Stock 6" 3 nub wheels on 12" CPP disc brakes?

[Drummerboy]

I have a '68 that I converted to a CPP power disc brake kit with 12" rotors. I haven't mounted them yet but I'd like to know if these stock 3 nub wheels with clear the larger diameter rotors? Right now I have a set of 8" four nub 4x4 wheels on it. They're to wide for my liking on the front so I picked up these stock wheels for it. I'm not sure if there 5.5" or 6" wide. One day after work, I plan on jacking the truck up and trying one.

[jocko]

three nub are normally an indicator of pre-disk brake days, they may not fit because of the shape of the inside of the rim. Rotors aren't the issue, the inside of the taper between wheel center and rim rubs the caliper. 71+K wheels fit over STOCK calipers - so you'd need to find a stock skinny set of K5/10 wheels from 71 or newer. Since you have the 3 nubs, I'd still give it a try before mounting tires just like you mentioned - but 3 nubbers normally won't clear the caliper, sorry.

[Drummerboy]

Yea I have 71 or newer four nubs on it all around now. Tally hoping to run a skinnier front wheel.

[Ol Blue K20]

I don't think the three nubs will work. They won't even clear stock rotors and calipers

[Drummerboy]

Man this is a huge bummer! I guess I'll have to buy two aftermarket wheels.

[Drummerboy]

Couldn't I just run a 3/8" wheel spacer?

[leddzepp]

I think the first thing you need to do is physically install the wheel and go from there...

[special-K]

Three nub wheels were made for drum brakes and when disc brakes came along they started stamping four nub centers. What you need are stock wheels from a 71-91 K5 or K10 truck or Suburban. Those had six lugs and disc brakes.

[Drummerboy]

Originally Posted by special-K

Three nub wheels were made for drum brakes and when disc brakes came along they started stamping four nub centers. What you need are stock wheels from a 71-91 K5 or K10 truck or Suburban. Those had six lugs and disc brakes.

I believe the wheels that are on my truck now are stock 71+ K5 four nub wheels. They fit fine of course.

I'm trying to run a narrower front wheel and tire. These K5 wheels are wider than I want on the front.

[Drummerboy]

So I tried a wheel out this morning. They went on fine without hitting or rubbing on the rotor itself. The problem is, the wheel rubs on the caliper. I took photos showing the rub marks and also showing the clearance for the rotors.

[jocko]

Yes, as stated above in the beginning - the calipers are the problem, not the rotor. At least now you know for sure. Standard 6 lug 71 and newer K5/10 wheels were 6" wide. If you want narrower than that, you'd probably need to go custom. How wide are your current 4 nub wheels? The next step up from 6" for a stock (optional) 6 lug K5/10 wheel is 8.25". There were 5" wide optional 6 lug wheels available, but I've never seen any personally - but not sure you're seeking something that narrow. It sounds like the standard 6" 71 and newer K5/10 wheel is what you're looking for? Might want to post a WTB ad. They're out there, and, to be honest, it seems the 8.25" wheels bring more $, so maybe someone can help you out with your WTB. They are a niche wheel though -highly sought after by the pre-71 crowd (including 60-66) because many folks are doing exactly what you are doing - disk retrofit onto a truck that never had stock wheels that would clear the calipers. There is always the aftermarket if you can't find originals though. Hope that helps.

[Drummerboy]

Originally Posted by jocko

Yes, as stated above in the beginning - the calipers are the problem, not the rotor. At least now you know for sure. Standard 6 lug 71 and newer K5/10 wheels were 6" wide. If you want narrower than that, you'd probably need to go custom. How wide are your current 4 nub wheels? The next step up from 6" for a stock (optional) 6 lug K5/10 wheel is 8.25". There were 5" wide optional 6 lug wheels available, but I've never seen any personally - but not sure you're seeking something that narrow. It sounds like the standard 6" 71 and newer K5/10 wheel is what you're looking for? Might want to post a WTB ad. They're out there, and, to be honest, it seems the 8.25" wheels bring more $, so maybe someone can help you out with your WTB. They are a niche wheel though -highly sought after by the pre-71 crowd (including 60-66) because many folks are doing exactly what you are doing - disk retrofit onto a truck that never had stock wheels that would clear the calipers. There is always the aftermarket if you can't find originals though. Hope that helps.

I have four 8.25" now. I need two of the 6". Thank you for this info, extremely helpful!

[special-K]

Originally Posted by Drummerboy

I believe the wheels that are on my truck now are stock 71+ K5 four nub wheels. They fit fine of course.

I'm trying to run a narrower front wheel and tire. These K5 wheels are wider than I want on the front.

The wheels that are on your truck now are optional 8" wide steel wheels. I read that in your first post, and that you want to use narrower wheels. The wheels I told you about are stock width, 6"-6.5". The width you want in the disc brake profile you need. I don't know of any 5" wide disc brake 6-lug 15s ever made. The 16" wheels were that narrow.

[demian5]

Grind down that caliper. I had to do that to mine.

[Drummerboy]

Originally Posted by demian5

Grind down that caliper. I had to do that to mine.

Is that all you had to do?

[demian5]

Originally Posted by Drummerboy

Is that all you had to do?

Yes, just the corners of the caliper at the ends. Rounded them out and all good.

[Drummerboy]

Originally Posted by demian5

Yes, just the corners of the caliper at the ends. Rounded them out and all good.

Would it be possible for you to send me a photo of how much you trimmed? I'm concerned that we have two differnt shaped calipers and exactly how much I'd need to grind.

[special-K]

I never heard of anyone doing that to make them fit, with all the talk about the nubs/drum/disc thing here. Good to know. I know I ground the K/20 calipers on my first '71 to fit the 10 x 15 8-lug wheels that came off my '69 Power Wagon when I wrecked it. Just had to grind the ridge/casting seam some along the radius.

[demian5]

Originally Posted by Drummerboy

Would it be possible for you to send me a photo of how much you trimmed? I'm concerned that we have two differnt shaped calipers and exactly how much I'd need to grind.

Post a picture of your caliper without the wheels on and ill mark where I had to grind.

[Drummerboy]

Originally Posted by demian5

Post a picture of your caliper without the wheels on and ill mark where I had to grind.

Here ya go

[Drummerboy]

One more.

[jocko]

Yes, they can be ground a little. The problem is the definition of "a little". NObody really knows the thickness that remains, nor how much really "should" remain before strength is affected. One guy's approach may never cause a failure, but I'm not willing to be the "other guy" that goes veering hard left or right in a panic stop because my caliper housing just got overstressed and cracked. In other words, I doubt GM left a ton of extra material on there just to make it pretty, they are purpose built, and while it probably can be done without sacrificing overall integrity of the caliper - there's really no way to know if it has been sacrificed, unless it fails. Grinding off 2mm may not sound like a lot, unless the thickness there is already minimized to save weight - and that little 2mm of grinding now make sthe caliper susceptible to crack propagation. It comes down to a personal decision. You'll find a lot of folks aren't wanting to accept that unknown risk and that's why K5/10 wheels are at a premium. Don't get me wrong, I'm not saying it's wrong to grind a caliper housing, but it's one of those eyes wide open decisions someone has to make based on their own personal comfort level. It exceeds mine personally. In your case Tim, I'd agree, a casting seam probably has zero effect on part integrity. If min cross-sectional thickness in the area of the grinding is affected at all, that's when I'd start to have concerns personally.

[Drummerboy]

I won't be grinding on them. I'm currently looking for the correct wheels.

[special-K]

I figure GM puts a little extra fat on as liability insurance. Their quality is a good bit higher than 'just enough'. It all depends on how much is needed off. Grinding a little off isn't going to cause some catastrophic failure. If it's along the radius in the center, that is high from being at the casting seam. I'm curious to know the details.

[demian5]

Start by looking for "witness" marks where the wheel rubs.

Its probably in the Red. But the Green may rub as well.

Look close for where its hitting then grind there. there is NO fluid running through this part of the caliper so you are good to grind a bit away.