Larger Tires Question???

[Grimm_Reaper19']

Hello all, So I am looking to go up in tire size, im tossed between runnin 35's or 37's, Truck is used about 80% on road and 20% off-road, mild trail riding. nothing major. I am looking between 4" - 6" lift. I very rarely tow, if I do it would be a small travel trailer.

My question is running 37's what kind of stress will that put on the truck if any, ie. rear end, brakes, towing...? will I end up running into issues, should I step down to a 35 or will my truck not notice any difference with the 37's? Will I need to re-gear or upgrade brakes at all?

Currently my truck is a 2019 2500 6.7l CC SRW completely stock setup, nothing modded, except soon to do lift but I do not want to run a 6" lift and figure out that 37's will become issue and have to go down to 35's!!!

 

[lpennock]

35's will fit without a lift as long as you watch the wheel offset. A -18mm rubs. Too much negative offset and they will rub on turns. A 9" wide +18mm works well.

 

[R.Taylor]

You'll notice lower fuel economy with the 37's. Personally I'd go with a 4" lift if your really not hitting the dirt every weekend. My 06 had a 4" lift with 35's.... I ran 37's one time and noticed about a 1.8mpg loss. I'd watch the offset as Ipennock says.. I ran the Toyo OpenCountry ATII 35x12.5 tire on a 20" X 9" Fuel wheel with a 18mm offset.... Never had a rub issue and everything had plenty of space. I'd get about 40k out of the tires but you gotta rotate religiously and keep the psi set right. Now with my new 2019 3500 I'm getting on the suspension/wheel/tire itch and looking at a 4" Carli lift running 35x12.5's on 20's again. It's a nice combo and fills the wheel well nicely. Now if you go with a 6" lift you'd might as well go with a 37" as a 35" tire will look a tad small on a truck that high.... Just my 2 cents.

How ya like your 19'?

 

[Grimm_Reaper19']

Thanks guys for the advice, makes a lot of sense. I'm prob. leaning towards a 6" lift with the 35x12.5 on 18x9. I'm thinking it will give me room to step up to a 37 down the road if I feel the itch, plus it will give me time to bump the front & rear gearing from the stock 3.73's to more like a 3.92 or 4.10's. And beef up the brakes to a Power Stop kit for better stopping power.

I love my 19' it's rides so much nicer than my 02, dont get me wrong I miss the ol 5.9, but this one is pretty much bulletproof right of the lot. I love it!! I'm getting about 18.5 - 19 mpg currently, so I could still sacrifice some mpg's and getting better mileage than I was in 09 HEMI, I had before this one.

Thanks for the advice all!!
Please share what lift wheel tire combo you will be ending up with if you dont mind.

 

[Cummins12V98]

If anyone wants better brakes install the EBC Orange HD towing pads. You WILL thank me.

 

[MRoberts]

I think a 6" lift with 35's will look odd, not enough tire. I have a 3" Carli Backcountry suspension on mine with 35's, it has a very balanced look. OP - note there is a big difference between a lift and a suspension. You will have a much better ride overall with a suspension. 35's and the 3:73 will be fine, if you go to 37's, you and your transmission will be happier with 4:10's.

 

[AEdelheit]

I would stay with 3" lift or less as you do not gain any suspension performance once you go taller but you add more components to fail and driveline issue. There are many trucks running 37's on a 2.5"-3" lift and look great, 35" on a 6" will look funny.

I have ran 37's for over 10 years now, it will go through brakes and steering components faster but not terrible, for how I use my truck its worth it but did regear.

 

[kwb]

I just got a 2020 2500 and want to do the same thing... I am trying to decide between 35's and 37's. People always talk about fit and mpg. I am mainly concerned about RPM. I am going to do a Carli suspension either way - their 2.5" lift will fit 35's or 37's with the right wheel offset.

The truck comes with a 3.73 rear end and with the stock tires (33") - I have the off-road pkg from the factory

The actual RPM I see:
Speed: 65mph - RPM 1500
Speed 75mph - RPM 1700 (The sweet spot for this motor feels like 1750 RPM, it produces maximum torque at 1700 RPM).

According to some charts I looked at, the mph / RPM would be:

37":

Speed: 65mph 1400 RPM
Speed: 75mph - RPM 1620

35":

Speed: 65mph - RPM 1490
Speed: 75mph - RPM 1720


I love the way the 37's look, but I don't want to run the engine below 1500 RPM, it just feels like its working too hard.

So I may do 35's and if I later to decide to get 37's - I think I would need to change out the gears (which I really don't want to do)

Does anyone here have hands on experience with running 35's or 37's with the newer trucks (68rfe 3.73) that could share their experience - in particular MPH/RPM?

** I also can not validate the accuracy of the chart I am using and question the numbers since they don't look quite right...

Thanks!

 

[lpennock]

I have a spread sheet that I built that calculates rpm at speed and the chart you had matches my spread sheet within about 50 rpm. Since I just guessed at the actual rolling diameters for my quick check I would call the chart correct.

 

[gtwitch]

I have 3.43 gears in my 17 2500 with 68 RFE trans and I sure wish I had the lower gears. I purchases the truck used with 23K miles on it (at a bargin price) and by the build sheet, It should of had 3.73 and 17"wheels/tires, but when the buyer added the "Snow build package" the tire size was changed to 18" and the gear ratio was changed to 3.43. I pull a 33 ' enclosed snowmobile TOY HAULER and never unhook it from late Oct till about now Mid May. The run down the road at 67 mph is around 1550 rpm and this is below the "sweet spot" mentioned above and I notice that also! gtwitch in wyoming

 

[elephantrider]

stay with 35's unless your going to regear to 4.10's for 37's.

 

[AH64ID]

I have 3.43 gears in my 17 2500 with 68 RFE trans and I sure wish I had the lower gears. I purchases the truck used with 23K miles on it (at a bargin price) and by the build sheet, It should of had 3.73 and 17"wheels/tires, but when the buyer added the "Snow build package" the tire size was changed to 18" and the gear ratio was changed to 3.43. I pull a 33 ' enclosed snowmobile TOY HAULER and never unhook it from late Oct till about now Mid May. The run down the road at 67 mph is around 1550 rpm and this is below the "sweet spot" mentioned above and I notice that also! gtwitch in wyoming

All SRW diesels have 3.42's from 13-18. The 3.73 is the standard gear set on gas trucks, as soon as a diesel is selected the gears change to 3.42.

I pull a decent amount of miles in the mountains from 19-24K and I wouldn't want 3.73's over my 3.42's. 3.73 might have some slower speed advantages, but at highway speeds 3.42's turn better rpms for my use.

 

[kwb]

Thanks for the replies. I'll go with the 35's - should be fine. I'll post some pics when they're installed.

 

[Conifer]

I’ve got 37’s with no lift on my 2016 3500. Just needs the correct wheel offset and a little trimming.

 

[crazy jerry]

37s open a whole other can of worms that i dont think youll want to get yourself into. 35s or a similar metric size would be good and prevent any grief of the larger tires. thuren or carli are the only suspensions i would even consider . out of those two, i like what thurens doing a bit more. but if your happy with the factory ride i wouldnt even mess with suspension. unless you want alittle better shocks or something. keep wheel offset around +18 or higher. any less and youll start to get the bro dozer look and the tires may grind into the fenders

 

[josh richter]

37s open a whole other can of worms that i dont think youll want to get yourself into. 35s or a similar metric size would be good and prevent any grief of the larger tires. thuren or carli are the only suspensions i would even consider . out of those two, i like what thurens doing a bit more. but if your happy with the factory ride i wouldnt even mess with suspension. unless you want alittle better shocks or something. keep wheel offset around +18 or higher. any less and youll start to get the bro dozer look and the tires may grind into the fenders

Assuming it’s +18 wheels and 37s with no lift, what issues would he have besides gearing?

 

[crazy jerry]

ive seen people use 37s on stock powerwagons but never on the standard trucks . even with the powerwagon extra height , the wheel wells looked over stuffed for my liking, withoutout an additional 1.5" or so of lift. since the op was asking about lifts, im thinking he doesnt like the overly stuffed look. so factor in a lift kit to price. mine from thuren was 3grand just to give you a idea. if your gonna do it, might as well do it right

fender trimming may or may not be needed. if its lifted and ever goes off road mostly determines this. dont overlook trimming as a real possibility though. mentally its tough to hack up a new truck

then you have gears. the truck will still go down the road and get you from point a to point b but the trans ratios are out of wack. regear is 2k-2500.

heaven forbid he doesnt want 37s anymore or simply doesnt like the truck and wants something else. how easy or hard is it to sell with the axles regeared . everyone thinks theyll keep the truck forever but alot of times it doesnt happen

i dont think fuel mileage and brake wear would be hugely impacted but still it takes more throttle and brake to get 37s moving and stopped
also it can put you to high to fit in some garages

my only point is he wont have the grief of the things listed above if he stays with a smaller tire. i went to 37s and dont regret it but it wasnt cheap and i had to deal with everything above ( fender cutting, regear, bigger loss of fuel mileage because i have gas engine, truck wont fit in garage now and hopefully i never have to sell because it might not be easy)

 

[Grimm_Reaper19']

So I ended up going with a 6" Ready Lift kit & 35x12.50 Toyo R/T's, I have had it on for 3 months now. I love the setup, absolutely no issues, rides on the highway just as well as it did when it was stock. I have taken on some trails and out to the desert, with no issue, even ran it a little hard down some woops, did very well. I am extremely happy with the setup.

 

[kwb]

Looks nice - congrats! Are those 18's? Did your RPM's change much?

 

[gsbrockman]

Needs 37’s or 38’s .......waaaaaaaaaay too much wheelwell gap now.