The Stovebolt Site Forums The Shop Area Driveline 15” Rims to fit Disc Brakes

I’m in the process of installing power disc brakes from CPP on my ‘52 1/2 ton with the original straight axle and six lug hubs. When I got the first disc and caliper installed on the passenger side, I tried a rim and it fit with plenty of clearance. After completing the installation of the drivers side and Power Booster I went to reinstall the drivers side rim and it didn’t fit. The caliper was hitting the rim preventing it for going on completely.

I looked at the two back rims and one was identical to the one I tried, but the other looked like it had a bit more clearance, but that one didn’t fit either.

The rims on the truck are 15”x 8” and I don't know the exact offset if any. So now I have one rim the fits, two that don’t that are a match and another oddball. I don’t have a spare and did install the 3/16” spacer that came with the kit.

I would like to locate a replacement rim from a Auto Salvage Yard if possible. So my question is were there any trucks that came stock with 6 lug 15” x 8” rims so I know what to look for?

The photos are of the rim that fits.

Early 70’s Blazers 4x4 Rally wheels will work. Not likely to find them in junkyard though

I used '77 Chevy 1/2 ton 4x4 wheels on my '57 GMC with front disk brakes. I didn't need spacers. Finished them off by adding a fake "knock off" to the 4x4 "hub cap", a "GMC" sticker I found on the WWW in the middle of the knock off and a set of "beauty rings".

BTW the hub under the wheel shown in the picture was removed from a '52 Chevy in a local junk yard.

A few things come to mind. #1, make sure your caliper is installed correctly. Proper side of the mounting plate, etc. Get a ruler or tape measure out and verify from a known point that is the same on both sides. Spindle mount, king pin, whatever. Just make sure you are measuring from the same point on either side. #2, measure your offset. It's easy to do. Place a flat piece of metal or wood across the wheel edge of the backside of your rim. Take a ruler and measure down to the mount area. Repeat 3 more times. While you're at it, verify your rim diameter.

Verify what you got before you throw more money and parts at it.

MNSMith, the measurement you describe is Backspace, not Offset.

Offset is the measurement of the distance between mounting surface and wheel center.

Positive offset places the mounting surface away from the center toward the outside of the car. Negative offset places the mounting surface away from the center toward the vehicle.

ISTM that you need to fit the wheel to the brake kit you are using.

In my case, the rotors and calipers are as found on Camaros, Novas, G10 vans, etc. I found that a wheel as small as 14" would fit. I eventually used 15" wheels from a G10 van. (Yes, these are 5 bolt wheels)

If you know what the rotor and calipers you are using are designed for, it should help you find the wheels you need. CPP seems pretty good at providing this info.

I found Craig's list and Facebook marketplace cheaper than the auto wreckers for wheels.

You are correct. Which is important for trying to fit calipers in a wheel. Especially if the passenger side fits but the drivers doesn't.

Phak1: Have you taken the one good wheel and made sure it fits both sides? I don't know about that kit, but I have seen others where the caliper can appear to he mounted correctly, but only one bolt is threaded properly and it sticks out enough to block the wheel.

Just want to make sure it is a wheel issue, not an installation one.

I’m pretty sure it’s a rim issue but that’s a great idea just to be sure. I’ll check that tomorrow. Thanks.

My truck had 235/75/15s on all 4 corners. When I lowered it, I upgraded to new style tie rod ends and used a drop axle from Nostalgia Sid's. With the wheel mounting location effectively moved up 3 inches in relation to all the other components in the front end, and the new style tie rod ends being a little bit bigger than the factory 1950 style, I discovered I had interference between the sidewall and tie rod end. I went with a narrower tire and ground the casting seam off the driver's side tie rod end to make clearance.

I don't know if you have anything else going on besides disc brakes, but that would be another place to check.

I am running those same wheels, but 15"x6", on mine with the CPP kit.

When I downsized my Ram 1500 pickup from 17" to 16" wheels to get a little more user-friendly cruising speed, I discovered that the smaller diameter wheels would drag on the calipers, front and rear . I ended up installing longer lug bolts in the hubs and adding spacers between the hub and the wheel mounting surfaces to move the wheels out 3/4" in the rear and 1/2" in the front. The shorter profile tires moved the 2K RPM cruise speed "sweet spot" in overdrive down from 75+ MPH to 65. No more "speeding ticket magnet"!
Jerry

I tried the rim that fit the passenger side on the drivers side and it cleared as it did on the passengers side. So both sides are installed correctly and it’s definitely a rim issue. One thing I did notice was there is a stick on balance weight attached to the inside of the rim. As I rotated the wheel, it lightly scraped on the caliper. The weight is 1/8” thick so there is really not much clearance between the rim and the caliper. I would need to move the weight to use the rim but now I question if 1/8” is really enough clearance. It’s looking more like 4 new rims may be the best option.

If your rim can move 1/8" relative to the spindle/caliper, you will have bigger problems...

Getting a matched set of something would be nice though.

I know that the tire shop I go to will use tape weights or clip on at the customer's request.

Yeah, I suppose your right. I’m going to see if I can find a suitable replacement. I would really prefer buying the new rims and tires after the truck is painted. Sort of the icing on the cake!

Phil, have you tried to locate a P/N on the rim that clears the caliper? I would think you could buy matching rims off eBay, maybe even Coker or Wheelsmith could help you out.

If you are planning on new rims you may want to consider 16 inch .

The disc brake clearance problems aren't necessarily caused by the diameter, but by the contour of the center of the wheel as it transitions to the hoop. If it's got too wide a sweep, it will hit the caliper, while a sharper bend will go around the caliper. A stock 16" AD truck wheel won't fit without spacers. I tried a buddy's 15" artillery one day for grins and giggles and it doesn't fit either. The 15" six lug 72-91 (+/- a year) Blazer and 4x4 wheel is what is supposed to fit because it came on trucks with disc brakes from the factory. That's what the OP has pictured in the first post (four hubcap nubs, flat between the stud holes). Why one doesn't fit is still a mystery I guess, unless it's actually an aftermarket trailer wheel..?

Phak1, Some numbers for the 15" x 6" wheel are 14001279 and 560-00942, and there are several on eBay. I'm not having any luck with quickly finding numbers for the 15" x 8" wheels, and I don't have time to dig deeper because I'm at work...

One last note- when I was getting my parts in order to do the disc swap on my truck, I called one of the aftermarket wheel sources, maybe Wheel Vintiques? I gave them the measurements they asked for and they responded by saying I'd need at least a 17" wheel to fit. Clearly I did not, because I've been running these 15's for years. It's possible he meant all they offered that might fit would be a 17", but it was not stated that way.

Not to bore anyone here but to add another consideration...if you have a stock front end/suspension, the best way to preserve the steering geometry designed into it will be to match as closely as possible the width and height of the wheels/tires originally used plus the wheel offset (if your new wheel deviates from centerline orientation). There were 2 types of 600/16 tires: car and truck. The specs for the truck tires were: 28.8" diameter and 6.8" wide. The closest thing you'll find in a 16 inch radial is 205/75r16 and the specs on it will be 28.1" with a width of 8.1"...which ought to be okay although the extra width could work against you a bit. The diameter and width aren't important on your rear end but they are important on your front end. You don't want to wreck your scrub radius and that can happen easily...the scrub radius being figured by measuring the point at which your steering axis line hits the ground and figuring the distance between that and the center of your tire. In the AD trucks (all weights and sizes of them) this measurement was called the King Pin Inclination Angle and it was 7 degrees 10 minutes plus/minus 1 degree. Only an axle shop will be able to adjust this because it is permanently set into your axle. If you draw a line right through your king pin and down to the ground you'll discover it was designed to produce a positive scrub radius with stock wheels and tires (this is important). If the line had hit dead center your scrub radius would be zero. Some think that's okay, but it isn't. If it hits closer toward your frame your scrub radius is positive and if it hits on the outside of the center point (heading away from your wheel) your scrub radius is negative. All measurements of your new wheel/tire (diameter, width of tire and offset of wheel) affect this. Looking only at diameter, the further you move away from 28.8" the more negative your scrub radius will be. The more you move toward a number smaller than 28.8" the more positive your scrub radius will be. Wherever your king pin inclination angle hits the ground will be your pivot point. That's unavoidable. A positive scrub radius will make your steering easier...up to a specific point, anyway. A negative radius will make your steering harder...and this little understood factor can have a big effect on things. My experience has been the more negative your scrub radius becomes the difficulty of steering increases exponentially.

Here is what the AD Shop Manual says:
"The purpose of kingpin inclination is to keep the wheel spindles pointed outward in line with the axle to decrease frictional resistance of the tires against the road when turning right or left which results in easier steering." And their figure 14 shows an obvious positive scrub radius.

Just a thought some folks don't consider. Many of my friends have used wheels and tires which change their scrub radius and have wondered why it is so difficult to drive around in town after the change. This is one of those things which will affect that. Good luck! I'd keep this in mind when changing wheels/tires.

I didn’t think this was going to become such an issue. I went to several salvage yards and did not find any rims that I could use. I spoke to one guy and he pretty much supported what EchoBravoSierra said about the 70’s 4x4 rims. Unfortunately anything he had was rally style wheels that won’t match what I have.

I took a deeper look at the rim and found “ K1-3” a stamped on the outside of the rim near the lugs and a backwards “F”. I googled this and found that it may be a Kelsey Hayes rim from a GM 4x4. Here is a set on ebay, a way out of my price range, but exactly what I am looking for. https://www.ebay.com/itm/2043731964...r=&widget_ver=artemis&media=COPY

Any help positively identifying or locating a suitable replacement would be greatly appreciated. It has a 3-3/4” backspace.

Just for grins, try spacing the wheels out 1/2 inch. Ebay has lots of options for doing that, and the simple flat spacers that use the same lug studs are very safe and simple to install. I've run spacers like that on my Ram pickup for thousands of miles with no issues at all. Even if you end up needing to install longer wheel studs, the cost will be a lot less than new wheels.

www.ebay.com/itm/371477961416?

Jerry

The rally rims are great looking rims if their price is not bad ,and they sell the aftermarket centre caps fairly priced as well .I have the centre caps on a pair of white spoked rims they are plastic instead of cast .Also the rally rims I would think are also hard to find .

The wheels on my 54 have 2 different bolt patterns on the same wheel, the front is Ford and the back is Chevy so they are interchangeable. They came from one of the major street-rod wheel suppliers and the name is buried in the recesses of my mind but I will dredge it up. Or from my book of receipts. Well, it just surfaced, Wheel Vintigues.

Phil, I feel your pain on that price tag - OUCH!. Maybe post an ad in Truck Parts Wanted? I know a fellow "Truck Guy and his Son" here in KC area that both have early 70's 4X4 Blazers, one of which is in the process of being converted into a custom ride with complete new chassis. They may have or know someone that has some of these wheels??? Will give him a shout today and let you know.

Oh yeah, how many wheels do you need?

Just one for now. The rims are too wide for the correct steering geometry so I really need to change them all but wasn’t planning on that expense now. I really just want to finish up my power disc brake upgrade and test them out. I need to do that before moving on to another project. I will post an ad. Thanks!