Performance Effect With 35" Tires?
Senior User
Joined: Dec 2007
Posts: 145
Likes: 0
From: Dickson, Tennessee
I just purchased a 2001 with 315's and it seemed to be a little off in all aspects of driving (shift points, tq converter lockup etc.). I looked at getting the truespeed. I did some looking around the net and found that the stock computer can be re-programed up to a 315......took it to the local ford dealerand did the CPS recall and had them re-flash the computer for the 315's....took about 15 min. and $37 and now the truck seems like a different truck. it shifts right speedo is right runs great and I just completed a 2000 mile trip and got 18MPG.
Senior User
Joined: Dec 2007
Posts: 145
Likes: 0
From: Dickson, Tennessee
I just went to Diesel Innovations web site and in the section for tech close to the bottom of the first section you can download a PDF file to take to the dealer with the program numbers for tire size
Lead Driver
Joined: May 2007
Posts: 5,613
Likes: 9
From: Flagstaff, Arizona
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
Do bigger tires affect performance? Yes, but not as much as you might think.
Swapping for larger tires and keeping the stock gears will affect bottom end grunt. Mid and high RPM ranges will still have plenty of power, especially with a chip or tuner. If you want the bottom end grunt to come back, change gears to match the tires. I swapped gears because I wanted power in the low end. High altitude really does affect turbo lag and low RPM power, and especially EGT's. With 36" tires and 3.73 gears, I was lugging the engine driving up mountain passes. Makes for a ton of smoke and uncontrollable temps in overdrive. Swapping gears helps keep the engine in the proper RPM range when driving I-70 West out of Denver.
Here's some food for thought. When I first moved to Colorado my truck already had a DP-Tuner, intake, exhaust, and gauges. I was also running the tire/wheel size combo I have now along with my lift and stock gears. My E/T's at Bandimere that first summer were in the low 16's. All the other 7.3L SD's running the same engine mods were also running almost identical times, however all of those trucks were running stock size tires, and no lift. So as you can see, swapping for larger tires won't rob all your power away from you. Bottom end grunt will be gone until you swap gears, but that's about it.
Swapping for larger tires and keeping the stock gears will affect bottom end grunt. Mid and high RPM ranges will still have plenty of power, especially with a chip or tuner. If you want the bottom end grunt to come back, change gears to match the tires. I swapped gears because I wanted power in the low end. High altitude really does affect turbo lag and low RPM power, and especially EGT's. With 36" tires and 3.73 gears, I was lugging the engine driving up mountain passes. Makes for a ton of smoke and uncontrollable temps in overdrive. Swapping gears helps keep the engine in the proper RPM range when driving I-70 West out of Denver.
Here's some food for thought. When I first moved to Colorado my truck already had a DP-Tuner, intake, exhaust, and gauges. I was also running the tire/wheel size combo I have now along with my lift and stock gears. My E/T's at Bandimere that first summer were in the low 16's. All the other 7.3L SD's running the same engine mods were also running almost identical times, however all of those trucks were running stock size tires, and no lift. So as you can see, swapping for larger tires won't rob all your power away from you. Bottom end grunt will be gone until you swap gears, but that's about it.
Elder User
Joined: Mar 2006
Posts: 751
Likes: 0
From: Greeneville,TN
I am just like kris. I cant even think about roasting my tires. And I am a single stripper at that. I guess my truck is a dog.
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Lead Driver
Joined: May 2007
Posts: 5,613
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From: Flagstaff, Arizona
Senior User
Joined: Feb 2008
Posts: 282
Likes: 1
From: Quad Cities, Iowa
Funny, my goal has been not to break the tires loose!
To me, gears are the most important thing you can do. If you want to get the performance back with the new tires, a set of 4:56 gears will treat you right with the 35"
To me, gears are the most important thing you can do. If you want to get the performance back with the new tires, a set of 4:56 gears will treat you right with the 35"
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
4.56's and 35's might be a bit much, especially if you're on the highway often. I'm running 4.30's on my truck, and it's a good balance between highway driving and towing. I personally wouldn't recommend putting 4.56's on unless you are running 38's or 40's.
Mountain Pass
Joined: Feb 2003
Posts: 207
Likes: 2
From: parkersburg usa
As owner of many lifted trucks I will tell you it will lose power. The diesels are not near as bad as a gas engine as their low end torque realy help getting them going. I have a 2000 psd on 36 inch tires it runs good but the smaller tires are lighter and get you better gearing. I accept the power loss as I love the look of big rubber. Youll just have to try it out and see what you think.
Mountain Pass
Joined: Feb 2003
Posts: 207
Likes: 2
From: parkersburg usa
As owner of many lifted trucks I will tell you it will lose power. The diesels are not near as bad as a gas engine as their low end torque realy help getting them going. I have a 2000 psd on 36 inch tires it runs good but the smaller tires are lighter and get you better gearing. I accept the power loss as I love the look of big rubber. Youll just have to try it out and see what you think.
Freshman User
Joined: May 2007
Posts: 45
Likes: 0
From: N Stone, CT
I'm running 35's on my truck now and this is definitely what I'll be going with. I've done some fairly heaving towing with the 35s on 3.73s and its still pulls good but takes a little longer to get going than it use to. I'm looking forward to getting it regeared and having a TruTrac put in it.
As far as driving around I can still spin them from a stop or around corners but it takes a lot more pedal than it use to. The Pro Comps than I'm running are softer compound than the BFG all terrains and with the extra width they really grip the road. It seems to blow more smoke but I didn't get my DP retuned either (waiting to get a few more mods done before I send it back).