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Fab4Fan
Samba Member
Joined: June 17, 2005
Posts: 703
Location: Claremont, So-Cal
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 Posted: Mon Jul 07, 2008 2:02 pm Post subject: 145's tire pressure |
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Whats the recommended tire pressure for 145 tires on a 5.5" wheel?
these are for the front of a beetle.
Ive tried searching and didnt come up with much.
thanks |
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clarkbre
Samba Member
Joined: June 20, 2004
Posts: 1107
Location: Everett, WA
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| Posted: Mon Jul 07, 2008 2:28 pm Post subject: |
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What's the max pressure on the tire? This information will help figure out exactly what pressure will be good for your beetle. Chances are, it will be around 20psi.
There's a whole formula you can run to get the exact pressure your tires should be set at:
(Actual weight on the tire x Max tire PSI)/Max load on tire = Your estimated tire pressure
So in numbers, it should be (360x44)/950=17 PSI in your tire. It sounds extremley low but it is correct. You could always add a couple PSI to be safe. |
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Maimas13
Samba Member
Joined: July 06, 2004
Posts: 642
Location: Redwood City CA
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| Posted: Tue Jul 08, 2008 12:27 am Post subject: |
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| clarkbre wrote: |
What's the max pressure on the tire? This information will help figure out exactly what pressure will be good for your beetle. Chances are, it will be around 20psi.
There's a whole formula you can run to get the exact pressure your tires should be set at:
(Actual weight on the tire x Max tire PSI)/Max load on tire = Your estimated tire pressure
So in numbers, it should be (360x44)/950=17 PSI in your tire. It sounds extremley low but it is correct. You could always add a couple PSI to be safe. |
wow that is way off from how I have been told to calculate tire pressure. I was told max pressure - 10%
so 44-4.4=39.6, that sounds alot safer to me
_________________
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(.o\ ! /o.) 62 chopped, dropped, cal looked, oval grafted, 57 styled, ragtop with polk audio sound system, driven daily by an 18 year old
A must read for understanding tires sizes and wheel offsets
Go Bears!!! Mech E |
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clarkbre
Samba Member
Joined: June 20, 2004
Posts: 1107
Location: Everett, WA
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| Posted: Tue Jul 08, 2008 6:35 am Post subject: |
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| Maimas13 wrote: |
wow that is way off from how I have been told to calculate tire pressure. I was told max pressure - 10%
so 44-4.4=39.6, that sounds alot safer to me |
That sounds like a hard ride, bad braking, and less grip! A bug's front end only weighs about 720lbs over the front wheels. For the car to perform the way it should, it would require less tire pressure. |
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Kuncle
I am Kyle Deese
Joined: June 08, 2005
Posts: 1284
Location: Greer...South Carolina...
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| Posted: Tue Jul 08, 2008 6:39 am Post subject: |
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Like 75psi..  I ran 38-30 in mine when I had them
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Behemoth
Samba Member
Joined: September 02, 2003
Posts: 389
Location: Lenoir NC
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| Posted: Tue Jul 08, 2008 12:55 pm Post subject: |
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| clarkbre wrote: |
| Maimas13 wrote: |
wow that is way off from how I have been told to calculate tire pressure. I was told max pressure - 10%
so 44-4.4=39.6, that sounds alot safer to me |
That sounds like a hard ride, bad braking, and less grip! A bug's front end only weighs about 720lbs over the front wheels. For the car to perform the way it should, it would require less tire pressure. |
So then you give no creedence whatsoever to the tire manufacturers recommended tire inflation? And you also give no creedence to the tires handling characteristics as related to the suggested tire nflation pressure?
There's a whole formula you can run to get the exact pressure your tires should be set at
Where did this formula come from? It's the first I've ever heard of it and although I don't dispute it entirely I don't think it is necessarily correct for every tire made seeing as how there are many tires built on many different handling characteristics that require different pressures for proper use.
Help me out here. 
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Erik G
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Joined: October 16, 2002
Posts: 13263
Location: Tejas!
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| Posted: Tue Jul 08, 2008 12:58 pm Post subject: |
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Last time I looked, there was never a recommended tire pressue from the tire manufacturer. Max is the max the tire will hold. you should always use the specs from the manufacturer of the car
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Behemoth
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Joined: September 02, 2003
Posts: 389
Location: Lenoir NC
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| Posted: Tue Jul 08, 2008 2:05 pm Post subject: |
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| Erik G wrote: |
| Last time I looked, there was never a recommended tire pressue from the tire manufacturer. Max is the max the tire will hold. you should always use the specs from the manufacturer of the car |
True on the recommended pressure but flase on always using the specs from the car manufacturer. That is good for stock size and type tires but once you change to a different size and type then the pressure is going to change somewhat per this article at Sport Compact Tire
http://www.sportcompactcarweb.com/tech/0208scc_tire_pressure_guide/index.html
Excerpt
Yokohama, for instance, includes pressure recommendations for stock and plus-sizes, by vehicle, in its annual Fitment Guide, which your tire dealer should have a copy of. Typically, these are 0-3 psi higher for a Plus-one or Plus-two fitment. Also listed are maximum load ratings at maximum inflation pressure for each size of each tire Yokohama makes.
and this seems to be a formula for a place to start considering all our vehicles are different weights according to our likes.
In the event that you aren't able to find a recommendation for your car, or the tires on your car are so different from those that were originally fitted from the manufacturer as to be incomparable, we received the following rule of thumb from Oscar Pereda, an engineer for BFGoodrich. He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:
(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.
Example: Stock 911, 3,000 lb.
(3000/100) = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at rear
With modified suspension, the result is 30 psi front, 32 psi rear.
"There is no 'golden' tire pressure," Oscar said. The optimal setting depends on the individual driver and his preferences.
Good post Fab4, it's been a while since I had to go look for some really useful info.  And as Erik showed I asm fallable. 
_________________
63SunNotch...."Don't qoute me on it but I am pretty good when it comes to tits.
Been sucking on them since I was a baby. "
vdubmax..."I thought we were friends. I will be by to drop off your recently fucked up parts next weekend fool" |
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clarkbre
Samba Member
Joined: June 20, 2004
Posts: 1107
Location: Everett, WA
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| Posted: Tue Jul 08, 2008 2:54 pm Post subject: |
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| Behemoth wrote: |
| Erik G wrote: |
| Last time I looked, there was never a recommended tire pressue from the tire manufacturer. Max is the max the tire will hold. you should always use the specs from the manufacturer of the car |
True on the recommended pressure but flase on always using the specs from the car manufacturer. That is good for stock size and type tires but once you change to a different size and type then the pressure is going to change somewhat per this article at Sport Compact Tire
http://www.sportcompactcarweb.com/tech/0208scc_tire_pressure_guide/index.html
Excerpt
Yokohama, for instance, includes pressure recommendations for stock and plus-sizes, by vehicle, in its annual Fitment Guide, which your tire dealer should have a copy of. Typically, these are 0-3 psi higher for a Plus-one or Plus-two fitment. Also listed are maximum load ratings at maximum inflation pressure for each size of each tire Yokohama makes.
and this seems to be a formula for a place to start considering all our vehicles are different weights according to our likes.
In the event that you aren't able to find a recommendation for your car, or the tires on your car are so different from those that were originally fitted from the manufacturer as to be incomparable, we received the following rule of thumb from Oscar Pereda, an engineer for BFGoodrich. He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:
(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.
Example: Stock 911, 3,000 lb.
(3000/100) = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at rear
With modified suspension, the result is 30 psi front, 32 psi rear.
"There is no 'golden' tire pressure," Oscar said. The optimal setting depends on the individual driver and his preferences.
Good post Fab4, it's been a while since I had to go look for some really useful info. And as Erik showed I asm fallable. |
So using the formula that you and BFGoodrich provided:
A bug weighs roughly 1800 pounds so 1800/100=18 psi?
I'd also like to add the 1967 VW Bug manual states the front tire pressure should be 16 or 17 psi....BOY IS MY FORMULA OFF!!! 
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Maimas13
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Joined: July 06, 2004
Posts: 642
Location: Redwood City CA
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| Posted: Tue Jul 08, 2008 3:01 pm Post subject: |
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ok now im really confused... does that formula yokohoma provided apply to all size tires? if so then I really needa lower the psi in my front tires... alot
_________________
MAIMAS... read it backwards
(.o\ ! /o.) 62 chopped, dropped, cal looked, oval grafted, 57 styled, ragtop with polk audio sound system, driven daily by an 18 year old
A must read for understanding tires sizes and wheel offsets
Go Bears!!! Mech E |
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clarkbre
Samba Member
Joined: June 20, 2004
Posts: 1107
Location: Everett, WA
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| Posted: Tue Jul 08, 2008 3:05 pm Post subject: |
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| Maimas13 wrote: |
| ok now im really confused... does that formula yokohoma provided apply to all size tires? if so then I really needa lower the psi in my front tires... alot |
Yes, the pressure in the front tires of a bug should be below 20 psi. |
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Maimas13
Samba Member
Joined: July 06, 2004
Posts: 642
Location: Redwood City CA
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| Posted: Tue Jul 08, 2008 3:14 pm Post subject: |
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ok, just brought the front pressure down... so the back tires should be below 22 then?
_________________
MAIMAS... read it backwards
(.o\ ! /o.) 62 chopped, dropped, cal looked, oval grafted, 57 styled, ragtop with polk audio sound system, driven daily by an 18 year old
A must read for understanding tires sizes and wheel offsets
Go Bears!!! Mech E |
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EverettB 
Administrator
Joined: April 11, 2000
Posts: 69798
Location: Phoenix Metro
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| Posted: Tue Jul 08, 2008 3:30 pm Post subject: |
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| Behemoth wrote: |
He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:
(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.
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This makes sense for a vehicle that is equally weight proportioned front and rear. Beetles are not.
It makes more sense to take the actual weight on each tire and calculate using that. This is why the stock tire pressures in the owner's manual differ so much front to rear.
The '67 Bug owner's manual above is for bias ply tires. Add 2-3 psi for radials. I normally add 5 psi total over the bias ply ratings to allow for radials + highway driving.
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BrockGrimes
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Joined: September 18, 2006
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Location: Clovis, NM
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Maimas13
Samba Member
Joined: July 06, 2004
Posts: 642
Location: Redwood City CA
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| Posted: Fri Jul 11, 2008 6:15 pm Post subject: |
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| BrockGrimes wrote: |
I have 225-60-15 on the rear 26 - 28psi
145/15 front 26 - 28 psi.
Good performance, good wear, good gas mileage. |
ok so the width of a tire doesnt matter in determining tire pressure?
i have 195s and I should run them at the same psi as those of you running skinny 145s? or should my psi be slightly higher since I have 5 cm wider tires?
i am confused... still
(running front at 26 and rear at 36 psi)
_________________
MAIMAS... read it backwards
(.o\ ! /o.) 62 chopped, dropped, cal looked, oval grafted, 57 styled, ragtop with polk audio sound system, driven daily by an 18 year old
A must read for understanding tires sizes and wheel offsets
Go Bears!!! Mech E |
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BrockGrimes
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Joined: September 18, 2006
Posts: 1015
Location: Clovis, NM
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| Posted: Sun Jul 13, 2008 10:24 pm Post subject: |
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| Maimas13 wrote: |
ok so the width of a tire doesnt matter in determining tire pressure?
i have 195s and I should run them at the same psi as those of you running skinny 145s? or should my psi be slightly higher since I have 5 cm wider tires?
i am confused... still
(running front at 26 and rear at 36 psi) |
If your running 195's all the way around just follow the recommendation listed in the VW manual for your car.
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scottvw
Samba Member
Joined: November 17, 2004
Posts: 2821
Location: Centennial, CO
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| Posted: Mon Jul 14, 2008 6:30 pm Post subject: |
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| I run about 24lbs in mine. Anything more, they get a little dancy on me. |
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Fab4Fan
Samba Member
Joined: June 17, 2005
Posts: 703
Location: Claremont, So-Cal
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| Posted: Mon Jul 14, 2008 9:32 pm Post subject: |
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thanks for the help guys.
the tire installer originally had them pumped up to like 35psi(he said i needed more pressure because the tire was smaller than stock!) and i knew it was too high.
although im still sorta confused with all these formulas... I lowered them down to 22psi and they feel much better. |
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BrockGrimes
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Location: Clovis, NM
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| Posted: Mon Jul 14, 2008 10:43 pm Post subject: |
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22psi with a 145 on a 5.5 is fine.
I have one with a slow leak and it'll stay one the bead down at 9psi.
So you straight.
As long as it rides good and you don't get any weird tire wear your good to go.
Lay on the ground and look front to back at the tire, the tread should have a nice contact patch with the ground not all rounded up on the outer edges. The biggest worry besides wear is wet weather traction.
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Neil Davies
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Joined: July 31, 2005
Posts: 393
Location: Kidderminster, West Midlands, UK
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| Posted: Thu Jul 17, 2008 6:03 am Post subject: |
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Tyre size should have very little bearing on the pressure - you should be within a couple of psi of the original VW specs.
This is what I run:
145 fronts - 19psi
195/65 rears - 24-26psi.
If your pressure is too high you'll bounce and skip, too low and the tyre will roll on the rim in corners.
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