Go Back   EcoModder Forum > Off-Topic > The Lounge
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 04-26-2017, 09:59 PM   #11 (permalink)
Master EcoModder
 
Join Date: Sep 2012
Location: Victoria, BC
Posts: 522

Topoff (RIP) - '92 Geo Metro LSi
90 day: 48.54 mpg (US)

'91 Miata - '91 Mazda Miata
90 day: 27.18 mpg (US)

'86 Fiero GT - '86 Pontiac Fiero GT

Purple Penny Pincher - '95 Pontiac Firefly Base
90 day: 38.91 mpg (US)

Jett-Black - '01 Volkswagen Jetta
90 day: 39.32 mpg (US)
Thanks: 27
Thanked 161 Times in 117 Posts
Don't they time warp at 88psi or something like that?

__________________
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 04-27-2017, 08:00 AM   #12 (permalink)
Tire Geek
 
CapriRacer's Avatar
 
Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 637
Thanks: 0
Thanked 231 Times in 150 Posts
Quote:
Originally Posted by darcane View Post
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
  Reply With Quote
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)
Old 04-27-2017, 09:23 AM   #13 (permalink)
Master EcoModder
 
Join Date: Aug 2010
Location: Philippines
Posts: 1,808
Thanks: 930
Thanked 372 Times in 264 Posts
Quote:
Originally Posted by CapriRacer View Post
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.
  Reply With Quote
Old 04-27-2017, 01:01 PM   #14 (permalink)
Master EcoModder
 
Join Date: Jun 2008
Location: Earth
Posts: 4,628
Thanks: 181
Thanked 671 Times in 486 Posts
Quote:
Originally Posted by MetroMPG View Post
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.
  Reply With Quote
Old 04-27-2017, 01:46 PM   #15 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 8,053
Thanks: 1,707
Thanked 2,671 Times in 2,089 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.
  Reply With Quote
Old 04-27-2017, 02:42 PM   #16 (permalink)
Adrift in the slow lane
 
RedDevil's Avatar
 
Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
Posts: 2,054

Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 59.22 mpg (US)

It - '09 Hyundai I10 Active Cool
Team Hyundai
90 day: 31.87 mpg (US)
Thanks: 717
Thanked 805 Times in 519 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, UG, partial LGB, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop).
lifetime FE over 0.1 GigaMeter or 66 KiloMile

  Reply With Quote
Old 04-27-2017, 06:26 PM   #17 (permalink)
home of the odd vehicles
 
rmay635703's Avatar
 
Join Date: Jun 2008
Location: Somewhere in WI
Posts: 2,542

Silver - '10 Chevy Cobalt XFE
Thanks: 202
Thanked 391 Times in 297 Posts
Quote:
Originally Posted by RedDevil View Post
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
  Reply With Quote
Old 04-28-2017, 07:49 AM   #18 (permalink)
Tire Geek
 
CapriRacer's Avatar
 
Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 637
Thanks: 0
Thanked 231 Times in 150 Posts
Quote:
Originally Posted by RedDevil View Post
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
  Reply With Quote
Old 04-28-2017, 10:08 AM   #19 (permalink)
Adrift in the slow lane
 
RedDevil's Avatar
 
Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
Posts: 2,054

Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 59.22 mpg (US)

It - '09 Hyundai I10 Active Cool
Team Hyundai
90 day: 31.87 mpg (US)
Thanks: 717
Thanked 805 Times in 519 Posts
Quote:
Originally Posted by CapriRacer View Post
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, UG, partial LGB, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop).
lifetime FE over 0.1 GigaMeter or 66 KiloMile

  Reply With Quote
Old 04-28-2017, 12:44 PM   #20 (permalink)
Master EcoModder
 
Join Date: Jun 2008
Location: Earth
Posts: 4,628
Thanks: 181
Thanked 671 Times in 486 Posts
Quote:
Originally Posted by freebeard View Post
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.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com