Automotive

Another tire pressure thread (summer time only)

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Deal Guru
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Oct 5, 2008
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BDSL wrote: When you say performance, can you be more specific? Were you talking about fuel economy? Or braking/acceleration.

If you have been to the tracks, slightly lower pressure = more traction
i ran higher pressure than listed on the door jamb when i did a track day years ago....on the advice of actual racers.

EDIT: IIRC, stock was 35, i ran closer to 40
Temp. Banned
Jun 18, 2008
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Swerny wrote: i ran higher pressure than listed on the door jamb when i did a track day years ago....on the advice of actual racers.
Those were actual racers lol? I doubt it.

Raising tire pressure reduces the contact patch and therefore reduces grip. Grade 6 physics. Tire pressure is more important than compound. Unless you want to go on a top speed run in a straight line and require as little rolling resistance as possible you always reduce pressure on the track. Formula one tire pressures are 14-17psi. MotoGP runs similar pressures. You can see the tires squashing the tarmac on the super slow motion in corners. Unless your tracking a Chevette with 60hp and don't need to worry about wheel spin always reduce pressure on a track.
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Jul 22, 2014
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Swerny wrote: i ran higher pressure than listed on the door jamb when i did a track day years ago....on the advice of actual racers.
I bet they were driving some sweet civics. Racecar backwards is racecar, civic backwards is civic. Coincidence? I don't think so.
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Oct 13, 2009
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Swerny wrote: fail
U took the b8
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Aug 15, 2015
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ottofly wrote: Those were actual racers lol? I doubt it.

Raising tire pressure reduces the contact patch and therefore reduces grip. Grade 6 physics. Tire pressure is more important than compound. Unless you want to go on a top speed run in a straight line and require as little rolling resistance as possible you always reduce pressure on the track. Formula one tire pressures are 14-17psi. MotoGP runs similar pressures. You can see the tires squashing the tarmac on the super slow motion in corners. Unless your tracking a Chevette with 60hp and don't need to worry about wheel spin always reduce pressure on a track.
Did your grade six physics also teach you that when cornering at high speed a softer sidewall as a result of a lower pressure will build enough temperature to destroy the tire when flexing that much ? Comparing racing tires that have super stiff sidewalls with road tires used occasionally on a track is completely redonkulous.
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Mar 30, 2010
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ottofly wrote: Those were actual racers lol? I doubt it.

Raising tire pressure reduces the contact patch and therefore reduces grip. Grade 6 physics. Tire pressure is more important than compound. Unless you want to go on a top speed run in a straight line and require as little rolling resistance as possible you always reduce pressure on the track. Formula one tire pressures are 14-17psi. MotoGP runs similar pressures. You can see the tires squashing the tarmac on the super slow motion in corners. Unless your tracking a Chevette with 60hp and don't need to worry about wheel spin always reduce pressure on a track.
What about the tire sidewall folding over?
Sr. Member
Feb 10, 2015
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BDSL wrote: When you say performance, can you be more specific? Were you talking about fuel economy? Or braking/acceleration.

If you have been to the tracks, slightly lower pressure = more traction
You are correct, lower pressure (to a point) = better traction which is why I run my winters at the door jamb pressure.

I should have said higher pressure = better fuel economy
Deal Guru
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Oct 5, 2008
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ottofly wrote: Those were actual racers lol? I doubt it.

Raising tire pressure reduces the contact patch and therefore reduces grip. Grade 6 physics. Tire pressure is more important than compound. Unless you want to go on a top speed run in a straight line and require as little rolling resistance as possible you always reduce pressure on the track. Formula one tire pressures are 14-17psi. MotoGP runs similar pressures. You can see the tires squashing the tarmac on the super slow motion in corners. Unless your tracking a Chevette with 60hp and don't need to worry about wheel spin always reduce pressure on a track.
Yes an actual racer..who took me me for a lap in his full cage equipped track car that he ran in the Molson Indy support series races. So likely someone with more skills than you. This wasn't a drag race, it was the Mosport DDT.
iddqd85 wrote: I bet they were driving some sweet civics. Racecar backwards is racecar, civic backwards is civic. Coincidence? I don't think so.
See above smart guy.
Viperoni wrote: What about the tire sidewall folding over?
This

I was running 215-45-17 stock tires.
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Swerny wrote: I was running 215-45-17 stock tires.
I think we can also agree that a Formula 1/Indy/MotoGP slick is VERY different than the slick that you'd run on the "average" race car, which again would be very different than the street all season/summer tires you'd run on a regular car.
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Sep 9, 2012
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Potrice wrote: Interesting thread. I was wondering as well. On my ML350 they say 48 psi at the door jamb...I was like wtf? I've never seen tire pressure that high...all of my previous cars were in the 35 range. I would be worried at 48 psi...I'll have to ask on the MB forums.
The door jamb is probably referring to fully loaded psi recommendation.

Audi Q7 is 44 front and 49 rear fully loaded. This is on the door jamb. In the manual there's another recommendation for "normal load" which is 3 passengers or less where they specify 35 all around.

Check you manual.
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Leave it for RFD to turn a simple OP into a full-blown controversy LOL.
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Mar 25, 2005
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dilligafeh wrote: So what ? They specify many things that are not necessarily the best performance or for the longevity of the vehicle or tire. You're free to follow their rules off a cliff if you wish, I will have my reserves and use my best judgement however so no need to continue this discussion.
So you only inflate to a hot tire spec? Who quotes in hot tire specs? Do you drive a few minutes, jump out of the car, measure the air temp then pressure?
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Feb 16, 2016
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CanadianLurker wrote: The door jamb is probably referring to fully loaded psi recommendation.

Audi Q7 is 44 front and 49 rear fully loaded. This is on the door jamb. In the manual there's another recommendation for "normal load" which is 3 passengers or less where they specify 35 all around.

Check you manual.
Will do! Thank you sir!
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Jun 18, 2008
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Montreal
dilligafeh wrote: Did your grade six physics also teach you that when cornering at high speed a softer sidewall as a result of a lower pressure will build enough temperature to destroy the tire when flexing that much ? Comparing racing tires that have super stiff sidewalls with road tires used occasionally on a track is completely redonkulous.
Obviously you don't take a street tire and deflate it to 17psi the tire would indeed flex, overheat and be blistered in a few laps of hard driving assuming it even stayed on the rim. The only point I was making is that more air = less contact patch = less grip. He was referring to racing. I forgot I was on RFD where logic and common sense do not apply.
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Aug 15, 2015
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ottofly wrote: Obviously you don't take a street tire and deflate it to 17psi the tire would indeed flex, overheat and be blistered in a few laps of hard driving assuming it even stayed on the rim. The only point I was making is that more air = less contact patch = less grip. He was referring to racing. I forgot I was on RFD where logic and common sense do not apply.
Then you should have applied some common sense and safely assumed that he wasn't using F1 tires on his corolla. He was referring to going to a track where common folk drive their personal cars not the nurburgring . It is common for people to overinflate their tires a little in order to stiffen the sidewalls and avoid what I described above.
I see you don't like to admit you maybe jumped the gun on ragging on the guy so let's just leave it at this.
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Jul 22, 2014
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dilligafeh wrote: Just as they thought of the ignition switches at GM or emissions at WV, airbags anyone ? Manufacturers do things based on what maximizes profits not what yields the customer the best experience and value. I have always experienced feathering with manufacturer specs so I inflate my tires according to tire specs and make sure they're where I want them when driving even though it's only a couple of psi difference that won't hurt anything other than fuel when low.
I bet a bunch of manufacturers are in on this recommended tire pressure scheme. We should all have a "couple of psi difference day" to show those bastards what we really think.
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ottofly wrote: Obviously you don't take a street tire and deflate it to 17psi the tire would indeed flex, overheat and be blistered in a few laps of hard driving assuming it even stayed on the rim. The only point I was making is that more air = less contact patch = less grip. He was referring to racing. I forgot I was on RFD where logic and common sense do not apply.
You literally said:
Unless you want to go on a top speed run in a straight line and require as little rolling resistance as possible you always reduce pressure on the track.
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Aug 10, 2004
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I ran at 20 PSi on DR on Track
After Race back to 30 PSi.
On daily commuter car look at the door jabs and follow it
Commenly the are 35 PSi (cold)
It gives best overall performance.
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Aug 15, 2015
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What shoe size fits best ? I'm going to go and buy a pair for myself and want to know what will give me the best comfort and performance and I'm looking for suggestions from people on the net that don't know what I will use them for, what type of shoe I'm looking at buying (high heels, flip flops, steel toe, cross trainers,crocks, soccer cleats, ice skates, Rollerblades, aquasocks etc.)
Not all brands fit the same for a corresponding size either.
Obviously manufacturers will give you a ball park in terms of sizing and that's what that is, a CYA policy.
I prefer to try them on and adjust accordingly rather than be forced to follow an arbitrary suggested size.
That's all folks!
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Dec 27, 2006
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dilligafeh wrote: What shoe size fits best ? I'm going to go and buy a pair for myself and want to know what will give me the best comfort and performance and I'm looking for suggestions from people on the net that don't know what I will use them for, what type of shoe I'm looking at buying (high heels, flip flops, steel toe, cross trainers,crocks, soccer cleats, ice skates, Rollerblades, aquasocks etc.)
Not all brands fit the same for a corresponding size either.
Obviously manufacturers will give you a ball park in terms of sizing and that's what that is, a CYA policy.
I prefer to try them on and adjust accordingly rather than be forced to follow an arbitrary suggested size.
That's all folks!
Just remember to heat the shoes up before you try them on, they likely won't fit you if they're still cold. :lol:
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