Taller tires for my 1976 K20

[AuroraGirl]

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[bucket]

thank you so much for the GREAT information! Very useful and helpful. I will try to find some 16" Steel wheels which will fit my truck, accept larger tires, and my factory hubcaps. Thanks again!

I'm of the opinion that your current rims will work just fine with tubeless (and larger) tires. HOWEVER, I do like your plan lol. Because then you can keep the current wheel/tire combo mounted up and have a cool set of vintage looking tires that you can also run if you decide to go to some car/truck shows or something.

I don't know a ton about vintage truck wheels but I am a certified motorcycle technician and I can tell you that the reason many don't run tubeless tires on wheels that weren't designated is because they don't have a bead retainer formed or cast in the wheel. Obviously things become far more critical on a motorcycle but the danger lies where a tire finds itself at low pressure and experiences a side load for example during cornering, and suddenly de-beads itself and instantly loses pressure. I do know that modern car and truck wheels have a bead retainer which is why we hear a 'pop' when the bead seats. If older wheels don't have that bead retainer, and some probably don't, a tire without a tube holding the bead against the lip would certainly run that same risk at low pressure of suddenly losing all pressure during cornering, and that could be unsafe.

And in expanding on my previous post, yes I have run tubeless motorcycle tires on vintage cast aluminum wheels that don't have a bead retainer because I'm not particularly intelligent or easily spooked, but I know plenty of riders that would never, ever do it. Everyone's comfort level is different.

Bead retainers are a funny thing. I understand their purpose, but it's usually not the cut and dry situation that people think it is. At least, not with car and truck rims. Rather than try to explain it all (because I can't, lol), I'll just list some facts and those facts should speak for themselves.

Typically, 13, 14, 15, 16, 17, etc rim sizes have a bead retainer.
Typically, 14.5, 16.5, 17.5, 19.5, etc do not have a bead retainer.
There were/are a multitude of light, medium, and heavy trucks with a .5 size rim that came with tubeless tires.
They sell tire tubes that are specified for use with radial tires.
GM made many 16.5 truck rims that actually did have bead retainers (I believe they were used with tube and tubeless? Not sure about that part, so not "fact").
In the mid-late 90's, the 8-lug Dodge trucks with the chrome 16" rims did not have a bead retainer on one side of the rim. They were obviously a modern, radial type tire.

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That's a good picture and brought up another good thing to look at, without even having to remove a tire. With a steel wheel, you normally can tell from the outside if there is a bead retainer or not.

 

[75gmck25]

My ‘75 K25 Camper Special came originally with 9.50x16.5 tires and split rims.

When I switched to 16” tires I went to the pick and pull and found a newer GM squarebody (IIRC it was a 3+3 one ton) with 16” 8 lug rims and tubeless tires, and bought the set for $25 each. Then I bought new 245/75x16” tubeless tires with 10 ply load range (important for my GVW) and had them mounted and balanced. 235/85x16 would have also worked and would have been slightly taller. YMMV

 

[JBswth]

Rims designed for radials are indeed stronger. If you no longer load your truck up and just tool around in it, you will be fine, but if you still work you truck, using radials on older lighter rims is pushing it.

J.B.

 

[75gmck25]

Was there ever an OEM “lighter” version of the 8 lug steel wheels? All major manufacturers used the same 8 lug pattern for a while, and I assumed it was only on 3/4 ton and higher GVW.

Aftermarket did offer some 8 lug alloys, but I don’t know much about them.

 

[idahovette]

Rims designed for radials are indeed stronger. If you no longer load your truck up and just tool around in it, you will be fine, but if you still work you truck, using radials on older lighter rims is pushing it.

J.B.

I don't believe this?? Maybe newer stuff, but not 70s wheels.

 

[bucket]

I don't believe this?? Maybe newer stuff, but not 70s wheels.

Agreed. It doesn't matter what type of tire is in use, the wheels still need to handle the load rating of the truck.

 

[JBswth]

Agreed. It doesn't matter what type of tire is in use, the wheels still need to handle the load rating of the truck.

Problem is, radials exert more outward pressure at the bead, but to each his own.

J.B.

 

[bucket]

Problem is, radials exert more outward pressure at the bead, but to each his own.

J.B.

How so? I would think that the difference is insignificant compared to what's required for cornering and braking forces of a fully loaded pickup truck.

I'm not trying to argue or say you are wrong by the way, I'm just interested in a discussion where one or the both of us can gain some knowledge.

 

[Ricko1966]

How so? I would think that the difference is insignificant compared to what's required for cornering and braking forces of a fully loaded pickup truck.

I'm not trying to argue or say you are wrong by the way, I'm just interested in a discussion where one or the both of us can gain some knowledge.

I've heard this both ways and seen some pretty good information to say this is more rumor than fact. Some claim they changed they alloy of the metal when the went radial,and the centers flex more,fatigue,and break using radials on older rims. Others in the industry say B.S. the wheels have the same metallurgy. I really tried to stay out of this but couldn't. I call B.S. I remember when radials were the new greatest thing,and everybody switched,and nobody bought rims and nobody recommended rims,and Sears,Motgomery Wards,Kmart,Western Auto, etc didn't get their as es sued off, like when the Firestone radials started blowing up. By nature the radials have a softer sidewall which absorbs more of the stress. And with the number of 50's 60's 70s iron running around with radials replacements,failures would be common.

 

[AuroraGirl]

One of these days Ill a wheel off my 1975 grand am and dismount the tire(if im lucky there already is a tire popped off a rim while it sinking in the ground!)

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That car was one of the first production cars to run radials , in a year which most tires were bias ply. If I have a similar wheel around from another application it will probably be bias ply originally. I can compare
Be a good opportunity in which to elevate what remains of the frame above the ground so its not as difficult to remove in the future and also keep what may be good from getting worse ;(

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Poor thing ;(

In defense of the "it doesnt matter crowd" a lot of these 70s eras cars came with bias plys, or radials, and had owners manuals which clearly said they could be operated with either but to 1) never mix and match tire tech on the vehicle 2) The rotation and ride and wear would be different between the two

Maybe this meant the wheels on the cars came ready for radials but you could just equip bias plys, but maybe not. Its important to note that P-Metric tire sizing generally corresponded with radial tire changeover but that isnt a rule and you could have a p-metric tire be bias ply, but a standard sizing sized tire could be radial. And early radials usually made a point to make sure you KNEW they were radials lol!

Fun fact, a Bias ply tire in P-metric sizing will be the same number "P225/60/16" except instead of R16 it will be D16. The best way to find this type of tire is old space saver spares.

 

[bucket]

One of these days Ill a wheel off my 1975 grand am and dismount the tire(if im lucky there already is a tire popped off a rim while it sinking in the ground!)

You must be registered for see images attach

That car was one of the first production cars to run radials , in a year which most tires were bias ply. If I have a similar wheel around from another application it will probably be bias ply originally. I can compare
Be a good opportunity in which to elevate what remains of the frame above the ground so its not as difficult to remove in the future and also keep what may be good from getting worse ;(

You must be registered for see images attach

Poor thing ;(

In defense of the "it doesnt matter crowd" a lot of these 70s eras cars came with bias plys, or radials, and had owners manuals which clearly said they could be operated with either but to 1) never mix and match tire tech on the vehicle 2) The rotation and ride and wear would be different between the two

Maybe this meant the wheels on the cars came ready for radials but you could just equip bias plys, but maybe not. Its important to note that P-Metric tire sizing generally corresponded with radial tire changeover but that isnt a rule and you could have a p-metric tire be bias ply, but a standard sizing sized tire could be radial. And early radials usually made a point to make sure you KNEW they were radials lol!

Fun fact, a Bias ply tire in P-metric sizing will be the same number "P225/60/16" except instead of R16 it will be D16. The best way to find this type of tire is old space saver spares.

Of the cars you have sitting around, that one is still one of my favorites.

 

[AuroraGirl]

Of the cars you have sitting around, that one is still one of my favorites.

I wish It could have been gotten to around the time I was born, 1998, because it would have only been sitting for 6 years according to that plate tag, and it would have had a chance.

Same with the 1980 cutlass... other than running poorly nothing stopped it from being repaired in 2003 and it would have been in MINT shape for a 23 year old car. Never being used in winter would have meant it would be something today!!

 

[JBswth]

I've heard this both ways and seen some pretty good information to say this is more rumor than fact. Some claim they changed they alloy of the metal when the went radial,and the centers flex more,fatigue,and break using radials on older rims. Others in the industry say B.S. the wheels have the same metallurgy. I really tried to stay out of this but couldn't. I call B.S. I remember when radials were the new greatest thing,and everybody switched,and nobody bought rims and nobody recommended rims,and Sears,Motgomery Wards,Kmart,Western Auto, etc didn't get their as es sued off, like when the Firestone radials started blowing up. By nature the radials have a softer sidewall which absorbs more of the stress. And with the number of 50's 60's 70s iron running around with radials replacements,failures would be common.

You might be right.

 

[Griffbl]

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