I can see how the tire size is a contributor but it was the same experience with 265s. Maybe not as extreme.
Once I wear these out I’ll probably go down to 275s or do the 255/80
But that’s a ways off.


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Hey mscot,

I didn't read all the replies but wanted to chime it. I'm also in Denver and have the same ToyTec lift as you do. I started with K02's at the time of the lift and had the same crazy harsh ride you are referring to. I switched to the Ridge Grapplers and really wish I would have started there. The ride is literally half as rough as it was with the K02's. Night and day difference, IMO. Also, not sure if your running spacers but they will greatly increase the harshness as well. For driving at altitude, I can say the Sprint Booster is almost a must have for our rigs in the Mtns. It's made a HUGE difference for me both around town and in the high country. I do have a CAI and a high-flow exhaust as well, which I'm sure helps "some" . Good luck!

I upgraded my Toytec lift to Icon and moved to California.

Solved both problems.

So general question - with larger tire choices is it the weight or the diameter that really has an effect? Im running KO2 E 275/70/17 which claim to be 56 lbs each - I've been thinking of going to the P rated Falkens 285/70/17 which list as 51 lbs each - does the jump in diameter offset the drop in weight?

the diameter will have more affect. it changes the overall gearing. it just slows the crank down too far, gets its below the necessary torque area.

Interesting. I've had a 2nd Gen Tacoma, 4th Gen 4R V6, and 2 5th Gen 4Rs and haven't had the issue you speak of. I could definitely feel the effects on the Tacoma after switching from the stock 31" tires to aftermarket 32" tires. All of the 4Runners had/have stock sized tires and I felt there was plenty of power for the I70 racetrack.

For performance, both.

The Wildpeaks will be better than Ridge Grapplers in the rain, but the latter are 44 lb in 285 and that will make a difference. Maybe the G2 is better in the rain than RG and just as light, not sure if available in P285 though.

For tire size, neighboring sizes can almost overlap depending on models. In your case, the KO2 is 32.2 and the Wildpeak is 32.8. It is not a huge difference but it will be easily felt vs stock. For tread width, they totally overlap and a 265 can be wider than 275 or even match a 285.

So you gotta look at all numbers. Tire Rack is the best for that purpose, for the tires they carry anyway.

Stock tires are 39lbs each, 56lbs is super heavy! Why are you running an E rated tire? I'd drop down to a stock size or 255/75/17 in a P rating, that will be more like the stock weight and should make a noticeable difference. For instance, a 255/75/17 Duratrac weighs 39lbs.

Also, I had my 4R in NH last week, It was struggling in the 3000' altitude range, I cannot imagine driving this thing in CO. Honestly, if I frequently drove in the mountains I would not have bought this.

It’s hard for me to believe that all of us knuckleheads running 33s in CO have spent $2k+ on regearing.
I may try the CAI and leaving it in 4th while climbing to see if that helps.

Kinda stuck on the suspension. I’m worried about spending more money and it still riding this stuff - knowing that no two 4runners are the same.
Maybe I can ride in someone local with a king set up and a eibach pro set up to see what it think.

Nonetheless thanks for all the advice everyone.


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Update: a week or so ago I went over to Toytec and road in a truck with KDSS that had their 2" Boss on it. It was a much smoother ride.
After some thought, I ended up buying the Eibach Pro Truck that people have been raving about.
I'll be picking it up tomorrow or Wednesday and installing it asap.

That means there is a very lightly used Toytec Boss Performance 2.5" suspension that will be on the market soon if anyone is interested.

it feels pretty rough all over. I could definitely put the eibachs on the rear first and drive it around as I'll probably do it over two days anyway.

I had one of the guys at Toytec drive it and he said it's riding exactly as designed. Its just more shock than I need and I don't get out as much as I thought I would.

For me it was an altitude/temp combination under load. Mostly the truck was fine, but dragging 3000lbs of trailer 2000ft up (I know, nothing compared to out west) at 94F ambient and 80+% humidity the truck was a dog trying to get up the grades of backwoods KY. I ended up with a SC, but there was an interim step where I was extremely happy for the cost. It was a combination of the aFe MomentumGT CAI and URD's MAF Calibrator.

Adding a CAI doesn't do much if you're not adjusting the computer for the additional air flow. This is especially important if you've changed the diameter of the tube near the MAF sensor, between the air filter and the throttle body. Adding a Sprint Booster or the like will change the throttle mapping, kind of like going to sport mode instead of eco-mode in some other vehicles. URD's MAF Calibrator will correct the readings of the MAF Sensor to be appropriate to the diameter of the inlet pipe and amount of air flowing through it. There was a noticeable (though not large) performance increase over stock in this configuration.

Also what octane fuel are you using? The engine will automatically adjust timing on a variety of variables. The smaller partial pressure (thinner air) at altitude means advanced timing because it takes longer to burn. Because of its tendency to pre-ignite, low octane requires retarded timing. The idea of 85 octane at altitudes came with vehicles pre-1984 when timing had to be manually adjusted. At that point the thinner air meant you could run a lower octane fuel which costs less and balanced with the timing advance required for higher altitude operations, hence less tuning and adjustments required. It was simpler for lower octane fuel to be sold in high altitude areas than to adjust the timing of every vehicle when they happened to drive through those areas. For those who live there, a timing adjustment was a better long term solution. On modern vehicles the computer will automatically adjust timing, so this is not as big of a deal. However, if you want more efficiency (which can translate into more power), try running a higher octane. Just know that it can take a couple full tanks for the computer to adjust to the better efficiency (or you can reset it by disconnecting the battery for about 2 hours).

Like anything it's likely a combination of multiple factors, high altitude, ambient temps (summer vs winter), lower octane fuel?, larger diameter tires, wider tread (more friction), lift (increased air resistance), and even more!
FWIW I also didn't care for the rough ride on the KO2 E load tires and dumped them in almost new condition less than a year after I bought them. Now running the Cooper Discoverer AT3's and they're much better.

Hey MSCOT,

I'm diwn in castle rock, just wondering how much uppity we're gonna sell your suspension for?

A turbo is the only real solution at altitude. I travel to the eastern sierras on a regular basis and have to climb the Sherwin grade. My 4runner needs to be high in the power band to maintain 70+ up the grade. In contrast my truck with a turbo diesel basically idles up the grade at 70+, even with my camper on it climbs better at elevation than the T4R.

Welcome to my world. I commute down to Golden for work a few days a week and just ended up getting a small turbocharged commuter car instead of constantly flogging the 4R over Berthoud Pass. Plus it helps keep the miles off of the 4R.

HP loss at altitude is real and you have to flog this truck a bit to get it to really move heading up Berthoud or Loveland... heck, even Genessee Hill.