Interesting read on Bias vs. Radial tires & rims

[clonelark]

[deco_droid]

Very interesting... and makes sense to me

[Chantony]

I'd agree that the rims can be a problem.I've had rims crack with fatigue after years of heavy use on car haulers,though not on cars.These rims were all the same and ran radial and bias-ply tires at the same time,load and mileage.The rims didn't seem to care what tires were on them-they died equally well!!The problem was the rims were for a car weighing a little over a ton and were always carrying nearly a ton and a half and up to two tons.They were over stressed and were replaced as they developed the problem.At the time,little else was available for trailers in Australia.
Regardless of the type of tire,the stress is based on the tonnage the surface of the tire is resisting while in contact with the road,mainly on cornering.Some rims have an inherent amount of give or flex as they rotate carrying a load,especially the more the bolt mounting points are moved away from the center point of the tire where it contacts the road,ie.the offset.It is possible that a radial tires flexibility may act like a shock absorber to take up the minor road surface blemishes,but I've never seen any data to back this up.
Regarding old rims versus new...if you treat the rim as a disposable item,that is it will ultimately WEAR OUT,then the logic would be that new has to be better than old.Some alloys and steels become crystalized with age,though this can mean 100 years or more.
If the rim has had a lot of rust,then has been sandblasted and painted then it will never be as good as a clean low mileage rim. Sandblasting can cause metal embrittlement as it tends to "shot blast" the steel,so it's not always a good idea.I'd sand blast just enough to clean the rim up,but not go ballistic with it as some operators do.
At the end of the day though if the rim shows no cracks and looks to be clean and you're not doing drag racing or rallying in your Stude as a daily event,then I don't believe there is much to worry about.I did about 600,000 miles on an old set of rims with a multitude of tires,most of the time with a car trailer attached and often loaded.The rims are still okay.

A.C.Moisley

[Jim B PEI]

I agree with Bill Chapman's analysis almost 100%. I don't understand either how radials per se create any additional stresses on rims than bias. However, there is an elephant in the room, I feel. If all things were equal, I would agree wholeheartedly. I'm no engineer and have no technical qualifications of any sort, just my observations over 40 years and about 6 million km of driving. YMMV.

If you drove, for example, a 49 Kaiser with bias tires, as I do, and compared rim failure using those tires to similar/equivalent radial tires on the same rims, and you drove these two cars in an identical fashion, I don't believe there would be much difference if any.

Modern radials grip better, partly because tires are wider now and partly inherent design, and so people drive faster and harder and exert more stress than the original expected use. JBYCDMYS!!!

I drive my Kaiser at 45-50, sometimes 55 or rarely 60 on perfect surfaces. That is all there is with straight gearing and a 100hp flathead six. Off ramps are 20-25 mph not 40-50. Any faster, and the tires complain loudly. Unfortunately, with radials you can reach the over-stress point without necessarily having that audible warning that you are going too fast for the tires/rims.

So, on a 50s Champion sedan, I don't worry about really skinny radials on original (unrusted, never abused, good condition!!) rims as long as I keep to 50s style 2 lane highways, and about 45-50 mph, same as I would with bias. For my V8 Wagonaire, or any V8 car, I have modern Ford rims with radials because I drive them faster and harder, and they are heavier cars. Mind you, all OEM Studebaker rims are getting pretty old no matter what type of tire used...time to update, and then there is no reason to stick to bias.

Sooner rather than later I will update the Kaiser to radials as well, and new rims because they are now over 60 years old. Finding correct modern rims are even more difficult than with Studebakers, though. Choice is very limited on what will fit, and they are all junkyard stuff, only half as old.

Jim B on PEI
63 Wagonaire 259 o/d
57 Champion W4 o/d
57 Champion W4 automatic
57 Commander W4 automatic

[clonelark]

I'm going to send my Henry J wheels (2 of them) to california to get widened for larger tires for the rears, i'm sure they will use newer outer rims with the older centers.

[gordr]

Something else the first posting failed to mention: mass distribution in tires. Steel-belted radial tires are heavy, and a lot of that mass is concentrated in the steel belt. Now factor in dynamic balance, or lack thereof. You can have a tire/rim pair which balances perfectly on a bubble balancer, but the mass at 12:00 could be slightly offset toward the outer face of the tire, and the mass at 6:00 offset slightly toward the inner face of the tire. Such a wheel will tend to wobble at speed, creating reversing forces which tend to flew the rim. And the mass of the steel belt means that those forces are more likely to originate at the tread, giving them the longest possible moment arm to work on the rim.

Now add to this, the fact that properly-sized radials for Studebakers are almost impossible to find, you get people mounting 205 or 215 millimeter tires on rims that were intended to accept a 6.5 or 6.7 inch tire. (an inch is 25.4 mm, you do the math) Oversize tires will not have the proper profile on a narrow rim, and that might well exacerbate dynamic balance problems. What cannot be debated is that they are A LOT heavier. Compare the weight of a 205-75R15 steel-belted radial, and a 6.50X15 bias-ply, and see for yourself.

Now, if we could induce some manufacturer to make a run of 185-80R15, or 195-80R15 fabric-belted radials, these would be a near-perfect fit for most post-war Studebakers, and wouldn't have anywhere near the weight problems of steel-belted radials. When I bought my first Avanti, I had 195-75R15 fabric-belted radials mounted on it, and they lasted a long time, with zero rim problems.

Until such time as suitably-sized radials become available, I'd say the only prudent thing to do is to use Ford or Mopar rims and 205-75R15 steel-belted radials to keep a fairly stock appearance. If you want to run performance tires, then a rim change is obviously required. But running 205s on stock Stude rims is dicing with the Devil, IMHO. I have had rims fail, cracked right around the outer perimeter of the bolt circle plane. And I posted a pic of an incipient failure here a year or two ago.

Gord Richmond, within Weasel range of the Alberta Badlands

[Jim B PEI]

Gord Richmond is the man with the facts--I was just moving a bias tire and a steel belted radial tire, both on OEM Studebaker rims a few minutes before I posted, and thought 'sure is a difference'. The penny didn't drop for me, though, even though I have seen pictures of failures and incipient failures.

Jim B on PEI
63 Wagonaire 259 o/d
57 Champion W4 o/d
57 Champion W4 automatic
57 Commander W4 automatic

[Dave Bates]

Would over-tightening the wheels play some part? I've had trouble with rotors warping at tire shops that didn't use a torque wrench.It couldn't be good for the wheels.

[hotrodstude]

being a chrome reverse guy i have had one one rim failure in my life time but you must check c/r wheels at lease once every 2 or 3 months because chrome platting makes the steel brittle which will lead to failure.

2006,f-150,2x4,v-6,5-speed manual,8ft bed,

[woodysrods]

I have never had a wheel failure in my 41 years of driving, but last year I found out what can happen to an under inflated radial, that is speed rated for 112 mph, when you are doing 130 mph + they get very hot and by time I got my truck pulled to the side of the road there was no tire left except fot the two beads that where still firmly attached to my Chromed reversed rims. Wish I could post the pictures. That little test cost me over $500.00 to replace the two back tires on my truck, without the cost of the repair required to the rear fender.[xx(] These were BF Goodrich fat whitewalls.[V]
So check your air pressure regularly.[?] I was just glad it was a rear that gave me that lesson at that speed as I was on a regular hiway coming int a long curve.[:I]
Good Roads
Brian

Brian Woods
woodysrods@shaw.ca
1946 M Series (Shop Truck)