Flipsonic

I have aftermarket wheels. Do I use the stock tire pressure, or go by whatever the tire manufacturer suggest?

JMorton

You ask a good question. Reading posts on this forum indicates that others have found that the Lexus tire pressure spec is too low. The OEM Goodyear tires on my 2004 RX330 had excessive wear along the inside and outside edges of the tread at about 28,000 miles despite maintaining 32 lbs. I put off replacing these tires (the tread was good except on the sides) until I scared myself on the Interstate when it rained hard. The rear end would fishtail on puddles unless I slowed to under 50 MPH. Yikes!

I replaced the Goodyears with the same size Bridgestone Dueller H/L Alenza tires. User reviews for this tire uniformly praised the tread life (65,000 mi.). Lacking the "P" in front of the 235 spec, I presume The Bridgstones are truck (not Passenger) tires. The tire shop inflated them to 36 psi per their own choice. They never asked me what I wanted. The ride was noticably more firm than I had with the Goodyears. I reduced the pressure to 32 psi and now the Bridgestones ride like the OEM. It's been two months now and maybe I'm being paranoid, but I'm thinking these tires are beginning to show the slightest signs of under inflation. I'm thinking that 36 psi might be the best bet after all, despite the firm ride. At about $800 for the set, do I want to be buying new tires every 2 years? But at 32 psi, the RX rides and handles real good. Decisions, decisions! Maybe 34 psi would be a good compromise.

Good luck with your choice for tire pressure.

JMorton

mitsuguy

iTrader: (2)

Alright, here's the real deal answer...

It depends...

A couple things you want to take into account.

Load Index and original tire pressure...

Load index of the first tire versus OE tire pressure, and load index of the new tire versus the weight it needs to carry...

If the load index numbers are the same, and we haven't changed load ratings (going to a LT tire instead of a metric/p-metric tire), then you can keep anywhere from the stock pressure up to the tires max pressure, cold. If you drive fast often, increase tire pressure by 3-5 psi to account for reduced load carrying at high speeds (above 100 mph). There are charts you can find that show exact increase per speed.

Now, if you didn't keep the same load index (the number after the size, usually accompanied by a letter which is the speed rating, ie: 205/55-16 96y would be 96 load index, y speed rating), you will need to do some research... as a general rule, if you went up in load index, you can keep the same inflation as stock, up to the max of the tire (you can actually use a little less pressure than stock, but you would have to find the chart that shows the differences to be 100% sure). If your new load index is less than stock, you will need to increase inflation pressure, and ensure the new tire is really capable of carrying enough weight to support the vehicle...

find the vehicles Front and Rear GVWR and divide each by 2. The max weight carrying capacity per tire should exceed this number, if not, you need a different tire....

(keep in mind on staggered fitments, the fronts and rears will more than likely have different load indexes)

JMorton - any truck tire will have LT in place of the P in front of the tire size... if nothing is present, then you have a European Metric tire... effectively the same as a P-metric tire, though weight carrying capacities may and will be different, as well as different max inflation pressures... All P-metric tires carry their max weight at 35 psi (unless marked with an XL, which is then 41 psi); whereas Euro-metric tires may carry their max weight as high as 51 psi...

JMorton

Thanks for your explanation. After reading your comments, I compared the load index of the OEM Goodyear with my replacement Bridgestone tires. The Bridgestones I got have a slightly higher load rating (100V vs. 99V), and 55 lbs higher max load rating than the OEM. So I think I'm OK with my choice of replacement tires, although luck had a lot to do with it (I don't know jack about tires).

As you stated, the Bridgestone's European metric sizing does allow up to 51 psi vs. the Goodyear's 44 psi, so, as I understood what you wrote, I can inflate my Bridgestones to Lexus specs with no problem.

The only problem is that 32 psi Lexus-spec tread wear on the OEMs wore the inside and outside edges off the treads (i.e. they were under inflated). Not wanting to repeat that with my new tires at 32 psi, I think I should go higher.

What psi would you recommend? My Bridgestones are "good" for 65,000 miles only at the correct inflation pressure.

mitsuguy

iTrader: (2)

was it all 4 tires worn like that or just primarily the fronts?

all cars tend to do this to tires left on the front for too long...

You are probably good on your pressure, personally, I just think the stock goodyears are junk (goodyear does make good tires, just not the Lexus OE tires)...

JMorton

All 4 tires had the same wear. Ditto regarding the OEM Goodyears. Your suggestion to keep 32 psi makes sense, and has been echoed by others. Higher inflation pressures make for a noticeably firmer ride, very unbecoming to a LEXUS, so I'll follow your advice,

Knowing my propensity for ruining tires from underinflation, I'll finally have to monitor tire pressure on a regular and frequent basis. These new Bridgestones weren't cheap!

Thanks for your comments.