# Correct tire pressure?



## DJD-Rod (Sep 23, 2011)

Hey guys. So I bought some new wheels and all and since there different then the stock wheels, the recommended tire pressure on the drivers door no longer applies.

I'm just wondering what tire pressure I should be running.

Little info:

Jetta mk4 1.8t 
Tires- nakang ns2 225/40/18
Wheels- Msr 095 black pearl .

Thanks guys!


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## DJD-Rod (Sep 23, 2011)

And sorry! There 18 inch wheels!


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## Airy32 (Nov 15, 2007)

Stick pretty close to the recommended pressures regardless of tire size.


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## ECS Tuning (Oct 2, 2006)

35 psi


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## DJD-Rod (Sep 23, 2011)

Thank you!


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## dennisgli (May 17, 2003)

DJD-Rod said:


> I'm just wondering what tire pressure I should be running.


The recommended tire pressure on the drivers door!


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## DJD-Rod (Sep 23, 2011)

There aftermarket tires , the door is only for stock tires


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## dennisgli (May 17, 2003)

DJD-Rod said:


> There aftermarket tires , the door is only for stock tires


Where does it say that?










195/65-15 is 30F, 28R
205/55-16 is 30F, 28R
225/45-17 is 30F, 28R

Gee - I wonder what 225/40-18 would be...


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## Euro Dub (Mar 4, 2003)

On a 45 or higher sidewall I run 35-36 PSI. With your 40 sidewall maybe 33-34, honestly don't have 18s or 40 sidewall so it'd be something I'd experiment. The lower a profile tire is, the harsher ride becomes given same PSI between two sidewalls. A car manufacturer's no load/half load recommendation is aimed toward the comfort side of things. A few PSI less = more absorption over bumps. I always add a few PSI to their recommendation to gain a little more fuel economy. Firmer tire = less friction (resistance). Anymore and you risk being over the tire manufacturer's max PSI recommendation once the tires start to warm up. Trust me, in the summer on hot asphalt your tires have more PSI in them unless you fill with nitrogen. 

Plus it gives a few psi (above) cushion if you have alloy wheels which tend to lose 1-3psi on a monthly basis. i.e. if you are forgetful about checking tire pressure on a regular basis. 

P.S. Never run less PSI then the door sticker recommends. You'd be asking for a sidewall blowout from an under inflated tire that is low profile to boot.


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## Airy32 (Nov 15, 2007)

Euro Dub said:


> On a 45 or higher sidewall I run 35-36 PSI. With your 40 sidewall maybe 33-34, honestly don't have 18s or 40 sidewall so it'd be something I'd experiment. The lower a profile tire is, the harsher ride becomes given same PSI between two sidewalls. A car manufacturer's no load/half load recommendation is aimed toward the comfort side of things. A few PSI less = more absorption over bumps. I always add a few PSI to their recommendation to gain a little more fuel economy. Firmer tire = less friction (resistance). Anymore and you risk being over the tire manufacturer's max PSI recommendation once the tires start to warm up. Trust me, in the summer on hot asphalt your tires have more PSI in them unless you fill with nitrogen.
> 
> Plus it gives a few psi (above) cushion if you have alloy wheels which tend to lose 1-3psi on a monthly basis. i.e. if you are forgetful about checking tire pressure on a regular basis.
> 
> P.S. Never run less PSI then the door sticker recommends. You'd be asking for a sidewall blowout from an under inflated tire that is low profile to boot.


 Wow, lots of misinformation there :screwy:


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## Airy32 (Nov 15, 2007)

All you need to know can be found here http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1 

Check all the related links at the top right of that page if you don't see what you're looking for.


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## temp_user (Jan 3, 2013)

This helped a lot when mapping recommended tire pressures for OEM setup (i.e. the sticker in the door) to aftermarket tires:

https://toyotires-1524598101.netdna...ication_of_load_inflation_tables_20151020.pdf

TL;DR is that yes there is a science to this and yes really smart people already figured it out.


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