37 vs 35 Tires

[Sgt Beavis]

Coming from the Jeep world I’ve seen a lot of people upgrade to 37s. I put them on my Jeep just last month. That rotational mass impacts milage, braking, wear and tear on components, etc., etc. On my Jeep, of course I had to install a good lift to fit 37s. Eventually I’m going to have to replace the axle shafts and re-gear the front and rear diffs. I also expect I‘ll have to upgrade the steering at some point.

That’s the great thing about the Gen3 Raptor’s 37” tire package. Ford already knows this stuff and will have upgraded anything that needs upgrading. Honestly that package is a bargain compared to doing it yourself the RIGHT WAY. Just placing a MetalCloak Gamechanger 3.5” lift on my Rubuicon was $2300 for parts and $2200 for labor. I haven’t even touched those other things. A set of diff gears is about $1000 + the labor. Steering upgrades are over another $1000 in parts. It’ll be even more than that if I upgrade to hydraulic steering.

 

[combatninja]

Rotating mass does play a factor but the bottom line is that the farther out from the axis you place said mass, the harder and harder it becomes to turn. As in, the more power it 'consumes' to overcome inertia. You could have a theoretical 37" tire that is lighter than a 35" tire but still be harder to turn because of where the mass is located (and the heaviest parts of tires are the steel belts and tread, at the outside). The inside is basically empty space.

The other factor to consider is gearing. Going to larger tires essentially gives you a taller final drive which is why you see so many Jeep guys talk about "re-gearing" when going big. This also has to do with their gutless power plants as well. That Pentastar V6 is just weak even with stock tires. The 37" package for the Raptor makes no mention of a different final drive so we can assume that a 37" vehicle will be a bit slower off the line than a 35" truck. Interesting that the new Bronco does change the final drive if you upgrade to the Sasquatch pack with the big 35" tires.

All this said, I find it more than a little ridiculous for people interested in a 5500 pound truck to fret over a bit of rotating mass or the loss of a tenth in 0-60 time.

 

[MrGable27]

If you actually offroad? None. The only downside is extra mass, however 37” BFGs are only 4-5lbs heavier per corner than 35’s. Better ride, more rubber between you and the road/trails, and hell even my mpg went up after I switched to the bigger tires.

 

[King Paul II]

that being said you are looking at new springs up front and new leafs in back correct?

you don’t need new leafs in the back just springs in the front. New leafs would help but not absolutely necessary. And depending on offset of wheels very little trimming up front

 

[Gdog]

you don’t need new leafs in the back just springs in the front. New leafs would help but not absolutely necessary. And depending on offset of wheels very little trimming up front

I want the truck level. Current have 1.5" collars up front and very close to level now with 35's. Guessing springs up front would lift closer to 2 3/4".

 

[pbtjrlmrt]

For anyone with 37" tires, what are the disadvantages? The biggest for me which I have heard so far is loss of power at the wheels. Anyway to quantify this? For the MPG loss, it sounds like it is usually around 1 MPG, is this right? What is it like driving on them versus 35's?

Every single comment except for Teghogh so far is ordinary incompetence. You don't need to look very hard to know that...unless your mall crawling...37s will rub. The worst part is that you will be stressing your suspension in ways that it wasn't designed for...parts will wear or break much sooner. 37s done right will cost 10-15k. Proceed at your own risk. What ever you decide...please please please ignore the idiots on this forum that run straight for Geiser/Deaver setups and tell you that 37s are no problem. You know their idiots because they don't even ask you how you use your truck. Do yourself a huge favor and talk directly to a suspension expert...someone familiar with Raptors...not someone trying to sell you parts. Tell them your use case and discuss options. The guys at RPG are pretty good but I would get a couple of opinions from experts. Suspension is the most personal and expensive thing you'll do...if done wrong you will have wasted your money and perhaps shortened the lifespan of your truck...you'll certainly void your warranty and will be generally unhappy. There are a few guys on here that know their stuff but the problem for you is knowing exactly who that is. For the most part people on here are just ignorant and do not hesitate sharing their ignorance when it comes to suspension mods. I am not an expert and my suspension mods were carefully worked out with the help of paid professionals and the end result is perfect for my use case.

 

[Leo Hunerjager]

Every single comment except for Teghogh so far is ordinary incompetence. You don't need to look very hard to know that...unless your mall crawling...37s will rub. The worst part is that you will be stressing your suspension in ways that it wasn't designed for...parts will wear or break much sooner. 37s done right will cost 10-15k. Proceed at your own risk. What ever you decide...please please please ignore the idiots on this forum that run straight for Geiser/Deaver setups and tell you that 37s are no problem. You know their idiots because they don't even ask you how you use your truck. Do yourself a huge favor and talk directly to a suspension expert...someone familiar with Raptors...not someone trying to sell you parts. Tell them your use case and discuss options. The guys at RPG are pretty good but I would get a couple of opinions from experts. Suspension is the most personal and expensive thing you'll do...if done wrong you will have wasted your money and perhaps shortened the lifespan of your truck...you'll certainly void your warranty and will be generally unhappy. There are a few guys on here that know their stuff but the problem for you is knowing exactly who that is. For the most part people on here are just ignorant and do not hesitate sharing their ignorance when it comes to suspension mods. I am not an expert and my suspension mods were carefully worked out with the help of paid professionals and the end result is perfect for my use case.

 

[SkyPilot]

Most guys look at acceleration and think about a gear change to fix it and forget about braking. As a kid engineering student I put a 327 chevy V8 in a Willy's Jeep. Rocket time. But I didn't have the money to upgrade the brakes.... I'll just do that later..... Wrong answer... I ended up T boning a drunk driver that turned in front of me. Correct there is no squared term in the basic pounds-feet torque equation, but the difference in stopping power can be substantial.

 

[jondle]

I have a Gen1 and have run 37" with HEAVY off-roading for 7'ish years, after heavy off-roading with 35's for 3 years, with simply deavers, mid-perch, pinch weld flattened, and +2/+2 fenders (which weren't really necessary). Only issue has been minor rubbing on the fender liner, which I fixed with fender washers and self-tapping screws. Saying the people on this forum are incompetent is ignorant and scaring people out of going to 37's because the suspension will wear faster, which is theoretically true, is grossly over dramatizing it. You are giving the extreme worst case scenario; others are giving real-life, multi-year experience with their actual Raptor.

I think the bigger issue than suspension failure is the things the majority of people are explaining, with their real world experience. The combination of higher moment of inertia and the gearing difference can make the truck feel slower than with 35's. Moving down a gear ratio would put it closer to stock. Gas mileage should be fairly close to unchanged as the higher gearing *should* compensate for the extra weight and inertia (disclaimer, no math done on that sentence), unless you drop gear ratios to compensate.

In fairness, I'm on my third power steering pump. This may have been hastened by the 37's, but I know plenty of people with Gen1's on 35's that have had issues with the PS pump. I'd say the same thing about the Gen2 racks; a lot of people have had issues with their electronic rack, which the 37's may speed up issues with. That said, at the moment, I don't think there is a reasonable upgrade even if you wanted to.

 

[Teghogh]

I have a Gen1 and have run 37" with HEAVY off-roading for 7'ish years, after heavy off-roading with 35's for 3 years, with simply deavers, mid-perch, pinch weld flattened, and +2/+2 fenders (which weren't really necessary). Only issue has been minor rubbing on the fender liner, which I fixed with fender washers and self-tapping screws. Saying the people on this forum are incompetent is ignorant and scaring people out of going to 37's because the suspension will wear faster, which is theoretically true, is grossly over dramatizing it. You are giving the extreme worst case scenario; others are giving real-life, multi-year experience with their actual Raptor.

I think the bigger issue than suspension failure is the things the majority of people are explaining, with their real world experience. The combination of higher moment of inertia and the gearing difference can make the truck feel slower than with 35's. Moving down a gear ratio would put it closer to stock. Gas mileage should be fairly close to unchanged as the higher gearing *should* compensate for the extra weight and inertia (disclaimer, no math done on that sentence), unless you drop gear ratios to compensate.

In fairness, I'm on my third power steering pump. This may have been hastened by the 37's, but I know plenty of people with Gen1's on 35's that have had issues with the PS pump. I'd say the same thing about the Gen2 racks; a lot of people have had issues with their electronic rack, which the 37's may speed up issues with. That said, at the moment, I don't think there is a reasonable upgrade even if you wanted to.

Coming from the jeep world I have read a lot of stories about axles snapping in offroad situations when the wheel has no traction and rotates and suddenly finds traction and bang broken axle due to extra torque that is 100% exasperated by going to 37s. If you are off-roading stinger axles are required even in common situations described above. On the street your gas mileage will suffer about 3mpg at the very least. You can compensate for the loss of torque by going to a lower ratio but you will pay for it on the top end as the engine has to run at the higher rpm to keep the same speed if you are overgearing it. So will your braking as mentioned above.