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07-19-2019, 01:15 AM | #1 |
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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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07-19-2019, 04:21 AM | #2 |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
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07-19-2019, 08:24 AM | #3 |
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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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07-19-2019, 09:15 AM | #4 |
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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?
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07-19-2019, 09:31 AM | #5 |
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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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07-19-2019, 09:53 AM | #6 |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
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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. Last edited by 30 Closed Cab PU; 07-19-2019 at 09:54 AM. Reason: typos |
07-19-2019, 10:39 AM | #7 |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
52.2 mph
Last edited by Y-Blockhead; 07-19-2019 at 11:04 AM. |
07-19-2019, 10:47 AM | #8 |
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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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07-19-2019, 10:48 AM | #9 | |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
Quote:
It works out to 51.28 mph with the 3.54s, 48 mph with the 3.78s. Last edited by Y-Blockhead; 07-19-2019 at 11:00 AM. |
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07-19-2019, 11:07 AM | #10 |
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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. |
07-19-2019, 12:39 PM | #11 | |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
Quote:
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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07-19-2019, 01:34 PM | #12 |
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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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07-19-2019, 02:16 PM | #13 |
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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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07-19-2019, 02:37 PM | #14 |
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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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07-19-2019, 03:30 PM | #15 |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
Unread Today, 11:07 AM #10
MikeK Senior Member MikeK's Avatar Join Date: May 2010 Location: Windy City Posts: 2,804 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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07-19-2019, 04:10 PM | #16 | |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
Quote:
Just went for a drive 2000 RPM = 49 mph |
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07-19-2019, 04:45 PM | #17 |
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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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07-19-2019, 07:37 PM | #18 | |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
Quote:
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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07-19-2019, 08:28 PM | #19 | |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
Quote:
https://www.motorsportmagazine.com/a...peed-volvo-122 |
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07-20-2019, 08:58 PM | #20 |
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Re: changing to 5.50 Bias Ply = changing to 3.54 ratio
i think you are right.
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