Why 30x 3 front and 30 by 3 1/2 rear tires?

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Model T Ford Forum: Forum 2015: Why 30x 3 front and 30 by 3 1/2 rear tires?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Sunday, January 18, 2015 - 01:39 pm:

I've wondered why Ford chose to use different rims and tires on the front and back of the Model T. It seems to me it would have been cheaper and faster to build cars with all four tires and wheels being the same. Pre Model T Fords had the same size tires/rims all around. Following are two period explanations for smaller tires on front:




Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Sunday, January 18, 2015 - 02:10 pm:

Evidently the Canadians never read about it because their model T's were 30x31/2 from the word go?? Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Sunday, January 18, 2015 - 02:11 pm:

Years ago when I began having an interest in T's and after reading and studying about them the same thought came to my mind.
A lot of T owners thought the same thing back in the day evidently as they began to use the same size all the way around. At least it gives the purist folks a bit more to do in trying to get things on their cars 'more correct'!

I wonder if Murray Fahnstock (don't know if I spelled his last name correct) had any comments about it or if any other Ford engineers had a reason for it.

I always thought Ford was for uniformity but the different tire sizes always made me wonder.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Coco on Sunday, January 18, 2015 - 02:24 pm:

I would think it has to do with tire loading. At a certain pressure, a tire is going to have a certain contact surface, or tire patch, on the road. A smaller tire will have to "flatten" more to support the weight (since the pressure per square inch on the road equals the pressure per square inch in the tire, discounting any sidewall support).
At rest and empty, I would think a T might be slightly heavier on the front axle. With 4 or 5 grown men inside, I'd think the rear axle then carries more weight. Thus, the larger tire on the back could have a sufficient contact surface without being too "flat".

In fact, the more I think about it, the rear axle may have more weight to start with, the body and upholstery probably weigh as much as the engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Sunday, January 18, 2015 - 03:15 pm:

Rob...

It was probably an understood axiom in the era that smaller side walls provided better responsive steering...science of the era was simply because a few guys said so and not any real methods of proof.

Today conventional wisdom, all car guys will tell you that a 50 sidewall is great for steering and handling, yet will also whisper that the 50's are horrible for a general 'ride', the 70 behaving better. I am not sure that's just radials...perhaps inherent...and I am not sure that the cord pattern in the T era didn't differ between sizes...(it does now)

The real answer from the era is that you have to go back to how the tire people themselves rated tires...and how the engineers took to their duties.

30x3 Size were factory rated 450 pounds total load as fronts, 375 pounds as rears

30 x 3-1/2 were rated 550 pounds as fronts, and 450 pounds as rears.

Ford claimed in the era that they designed 'balanced' and that there were big bucks to be saved with the smaller fronts along with more responsive steering (hah!).

I'd have to think more about it, but something tells me that in the early brass era...some 30-35% of the car cost was the tires even with the mixed sizes? (Somewhere there is a list of what the tire guys got vs. what the DB got for their part, I just can't put my finger on it handily)





Top of pagePrevious messageNext messageBottom of page Link to this message  By David Coco on Sunday, January 18, 2015 - 03:56 pm:

1910, average price was $35.95 for tire, $11.90 for tube, both prices 30x3.5....a lot of cash back then for 4 new ones!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker on Sunday, January 18, 2015 - 04:39 pm:

I remember Bruce (RIP) writing that the different tires was a cost saving measure. That seems consistent with what we know about Henry Ford


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph W. Rudzik on Sunday, January 18, 2015 - 04:47 pm:

My dad always said the narrow tires were in front to track through the mud and snow and the wider tires on the back to widen the original track and get a better grip for the car.
That was dad's concept from the scientific guys of the time and, may be true!

Joe R.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Sunday, January 18, 2015 - 05:36 pm:

The price quoted by David Coco for a tire/tube in 1910 is equivalente to over 1000 Dollars today!

Make it obvious as to why Ford sold the cars with an extra wheel (on demountable rim equipped cars) but the extra tire was not included...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jared Buckert on Sunday, January 18, 2015 - 07:56 pm:

In the old days, people also thought front wheel brakes would affect the steering if applying brakes during any kind of turn. Science has helped to prove a lot of "conventional" thinking wrong.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Sunday, January 18, 2015 - 08:56 pm:

It can still affect steering, but the need to stop is sometimes more important than ability to steer. Back around 1958, I had a 1953 Ford and was on a highway trip when the vehicle in front of me suddenly slammed on the brake. I also slammed on my brake (4 wheel brake). I thought I was going to hit the car in front of me, and turned the steering wheel sharp to the right to go off the road rather than hit the car in front. Well the wheels were locked by the brake and I kept sliding forward. Fortunately I stopped a few inches before hitting the vehicle, but I had flat spots on all 4 tires, and the wear pattern on the front tires showed that they had been turned to the right and had slid sideways. Anyway I was very fortunate. The car in front hit another vehicle in front of it.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Sunday, January 18, 2015 - 10:51 pm:

David makes a good point about tires costing almost $40 (with tube). Eric adds that the equivalent today would be over $1000. Keeping everything in perspective, that means a Model T in 1909-10 cost over $20,000 in todays money, still not a car everyone could afford.

Thanks for the interesting comments,
Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Coiro on Monday, January 19, 2015 - 01:02 am:

Know-nothing newbie logic:

It was recently explained to me by an exec at Lucas Tires (manufacturer of the reproduction Montgomery Wards Riverside) that the difference in size between a 30x3" and a 30x3.5" tire is not in the width of the tread but in the distance between the bead and the tread. -With that in mind, I'm guessing it wouldn't be particularly advantageous to put the larger size up front because, unlike the rear wheels which absorb braking and acceleration torque, the greatest stress on the front road wheels are side-loads from steering around curves. -For side-loads, a shorter distance between bead and tread would make for better safety and handling due to less flexing (sort of like a low-profile tire).

If the typical Model T Ford handles like my '15 Touring, the car under-steers rather than over-steers (meaning that while going around a curve, the front end wants to skid sideways rather than the rear end) and this might be another indication that the rear wheels don't absorb as much side-load as the front wheels.

And if my speculation about the above is correct, it leads in the direction of the familiar conclusion that Mr. Ford found a justifiable reason to save a few dollars, this time by putting smaller tires up front (and sticking the owner with the inconvenience of dealing with two different size spare tires). -As usual, the Canadian product, with 30x3.5" tires all around, and four operating doors, was simply a nicer car to own.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Monday, January 19, 2015 - 01:46 am:

In case anyone wants to calculate the equivalent value of a dollar then and now.
Makes you realize that a few cents wasn't just a drop in the bucket.

http://www.usinflationcalculator.com/


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Coco on Monday, January 19, 2015 - 07:59 am:

There was also a 31 x 4 tire available aftermarket, possibly later after the T production was over. This tire size fit the T rim, but could handle a larger load.

In researching prices on tires in 1910, I also came across the price for a 34 x 4 tire (I have a Model 16 Buick with that size tire) and they were about $50 each in 1910, without tube!! The price of rubber was high, and every additional ounce of rubber in a tire added to the cost...


Top of pagePrevious messageNext messageBottom of page Link to this message  By william schaller on Tuesday, January 20, 2015 - 01:03 am:

what stopped ford from doing 30x3 on all fours?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, January 20, 2015 - 06:18 am:

The period rating table from the tire manufacturer above rated 30x3" to 425 lbs if placed in the front but only 350 lbs in the rear, so a larger tire was needed in the rear but not in the front and since Ford wanted to make the T as light and as cheap as possible - but not under-dimensioned, different tire dimensions were chosen.

But I don't know why Canadian production had 30x3,5" all around from start..? Did the contact with colonies through the commonwealth give cheaper rubber in Canada?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Tuesday, January 20, 2015 - 06:52 am:

Personally I doubt it was the expense that determined different tire sizes. With tire orders in the thousands, and considering the amount of difference in rubber used, I think it was a matter of safety or performance, as suggested in the first articles. NRS and K, and all earlier Fords did not use different tire sizes (front and rear), and I believe cost savings were as big a factor with the Model N as with the T. In fact, Ford set $500 as the N price and needed to raise the price by the time production ramped up in early 1907. Part of the increase in cost of the N was attributed to the switch to 28x3 tires (from 28x21/2). Had Ford been looking for cost savings they could have kept the 2 1/2 in tires on front, but didn't. Just my uneducated opinion.

Another question, if it was a cost saving decision, why did Ford eventually switch to one size?

Thanks for all the good comments,

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, January 20, 2015 - 07:17 am:

I think it was the market demand for demountables that caused the change to one size all around - on the demountable equipped cars only. The cheapest open cars kept 30x3" on non demountable wheels and ball bearings in the front for several years after demountables were made available in 1919, up until 1925 I think.

Maybe tires were relatively cheaper by the 20's?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Coco on Tuesday, January 20, 2015 - 08:12 am:

I've collected and studied and been fascinated by antique cars for over 50 years. In that time I've often heard people talk about early cars like they were just thrown together, fit and finish wasn't very good, driving qualities were poor, and so forth.

How many times have you heard noisy mechanicals, or driven a poorly performing car, or seen badly fitting body panels, and the comment heard is "That's how it left the factory, they all were like that back then".

Horsehockey.

Henry Ford was sufficiently smart, but he had engineers working with him, and if there were different size wheels and tires front and back, it's because an engineer studied the problem and decided that was what was required for the car to perform correctly. If one studies the engineering of the early cars, one sees that things were done for a reason, and in most cases, done quite well. If later a change was made, it was also studied from an engineering standpoint, possibly advances in tire making technology allowed them to put the smaller tire on rear wheels.

Model T would not have sold so well if it wasn't reasonably attractive, reasonably quiet, easy to drive, and of sufficient strength to handle the roads of the day. (Note that I didn't say "The Model T"; most period written pieces didn't use "the" to start the name)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Tuesday, January 20, 2015 - 10:05 am:

David,
Good points. I group Model T into a few categories. From Oct 1908 through about 1913, I consider the cars to have been among the best in the world, period. Once the initial weaknesses (rearend, waterpump, straight axles, etc) were sorted out, I think the early T were a tremendous value, and state of the art too. Mono-block, enclosed engine/transmission and magneto were all items seldom seen on other cars, and certainly not on cars costing less than $1,000.

Between 1913 and about 1916, I think the T was still a competitive car in it's own right, although technology was moving forward and other cars were adding features and improvements that made the T a "middle of the road" car in terms of advancements. However, the T was becoming less and less expensive, opening more and more markets to offset a lack of innovation.

From 1917 on, I think of the T as an inexpensive tool, still opening new markets, as it became less and less expensive, to again offset old technology.

Of course these are just my poorly worded impressions, and as always, my opinions are subject to change. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Coco on Tuesday, January 20, 2015 - 10:22 am:

Rob, I never thought of the "different ages" of Model T as you put it, but that's true....it went from a great value to a good value to a tool...interesting.....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Layden Butler on Tuesday, January 20, 2015 - 12:46 pm:

31x4 tire size was an early introduction. It is my understanding that during WW1 the 30x3 1/2 was obsoleted in favor of the 31x4 but to not confuse the buying public the tires were marked and referred to as 30x3 1/2 oversize. A designation which continued to recent times.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker on Tuesday, January 20, 2015 - 01:30 pm:

I think Rob correct about the three phases of the Model T.
I still think Ford used the lowest cost tires that would meet the demand, thus the smaller tires on the front. Once he offered demountables, then cost was not an important criteria, the convenience of the equal sizes easily cancelled out the increased cost.
My 1917 initially came with three inch tires on the front. Later I changed to all demountable using 3 1/2 all round. I could detect no change in the handling.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Tuesday, January 20, 2015 - 02:04 pm:

Tony,
I checked my copies of the Ford board of directors minutes, hoping to find something regarding the two tire sizes, with no luck. Maybe we'll find something definitive as to tire size difference (and why). I know a few high end cars of the period also used two sizes. Great discussion, thank you all for your input,
Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By george house . . .caldwell county, TX on Tuesday, January 20, 2015 - 02:38 pm:

Interesting initial question Rob and a lot of good input from everyone. At the risk of highjacking this thread I've had a long-time similar question: Why 10 spoke front wood wheels on a lot of marques (not Ford) and 12 spoke rears? I see many every HCCA Gazette issue and specifically the 1911 Hupp I just restored. Certainly the greatest weight is the engine and that'll be on the front axle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Layden Butler on Tuesday, January 20, 2015 - 05:17 pm:

George,
Torque! The rear wheels drive the car thru the spokes to the tire and even more force is braking.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Rose on Tuesday, January 20, 2015 - 06:04 pm:

Model Ts make all that noise and smell bad so blind people can hate them too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, January 20, 2015 - 07:48 pm:

I have experience to show that turning or side loads are harder on the front spokes than any straight load on the rears.

The rearend locked up at 55mph when the ring gear broke in pieces. It badly flat spotted the new tires and damaged the diffy housing. The 10 tooth pinion was fine. That was with oak spokes.

A front wheel later collapsed at 10mph in a skid.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Tuesday, January 20, 2015 - 07:55 pm:

I'm no Paul Harvey,but i know there is more to the story!!!!!!!!!!!!!!!! Bud.


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