Upsized Tires/Wheels & Vehicle Performance
- Thread starter Ramblejam
- Start date
'06 Wrangler Unlimited Rubicon
4x4junkie
Explorer
This is why regearing is so important.
If they were to regear the axles from the stock 4.10s to say, 4.88 or 5.13, those performance numbers (acceleration, mileage) would likely be within 10% of each other. Though the figure of 218 feet for braking seems a lot longer than what it takes to bring my Ford on 35s to a stop... makes me wonder if there was either something wrong with it's brakes, or Jeep just doesn't build much reserve power into their brake systems.
If they were to regear the axles from the stock 4.10s to say, 4.88 or 5.13, those performance numbers (acceleration, mileage) would likely be within 10% of each other. Though the figure of 218 feet for braking seems a lot longer than what it takes to bring my Ford on 35s to a stop... makes me wonder if there was either something wrong with it's brakes, or Jeep just doesn't build much reserve power into their brake systems.
Ducky's Dad
Explorer
Re the acceleration, braking and mpg figures, we don't know at this point what corrections they did for tire diameter, either mathematically or for speedo/odo readings or trans shift points. It'a a pretty big jump from a 265/75-16 to a 35-12.50-17, but their numbers look funky to me. And the Toyo may not be the right 35 for a Jeep. It's a load range E tire, and probably overkill for most Jeeps. Numbers may be accurate, but I'll wait until I see the details.
comptiger5000
Adventurer
Re-gearing will get a lot of the acceleration back, although there will still be an mpg penalty from the extra rotating weight. The brakes will always be weaker with the larger diameter and heavier tires (they have more momentum to stop and less leverage to do it with). Considering TJ brakes are a little on the weak side to start with (at least without good performance pads), I'm not surprised the braking is downright awful with heavy 35s on there.
jeep-N-montero
Expedition Leader
The WJ front brake swap is a well documented upgrade for the TJ/XJ/ZJ, add in a re-gear and more aggressive pads and you can get back to near stock specs when running 35's, there is really nothing new to the topic.
professorkx
Observer
Three real world examples:
My son has 35's on his 2007 JKU and had to regear for the jeep to be useful in 5th or 6th gear.
I have a 2014 Rubicon X, and I run 35's just fine with the 3.6 motor and 4.10 gears, and I can easily maintain 6th gear on the highway. I also get 17.5 mpg city/highway after installing the flashpaq and using the 87 octane tune.
My wife has a 2009 JKU X, and runs the 305 KM2 tires with stock gearing and does just fine. We have even towed 1800 pounds 1000 miles without a problem. She has trouble staying in 6th gear on the highway on uphills, but still gets 18-19 mpg with her larger than stock tires. I've offered to buy her a new jeep, but she has not interest since she has owned the 2009 since day one and loves it. She actually likes her 2009 more than my 2014 Rubicon X...except the leather and heated seats.
If you are going with 35's on an older wrangler, plan on changing gears, which is going to get expensive. My son had them toss in air lockers front and rear since there wasn't any additional labor to install. I think he has about $3500 into the upgrade, including the compressor and pillar switches.
J - just
E - empty
E - every
P - pocket
My son has 35's on his 2007 JKU and had to regear for the jeep to be useful in 5th or 6th gear.
I have a 2014 Rubicon X, and I run 35's just fine with the 3.6 motor and 4.10 gears, and I can easily maintain 6th gear on the highway. I also get 17.5 mpg city/highway after installing the flashpaq and using the 87 octane tune.
My wife has a 2009 JKU X, and runs the 305 KM2 tires with stock gearing and does just fine. We have even towed 1800 pounds 1000 miles without a problem. She has trouble staying in 6th gear on the highway on uphills, but still gets 18-19 mpg with her larger than stock tires. I've offered to buy her a new jeep, but she has not interest since she has owned the 2009 since day one and loves it. She actually likes her 2009 more than my 2014 Rubicon X...except the leather and heated seats.
If you are going with 35's on an older wrangler, plan on changing gears, which is going to get expensive. My son had them toss in air lockers front and rear since there wasn't any additional labor to install. I think he has about $3500 into the upgrade, including the compressor and pillar switches.
J - just
E - empty
E - every
P - pocket
SWITAWI
Doesn't Get Out Enough
Here's the link - http://www.fourwheeler.com/how-to/wheels-tires/1512-what-concessions-are-made-when-adding-big-tires/
Overall I think it's a good object lesson, especially for a vehicle like a Pre-JK wrangler or 80-Series Land Cruiser. Neither are the most overpowered of 4x4s when equipped/fully loaded for travel in the boonies.
Overall I think it's a good object lesson, especially for a vehicle like a Pre-JK wrangler or 80-Series Land Cruiser. Neither are the most overpowered of 4x4s when equipped/fully loaded for travel in the boonies.
Ducky's Dad
Explorer
Here is what the article said:
Absent further details, I think their acceleration and mpg numbers are questionable. They obviously have a Diablo Trinity, but there is no indication that they even reprogrammed the tire diameter. And if they were running the stock tune, the ECU had no idea where the correct shift points were. Braking is horrible, regardless of tune or shift points, but I think that Toyo is the wrong tire for a stock Heep that is underpowered and underbraked to start with.
IdaSHO
IDACAMPER
Agreed.
And regardless of vehicle and power, the fact is simple.
Adding additional rotating mass robs engine power and adds a good deal of additional weight for the brakes to contend with.
The actual results are impossible to cover with a blanket statement. Each vehicle is different, as is the driver.
Regearing seems to be the end all solution for most people, yet it does nothing to aid in braking, which is certainly MORE important that acceleration.
Ducky's Dad
Explorer
Seems like the writer is not too strong in math, either. Says the wheel/tire combo weighs 106#, then says it's 70# for the tire and 38# for the wheel?