"Back in the day" when we were dealing with bias ply tires, there was not so much rotational mass (weight) on the outside diameter of the tire. The most of the weight of the wheel was the wheel itself which by definition was closer to the center of rotation. The wheels were narrow - frequently 4.5 to 5 inches wide. Roads were rougher and speeds were lower. Suspensions were probably less sensitive to transmitting road feel.
Balance became more of a problem when we went to bias belted tires in the early 70's and then radials with steel belts on the outer diameter creating a much different weight distribution within the tire / wheel assembly. These also came with wider wheels (6 to 7 inch). And roads were improving as well as car suspensions. Speeds were increasing.
Now think of an individual tire - the reason we balance them is that they are imperfect with respect to weight distribution - there has to be a splice in each ply where the carcass is built up. This results in a local area where there is overlap and non uniform weight. The rubber mixture may also be less than uniform density - after all it is a mixture that is extruded into sheets that are also spliced. So if a tire is perfectly uniform, it is unusual. And the rims may be imperfect also as steel rims are frequently welded together and aluminum wheels may have nonuniform density due to casting.
A tire can be modeled as a rotating circular disc - but now think not of disc representing the tire geometry but the disc representing its mass (weight) distribution. It you tilt the disc to where the disc runs thru the center of mass (weight), the heavy spot causes the plane of the disc to tilt from the disc representing the center of geometry of the tire which is still the center of rotation. But the tire wants to rotate with the plane representing the center of mass and hence wobbles creating the vibration we feel from imbalanced tires.
In rotational bodies there is a resonant frequency which is a function primarily of outer diameter and rotational speed. When imperfect objects rotate they create forces due to the imbalance, but these forces may be relatively small at speeds not near the resonant frequency. Typically for older vehicles this was roughly 60-65 mph so you would feel the worst vibration at that speed. The frequency is purely a function of revolutions per minute and hence tire diameter and vehicle speed. The vibration will be worst at this speed - and you may actually be able to reduce the severity of the vibration by increasing or reducing speed - though it will probably still be present.
We balance tires and wheels to make the car think the assembly is perfect and the planes of rotation and mass are the same. But how do you do that when heavy spot may be on inside or outside of tire and there may be more than one at different placed around the tire.
The first fix was to add a weight opposite the heavy spot - this worked at low speeds but failed at the resonant frequency (specific vehicle speed). In reality, a single point balance or even a 2 point balance on the back only has a 50-50 chance of aggravating the problem - If you are unlucky and the heavy spot is on the front (outside) of the wheel and the balance weights are opposite and on the back (inside), you have increased the effect of the tilt of the plane representing the center of mass.
We then went to a "4-point" balance to try and better distribute the heavy areas compensating for the imbalance. In this method you put 2 weights on top and 2 on bottom spaced apart so that there were really 3 heavy spots spaced around the tire - this worked pretty well as speeds increased with bias tires..
But the first belted tires with more weight and more splices on the outside diameter required more sophistication - hence the development of on car rotational balance and eventually computer spin balance.
Sorry for the history lesson and the tech-speak, but I tried as best I could to make it understandable. Hope this helps.
Edward Mills Antique Tractors 1930-1960 Antique Cars 1960-1985
On 7/29/2019 1:05 AM, 'Rich Barber' c300@xxxxxxx [Chrysler300] wrote:
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For appearance sake, I directed my tire guy at the time to mount all weights on the inside of the 15??? OEM Motor Wheel wire-spoke wheels.?? H said he would, but the wheel would not be dynamically balanced. I ran those old Bias-ply Remington???s a lot of miles at high speed and never felt any pronounced out-of-balance sensation.?? I believe the computerized wheel balancer directs the technician how much weight and where, ,including inside or outside.?? I don???t understand the physics of splitting the weights inside and/or outside but there must be a good reason.?? Tire and wheel guys:?? What, if anything do we lose by placing all weights on the inside??? And, why split the weights inside and out anyway?
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Rich Barber
Brentwood, CA 105F today.
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Curtis and Group,
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One final 'road-tested' comment from me re the 235/75R14 American Classics I'm running on my 300-F. Just drove back to Chicago from our wonderful Minneapolis Fall Meet tonight - have now put 4,300+ miles on my tires since having them mounted on the F's stock 14"x6.5" steel wheels in April, a few days before heading down to Texas for our Spring Meet. Homeward bound through northern Wisconsin, with strong crosswinds and torrential rain for 100+ miles tonight, in addition to the heavy rains I encountered for a good part of the trip to/from Dallas, these tires have performed very well. There's no sense of fighting the car to keep it stable through these heavy downpours. I'm very happy with their performance.
I purchased my 4 tires through a Coker special promotion at a Mecum auction last fall - cost including free shipping and road hazard warranty was about $1,040. Whitewalls are 2 1/2". If your purchase them, be sure to read the online instructions for mounting - including the recommendation that wheel weights be only mounted on the insides of the rims, so as to not blemish the whitewalls.
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Noel Hastalis
Burr Ridge, IL
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On July 28, 2019 at 8:00 PM EMills_ATC <millserat@xxxxxxxxxxxxx> wrote:
Sorry for late reply - probably already solved, but here are some data I have compiled from 1960's to 2015 on tires.
First I will list 8.00-14 as it evolved to P215/75R14 (P/225/70R14), noting that P215/75R14 is largest 14 inch whitewall (Narrow White) in current full scale production as of 2019. (Hankook Optima H724 price around $65-80). There are other specialty tires ($200-300 range) including 8.00-14, G78-14, and P215/75 R14 including wide whitewalls, but for the most part these are limited production specialty runs, in some cases using outdated equipment. There is also an American Classic in P235/75R14 in whitewall (Wide and Narrow White?).
I will note that in early days, to provide a soft ride, tire design was based on 24 psi, frequently with note in fine print to increase pressure (up to 32 psi) for sustained high speed or increased load. If I recall correctly the 24 psi assumed driver plus 2 passengers and 1 suitcase. Anything more moved you to higher load. And Speed limits were mostly assumed to be 60 mph. Later load capacities were based on 32 psi, and most current standard load range radials are based on 44 psi - so dont assume load ratings are directly comparable - and it your rims are old beat up rusty things, dont assume you can go to 44 psi safely.
Also, belted and later radial tires tend to have more flexible sidewalls and give lower ride height for a given diameter. This is reflected in the SLR (Static Loaded Radius) column if I had any data from manufacturers data sheets. Most likely your 8.50-14 had a SLR of about 13 in, while a P215/75R14 would be closer to 12 inches and even the P235/75R14 is likely to be only 12.5 to 12.6 inches, hence lowering the car about a half inch despite being oversize to the P225/75R14 equivalent to the original 8.50-14
Second I will list the 8.50-14 to P225/75R14 specifications as these are more likely applicable to C-body cars. Unfortunately the last P225/75R14 I know of were produced by Cooper in 2006.
Lastly I will provide data for 9.00-14 to P235/75R14 - again, I believe the American Classic is currently available in the P235/75R14 as of 2019.
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SIZE | MFG | TYPE | Sidewall | OD | LOAD | RPM | LR | SWid | RimW | TWid | SLR | Cost | Source |
8.00-14 | BFG | Deluxe Silvertown (3-60 Mfg Spec) | | 27.54 | 1175@24 | | | 7.5 | 5.5 | 4..53 | 12.79 | ?? | 1960 BFG |
8.25-14 | GoodYear | Power Cushion (Mfg Spec) | | 27.56 | 1380@24 | | | 8.2 | 6 | ?? | ?? | ?? | 1967 Goodyear |
205R14 | Michelin | XWW (Mfg Spec) | | 26.9 | 1620 | 778 | | 8.1 | 6 | ?? | 12 | ?? | Michelin 1979 |
G78-14 | General | Belted Jumbo 780 (OE) | | 27.27 | | | | 8.54 | 6 | ?? | 12.47 | ?? | General 1971 |
GR78-14 | Michelin | XWW (Mfg Spec) | | 26.8 | 1620 | 782 | | 8.4 | 5.5 | ?? | 11.8 | ?? | Michelin 1979 |
P215/75R14 | Michelin | X (Mfg Spec) | | 26.8 | 1665 | 776 | | 8.7 | 6 | ?? | 11.9 | ?? | Michelin 1985 |
P215/75R14 | Hankook | H724 | NW | 26.7 | 1664 | 778 | 98S | 8.5 | 6 | 5.3 | ?? | $81 | Hankook 2014 |
P215/75R14 | American Classic | NW | 26.69 | 1664 | | 98S | 8.5 | ?? | 5.68 | ?? | ?? | Coker 2014 |
P215/75R14 | Toyo | Extensa A/S | Black | 26.7 | 1664 | 778 | 98S | 8.3 | | | 12.0 | | Toyo 2014 |
225/70R14 | Hankook | H725 | Black | 26.3 | 1675 | 789 | 98T | 8..9 | 6.5 | 6.6 | ?? | ?? | Hankook 2014 |
225/70R14 | General | Altimax RT43 | Black | | | | | | | | ?? | ?? | ?? |
225/70R14 | Cooper | Cobra GT | RWL | 26.27 | 1675 | | | 8.92 | 6.5 | 7.2 | ?? | ?? | ?? |
225/70R14 | BFG | RedLine | Red | 26.3 | 1675 | | | 8.9 | ?? | 6.7 | ?? | $186 | Coker |
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SIZE | MFG | TYPE | Sidewall | OD | LOAD | RPM | LR | SWid | RimW | TWid | SLR | Cost | Source |
8.50-14 | BFG | Deluxe Silvertown (3-60 Mfg Spec) | | 28.3 | 1265@24 | | | 7.86 | 5.5 | 4..73 | 13.07 | ?? | 1960 BFG |
8.50-14 | Firestone | Deluxe Champion (3-61 Mfg Spec) | | 28.4 | 1265 | | | 8.04 | 5.5 | ?? | 13 | ?? | 1961 Firestone |
8.55-14 | GoodYear | Power Cushion (Mfg Spec) | | 28.24 | 1510@24 | | | 8.5 | 6 | ?? | ?? | ?? | 1967 Goodyear |
8.55-14 | General | Jet-Air II Rayon | | 28.26 | | | | 8.54 | 6 | ?? | 12.81 | ?? | General 1971 |
8.55-14 | BFG | Deluxe Silvertown Coker | | 28.1 | 1740 | | | 8.35 | ?? | 4..75 | ?? | ?? | Coker |
215R14 | Michelin | XWW (Mfg Spec) | | 27.4 | 1770 | 765 | | 8.4 | 6 | ?? | 12.2 | ?? | Michelin 1979 |
HR78-14 | Michelin | XWW (Mfg Spec) | | 27.5 | 1770 | 759 | | 8.9 | 6 | ?? | 12 | ?? | Michelin 1979 |
H78-14 | General | Belted Jumbo 780 (OE) | | 27.85 | | | | 8.8 | 6 | ?? | 12.65 | ?? | General 1971 |
H78-14 | coker | coker | WW | 27.6 | 1770 | | | 8.86 | ?? | 5.75 | ?? | ?? | Coker |
HR78-14 | Phillips66 | used | NW | 27.45 | | | | 8.75 | 6 | 6 | ?? | C300 | ?? |
P225/75R14 | Michelin | X (Mfg Spec) | | 27.6 | 1795 | 757 | | 8.9 | 6 | ?? | 12.1 | ?? | Michelin 1985 |
P225/75R14 | Firestone | 721 Steel Belted Radial | NW | 27.35 | | | | 9 | 6 | 6.15 | 12 | ?? | Firestone 10-86 |
225/75R14 | Cooper | TrendsetterSE | NW | 27.05 | 1797 | | | 8.7 | 6 | 5.6 | ?? | ?? | Cooper 2006 |
H70-14 | GoodYear | Speedway WT (Mfg Spec) | | 27.78 | 1510@24 | 764 | | 9.1 | 6 | 6.81 | ?? | ?? | 1967 Goodyear |
P235/70R14 | Firestone | SS Radial | | 26.66 | | | | 8.85 | 6.5 | 6.27 | 11.54 | ?? | Firestone 10-86 |
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SIZE | MFG | TYPE | Sidewall | OD | LOAD | RPM | LR | SWid | RimW | TWid | SLR | Cost | Source |
9.00-14 | BFG | DS (3-60 Mfg Spec) | | 28.8 | 1355@24 | | | 8.25 | 6 | 4.93 | 13.26 | ?? | 1960 BFG |
9.00-14 | Firestone | DC (3-61 Mfg Spec) | | 29 | 1355 | | | 8.53 | 6 | ?? | 13.2 | ?? | 1961 Firestone |
9.00-14 | BFG | DS Coker | NW | 28.68 | | | | 8.8 | ?? | 4.8 | ?? | $184 | Coker |
8.85-14 | General | Jet-Air II Nygen | | 28.3 | | | | 8.96 | 6 | ?? | 12.99 | ?? | General 1971 |
8.85-14 | BFG | DS Coker | NW | 28.68 | 1860 | | | 8.8 | ?? | 4.8 | ?? | ?? | Coker |
J78-14 | General | Dual S-90 Sidewinder | ?? | 28.24 | | | | 9 | 6 | | 12.81 | ?? | General 1971 |
J78-14 | GoodYear | OE Polyglas | DW | 28.2 | | | | | | | ?? | 67 NY | measured 67 NY |
235/75R14 | American Classic | NW | 27.87 | 1930 | | 104S | 9.25 | ?? | 6.3 | ?? | ?? | Coker 2014 |
245/70R14 | generic | No known examples | | 27.6 | 1940 | | | | | | ?? | ?? | ?? |
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Edward Mills Antique Tractors 1930-1960 Antique Cars 1960-1985
On 6/25/2019 7:33 PM, 'Rich Barber' c300@xxxxxxx [Chrysler300] wrote:
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Well, that's an easy decision, my 65 300L is original from front to back & I was hoping to keep the wheels & hubcaps!!!
Amazingly after sitting for 25 years in a garage, it still has original bias ply tires.??
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