twas_brillig
Jedi Knight
Offline
I've been going through posts regards wheels and tires in order to come up with what I want to put on our Bug-Eye project car (using 13 x 5 rims) and have come up with the following summary:
Rick Horler in <span style="font-weight: bold">"Original Sprite & Midget - The Restorer's Guide"</span> states:
"Made by Rubery Owen, the road wheels, of 13in diameter and 3.5in rim width, were formed with a 'D' rim pattern". He identifies the OEM tyres as "Dunlop Gold Seal 5.20-13 tyres were standard, these being a tubelss crossply of four-ply construciton. Heavier duty Dunoop Fort six-pl.y tyres could be ordered for an additional 7.2.6"
The <span style="font-weight: bold">Austin-Healey Sprite Mark I Workshop Manual</span>, Issue 6, from The British Motor Corporation (no date)advises:
"The Austin-Healey Sprite is fitted with 5.20-13 tubeless tyres upon 15x4J ventialted steel disc wheels, each wheel being secured by four nuts"
"Tighten the road wheel nuts to a torque wrench reading of 37 to 39 lb. ft. (5.02 to 5.4 kg.m.). Do not overtighten."
From 'General Data' in the same workshop manual:
Pressures:
Front 18 lb./sq.in. (1.27 kg.cm2)
Rear 20 lb./sq.in. (1.41 kg.cm2)
For sustained speeds in excess of 80 to 85 m.p.h. (129 to 137 k.p.h.) increase pressures to:
Front 24 lb./sq.in. (1.69 kg.cm2)
Rear 26 lb./sq.in. (1.83 kg.cm2)
Web sites that have been referenced in this forum:
Everything to do with tires:
https://www.carbibles.com/tyre_bible.html
Tire comparison/calculator sites:
https://www.mintylamb.co.uk/?page=tyre.htm
https://www.1010tires.com/TireSizeCalculator.asp
https://www.miata.net/garage/tirecalc.html
Determining modern vs original tire sizes:
https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=45
https://www.tirerack.com/tires/tiretech/45_conversionchart.html
https://www.carbibles.com/vintagetyresizes.html
Wheels:
https://www.tirerack.com/wheels/tech/techpage.jsp?techid=101
Wheel width vs. tyre size:
https://www.carbibles.com/tyre_bible_pg2.html
(about a third of the way down)
Application:
The original Bug-Eye tire size of 5.20/13 doesn't apear in the Tire Rack chart (the smallest 13 inch tyre shown is 5.60 x 13); members on the Forum have advised that the modern equivalent of the original 5.20 is 145/13.
Carbibles provides these equivalents in their vintage tyre table: 135/80-13; 145/70-13; 165/60/13, and 130/100-13 in their script calculation on page one.
We have one running BE with 155/80-13 tires on it. Comparing rolling radii:
145/80-13 has a rolling radius of 281.1 mm
155/80-13 RR is 289.6
175/65-13 278.85 mm
175/70-13 287.6
185/70-13 294.6
The 175/70-13 appears to the optimum tire size for the new rims for our second Bug-Eye - I'll be checking for availability tomorrow..
Additional wisdom/thoughts sure are welcome.
Doug
Rick Horler in <span style="font-weight: bold">"Original Sprite & Midget - The Restorer's Guide"</span> states:
"Made by Rubery Owen, the road wheels, of 13in diameter and 3.5in rim width, were formed with a 'D' rim pattern". He identifies the OEM tyres as "Dunlop Gold Seal 5.20-13 tyres were standard, these being a tubelss crossply of four-ply construciton. Heavier duty Dunoop Fort six-pl.y tyres could be ordered for an additional 7.2.6"
The <span style="font-weight: bold">Austin-Healey Sprite Mark I Workshop Manual</span>, Issue 6, from The British Motor Corporation (no date)advises:
"The Austin-Healey Sprite is fitted with 5.20-13 tubeless tyres upon 15x4J ventialted steel disc wheels, each wheel being secured by four nuts"
"Tighten the road wheel nuts to a torque wrench reading of 37 to 39 lb. ft. (5.02 to 5.4 kg.m.). Do not overtighten."
From 'General Data' in the same workshop manual:
Pressures:
Front 18 lb./sq.in. (1.27 kg.cm2)
Rear 20 lb./sq.in. (1.41 kg.cm2)
For sustained speeds in excess of 80 to 85 m.p.h. (129 to 137 k.p.h.) increase pressures to:
Front 24 lb./sq.in. (1.69 kg.cm2)
Rear 26 lb./sq.in. (1.83 kg.cm2)
Web sites that have been referenced in this forum:
Everything to do with tires:
https://www.carbibles.com/tyre_bible.html
Tire comparison/calculator sites:
https://www.mintylamb.co.uk/?page=tyre.htm
https://www.1010tires.com/TireSizeCalculator.asp
https://www.miata.net/garage/tirecalc.html
Determining modern vs original tire sizes:
https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=45
https://www.tirerack.com/tires/tiretech/45_conversionchart.html
https://www.carbibles.com/vintagetyresizes.html
Wheels:
https://www.tirerack.com/wheels/tech/techpage.jsp?techid=101
Wheel width vs. tyre size:
https://www.carbibles.com/tyre_bible_pg2.html
(about a third of the way down)
Application:
The original Bug-Eye tire size of 5.20/13 doesn't apear in the Tire Rack chart (the smallest 13 inch tyre shown is 5.60 x 13); members on the Forum have advised that the modern equivalent of the original 5.20 is 145/13.
Carbibles provides these equivalents in their vintage tyre table: 135/80-13; 145/70-13; 165/60/13, and 130/100-13 in their script calculation on page one.
We have one running BE with 155/80-13 tires on it. Comparing rolling radii:
145/80-13 has a rolling radius of 281.1 mm
155/80-13 RR is 289.6
175/65-13 278.85 mm
175/70-13 287.6
185/70-13 294.6
The 175/70-13 appears to the optimum tire size for the new rims for our second Bug-Eye - I'll be checking for availability tomorrow..
Additional wisdom/thoughts sure are welcome.
Doug