Proper Inflation for Non OEM Tires

[MiamiHalo]

Ok guys. I just got some 17's for my ride. Nice rims with new Hankook tires. Edgeracing sent me the tires inflated to 42 psi as you know the base Vibe has a recommened psi of 32. Which do I go with? The car manufacture's recommendation or the tire company's recommendation? Pls shed some light on my issue.

[ragingfish]

ALWAYS inflate to the car manufacturer's recommended pressure.They probably came overinflated to help set the bead.

[AKLGT]

do you? i would think it's supposed to be the TIRE manufacturer. he's going to a different size and different tire. that means, there is a change in the psi needed. i'll let Mav answer this one as he knows more about the technical side, especially tires.

[Raven]

I run 42psi in my Hankook Ventus V4 ES. I ran up to 46psi in my Falken FK451's. I experiment with pressures until I get the best combination of handling and ride quality. On the Hankook's 42psi is the number.

[nuvibe]

I would go with the tire manufacturer recomendation (psi), reason not to go with OEM (psi) is becuase it not the same demention and geometry as the aftermarket tire... nuvibe

[BlueCrush]

If the Car PSI is diferent from the tire PSI then I would split it between the two and adjust it accordingly. Not all tires are the same so you can't always go by the car Mfr. specs.

[engineertwin2]

Time out! Wait a second here...BlueCrush is right - not all tires are the same. However, tire manufacturers provide a maximum recommended inflation value.The vehicle manufacturer (Pontiac) determines the proper inflation pressure that the suspension and handling have been designed around. This is a key factor in getting the proper handling out of your vehicle.The only time I would say to not adhere to the car's listed psi is if it exceeds the maximum rating for the tire. However, in most cases, the tire manufacturer's maximum pressure rating will exceed that of the car, in which case, you should use the car's listed pressure.So, use the car's listed pressure rating.

[JustinVGT]

I remember I brought this up for discussion a couple years ago when I bought my new tires/wheels. The overall consensus was to still go by GM's specs, 32 psi. It was because the weight of the car is what affects the needed tire pressure. With my last set of Kumhos, I used ~34psi for the front and ~33 for the rear. As the tires were nearing replacement, I found that the center of the tires were actually slightly more worn then the edges. That would mean over inflation. So, I now use 32-33psi on my newer set of 18" Kumho tires.

[Raven]

I have Tein springs and a Progress RSB and a DC Sports strut bar and 225/45/17 tires, so very little has anything to do with stock. Those Hankook's work best with 42psi.

[DavidPIL]

Hey all...I have to believe the construction of the tire (non-OEM) and the size of the wheel also would affect what you set the pressure at.Stock wheel (17x7) and tire Dunlop SP9000 for me would have been a very uncomfortable ride at much above 32psi. Though when I had the tires changed at 11,000 miles, the outsides were more worn than the centers. I did religeously check and adjust air pressure along with alignments and rotations.As for my replacement tire... I got 235/45R17 on those same wheels. Because the rim width was smaller than the recommended for the tire, I have to believe it caused some flex or distortion on the treads. The tire place inflated to 44psi when installing (Max rec pressure for the tire) but my steering response lagged way behind the input. Very floaty. I decreased the pressure to 32psi, still somewhat floaty but better.I then upgraded the wheels to 17x8, the recommended width for the tire. The drive became less floaty but the steering response was still sluggish. I then upped the pressure by 2 psi until I found the right combination. 36-37 was the sweet-spot.Now with my latest tires, 245/45-17, my tire place inflated them to 32 (the oem rated), ride was very nice though once again, sluggish steering response. I upped by 2psi again up to 44. The ride became harsh but no sluggish steering cropped up and no floatiness, just a rougher ride. I now have compromised down to 38-40 for the Summer. Very nice, smooth and not near as rough as the Dunlops at 32psi.I do notice that when it's cooler Basically, a lot of factors seem to play on the ride quality, and treadlife/wear of a tire. The OEM psi is for the OEM tires and wheels and is a good starting point for when you get a different size, brand,type of tire or tire and wheel. Tweaking the pressure is ok to do, but only if you don't exceed the Max psi for the tire itself. But for safety's sake, stay somewhat below the max for the tire. Just my take on the whole tire pressure thing....Dave

[MiamiHalo]

Thank u all for your comments. After all the back and forth, I decided to go straight to the source. Hankook USA and here is what is on their website (duh) I should of thought of that from the get go.Inflation pressure must be adjusted to load. Follow inflation pressure recommendations issued by the automaker. If there are no guidelines from the car maker, tire manufacturers can supply the information. Thanks again and ride on!!

[1oldbanjo]

The tire pressure listed by the manufacturer is based on getting even tread wear across the width of the tire and a smooth ride for the stock wheel and tire size. For Autocross with stock wheels and tires it is common to increase tire pressure to keep the tire from rolling over onto the sidewalls of the tires. This additional pressure will cause the tires to wear the tread in the center faster if you keep the extra pressure in the tire all the time and the pressure should be adjusted back down at the end of the autocross. When I was an avid autocrosser we would mark the sides of the tires with white shoe polish and adjust the pressure so that the shoe polish would wear off the tread - but remain on the sidewall. Touring tires usually have pretty square edges where the tread meets the sidewalls as the cars will be driven normally and not pushed really hard in the corners. Performance tires have much rounder edges to the tread as the tires are expected to be driven harder and the tires will roll over on the edges when cornering. The tire manufacturer lists the maximum pressure for the tire and this relates to the maximum load rating for the the tire - most all cars never reach the maximum load rating for the tire and do not need to use the maximum pressure in the tire. Putting the maxum pressure in the tire will result in a very harsh ride, poor cornering traction as the footprint of the tread will be reduced, and your will probably wear the tread out in the center of the tire pretty fast. In theory the wider the tire diameter and the bigger the radius - the less pressure you will need to keep an even pressure across the tread which will result in even tread wear. This is not completely accurate however as the wider tires and construction of the tire carcass will have some affect on how the tread wears. The way you drive will also have a big affect on tread wear. If you drive long distances in straight lines you will want a lower pressure than you do if you are one that goes around corners and freeway ramps at full speed.The best way to determine the needed tire inflation is to start with the manufactures recommendation and start watching the tread wear. If you are wearing more on both the inside and outside edges of the tire you need to add some pressure to stiffen the tire up and keep it from rolling over onto the edges of the treads. If you are wearing the tread more in the center you need to lower the pressure a little bit. If you are wearing the tires more on either the inside or outside edge you have alignment issues or are cornering too fast too often. If your left front tire is weariing on the inside and your right front tire is wearing on the outside you are going too fast around too many cul de sac streets. If your left front tire is wearing on the outside and your right front tire is wearing on the inside - it is probably too many freeway ramps that turn to the right. The rear tires on a front wheel drive car are pretty much just coasting along and they are not going to wear much at all - the front ones are doing the work and will wear much faster. I would suggest putting a few pounds less air in the rear tires as the back of the car is lighter and needs less air pressure in the tires for an even load across the tread - follow the car manufacturs recommendations as a guide for how much of a difference between the front and rear. (I had a friend the had a VW Scirocco and he never rotated his tires and only bought new front tires for the car when they wore out - he went through 6 pairs of tires for the front and the rears had plenty of tread and worked fine - until they split from being so old and weathered).In general a lowering tire pressure will give a smoother ride and a little less steering response - increasing pressure will provide a stiffer ride and better steering response. Having too too little or too much pressure will ruin both the ride and the steering response. With too little air in the tires the tire can roll around and does not have enough stiffness to work properly - with too much air pressure the tire is running on a very thin portion of the center of the tread and the tire is so hard it does not flatten out where it touches the road to provide traction.Dave