Bigger Tires - Acceleration Impact?

[NCtrail4R]

I'm currently running a 30.2" tire and want to go taller. This is already about an inch taller than stock. The stock tires were 29.2" and I want to go to a 31.7 (235/85s). Don't plan to regear with the change and wonder about the impact on the acceleration.

I've run larger tires on other trucks and have suffered with sluggish acceleration, short shifting and the auto trans downshifting on slight inclines. 2.5" doesn't seem to be alot of increase, but the truck doesn't have alot of power to start with.

Any feedback on running a 2.5" taller tire with stock gearing? Tires are around 10#s heavier each and will be more aggressive treads too - going from a road oriented AT tire to a Duratrac or Hankook MT (still on the fence between the two).

 

[Dave Bennett]

You will lose power.

 

[mountainpete]

The amount of acceleration change depends on your truck, engine and current gearing. It will go down, but tell us more about your ride first.

Pete

 

[FlatlinesUp]

excellent little online tire app:

http://www.miata.net/garage/tirecalc.html

 

[Cody1771]

since your engine only puts out a specific torque, and torque=Force x distance, where in this case your distance is the diameter of the tire, and since the engine can only exert a set torque then the larger the diameter of the tire the force will required to change to get the same torque, and Force = mass x acceleration, and mass will remain basically the same. so if the torque of your engine is constant,the diameter of your tire changes, your force has to change as well, and the only thing that will change in your force is your acceleration, larger diameter = less acceleration on a given torque, hehe

 

[NCtrail4R]

Truck is a 2000 Nissan Pathfinder SE with the stock 3.3L and 4.63 gearing. No engine mods and stock alloy wheels. Running OME coil lift and KYB shocks and struts. Currently running Pirelli Scorpion ATRs but looking to go to something a little taller for more clearance and with a more aggressive tread.

Had a Nissan Titan and making the move to bigger tires was no problem with all that horse power and torque, but the Pathfinder is another story.

 

[Cody1771]

all said and done i doubt you would feel any real difference between 30 and 32 inch...

 

[Desert Dan]

T think you will notice a difference in power and mpg

 

[bat]

I would think with 4.63 gearing you would hardly even notice.

 

[mountainpete]

Truck is a 2000 Nissan Pathfinder SE with the stock 3.3L and 4.63 gearing. No engine mods and stock alloy wheels. Running OME coil lift and KYB shocks and struts. Currently running Pirelli Scorpion ATRs but looking to go to something a little taller for more clearance and with a more aggressive tread.

If it's a 2000 with a 3.3L, you either have the 96-2000 body style or one of the few 2000.5's that didn't come with the 3.5. Big difference between the 3.3L and 3.5L. Turned the Pathy from a turtle to a powerful truck - at least a 70 hp power boost!

My experience was quite a number of years ago, but I had a 97 Pathfinder SE, auto, 3.3L with 15" wheels. I upgraded from the stock tire which I believe was around 29" to a set of BFG AT's in 31x10.5x15.

Around town the difference was only noticeable on merge ramps or really booting it from light to light. Off-road in 4wd low the difference was also noticeable, but that truck usually stayed on the easier trails so it wasn't a concern. But I really noticed a difference on the highway - the "sweet" spot raised to the point where I would often have to manually disengage overdrive to prevent it from constantly shifting back and forth. It was even more noticeable with a load of people/gear or when towing.

With that said, I always considered the power loss acceptable compared to the benefits the larger tire gave me. That Pathfinder always surprised me and anyone I trailed with. If it wasn't for the terrible fuel mileage I got with it, I probably would have kept it longer then I did.

Hope that helps.

Pete

 

[NCtrail4R]

Thanks for the feedback. The model I have is after they updated the 'look' of the truck, but before they updated the engine to the 3.5.

Want go to 32s, but may just split the difference & go to 31s. Tire Rack is showing the 245/75/16s as being pretty close to 31x10x16.

 

[milo12]

I doubt you will notice any acceleration changes. Acceleration happens very slowly so a small size/weight difference is nothing.

You will notice a braking difference. Your braking effort will go up and stopping distance will go up. I upgraded to EBC pads and that made a significant improvement. As long as you have the clearance I would go with the larger tire.

 

[dustboy]

I'd wager that in a year you will be regearing, although your factory gearing seems capable. My tacoma started with the same 29" tires, and now I'm running the 235/85r16s. Between the tires and all the weight I've added, I'm now spending over $2000 to regear.

 

[Incusus]

all said and done i doubt you would feel any real difference between 30 and 32 inch...

...said the guy with the 406CID V8 and 37-inchers... :Wow1:

I'm running a 3.5V6 (230hp, considerably less at the wheels) and auto trans in my 4500# (dry weight) Trooper with 4.6 gearing and an OME 2/3" lift, so I'm a bit closer to your Pathfinder and can honestly say you will feel a noticable difference in performance and gas mileage.

I went from 245/70 16 (29.5")street tires to 265/75/16 (31.6") A/T's (bfg t/a's), then to same sized M/T's (bridgestone), and finally two weeks ago back to A/T's (goodyear silent armour)

Based on my experiances (and from what I've read from owners of my truck that went as far as 285/75's (32.8")), heres my experiance (compared to stock):

-31.6" BFG A/T's- lost 1 MPG average, noticable reduction in power but still plenty to move the truck. tires heavier to turn but again still manageable on-road as a driver

-31.6" M/T's- lost 2 MPG at least, distinct drop in power, just enough power to keep me happy on road, fair power off road, tread good. If this vehicle was off road more than %70 of the time, I would have kept this setup and possibly considered regearing if the transfer case needed a rebuild. My Trooper is in terrain more serious than dirt roads maybe %30 of its mileage.

-31.6 Goodyear A/T's- Lost 1 MPG, reduction in power but not as much as the BFG's. Weight of the tires were noticibly less the the BFG's, and signifigantly less than the M/T's. Handeling was the most improved of the 3 larger sets of tires.

I considered 32.8's (285/75/16), but based on the complaints of other trooper owners who were running stock gearing, its just too much for a 3.5 with <230hp and 4.6's. Its do'able, its just too much. If were to keep the truck as strictly (%100) off-road, I'd go ahead and regear and do 32/33" tires. (Probably do terralows, a locker and 315's too, but I digress...)

In short, I'd keep it below 32" and seriously factor in the weight of your tires along with the tread. The weight of my Goodyears vs. BFG a/t's was slightly less, but made for a world of difference in power and handling. I'd go with a 31-32" A/T tread, unless you see alot of mud or are better than %70 off road with this vehicle.

Just my $.02

 

[Cody1771]

ya ya ya i know my truck is EXCESSIVLY over powered lol... who really needs 350hp at the wheels? :smiley_drive: but if you look at some of my posts most of my wheeling is done with early 80's yotas... and those 22R motors definatly didnt have the power...