of 20x8.5 w/4.75" BS fronts and 20x10 w/5.5" BS rears for my '67 stepside. I'm either going with a 295 or 315 out back but going to get my wheels on first and measure. I'm prepared to cut my bedsides, run a narrower rear end and roll the fender lip if need be.

Here's my '67 with 18s. Fronts are 18x8 0 Offset, and 18x9.5 +6 rear. Rear tire is a 255/55/18.

I agree that for the 18" you are fairly limited with rims style and choice.

I just came back from a local rim shop where I will be buying the tires and installing them on the rims from Detroit Steel, we put on the front a test wheel 9x20 with +1 offset with a 275/45/20 and man it was a perfect fit for the front no rubbing and still room to lower it more which is exactly what I wanted, and for the back I am going to keep it at at 9x20 as well with a bigger tire. all around 5" backspace.
Btw, my truck's original colour is the same as your Chester.....the inside is still that original colour

[Mike C]

I was going to call you guys out for no tire choices in 18’s, but you are exactly right. I looked at replacing my 17 combo with new rubber and even that may not happen at this point.

Which really pisses me off. I can’t describe the aversion I have for 20” rims. Ah, more progress.

[slowcpe]

Originally Posted by Mike C

I was going to call you guys out for no tire choices in 18’s, but you are exactly right. I looked at replacing my 17 combo with new rubber and even that may not happen at this point.

Which really pisses me off. I can’t describe the aversion I have for 20” rims. Ah, more progress.

Yup, I've got HOURS in looking at tire combos. I really want to run a 275 rear tire that is around 29" tall and have found 1 or 2 but can't find a good matching front tire.

The best setup I've found is the Nitto 555 G2s with a 245/45/18 front and 295/45/18 rear. There's a possibility I'm going to have to run a 1/4" spacer in the rear and will be spending more money on tires than I had hoped. But it should be a good looking combo. Now this is for a fleetside.

[Mike C]

That's almost a 27" front and almost 29" rear which should work out pretty well. Too wide in the back for a stepper without trimming the inner bedsides and building new inner fenders. Which is always an option and I have considered in order to run BIG tires in the back.

I went with the Hankook Ventus AS on my truck just because they had matching sizes in what I wanted, but it looks like that is no longer the case.