What size tire? Want to go smaller than stock -

2007 Tacoma base with 2.7 auto - five lug wheels

Stock tire size was P215/70R15 - truck came with inexpensive brand that I can't remember.

I installed a work cap with a full ladder rack and a bunch of work-related stuff.
The stock tires were bulging out ridiculously at the sidewalls.
I added air bags to the rear suspension and run about 20 lbs.
I installed LT235/75R15 Michelins

This made the truck a tiny bit sluggish off the line and also downshift to make it up any hill. At anything over 65-70 mph top it will not maintain top gear - the wind resistance inevitably drags the speed down enough to make the trans downshift.

The Michelin tread still looks like new but the tires are old and Still too big. <g>

I carry less weight now - don't really work out of it any more - but I'm still leery of using a P rated tire. I would actually like to now install a 'smaller diameter than stock' tire but LT tires don't come in low enough ratios (like a 60 series) and the smallest LT tire I can find (LT215/75R15) is slightly bigger / taller than stock.

Stock Tire - P215 70 15 - 26.85" OD / 751 revolutions per mile

Present Tire - LT235 75 15 - 28.88" OD / 698 revs per mile

Smallest LT I can find - LT215 75 15 - 27.7" OD / 728 revs per mile

With the cap being 4" above the roof, and all the wind drag of the ladder rack, I'd really like to have something smaller - but to do that I have to mount a P tire.

The gas mileage already blows so that's not much of a factor. I'd rather let the engine rev more and make the truck play nicer all around. I can always lock the trans out of overdrive / drive in tow-mode all the time but since the big Michelins are aged out anyway - I'd like to maybe handle it with the tire change.

What would you all do? How would you handle it? Risk the new P tires not handling the weight (if I do load the truck) or risk the LT tires still leaving the final gearing too tall to push the wind resistance easily?

PHM
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Go with a stockish size in a non LT rated of a name brand (michelin defender LTX M/S's get my vote) and call it good.

215/75R15 Michelin Defenders LTX M/S's are rated for 1764 lbs per tire!

 

Don't overthink it. Changing tire sizes up or down within 1" either way isn't going to make any real difference. People forget, or never consider that tires get smaller as they wear. Any tire you choose will be about 1" smaller after 40,000 miles. The revolutions/mile will change as the tire wears. It can vary depending on how much air you run in them. If you have to downshift, downshift. That is why you have more than 1 gear.

Unless you drive off road and need a tougher tire you don't need LT tires. I'd imagine any P series tire will carry more weight than the truck is rated for. If the sidewalls were bulging out you were overloaded.

I'd go with either a P225/75/15 or P235/75/16 and probably the latter. Those trucks already have 4.10 gears in the axle. You don't have a gearing problem, you have a horsepower problem. And I suspect being over loaded made things worse.

 

What is the actual difference between a Michelin LTX and an actual LT rated tire?

I had some Hankook tires come apart (on a different truck) on me driving to Florida. A GMC van full of heavy stuff and running 150% of the speed limit - so I don't blame the tires. The second tire came apart near a Sams's Club so I went in for a set of LT235/75-16's but what they installed were Michelin LTX tires in 245/70.

Later I mentioned it to someone and they said: "But Michelin LTX tires are not actual LT tires."

So do you know 'why' they are not LT tires - when they at least 'seem' to say something like that on the sidewalls. <g>

PHM
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Well; Yeah - the sidewalls were bulging because I overloaded the truck. <g>

But that's why I then changed to LT tires.

It's annoying that the truck downshifts every few minutes while I'm driving along a highway. The final drive ratio is apparently too tall - but a lower final drive ratio would go a ways towards fixing that. And that's all that really happens by leaving it in 3 gear - right? The final drive gearing ratio is lower. <g>

That's all I was thinking to accomplish with the smaller tires. And changing tire sizes Does change the gearing - if it didn't the speedometers would always read accurate no matter what size tire was used.

PHM
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If that were up to me I would sure use P tires in that application. The reason being that I would prefer to temporarily overload P rated tires from time to time instead of chronically under loading LTs and dealing with the poor ride quality always. So, get the Ps in the size you want for best driveability.

 

extra load tires

 

The Michelin Defender LTX M/S tire is just the name, it comes in standard and LT load ratings.

 

Thanks. And yesterday I found a way to experiment your proposal - and for cheap. Which is something that tends to delight me. <g>. I arranged to buy four stock wheels with original sized tires on them for ten bucks each. I guess I am the only idiot who wants stock wheels. <g> I haven't bolted them on yet - but today or tomorrow I will.

BTW: I always enjoyed the 'truck-like feel' of the present LT tires. To me they were an improvement in both feel and performance. In terms of loading I mean - Not the tall gearing 'issue'. With the LT tires the truck just felt 'truckier' to me. <g>

I wasn't willing to risk $400. on a stock-P-tire 'trial' - but for $40 . . . . what the hell? <g>

I'll let you know what happens.

PHM
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