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Old 07-19-2019, 01:15 AM   #1
M2M
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Thumbs up changing to 5.50 Bias Ply = changing to 3.54 ratio

475-19 Goodyear diamond tread. USA made in 4-ply poly.
Diameter= 28.82"

550-19 Bias Ply BF Goodrich Silvertown. USA made in 4-ply poly.
Diameter= 31.10"
(this size tyre was factory fitted to later production Soviet GAZ-A)

475-19 Goodyear
Motor RPM= 2000
Differential Ratio= 3.54
MPH= 48.5

550-19 Bias Ply BF Goodrich
Motor RPM= 2000
Differential Ratio= 3.78
MPH= 49

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Old 07-19-2019, 04:21 AM   #2
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

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Old 07-19-2019, 08:24 AM   #3
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Hotrod overdrive,its why big rear tires were put on them..today its about 'stance',back then it was about road speed.
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Old 07-19-2019, 09:15 AM   #4
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Now what speed do you get with the 550 tires and the 3.54 rear?
Jack
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Old 07-19-2019, 09:31 AM   #5
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Is there a brand I can get them in cheap? around $100. or what do they cost? The speed is probably worth it.
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Old 07-19-2019, 09:53 AM   #6
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

M2M

I am running 7 X 16 Tornel bias ply with a 3.54, circumference 30.8 inches.

I have checked speed at multiple side of the road radar displays and am dead on. Went with these because they give me the same results as standard OEM rims/tires.

Picture shows tires, spare is standard rim/tire.

If interested I will go for run and see what speed is 2000 rpm. Let me know if interested and I will post back.
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Old 07-19-2019, 10:39 AM   #7
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

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Now what speed do you get with the 550 tires and the 3.54 rear?
Jack
52.2 mph
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Old 07-19-2019, 10:47 AM   #8
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

If you went with the 31.10 inch tire and the 3.54 gear you would get 52.2 at 2000 RPM.
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Old 07-19-2019, 10:48 AM   #9
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

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Originally Posted by mike657894 View Post
Is there a brand I can get them in cheap? around $100. or what do they cost? The speed is probably worth it.
Mike the new Lucas Nokia 5.50-19 can be had for $129. It has a slightly smaller diameter than the Goodrich at 30.50".

It works out to 51.28 mph with the 3.54s, 48 mph with the 3.78s.
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Old 07-19-2019, 11:07 AM   #10
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

One very slight problem with the above calculations- The measured diameter of a tire is not equivalent to the rolling diameter. Even for tires of the same size, this will vary between manufacturers, construction, and tread.

Many tire manufacturers list revolutions per mile for each tire they produce. That is the most accurate way to figure speed vs. RPM.
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Old 07-19-2019, 12:39 PM   #11
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

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One very slight problem with the above calculations- The measured diameter of a tire is not equivalent to the rolling diameter. Even for tires of the same size, this will vary between manufacturers, construction, and tread.
And of course Mike is correct. These calculations are all on paper and the results will be different in real life.

I just wish I could get that fact into the heads of engineers where I worked (now retired). They kept coming up with these "new ideas" (and I'm sure still do) to make a better product or save money that don't work in real life.
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Old 07-19-2019, 01:34 PM   #12
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Years ago, I had a Volvo 122S that could get to 100 with its stock tires (15 inch wheels). I changed to bigger rear tires and suffered loss of gas mileage and performance. Maybe it was the dynamics of that particular car that made the use of larger rear tires counterproductive.
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Old 07-19-2019, 02:16 PM   #13
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Arrow Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

I recently went from factory spec 225/60-17 to 235/65-17 on my modern car. Before the change my speedo showed 1-2mph MORE than the GPS. After fitting the larger diameter tyres my speedo showed 2-3mph LESS than the GPS. So don't let anyone tell you changing to a larger diameter tyre has no real world effect.

I was lucky enough to buy two new 550x19 BF Goodrich Silvertown Bias Ply for $130 each, they are normally $204 each.

The great thing about these BF Goodrich is they do not look like a "hot-rod" addition. Though beefier looking than the Goodyear they look at home on the Model A, especially on a Fordor, Tudor or pickup. The Russian GAZ-A got them and I've been told so did the Ford A 1931 Woody Station Wagons.

The Nokia 550x19 are cheaper because they are made in Viet (not USA) and are nylon not poly. They are probably a good tyre but I've heard of no reviews yet.

Apart from the BF Goodrich there's another 19" option. The beefcake Firestone 550/600-19 Bias Ply USA made 32" diameter 6-ply poly at $230 each. Apart from making a Mitchell o/d obsolete (just kidding!), if you plan to haul a few dozen cement bags in the back of your pickup you need these for their load capacity

My Tudor has a 3.78 I believe and I do not want an overdrive and I do not want to add a 3.54 or 3.27 unless my rear end needs a rebuild. Apart from that a bit more rubber on the ground for road holding and braking isn't a bad thing.
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Old 07-19-2019, 02:37 PM   #14
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

This thread shows what 550x19 bias ply look like on a car:

https://www.fordbarn.com/forum/showthread.php?t=242572
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Old 07-19-2019, 03:30 PM   #15
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Unread Today, 11:07 AM #10
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
One very slight problem with the above calculations- The measured diameter of a tire is not equivalent to the rolling diameter. Even for tires of the same size, this will vary between manufacturers, construction, and tread.

Many tire manufacturers list revolutions per mile for each tire they produce. That is the most accurate way to figure speed vs. RPM.


Mike V In my opinion is closest to correct. However I Think the most accurate is to get the distance from the center of the wheel to the ground with the proper inflation air pressure. double that to get the effective diameter. This will be slightly less do to the weight on the tire. I know this is very OCD but that is just me.
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Old 07-19-2019, 04:10 PM   #16
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Quote:
Originally Posted by 30 Closed Cab PU View Post
M2M

I am running 7 X 16 Tornel bias ply with a 3.54, circumference 30.8 inches.

I have checked speed at multiple side of the road radar displays and am dead on. Went with these because they give me the same results as standard OEM rims/tires.

Picture shows tires, spare is standard rim/tire.

If interested I will go for run and see what speed is 2000 rpm. Let me know if interested and I will post back.


Just went for a drive 2000 RPM = 49 mph
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Old 07-19-2019, 04:45 PM   #17
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Put a mark on the side of tire at the bottom and a coresponding mark on floor.
Move the car 1 revolution of tire and so mark is down. Mark floor and measure between 2 marks on floor.

That is the rolling circumference of the tire. Easy to compute rolling diameter.

John
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Old 07-19-2019, 07:37 PM   #18
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Quote:
Originally Posted by Peyton View Post
Years ago, I had a Volvo 122S that could get to 100 with its stock tires (15 inch wheels). I changed to bigger rear tires and suffered loss of gas mileage and performance. Maybe it was the dynamics of that particular car that made the use of larger rear tires counterproductive.
The restorer of my '28 Tudor fitted a 3.54 diff. A later owner fitted a 26% Mitchell O/D. I am going back to reduce the overall ratio because it is too highly geared as it is in O/D. Economy is poor and it hates hills. This is the same as you experienced.
By going back to 3.78, I am reducing the overall ratio by about 3.6%. By putting 5.00X19 wheels and tyres on it, I'm dropping by 3% - about the same. I have the wheels ready to go (the old 21" tyres are worn out) so I will try that option first ($$$).Before anyone criticises me for putting 19" wheels on a '28 car, this car is a go-er, not a show-er!
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Old 07-19-2019, 08:28 PM   #19
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

Quote:
Originally Posted by Peyton View Post
Years ago, I had a Volvo 122S that could get to 100 with its stock tires (15 inch wheels). I changed to bigger rear tires and suffered loss of gas mileage and performance. Maybe it was the dynamics of that particular car that made the use of larger rear tires counterproductive.
Looks like a small engine. Probably dropped off the good bit of the power curve.

https://www.motorsportmagazine.com/a...peed-volvo-122
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Old 07-20-2019, 08:58 PM   #20
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Default Re: changing to 5.50 Bias Ply = changing to 3.54 ratio

i think you are right.
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