47-55.1 Unexpected disk brake - wheel problem

[TX3100Guy]

A month or so ago, I installed four disk brakes on my 1953 Chevy truck. The manufacturer of the rotors/calipers claimed that they worked with 15 inch wheels. I also purchased a set of chrome "Smoothie" wheels from US Wheels and installed them after the brakes were already done and on the old wheels.

While working on my leaf springs, I tried to rotate one of the rear wheels when the rear axle was off the ground. I found the rear wheels unable to rotate. Removal of the wheel/tire proved that the rotors and axle were able to rotate on their own. Further investigation showed that the wheels contacts the outer edge of the caliper, preventing it from rotating.

The chrome wheels are 15 inch by 6 inch wheels with an offset of 6 and backspace of 3.75. In contacting the brake manufacturer, they indicate that they designed the rotor/caliper to works with "factory stock wheels". which is not what I currently have.

Interestingly, the front wheels/tires have no issue with rotating. Which means at a minimum I'm stuck with two brand new wheels and new tires that don't work properly with the rear brakes. Even more confounding is, I don't know what size or backspace of wheel to use on the rears now. Any helpful suggestions will be appreciated.

[leegreen]

Put some washers onto the wheel studs to space the wheel out until it turns, then measure the washers?
You may just need a wheel spacer, or at least you will have some idea how much different offset you need.

Avoid the temptation to drive with the washers in there.

[TX3100Guy]

Originally Posted by leegreen

Put some washers onto the wheel studs to space the wheel out until it turns, then measure the washers?
You may just need a wheel spacer, or at least you will have some idea how much different offset you need.

Avoid the temptation to drive with the washers in there.

In the stuff the previous owner had in a box were two wheel spacers of about 1/4 inch thickness. I did try those, but given the construction of the inner wheel, they forced the wheel to be pushed out nearly 1/2 inch and as a result the lug bolts were too short to even get one thread of the lug nuts on.

I will try washers tomorrow to see if that makes a difference. Thats a good plan, thanks.

[mr48chev]

This used to be real common when putting non factory wheels on disk brake cars in the early 70's or after we started swapping disk brakes to our trucks in the late 70's early 80's.

I've taken a grinder to the high spots on the caliper and rounded them off more than once, I have a pair of those same spacers hanging in the garage that were on the disk brakes on my 48 when I had it subframed. That means those are 41 years old.

The good thing is that all you need to have is enough clearance that the wheel doesn't hit the caliper, As the pads wear the caliper will move away from the wheel.

First step is follow Leegreens's advice and figure out how much space you need.

[_Ogre]

Originally Posted by mr48chev

I've taken a grinder to the high spots on the caliper and rounded them off more than once, I have a pair of those same spacers hanging in the garage that were on the disk brakes on my 48 when I had it subframed. That means those are 41 years old.

this. grind it

[dsraven]

I have done both of the aforementioned things with new disc brakes or new wheels or both. the other thing I am curious about is whether you have the steering connected to the spindles. I ask because the next problem you may encounter is that the outer tie rods may rub the wheels on their back side. if the wheels are aluminum they tend to be thicker that the steel wheels, for strength, so those thicker wheels are sometimes just thick enough to interfere with the tie rod joint.
I usually try to set things up so I can use a wheel with some common size and back space, that way you can find some cheap wheels and tires to use when working on the vehicle. no worries about getting welding slag burnt in or oversprayed with paint or primer. since building doesn't usually happen in a week sometimes guys that buy new wheels and tires when they start the build find that by the time the project is complete those new wheels are out of vogue and the tires are outdated, so possibly need replacing. We all start with good intentions but then life gets in the way.

[dsraven]

some steel wheels are also made with a deeper "groove" or recessed are in the center of the donut. this smaller diameter area is sometimes what rubs the brakes.maybe you can find a wheel with a larger diameter center section?

[57tailgater]

Did you get the kit for 5 or 6 lug wheels? The 5 lug will have rotors off a 70's Camaro with a smaller diameter rotor than the 6 lug kit which uses parts originally for 16" wheels and a larger diameter rotor. Even though the 6 lug kit says can be used with 15" wheels it can be tight depending on the wheels like you have found out. I have a 6 lug kit and with the wheels I am going to use it will take some grinding on the calipers, a spacer and no wheel weights on the area where the caliper is near the wheel.

[TX3100Guy]

Originally Posted by 57tailgater

Did you get the kit for 5 or 6 lug wheels? The 5 lug will have rotors off a 70's Camaro with a smaller diameter rotor than the 6 lug kit which uses parts originally for 16" wheels and a larger diameter rotor. Even though the 6 lug kit says can be used with 15" wheels it can be tight depending on the wheels like you have found out. I have a 6 lug kit and with the wheels I am going to use it will take some grinding on the calipers, a spacer and no wheel weights on the area where the caliper is near the wheel.

6 lug axle with 15 inch wheels. As I mentioned, the fronts are free and clear. The rear are binding on the outside rear edge of the caliper.

I just tried the spacer again and managed to get the lugs to catch by a thread or two. With the spacer and the gap that exists between the spacer and the chrome wheel due to its configuration (looks stamped) it adds about 5/16 of an inch, the caliper just clears, but not by much.

I need a quick study of offset versus backspace to determine what is needed to make this work. I'm tempted to try a 16 inch wheel, but that has a big financial penalty given I already own new 15 inch wheels and tires.

[TX3100Guy]

Originally Posted by TX3100Guy

I need a quick study of offset versus backspace to determine what is needed to make this work. I'm tempted to try a 16 inch wheel, but that has a big financial penalty given I already own new 15 inch wheels and tires.

So I just did a quick study of offset versus backspace. It appears to me that my issue is related to offset. My current wheels are 15 inch by 6 inch wheel, with an offset of 6 and backspace of 3.75.

The wheel is set back to far on the axle, allowing the inside edge of the rim to rub against the outside edge of the caliper. If the offset were 0 or negative, the wheel would be moved outward and away from binding on the caliper.

I went to the US Wheel website where I purchased the Chrome "Smoothies" and see that there is a 15 inch by 7 inch wheel available that has a "0" offset and a 4.0 backspace. By moving the wheel 6 millimeters outward I think my binding issue would go away.

Thoughts?

[57tailgater]

Sounds like you may have a somewhat easy solution. Just make sure you have fender clearance and sufficient thread engagement on the wheel studs for the lug nuts.

[mr48chev]

Wrong way, you need a 3 to 3.5 inch back space. 4 puts the inside rim closer to the caliper yet. Most likely you won't even be able to get a 4 inch backspace wheel on the hub with the caliper on.

[joedoh]

Originally Posted by mr48chev

Wrong way, you need a 3 to 3.5 inch back space. 4 puts the inside rim closer to the caliper yet. Most likely you won't even be able to get a 4 inch backspace wheel on the hub with the caliper on.

he is still gaining the 1/4 inch in offset, although you are technically correct that he will have more rim on the inside.

let me explain:

a 6 inch wide wheel is 7" lip to lip, a 0 offset would thereby be a 3.5" backspace. he has 3.75" backspace, which is 1/4" or 6mm offset.

a 7 inch wide wheel is 8 inches lip to lip, 0 offset is 4" backspace. he is still gaining the 1/4 inch in offset, and the width of the wheel on the barrel is 1/2 wider (half of the extra inch of width is added to the front side of the rim, half to the back).

at worst, the new wheel will fit exactly the same. at best, he will have gained the 1/4" offset he needs. it depends on where the wheel is hitting the caliper. my feeling is you are correct, the wheel is not different enough to make a difference.

my advice, grind the caliper slightly like other have said. no spacer, no new wheel, just a zip zip on the high spot, the caliper will never miss this small surface area.

actually i would probably switch back to drums there is very very very little gain to rear discs in 90% of driving. I have said before that you could probably disconnect the rear brakes in 90% of driving and never even notice. (do not disconnect your rear brakes!)

enough soapboxing, take the advice and just grind the high spot of the caliper. dont go crazy, just a little at a time and if it looks like you have to grind a big hunk off see where you are at then. you may order new wheels and find the same interference.

[TX3100Guy]

Originally Posted by joedoh

enough soapboxing, take the advice and just grind the high spot of the caliper. dont go crazy, just a little at a time and if it looks like you have to grind a big hunk off see where you are at then. you may order new wheels and find the same interference.

From under the car, I can see that the somewhat conical stepped shape of the inner wheel combined with how far out the caliper sticks out that unless I'm willing to live with about 1/16" in clearance, I'm going to need a better wheel fitment.

Last night I put the 1/4" spacer on, combined with one steel 1/2" washer. I was able to get the lugs on by a thread or two and from under the car and behind the wheel, see that I had about 1/16" clearance to the caliper. At that point, I was contemplating the longer studs that had been suggested earlier. When I saw how minimal clearance that produced, I wasn't happy.

When I consider the time it would take to disassemble the calipers, rotors, remove the axle shafts, press out the old lugs, press in new longer lugs, then reassemble only to get 1/16" clearance., getting new better shaped and offset wheels seems like a better idea.

[mr48chev]

This link that I snagged those images off does a fairly decent explanaiton.

https://www.roughcountry.com/blog/wh...explained.html


This may explain it a bit simpler Again 4x4 site but your problem now is too much backspacing and more backspacing will increase the problem. https://ok4wd.com/blog/the-differenc...d-backspacing/

[TX3100Guy]

Originally Posted by mr48chev

This link that I snagged those images off does a fairly decent explanation.


This may explain it a bit simpler Again 4x4 site but your problem now is too much backspacing and more backspacing will increase the problem. https://ok4wd.com/blog/the-differenc...d-backspacing/

I get it now. I need a wheel with a negative offset.

As for the trick with the washers, I stacked three 1/2 washers on each stud after measuring their thickness with my caliper. They were 9/32 of an inch or about 7 mm. Which is darn close to measurement of the other 15 inch wheel that I mentioned. While it fit and the wheel turned, the caliper was only clear by the finest measurement known to man (as my Dad used to say). It's unfortunately clear, that simply buying a 15 by 7 inch wheel with 0 offset and 4 backspace will not work and as you mentioned, is moving in the wrong direction.

Should I just consider moving to a 16 inch wheel with -6 offset and 3.75 backspace?

[TX3100Guy]

Maybe a good question for the group is, what size wheel and tires do you run on your truck? 15, 16, 17, 18 inch wheels? Tire size? Same tire size front and rear?

[_Ogre]

15x9 rims from wheelvintiques 4 wheel disc brakes, 4" bs

[TX3100Guy]

Originally Posted by _Ogre

15x9 rims from wheelvintiques 4 wheel disc brakes, 4" bs

Power steering? How does it steer with 9 inches up front?

[_Ogre]

Originally Posted by TX3100Guy

Power steering? How does it steer with 9 inches up front?

my bad. 8" rims with Tires BFGoodrich T/A P235/70 R15 all around
mustII w/ power steering

[leegreen]

1/16" clearance sounds like enough to me? As long as it does not rub I don't see any difference between 1/64" and 1/2". Just make sure there is no slop axle to spider pin that you might loose that clearance in corners

where does it hit the caliper? (picture?)
as suggested grinding can probably give you at least another 1/16

edit: but I do see your comment about the work to swap lugs!
Should be no need to remove axles to swap lugs though

I agree with joedoh, drums in the rear are fine for most of our trucks, simple, cheap, better e-brake.
For period correctness you could go drums on all 4, get some of those big finned aluminum '69 buick skylark drums for front. except those drums probably cost more than a disk conversion these days

[TX3100Guy]

Originally Posted by leegreen

where does it hit the caliper? (picture?)
as suggested grinding can probably give you at least another 1/16

edit: but I do see your comment about the work to swap lugs!
Should be no need to remove axles to swap lugs though

Here are some pics. BTW, I don't have a stock rear end, with the Hallibrand quick change diff the axle shafts need to come out to get to the lugs.

Originally Posted by joedoh

no, thats only going to be an additional 6mm. thats why i tried to explain the difference in offset and backspacing but i guess I did it poorly.

and finally its worth mentioning, if you have the room for the extra 1" wider wheel to have the extra width all the way on the front side.... just get some 1.25" spacers and dont worry about new studs, it will move the wheel center out away from the caliper for about $50.

You didn't do a bad job at explaining, I did a bad job at understanding...LOL I get it now.......I think.

When you say 1.25" spacers do you mean something like this?

[mr48chev]

I've run 14-7 on the front since around 1975 and used to run 14-8-1/4 Crager Mach 8's on the rear, Since around 1990 it has had Enkie 32's 14x7 on the front and 15x8 on the rear with 195-60 14 on the front and 255-60-15 on the rear. That for a staggered hot rod look with the percentage of sidewall to wheel on the fronts pretty close to the precentage of sidewall to wheel on the rear being fairly equial Per what Boyd Coddington suggested in the late 80's. Most of his earlier builds had a larger diameter wheel on the back than on the front and had that balance between front and rear.

Back when it still had the Crager Mach 8s on it.


Still and I know that some might get tired of me saying it, Wheel and tire choice have to match your total build theme and have to be a working and contributiting component of the total look. They shouldn't overpower the truck and turn it into a background for a wheel add but on the other hand they shouldn't look settled for as most white spoke wheels scream on old trucks. When you look at a vehicle your eyes should not pick out one specific component before they take in the whole vehicle as a total package. That is any part of the rig unless you are specifically looking for that part. If you scroll down the page or flip pages or are walking though a show and your eye picks out a component before you see the whole rig as a unit that component is wrong for that truck.

[TX3100Guy]

Originally Posted by mr48chev

I've run 14-7 on the front since around 1975 and used to run 14-8-1/4 Crager Mach 8's on the rear, Since around 1990 it has had Enkie 32's 14x7 on the front and 15x8 on the rear with 195-60 14 on the front and 255-60-15 on the rear. That for a staggered hot rod look with the percentage of sidewall to wheel on the fronts pretty close to the precentage of sidewall to wheel on the rear being fairly equial Per what Boyd Coddington suggested in the late 80's. Most of his earlier builds had a larger diameter wheel on the back than on the front and had that balance between front and rear.

Back when it still had the Crager Mach 8s on it.


Still and I know that some might get tired of me saying it, Wheel and tire choice have to match your total build theme and have to be a working and contributiting component of the total look. They shouldn't overpower the truck and turn it into a background for a wheel add but on the other hand they shouldn't look settled for as most white spoke wheels scream on old trucks. When you look at a vehicle your eyes should not pick out one specific component before they take in the whole vehicle as a total package. That is any part of the rig unless you are specifically looking for that part. If you scroll down the page or flip pages or are walking though a show and your eye picks out a component before you see the whole rig as a unit that component is wrong for that truck.

I pretty much agree with you. Given the pedigree of this truck (was a pusher truck on the Bonneville salt flats), a 1959 261cu/in inline six engine with a McCulloch supercharger, a vertex magneto, and a Hallibrand quick change diff. I'm definitely going for more of a hot rod look than a low rider.

While I have 15 inch wheels, I did have slightly different sizes 215/75/15 front and 235/75/15 rear. I'm really torn on what to do to correct my disk/caliper issue. It seems that when I find a wheel size that has the appropriate offset (negative) it seems too wide for the brand spanking new tires I already own.

[TX3100Guy]

Originally Posted by mr48chev

I've run 14-7 on the front since around 1975 and used to run 14-8-1/4 Crager Mach 8's on the rear, Since around 1990 it has had Enkie 32's 14x7 on the front and 15x8 on the rear with 195-60 14 on the front and 255-60-15 on the rear. That for a staggered hot rod look with the percentage of sidewall to wheel on the fronts pretty close to the precentage of sidewall to wheel on the rear being fairly equial Per what Boyd Coddington suggested in the late 80's. Most of his earlier builds had a larger diameter wheel on the back than on the front and had that balance between front and rear.

Back when it still had the Crager Mach 8s on it.


Still and I know that some might get tired of me saying it, Wheel and tire choice have to match your total build theme and have to be a working and contributiting component of the total look. They shouldn't overpower the truck and turn it into a background for a wheel add but on the other hand they shouldn't look settled for as most white spoke wheels scream on old trucks. When you look at a vehicle your eyes should not pick out one specific component before they take in the whole vehicle as a total package. That is any part of the rig unless you are specifically looking for that part. If you scroll down the page or flip pages or are walking though a show and your eye picks out a component before you see the whole rig as a unit that component is wrong for that truck.

I pretty much agree with you. Given the pedigree of this truck (was a pusher truck on the Bonneville salt flats), a 1959 261cu/in inline six engine with a McCulloch supercharger, a vertex magneto, and a Hallibrand quick change diff. I'm definitely going for more of a hot rod look than a low rider.

While I have 15 inch wheels, I did have slightly different sizes 215/75/15 front and 235/75/15 rear. I'm really torn on what to do to correct my disk/caliper issue. It seems that when I find a wheel size that has the appropriate offset (negative) it seems too wide for the brand spanking new tires I already own.