EcoModder Forum Fun video time! How many PSI to explode a 20 year-old, dry-rotted tire?

Register Now
 Remember

 04-26-2017, 09:59 PM #11 (permalink) Master EcoModder     Join Date: Sep 2012 Location: Victoria, BC Posts: 1,049 '91 Miata - '91 Mazda Miata 90 day: 27.11 mpg (US) '86 Fiero GT - '86 Pontiac Fiero GT Purple Penny Pincher - '95 Pontiac Firefly Base 90 day: 43.68 mpg (US) Jett-Black - '01 Volkswagen Jetta 90 day: 39.32 mpg (US) Firefly EV - '98 Pontiac Firefly EV 90 day: 107.65 mpg (US) Little Boy Blue - '05 Toyota Echo 90 day: 32.24 mpg (US) Thanks: 39 Thanked 300 Times in 224 Posts Don't they time warp at 88psi or something like that? __________________
 Today Popular topics Other popular topics in this forum... View the most popular topics in this subforum by views or by posts
Tire Geek

Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 676
Thanks: 0
Thanked 259 Times in 167 Posts
Quote:
 Originally Posted by darcane Cool video, thanks Metro. I wonder what it's rated pressure is, probably 35psig for an older tire? If so, that's still about four and a half times it's rated pressure. Typically in engineering, things are designed to a safety factor. Safety factor of 2.0:1 means that it was designed to twice the rated load. For the products we design where I work, because the failures could cause death, safety factors are 4:1, 6:1, or 10:1. I can see tires being in the same category, so I would expect a 4:1 or 6:1 safety factor. I'm impressed that the tire still has such a high burst pressure considering it's age.
Don't forget about fatigue. In tires, that's the most important thing.

If you look at a typical S-N curve for rubber - and consider that 100,000 miles is about 6 million cycles - then the S-N curve says the failure stress is about 1/4 to 1/5 the static value. If you divide 220psi by 4 or 5, you get 55 and 44 psi. Isn't that interesting!
__________________
CapriRacer

Visit my website: www.BarrysTireTech.com

 The Following 3 Users Say Thank You to CapriRacer For This Useful Post: Daox (04-27-2017), MetroMPG (04-28-2017), roflwaffle (04-30-2017)
Master EcoModder

Join Date: Aug 2010
Location: Philippines
Posts: 1,978
Thanks: 1,235
Thanked 443 Times in 315 Posts
Quote:
 Originally Posted by CapriRacer Don't forget about fatigue. In tires, that's the most important thing. If you look at a typical S-N curve for rubber - and consider that 100,000 miles is about 6 million cycles - then the S-N curve says the failure stress is about 1/4 to 1/5 the static value. If you divide 220psi by 4 or 5, you get 55 and 44 psi. Isn't that interesting!
Of course, they did say the tires were dry-rotted and old.

Don't ever plan on running tires that old.

Master EcoModder

Join Date: Jun 2008
Location: Earth
Posts: 5,005
Thanks: 214
Thanked 740 Times in 540 Posts
Quote:
 Originally Posted by MetroMPG I'm not going a pound over 125. I like the smoother ride of the low 100's.
Though when I stop to think about it, skinny little road bike tires normally inflate to 120 PSI or so.

 04-27-2017, 01:46 PM #15 (permalink) Master EcoModder     Join Date: Aug 2012 Location: northwest of normal Posts: 10,678 Thanks: 2,390 Thanked 3,375 Times in 2,663 Posts I had a set of the really nice European Klebers (they changed when they set up manufacturing in the USofA) on my 1956 sunroof Beetle. I parked it on dirt at my brother's place for 18 months and some micro-organisms in the soil ate the tread off one of them! The flat spot made the tire unusable. jamesqf — pneumatic tubes of a given wall thicken can withstand more pressure in a small diameter, less as the diameter grows.
 04-27-2017, 02:42 PM #16 (permalink) Duck duck duck     Join Date: Dec 2012 Location: Nieuwegein, the Netherlands Posts: 2,418 Red Devil - '11 Honda Insight Elegance Team Honda 90 day: 57.65 mpg (US) It - '09 Hyundai I10 Active Cool Team Hyundai 90 day: 30.71 mpg (US) Thanks: 873 Thanked 994 Times in 645 Posts I would think that higher tire pressure means the tire flexes less each rotation, so it should age slower? __________________ 2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut. lifetime FE over 0.12 Gm or 0.08 MM.
home of the odd vehicles

Join Date: Jun 2008
Location: Somewhere in WI
Posts: 2,784

Silver - '10 Chevy Cobalt XFE
Thanks: 241
Thanked 468 Times in 349 Posts
Quote:
 Originally Posted by RedDevil I would think that higher tire pressure means the tire flexes less each rotation, so it should age slower?
Yes, but impact stresses could make it easier to puncture or blow, that said at the pressures we run it's mostly a non issue

Tire Geek

Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 676
Thanks: 0
Thanked 259 Times in 167 Posts
Quote:
 Originally Posted by RedDevil I would think that higher tire pressure means the tire flexes less each rotation, so it should age slower?
If by that you mean less likely to crack, that would be so. But aging is more about the chemical and physical state of the rubber - how well it's strength is holding up and how well it is adheres to adjacent components. It's those things that cause the tire to fail. And those things seem to be more correlated to heat.
__________________
CapriRacer

Visit my website: www.BarrysTireTech.com

Duck duck duck

Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
Posts: 2,418

Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 57.65 mpg (US)

It - '09 Hyundai I10 Active Cool
Team Hyundai
90 day: 30.71 mpg (US)
Thanks: 873
Thanked 994 Times in 645 Posts
Quote:
 Originally Posted by CapriRacer If by that you mean less likely to crack, that would be so. But aging is more about the chemical and physical state of the rubber - how well it's strength is holding up and how well it is adheres to adjacent components. It's those things that cause the tire to fail. And those things seem to be more correlated to heat.
Heat is also correlated to pressure. Underinflated tires get very hot on the highway. I had a slow leak in my right rear and it was almost too hot to touch even though it wasn't riding the rim yet.
The other tires were about at ambient running 42 PSI.
__________________
2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.12 Gm or 0.08 MM.

Master EcoModder

Join Date: Jun 2008
Location: Earth
Posts: 5,005
Thanks: 214
Thanked 740 Times in 540 Posts
Quote:
 Originally Posted by freebeard jamesqf — pneumatic tubes of a given wall thicken can withstand more pressure in a small diameter, less as the diameter grows.
Yet on the other end, semi truck tires get inflated to around 100 PSI.