FIA rules for 1991

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CK
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Re: FIA rules for 1991

Post by CK »

From Pirelli website for current tires.

Dry tire:
front: 305/670-13
rear: 405/670-13

Intermediate tire (green):
front: 305/675-13
rear: 405/675-13

Full wet tyre (blue):
front: 305/680-13
rear: 405/680-13
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Re: FIA rules for 1991

Post by BullittStang »

This is fascinating, because I always saw a clear delineation between the 1989/90 cars, and their 91/92 equivalents. I always considered the 89/90 cars as a separate generation versus the 91/92 cars. Even though they're clearly not really that much bigger, they look larger.
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Re: FIA rules for 1991

Post by gp-models »

CK wrote: Wed Sep 22, 2021 2:06 am A measurements of Tamiya Jordan 191 tires and Hasegawa LC90 tires yield these numbers.

Front tire 25.0x10.0-13
Overall diameter: Tamiya - 24" (610mm) Hasegawa - 24.7" (627mm)
overall width: Tamiya - 12.74" (324mm) Hasegawa - 12.6" (321mm)
Tread width: Tamiya - 10.7" (271mm) Hasegawa - 10.6" (269mm)

Rear tire 26.0x15.0-13
Overall diameter: Tamiya - 25.6" (649mm) Hasegawa - 25.8" (654mm)
overall width: Tamiya - 17.8" (451mm) Hasegawa - 17.8" (451mm)
Tread width: Tamiya - 15.7" (400mm) Hasegawa - 15.5" (393mm)

The dimensions from 2 model manufactures with one in 1/20 and the other in 1/24 are so close. They should be accurate. Tire size could probably measured by Tamiya and Hasegawa. The delta can be due to different ware and tire pressure.
Today i was able to measure a rear tyre from Minichamps B192 in 1:18 with rain tyres and the numbers are coming close to what you measured on those kits,
I have an overall diameter of 634mm
overall width of 462,5mm
and a tread width of 414mm
Doing a math example to find out the real width of Jordan 191 as i found some datas about the track width of front and rear axle.
Front axle width is 1800mm, i assume that the offset of the rim is 0, so that it is centered, means on top of 1800 two half tyres (254mm), brings a total width on the front axle of 2054mm
Rear axle width is 1680mm, again i assume the the offset of the rim is 0, means on top of 1680 Two half rear tyres (381mm), brings a total of 2061mm on the rear axle.
Possible that it might be real, but there is no information if the offset of the rim is realy 0 on front and rear wheels, so it`s just guessing.
Last edited by gp-models on Thu Sep 23, 2021 10:09 am, edited 1 time in total.
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Re: FIA rules for 1991

Post by steinietrabi »

That sounds very plausible in any case and would fit the pictures that you find.
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Re: FIA rules for 1991

Post by gp-models »

Right, it`s comming close to that, but there might be a difference in real. As long as it looks scale i`m fine with those datas so far, with the correct wheelbase it should be double checked finaly. ;)
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Re: FIA rules for 1991

Post by CK »

Track width is the distance between the center lines of the tire pair. So measurements and calculations for J191 is correct.

For the recent couple of years, the width of the car defined by FIA excludes the tires. It is not clear how it is measured. Is it the maximum distance between the outface of the wheel rims with camber included? I have no idea. FIA does not define track width requirement.
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Re: FIA rules for 1991

Post by gp-models »

CK wrote: Thu Sep 23, 2021 11:42 am Track width is the distance between the center lines of the tire pair. So measurements and calculations for J191 is correct.

For the recent couple of years, the width of the car defined by FIA excludes the tires. It is not clear how it is measured. Is it the maximum distance between the outface of the wheel rims with camber included? I have no idea. FIA does not define track width requirement.
About the track width i`m not sure, on a streetcar you never have 0 as offset on a wheel, so the track width can not be calculated the way i did and as there is nothing to be found about the offset of the rims or where did you find this information?
I could not find such datas, but i think a few millimeters more or less would not make much difference.
Thanks to all for your input, never expected to become it that hard to find some basic datas about the cars.
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