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Tire size question

Soylent

Contributor
Sr. Member
Joined
May 4, 2016
Messages
685
Loc.
California
IMG_7739.jpeg


These are 33” on 15x8 steelies. Has 2.5” suspension lift. No body lift. Rubbed on the radius arms until I replaced with T-rex. AX15 with 4.10. Should have gone with 4.56. FWIW
 

Madgyver

Bronco Madman
Joined
Jul 30, 2001
Messages
15,030
I disagree(respectfully) some of it. The affect(lack of power, to be technically correct lack of torque ) you will see of bigger tires is at points of "acceleration" which is more at start when engine is trying to move vehicle from standstill to motion. (rotational mass) The issue is less at cruise, a body in motion tends to stay in motion. Especially when the gear diff is not noticeable it wont slip frequently at cruise speeds. A torque converter uses transmission fluid to compensate for the RPM differences between engine and transmission and has high stress when someone is trying to accelerate which causes max diff between RPMs. So a modulator adjustment will get the vehicle stay little bit more in lower gears of c4(2.4, 1.4) to get to speed and compensates for the gear loss. But if shift points are stock then you have to increase your throttle to compensate for power loss (to be technically right torque loss as power o/p is same at given engine rpm), that causes higher RPM differences between engine and transmission causing more heat. The effective gear ratio difference being not that big for a 33inch tires i.e 3.55 vs 4.1, your effective gear ratio is 3 meaning 0.5 overall gear ratio loss. its not noticeable on flat terrains. However if you go to 35 your effective gear ratio is 2.8 which is 0.7 difference/gear loss and will cause drivetrain damage over a period of time if gears are not changed . The reason engineering suggests gears to be changed at differential is two things 1)its the final stage of torque multiplier 2) its highly costly to change gears in transmission/change engine power to compensate for lost torque-diesel engines have higher torque curves. But in. principal what matters is overall gear ratio for wheels to turn which is transmission gear ratio x diff gear ratio.

All that said 33inch tires wont cause a noticeable difference on flat terrains if they are 10inch wide. 33 12.5s will cause some noticeable diff as you are fighting more rotational mass. 35s is when you really need to change gears imo.
is this AI? cut and paste?
way too much information to answer a basic question.
who would type all this?
 

Chiclassics

Full Member
Joined
Sep 2, 2025
Messages
253
Sorry I teach, so sometimes my professor instincts take over. Think Indiana Jones haha
 
OP
OP
AzBroncoGuy

AzBroncoGuy

New Member
Joined
Jul 8, 2023
Messages
40
Well, that doesn’t make sense when you take the pictures into account. Looks like you have a lot of lift, as others have stated already. But 3 inches in the front is 4 inches lower than stock. While 5 inches on the rear is 1 inch lower than stock.
Gets more interesting every day!
I measured to the rubber bump stops so it's probably close to what you have listed here.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
51,618
Ok, yeah that would make a big difference. Top of the axle tube, to the bottom of the frame rail. Nothing else, so no "appendages" in the way.

Paul
 

maxellfullmoon

Jr. Member
Joined
Jul 6, 2010
Messages
63
View attachment 950734

These are 33” on 15x8 steelies. Has 2.5” suspension lift. No body lift. Rubbed on the radius arms until I replaced with T-rex. AX15 with 4.10. Should have gone with 4.56. FWIW
Should have gone with 4.56? For off-roading or Highway? Asking because I'm installing an AX15 now on my 73. Changing out a C4. Also...what width of tires did you put on those 15x8s?
 
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