Thought I'd give a quick update on my thoughts having around 4k miles bone stock (35 Package) to now switching to a 37 setup pictured above last week. I recently did a 600 mile road trip and spent some time off-road in dried lake beds and FS Roads with around 12-16" of snow in places. I'll preface this by saying my experiences of this probably won't mirror the mass sentiment here. I spend a copious amount of time off-road and have raced anything with 2 or 4 wheels in that environment for many many years, needless to say I'm a picky SOB when it comes to change and vehicle dynamics.
First off, the general sentiment of adding 37's is no noticeable change I don't agree with. Is it a drastic change, not by any means. Is there definite drawbacks that can be noticed, absolutely 100% so don't trust the placebo effects from many of oh "it looks badass can't even tell". First off, the most apparent the MPG decrease is there for those that care. My anecdotal observation is I lost a solid 1.5mpg on average with a trip I frequently take which is inline with how Ford rates EPA of a 35 vs 37, so no surprise. The reason why though I feel is important. Adding 37's has a very noticeable impact on the final drive ratio and therefore really takes away the down low snappiness of the 10AT combined with 35's. It's now 200-300rpm lower in any given gear and almost always needs to be a gear lower than previous to have that same "take-off" and go. You start noticing things like turbo lag and torque converter slippage when it isn't locked in lower gears more than before. Once going at HWY speeds this is less noticeable however instead of 2,000k RPM at 70mph I'm now right at 1,700 RPM. So it will downshift to 8/9th more often all things being equal to stay in the correct TQ band. For reference, I also reset the PCM/TCU adaptations and reset my tire size per the Forscan instruction included on this forum. Oddly, I've also noticed much more clunking on downshifts from the 10AT after doing so but I don't believe this to be attributed to anything tire related...yet.
Although, my 37 wheel/tire combo is basically as light as you can buy currently I wouldn't say it rides better. OEM FP 37's although C rated have thicker sidewalls than the metric 315/70 (35") counterparts when I looked at both dismounted. I find under certain conditions 37's ride better but on broken or uneven pavement my 35's actually rode better and were less nervous traveling at FWY speeds of 70-80mph. The 37's I suppose from being skinnier actually tramline worse which is ironic given I thought they would less. Note: I run the same pressures for each at 38psi Cold. The biggest item to consider is off-road the 37's are less composed on moderately fast terrain. Think dry lake beds doing 40-60mph and hitting large dips at those speeds. The rebound dampening isn't quite there to support the larger tires overall. I would imagine this is where the 37pp is retuned to account for that. Changing to Sport or Baja mode helps this but doesn't fully mask it. Ultimately, any of the faster paced stuff 37's are a clear downgrade which again is to be realistically expected but was more than anticipated.
With that said, would I go back? I'm not 100% sure overall. Personally, I've never let looks generally dictate a modification given I "use" my vehicles for their intended purpose. However, I was woefully unimpressed with how pedestrian a stock 35 Raptor looks. To the point even with smaller tires my previous GMC AT4 almost had more presence. With the 37's the truck just looks right, fender proportions, how it sits, stance, etc. just fit the body lines of the truck perfectly. It has completely altered how I feel about the looks of the vehicle and I'm 100% pleased. From a performance perspective I'd being lying if it's not in the back of my head to go back to 35's though...
BFG 37x13.5.20 on Vossen HF6-4 (+15 offset) Gun Mental wheels - Minimal rubbing on my WhetherTech mud flaps in the front. No other mods, all stock suspension.
