Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > General Discussions > Off-Topic Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 11-06-2011, 01:19 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,797
tire pressure for non-original size tires

Does anyone have guidance on how to set tire pressure for non-original size tires? I'm surprised I don't see anything definitive at tirerack.com. What tire pressure should I run on an 87 300D with 205/55-16s (gas flap specs are for 195/65-15s) and a 97 'burb with 265/75-16s (door jamb specs are for 245/75-16s), assuming I'm happy with the specs for original size tires?

Thanks,
Sixto
87 300D

Reply With Quote
  #2  
Old 11-06-2011, 02:24 PM
MBeige's Avatar
Registered User
 
Join Date: Apr 2005
Location: SoCal
Posts: 3,746
If the "volume" is the same (bigger wheel size but lower profile to match, etc) then the stock pressure recommendation holds true IIRC.

But on my mother's 300TE w/ 16x7 wheels (same tire size you have), we went with 32F/34R since it's getting colder.
Reply With Quote
  #3  
Old 11-06-2011, 02:47 PM
TwitchKitty's Avatar
Я не хакер
 
Join Date: May 2004
Location: Varies
Posts: 4,325
There is a chart for the tire that specifies the weight load based on the inflation pressure. Match it to the vehicle that way. Doesn't take into account the match to the rim. Tire is not shaped right on the wrong width rim.
__________________
Don't believe everything you think. Especially don't believe everything that you feel. Radical Subjectivism is rampant on this forum.

Douchebags suck. Make douchebags great again or not.
Reply With Quote
  #4  
Old 11-07-2011, 12:29 PM
Posting since Jan 2000
 
Join Date: Sep 2011
Posts: 5,649
The chart holds true, but regardless what size, original or not. Add about 2PSI to make sure you don't get uneven wear. Set tire pressure only when tires are cold.
__________________
2 Thessalonians 3:10
Reply With Quote
  #5  
Old 11-07-2011, 01:16 PM
SwampYankee's Avatar
New England Hick
 
Join Date: Sep 2006
Location: CT
Posts: 1,501
Wouldn't that be determined by the manufacturer? I always assumed that's what they stamped on the sidewall, based on max load capacity. Is that an incorrect assumption?
__________________

1980 300TD-China Blue/Blue MBTex-2nd Owner, 107K (Alt Blau) OBK #15
'06 Chevy Tahoe Z71 (for the wife & 4 kids, current mule) '03 Honda Odyssey (son #1's ride, reluctantly) '99 GMC Suburban (255K+ miles, semi-retired mule) 21' SeaRay Seville (summer escape pod)
Reply With Quote
  #6  
Old 11-07-2011, 01:27 PM
Posting since Jan 2000
 
Join Date: Sep 2011
Posts: 5,649
Quote:
Originally Posted by SwampYankee View Post
Wouldn't that be determined by the manufacturer? I always assumed that's what they stamped on the sidewall, based on max load capacity. Is that an incorrect assumption?

The sidewall pressure is MAXIMUM inflation pressure.

I read a long time ago, and I believe it's true, that the car manufacturer designates a pressure for best ride and handling, the tire maker designates a pressure(in their books in the days of the tire stores, not what's stamped on the tire) for best tire wear.

I have learned that occasionally running the cold pressure indicated on the door jamb sticker will lead to uneven wear. Adding 2 PSI to that figure will prevent this.

If you load a truck or trailer to the max, or even a car with a trunk overloaded with moonshine, air the tires to the max pressure stamped on the sidewalls to prevent tire damage from internal overheating.
__________________
2 Thessalonians 3:10
Reply With Quote
  #7  
Old 11-07-2011, 01:41 PM
Registered User
 
Join Date: Dec 2005
Location: Carson City, NV
Posts: 3,789
There are several considerations in setting tire pressure:

1. Heating due to sidewall flex under load.
2. Ride quality.
3. Handling
4. Wear

If you know your axle weights, the Tire and Rim Association Year Book will give you the lowest pressure you can run and be ok with respect to sidewall flex/heating. I had a copy of it saved somewhere, but now I can't find it. Ride quality generally improves with lower pressure and gets worse with increasing pressure. Handling is usually bad with low pressure, gets better with increasing pressure up to a point, and then stops improving or even worsens as you continue to increase pressure. Wear can be uneven with too much or too little pressure. With some experimentation, you can find the tire pressures that work best for you.
__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 367,xxx miles
08 Triumph Street Triple 30,xxx miles, lowered 10mm in front, Pirelli Angel GT tires, EBC HH brake pads, otherwise stock.
88 Jaguar XJS V12 93,xxx miles. I should be in the garage now.
Reply With Quote
  #8  
Old 11-07-2011, 06:15 PM
Registered User
 
Join Date: Oct 2006
Posts: 254
Quote:
Originally Posted by TwitchKitty View Post
There is a chart for the tire that specifies the weight load based on the inflation pressure. Match it to the vehicle that way. Doesn't take into account the match to the rim. Tire is not shaped right on the wrong width rim.
I recently switched from P-Metric to LT tires on my Xterra and placed a request into the tire manufacturer for a recommended tire pressure. They used the methodology you suggested to arrive at an answer.

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 11:51 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page