Tire grade for Tacoma with old Skamper

[derekparr]

I apologize for tagging onto this thread, but my questions are largely the same as the op's. And perhaps a pop quiz is a good idea to see if I am understanding what I am reading. I have a stock 4 cylinder 2007 tacoma and am looking at a palomino truck camper being sold locally that will easily put my payload weight at or a little above the maximum (maybe up to 100 or 200 lbs over) after adding the weight of me, my girl and my dog (and other cargo). The camper fits well. We've put it in the truck. The shocks do not bottom out, even when jumping on the back bumper. It would be great for what I want to do with it.. but is my truck able to handle the weight? Are rear shock/leaf/air bag adjustments and higher quality C or D rated tires enough for these weight levels? Or are there other weaknesses in the truck that need to be dealt with? I also have an automatic transmission. Does this kill the idea of doing this? Or would a transmission cooler do the trick? Or is the extra weight not enough to worry about the transmission? I have noticed that the truck is rated to tow up to 3500lbs.

Like the op I am a newb, but not afraid of using a wrench. I have no intent of doing any 4wd driving (obviously), although the occasional very careful driving down a dirt or gravel road is not out of the question. I live in NC, and most trips will probably consist of driving on highways to the mountains or the coast. Please let me know what I am understanding correctly and understanding incorrectly, or what I have completely missed. Thanks a lot for the help.

 

[tanglefoot]

Stereo--the mechanic is probably talking about vehicles with full-time all-wheel-drive systems. They can experience wear of the center differential coupling and some extra strain on the driveline if all the tires don't have very close to the same rolling circumference.

With part-time 4wd, like our trucks, when in 2wd, there is no connection between the front and rear axles--each axle can be spinning at completely different speeds and the truck won't even know, unless you have anti-lock brakes--ABS doesn't like big differences in tire size. When in high or low-range 4wd, the transfer case locks the front and rear driveshafts together. That's when you want the tires to be about the same size, but you're not supposed to use it on paved surfaces. Any time the truck is in a turn, each tire has to spin at a different speed to follow the ground. On more slippery surfaces, the tires slip more easily to relieve the driveline stress in 4wd while turning. If you put the truck on a dirt surface, put the transfer case in 4wd and do a tight, slow turn, you can hear and feel the tires slipping against the ground and the truck will shuffle a little because the axles are forced to turn the same speed even though the wheels don't want to. The driveline's designed to hold up to this but if you use 4wd on the pavement much, the tires and driveline will wear faster.

Even in 4wd, it's not really a problem on the driveline to have slight differences in front-to-rear tire diameters due to wear or slight mismatches as long as we don't use 4wd on the pavement.

Derek--the weight capacities do have some safety margin built into them--if you exceed them by a little, you shouldn't expect to have any problems. It does help handling and weight-distribution to have some suspension help in the back though. Airbags work well but I'm just using some of those $25 bolt-on helper leaves from the auto parts store. Toyota's auto transmissions are pretty well-made and as long as you're easy on the truck on long climbs, it shouldn't build up too much heat. Don't feel like you need to hold the throttle open and keep up with traffic. Just give it a moderate amount of pedal and let it climb at a comfortable speed--even if it's 40-45 mph. I think most auto transmission heat problems occur when full-sized trucks with a lot of torque are pulling huge loads at too much throttle for too long......or when Chrysler minivans are pulling trailers--haha. Also, keep the speed down on the descents, downshift, use lots of following distance and anticipate stops to be easy on the brakes. Keep plenty of air in the tires. I like running the max pressure printed on the sidewall in the back tires and a little less in the front.

Your 2.7 16-valve is a powerhouse compared to my 2.4 8-valve and our loads are probably similar. You're also probably at lower elevation--that helps. I don't have an auto transmission but the 26-year-old truck has been completely reliable--just slow--35mph on the passes. We see more of the scenery that way!

You can still 4-wheel, but you might want to take the trail difficulty down a few notches and take your time getting used to the feel. It definitely feels more awkward with the camper on and you have to take it really slow on bumps and over gulleys. Side-lean and twisty situations also feel much less comfortable but you get a feel for things after a while. Do be cautious though--a side-flop with a camper on would likely completely destroy the camper.

Eric

 

[Stereo]

Eric, you'll have me beyond the Newbie stage in no time with all your great explanations. Thank you.

 

[derekparr]

Allow me to echo Stereo. Thanks a bunch for taking the time to answer our questions and explain them in such a thorough way.

 

[tanglefoot]

No worries--happy camping!

 

[Stereo]

Decision Time

I stopped by my local tire shop known for its honesty and talked with the owner about my existing tires. He confirmed what Tanglewood said about the Wranglers not having very deep cross-cut siping in the middle. Based on tread depth, the owner estimated I've got 5-10,000 miles of wear left. He also explained that modern-day tires no longer have 6, 8, or 10 plys even though they're still referred to by ply number; they all have the same number of plys though some plys might be thicker or stiffer than lower grades. He also said that I should be able to make a decision based on weight rating alone, which runs contrary to some of the advise I've received here.

So I guess for now, I'm going with Tanglewood's advice and at least put the camper on the truck and check out the existing tires. If I don't feel comfortable with them, I've decided to go with a skinny tire (215/85R16) that's -0.71% smaller in radius than my stock size (265/70R16).

Thanks again for all the advice.