Are 35s really the answer for off-road driving?

[Xtremluck]

I’ve always been a believer that 33 inch tires are the perfect size for our platform. This is when you think of mechanical reliability, affects on on-road performance and the level of effort to get things working properly. However, curiosity killed the cat and with a couple of really technical trails on my list for the next month I decided to upgrade. I didn’t want to go to a full size 35” tire so I decided to go BFG K02 in the 315/70/17. These tires are notorious for being undersized and at 62.4 lbs they were pretty light.

Mounted they stood just about 34” tall. Here is one mounted on a wheel next to an unmounted 285/70/17 Ridge Grappler with about 99% tread left.

As you can see once mounted it was really apparent I needed to do a ton of clearancing for these to work off-road.

So off I went to grind down more body mount and to flatten the pinch welds.

I had a camping trip planned this weekend so I knew I would be able to test them out. Before I went out I did a 100 mile loop to get some initial pavement impressions running a tire of this size with stock gearing. Here’s what I thought:

1. Power - There was definitely a hit on power but it wasn’t as bad as I expected it to be.

2. Engine Speed - RPMs at highway speed are lower than my previous setup. So at 65 mph my engine was spinning at just about 1600 rpms.

3. Transmission - Transmission temps and shifting were fine even when climbing a mountain pass

4. Gas Mileage - Fuel economy was still decent with average highway speeds around 65 mph. I returned 17 mpg hand calculated at the pump using the TFLTruck method over that 100 mile loop. I was really surprised by this.

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[Xtremluck]

Now it was time for some off-road driving impressions. We had a weekend up in the Western Sierras for some mountain biking and moderate wheeling. So I thought it would be a perfect opportunity to test clearancing. I removed my fender flares ahead of time because I knew they would be a problem.

So off into the mountains we went to find some great campsites and rocks and ruts to play on.

As expected the tires showed me where I needed to do more clearancing at full compression. Fenders need to be cut, BMC dialed back and firewall beat back.

So the real question was how did they do off-road? Here is what I think:

1. Steering - I definitely felt an increase in bump steer when going over rocks. Not surprising since these larger tires have a lot more rolling mass.

2. Clearance - It was nice to be able to roll over larger rocks without tagging my skids and rear bumper. I’ve done the rockier part of this trail many times before and there was definitely a difference there.

3. Crawl Ratio - When in 4 low the negative impact of messing up my crawl ratio was felt. The truck was rolling faster especially in 2nd which meant much more brake modulation descending steeps and crawling rocks. Obviously this will be corrected with gears later down the road.

4. Traction - Traction felt it was a bit reduced on dry loose rock vs. my Cooper ST Maxx I ran previously. Not surprising since these have a much less aggressive tread.

So for me the jury is still out on this size tire from my perspective. It required a lot of work to fit and will need even more in the future to do this really right. I also question the durability of the stock steering components now that they are turning such huge tires. I foresee also having to upgrade the rack in my relatively near future. Although I heard upgrading to an LC200/Tundra rack doesn't really solve things either.

At the end of the day these types of mods have diminishing returns and are also a balance of capability and durability. I think I may have overstepped a bit and upset that balance but time will tell. I have a 7/10 technical trail run coming up in a couple of weeks. So I'll really be able to put the new setup through its paces. I just hope I dont break anything trail side


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[1jzgte]

35's are for the 'gram bro

 

[lewdog998]

for the reasons you pointed out, the 33s are a good "governor" that keeps me off anything too radical and breaking stuff all the time.
the question is...do you want a rock crawler that can go anywhere with less reliability....or a swiss army knife that can do most things well, but not all great, and remain reliable.

 

[comtn4x4]

Thanks for posting this. Every time my tires start to get thin on tread I think about going to a 35.
You're on stock gears IIRC?
What is your caster set at now?
Wheel width and off set?


I know it's all in your build thread but I thought others might gain insight from this

 

[blksubykid]

285/70/17 all day but 285/75/17 might be a happy medium between "33s" and "35s". It fits with about the same effort as 33s, same contact patch but slightly taller, and less wear of you steering and drivetrain components than 35s. I personally think what type of tire has more impact on our 4runners than actual tire size. Of course, a Rubicon on 35s or 37s will out perform but its setup different than us. On Top of the World, I noticed my Yokos gripped better on the uphill portion and slid alot less coming down than my buddies and I am a lot heavier than them. Maybe it was my brake and throttle modulation, but I like to think it was my tires...and probably my gearing lol

 

[M_RED]

Narrow 33's are the answer??

I agree,, 33's are a happy place to stop. They have a near negligible effect on the daily driven aspect of my truck, and are just big enough to tackle everything offroad I want to (note. Sliders, skid plates, and good armor is just as important. )

I have had really positive experiences with Nitto Ridge Grapplers in 255/80s on mine. they stand about 33.3" tall, and are narrow enough on the TRD-Pro wheels to have clearance at full articulation with no need to chop body mounts. Aired down, they are a great tire option in the PNW in every season but winter....

 

[baldrik78]

I think for the average user, 33s are perfect. They look good and they do 99.99% of what people want them to do.

I just made the jump to 35s and it's been a lot of work - even with a much narrower tire. I had to have my BMC redone and cut further back, I've cut and hammered the pinch weld, I've hammered the inner fender, I've cut the fender trim, but not the actual fender yet. Every couple of days a trim a bit more, look for more rub, trim a bit more, look for more rub, etc. Honestly if I just removed my wheel spacers and used a wheel closer to a -10 offset, I'd be golden.

 

[Grug556]

OP a question on the tires

I see you went with 315s? I was wondering why? Arent wider tires mostly for floatation in mud? If so why the K02s? I have K02 and like you probably know its a great gravel and light dirt tire but a shit mud tire. So why the need for the extra punishing weight and width of the larger tire?

Not knocking your choice just wondering where the tradeoffs make the larger diameter worth it? Is it really that much better?

 

[Xtremluck]

for the reasons you pointed out, the 33s are a good "governor" that keeps me off anything too radical and breaking stuff all the time.
the question is...do you want a rock crawler that can go anywhere with less reliability....or a swiss army knife that can do most things well, but not all great, and remain reliable.

100% its definitely a balancing act and hard to nail down. My truck is a dedicated off-road vehicle that travels far distances on pavement to get to fun. I also love very technical trails and testing my equipment's durability. In some weird way I like when things break because I know that I'm really using them.

 

[Xtremluck]

Thanks for posting this. Every time my tires start to get thin on tread I think about going to a 35.
You're on stock gears IIRC?
What is your caster set at now?
Wheel width and off set?


I know it's all in your build thread but I thought others might gain insight from this

Ah good call, I mentioned being on stock gearing but I guess it was a bit buried. The gearing obviously affects power and the crawl ratio which would be both solved with gearing to 4.56 or even 4.88. However, I know changing the gearing will most likely result in a negative impact on fuel economy. Which is a factor to consider of course.

Caster is set to 4.1 driver and 4.0 passenger, that is the max you can get with Icon UCAs. My rims are 17x9 with a -25 offset which doesnt make things easier. However, even with a 0 offset wheel I can't see a world where you're not hitting your fender flares at full compression.

 

[Xtremluck]

I think for the average user, 33s are perfect. They look good and they do 99.99% of what people want them to do.

I just made the jump to 35s and it's been a lot of work - even with a much narrower tire. I had to have my BMC redone and cut further back, I've cut and hammered the pinch weld, I've hammered the inner fender, I've cut the fender trim, but not the actual fender yet. Every couple of days a trim a bit more, look for more rub, trim a bit more, look for more rub, etc. Honestly if I just removed my wheel spacers and used a wheel closer to a -10 offset, I'd be golden.

Yup its definitely a work in progress but I guess that is the fun part right?

 

[Xtremluck]

OP a question on the tires

I see you went with 315s? I was wondering why? Arent wider tires mostly for floatation in mud? If so why the K02s? I have K02 and like you probably know its a great gravel and light dirt tire but a shit mud tire. So why the need for the extra punishing weight and width of the larger tire?

Not knocking your choice just wondering where the tradeoffs make the larger diameter worth it? Is it really that much better?

I went with 315s because I do a lot of snow wheeling in conditions where the snow is very deep and I need flotation. Also mud is pretty rare here outside of the PNW and most of my wheeling is over dry rock which K02s are great on.

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[Inv4drZm]

I blew the end cap off the stock steering rack on the trail with 160k miles on the truck and 35's. Fluid went everywhere and I limped it off the trail.

However I haven't had an issue wheeling with that same rack and 37s. Haven't even broken a tie rod or a CV. This is on the Rubion, Fordyce, and Blanca Peak. Goes to show no matter your tire size you always have to prepare for the worst on the trail.

I grenaded the rear diff right after installing 35s on the trail but a rebuild with a solid pinion spacer would have prevented it, and the 5th gen rear diff is stronger than my 4th gen's. I upgraded to a dana 60 which is good for 40s.

A LC200 rack should be good up to 40s and is only a couple hundred more expensive than a stock steering rack.

So yeah I've had some breakage but nothing that can't be beefed up in advance, the only real expensive item is the rear diff solid pinion spacer but can be taken care of alongside a regear and lockers. And maybe the 5th gen rear diff is strong enough to handle 35s but I've seen at least 5 guys with factory untouched 8" rear diffs grenade them on 35s with 4th gens and FJs. But like I said once you replace that crush washer with a solid spacer it should be fine with 35's especially your 8.4 diff.

 

[comtn4x4]

Ah good call, I mentioned being on stock gearing but I guess it was a bit buried. The gearing obviously affects power and the crawl ratio which would be both solved with gearing to 4.56 or even 4.88. However, I know changing the gearing will most likely result in a negative impact on fuel economy. Which is a factor to consider of course.

Caster is set to 4.1 driver and 4.0 passenger, that is the max you can get with Icon UCAs. My rims are 17x9 with a -25 offset which doesnt make things easier. However, even with a 0 offset wheel I can't see a world where you're not hitting your fender flares at full compression.

I'll be interested to see how you sort it all out. You may need some longer bump stops.
What altitude do you wheel at?

 

[lewdog998]

In some weird way I like when things break because I know that I'm really using them.

too true.. I used to do a lot of track days. People would always wonder why i continued to do so when crashing was not unexpected. I always told them that "if you are not crashing, you are not trying hard enough"

i get it...always pushing you or your vehicle to the edge.

 

[Grug556]

I went with 315s because I do a lot of snow wheeling in conditions where the snow is very deep and I need flotation. Also mud is pretty rare here outside of the PNW and most of my wheeling is over dry rock which K02s are great on.

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Understood the float on snow. Thanks for posting the pic. ON mine I went the opposite way and went skinny and thin on snow. My area is like yours, not a ton of mud, but lots of gravel, rock and crap with tons of snow thrown in.

 

[Xtremluck]

I blew the end cap off the stock steering rack on the trail with 160k miles on the truck and 35's. Fluid went everywhere and I limped it off the trail.

A LC200 rack should be good up to 40s and is only a couple hundred more expensive than a stock steering rack.

I've had the same experience with 33s, my steering rack failed around 120K on a trail run but I was able to hobble out. I've also had a couple of outer tie rods bend on me and they were an easy trail replacement. I just saw a LC200 rack replacement failure on a 5th gen on 40s. Apparently a lot of the internals are the same as a stock 5th gen rack there is just more space for fluid volume.

So yeah I've had some breakage but nothing that can't be beefed up in advance, the only real expensive item is the rear diff solid pinion spacer but can be taken care of alongside a regear and lockers. And maybe the 5th gen rear diff is strong enough to handle 35s but I've seen at least 5 guys with factory untouched 8" rear diffs grenade them on 35s with 4th gens and FJs. But like I said once you replace that crush washer with a solid spacer it should be fine with 35's especially your 8.4 diff.

Good insight here, I haven't seen a stock 8.2" on a 5th gen blow up yet. Only grenaded diffs that were regeared improperly. So we will see how I do. I've got Slickrock in a couple of weeks and a full Rubicon run first week of Nov (If they open it up again).

 

[Xtremluck]

Understood the float on snow. Thanks for posting the pic. ON mine I went the opposite way and went skinny and thin on snow. My area is like yours, not a ton of mud, but lots of gravel, rock and crap with tons of snow thrown in.

Skinny tires work on snow that has pavement underneath it so you can cut down to the bottom. Not so much in snow that is 10-20ft deep in a lot of the off-road snow wheeling situations we have here. At least that has been my observations

 

[Xtremluck]

I'll be interested to see how you sort it all out. You may need some longer bump stops.
What altitude do you wheel at?

This weekend we topped off at around 7500 ft. Longer bump stops would definitely solve the problem but I want to keep as much up travel as possible. So im trying to clearance as much as I can.