Reality Check: Largest Tire Size 35" Tires on the 6th Gen 4Runner with Collar Kits & 2" Rear Spacers

[Trail4R]

After a long-winded Facebook Post the other day with 100+ Comments, there seems to be an interesting topic around collar kits and the biggest tire size you can run.

I am running a Peak Suspension 2.25" collar kit front and 2" rear spacer with +0mm Lock Off-Road Invader Beadlocks and 35X12.5R17 Arroyo M/Ts (without extended bump stops). After testing this setup over 3 days, we found that the true 35" tire was making contact with the front and rear fenders, front and rear fender flares, front felt liners, and mud flaps. This was after trimming for 35" tires in the front, and everything was clearing on-road.

This was 100% self-inflicted because I genuinely wanted to run the biggest tire possible, and the collar kits are affordable; however, this could have been prevented if I had just read through Peak's website first or waited for a full suspension. So, no fault of theirs at all, I just ordered the kit, installed it, and then mounted my 35" tires. There are many YouTube videos and guys in the Facebook Groups posting about 35" tires with these collar kits saying everything was fitting with plenty of clearance, I just figured everything would also work off-road. The global consensus as of two weeks ago was that 35" Tires are so easy to fit on the 6th Gen 4Runner - so I ordered all the parts, installed it all, trimmed the front wheel wells, flexed everything out at StellaBuilt on the Forklift, and everything looked like it was going to work. Unfortunately though, you can't torture test everything on a forklift. Sometimes you just have to get out there and see what's happening in the real world.

The Peak Suspension collar kit and rear spacer install were both fast and easy. Check out my full installation here. The kit provided much more room to fit the tires, but I overshot the tire size with a true 35" tire.

This really is a killer option for a lot of people out there looking to run bigger tires, and I highly recommend this kit, but there are limits. And, I found them.

The Peak Suspension Kit I'm Running:

• Front Two Piece Kit: https://www.peaksuspension.com/product/2025-toyota-4runner-2-piece-collar-kit-2-25-lift/
• Rear Spacer: https://www.peaksuspension.com/product/2025-toyota-4runner-rear-spring-spacer/

Debating Tire Size?​

While some companies and some users around the web recommend one aggressive tire size (35X12.5R17) with a collar kit, Peak Suspension recommends a more conservative tire size (315/70R17 - 34.36"), with more disclaimers and mentions the need for extended rear bump stops. The smaller, more conservative tire size (315/70R17 - 34.36") offers better off-road performance when paired with a collar kit, more wheel articulation before contacting bumps, and reduces the chance of contacting flares/fenders. I have a lot of respect for companies that underquote tire specs rather than overquote compatibility.

When running a collar kit paired with extended bump stops, the smaller tire (315/70R17 - 34.36") is a much better option for the 6th Gen.

35" tires come in a wide variety of sizes and will vary depending on the brand and terrain type you choose. A true 35" tire (35X12.5R17 and 35X11.5R17) are both bigger than a 315/70R17 (34.36" - depending on brand and/or M/T vs. A/T). 35" tires are also offered in a wide variety of metric specs and often classified as a 35" but may be under or over the actual 35" size, for example; 315/75R17 measures out to 35.6" which is almost a 36" tire.

That said, there’s been a growing misconception that you can run 35" tires (as a global statement) on the 6th Gen 4Runner with just a collar lift and 2" rear spacer, no problem. But after logging over 1500 miles through the black rock desert this past weekend on a Raptor run and hitting technical trails in Northern California for the past three days, we’re here to set the record straight: fitting true 35s is not the same as clearing true 35s off-road and the exact 35" tire along with specific offset you're running makes a huge difference in terms of clearance, trimming and general fitment.

35" Tire Sizes​

• 315/75R17 - 35.6" height X 12.4 Width
• 35X12.5R17 - 35" height x 12.5" Width
• 35X11.5R17 - 35" height x 11.5" Width
• 315/70R17 - 34.36" height X 12.4" Width - Largest tire size you should run on 17x8.5 Wheels, +35mm Offset with extended bump stops... if you plan on taking your vehicle off-road.
• 305/70R17 - 33.81" height X 12.01" Width
• 295/75R17 - 34.42" height X 11.61" Width
• 295/70R17 - 33.26" height X 11.61" Width

Why Smaller Tires Perform Better Off-Road​

When paired with collar kits:

• 315/70R17 tires offer more uptravel before contacting the body
• They reduce the chance of damaging fender flares and liners
• The slightly smaller overall size improves articulation and minimizes interference

With extended bump stops, this setup gives you the best blend of lift, travel, and clearance, without compromising your rear wheel wells or body panels.

What's The Largest Tire Size You Can Run?​

If you're going to off-road your 6th Gen 4Runner, and plan on a preload collar kit, stick with a 34" tire like the 315/70R17. Add extended bump stops front and rear to keep your suspension from cycling into the danger zone.

And if you’re set on running true 35s (like 35x12.5R17), just know:

• You’ll likely make contact with your fenders and fender flares
• You must run extended bump stops
• And even then, rear clearance is far tighter than people realize

Offset​

In addition to the variations of physical tire size, you have different offsets that determine how the wheel is positioned in the wheel well. The factory 6th Gen 4Runner wheels are around a +45 to +55 offset, depending on the model you get.

Most aftermarket wheels for these vehicles are being offered in a +35mm and +25mm offset, with +25mm offering the more aggressive stance.

For the best possible fitment all the way around, stick with a +25mm, +35mm, or +45mm offset. With that range, you are less likely to rub or bind at full lock.

If you prefer to run +25mm or even lower offset (like a +0mm offset), just know that you are looking at more rubbing, trimming and potentially more contact with your fender flares when off-roading.

What's the takeaway?​

After talking with a few people on Facebook, both 17x8.5 +35mm wheels with a 35x12.5x17 tire and 17x9 +25mm wheels with a 35x12.5x17 tire have been confirmed to cause body damage. Those tire/wheel specs will potentially cause damage to your 4Runner if you plan on off-roading hard. Again, they fit on the road but do not fully clear off-road.

I'm just giving you guys a heads up for what to expect in the rear world when you go to run a true 35" tire on the 6th Gen with these collar kits.

We’re not saying 35s are impossible with a collar kit (extended bump stops may help to prevent fender/fender flare contact), but if you want to err on the side of caution, stick with a mid-size 34" tire.

If you’re planning to send your rig with a collar kit and 35" tires, know what you’re getting into.

 

[4RunnerNation]

Okay okay, hear me out. We know the best tire size, wheel width, and offset to run if you don't want to rub off-road now with a collar kit - but let's say you want just a little rubbing and you're okay with a little more trimming. lol

Sounds like if you're looking to push it a little bit, then maybe a 35X11.5R17 +35mm on a 17X8.5 might be a win with minimal trimming?

 

[Trail4R]

@4RunnerNation - you're going to have trimming regardless in the 35" range - front and rear. The 35X11.5R17 is a skinner 35" tire paired with a skinny wheel (17x8.5) all on a +35mm... yeah that sounds like a better fitment but honestly it's hard telling not knowing and testing it.

I'm going to get a few parts in soon, and possibly move up to a +35mm wheel in a 17x8.5 on a 35X11.5R17 or 315/70R17 for some additional real-world testing.

I'll keep you posted.

 

[rustytaco]

Super solid information. This is the stuff you really need to educate yourself on before you come up short, especially on the trail. I have a new 4G Tacoma, the rear wheel well seems to be less problematic there. Looks like we still need to do some work, though. But even so, easier than the previous gen overall - I think...

 

[5G6G4R]

Usually, anything below a 0mm offset is going to be way too aggressive. The trailhunters and pros are on a +25 offset. Other models (TRD Offroad, Sport, Limited, etc. all have all+55mm offset. If you want more stance/poke, you’ll need a smaller tire or to remove mudflaps, crash plates, and pin the fender well back. I've seen the 285/70/18 Nitto Ridge grapplers (33.9") tire fit with no lift or rub, but on a stock offset of +25. These 4Runners are really designed around a max of +25mm offset with 285/70/18 tires. If you want to go with a 17" tire, then look at a 285/75/17 with +25mm wheels and you will be fine.