Opinions vs math on gear ratio

[Armo325]

I was going to post this as a follow-up in the 4.10 gear thread about re-calibrating the speedometer but it seemed like a bridge too far in terms of a thread jack so I thought I'd start a new thread.  I suspect I'm going to cover ground that has already been covered in a few threads so I apologize but hopefully this helps someone.  Also, if you don't want to waste your time with my nerd-ery throughout, just go to the last two paragraphs.

 

Re-gearing for different tire sizes is a topic that I have followed for some time with keen interest.  For one, I have a lifted truck with 35-inch tires (more on that later) still on the stock gears and am eagerly awaiting the moment I have enough cash to re-gear it.  I hope to do so in the next couple months.  Second, this topic is interesting to me because it seems to be loaded with opinions about the correct gear to choose, which is surprising since gear ratios and their effects are a known quantity.  Full disclosure: I have never worked in the auto industry and I am NOT a certified auto technician.  I do have a BS in Aerospace Engineering (I am NOT a practicing engineer) and a fair amount of technical experience so I consider myself at least partially qualified to discuss technical topics in general terms.  As always, there are definitely people that frequent these forums that know more than I do.  If you fit that description, please chime in and correct my errors.  Pointing out that I'm wrong won't hurt my feelings.  I will feel bad, however, if someone spends a bunch of money or makes a poor decision based on my bad information.

 

Everyone has different desires for their truck's performance so I always cringe when I see a new thread with the topic "What gear ratio should choose?"  The only thing that makes me cringe more is when someone posts in that same thread "You should get 4.56.  That's what I did and I love it.  You'll be happy."  That's great but it's also totally useless feedback in my opinion.  Without any explanation for the reasoning behind the decision and likely with no knowledge on what will make someone else happy that's a pretty big leap.  I find myself frustrated when someone's emotions drive their recommendation for a specific gear ratio based on how they feel when they drive their own truck.  I don't know anyone on this forum personally.  I respect all of you for our common love for our own trucks but I will always be skeptical when a relative stranger gives me a recommendation based on their "feelings."

 

On to my specific example: my own 2017 Silverado 1500 LT Z71.  I bought the truck from the dealer with a 6" lift, 20-inch wheels and 35-inch tires already installed.  I love my truck.  What I didn't do, largely due to a lack of experience and research was get new gears installed right away.  I wish I had.  I plan to do so soon so the natural question is "What gear ratio should I get?"  I don't tow much.  When I do, it isn't especially heavy.  I bought a 1500 for that reason.  I love the bigger, stronger trucks but at this point in my life I just don't need one.  So if you're like me and have 35-inch tires and the GM stock 3.42 differential gear (6-speed transmission), the determination on the new gear ratio now depends on what I want to do with the truck.  In my case, I want to get back to stock performance/drive-ability, or as close as possible.  To figure out how to do that, there is no opinion needed.  It's a question of geometry and its associated math.

 

If you Google the phrase "gear ratio tire size" you will be inundated with calculators that will tell you what you need.  I picked the first two that popped up.  One said my current effective gear ratio is 3.17 and I need to be a 3.98 to get back to stock.  The other said my numbers were slightly different but not by much.  The difference is likely because one calculator used a simple "tire diameter" figure and the other used actual tire sizes.  With that info alone, I will round to the next lower ratio (numerically higher) and go with 4.10 gears.

 

The common response to this line of reasoning that I see is "But, dude, what about the rolling mass of the new, bigger tires?!?"  Great point.  First off, I'm a nerd so what we should probably be referring to is "angular momentum" which is what is probably meant when people say "rolling mass."  Every wheel/tire out there is rolling mass but it's the angular momentum of that wheel and tire that we're concerned about.  Specifically accelerating when we're talking gears.  First, a few relevant formulas:

 

L=I*ω

"L" is Angular Momentum

"I" is moment of inertia

"ω" is angular speed, aka how fast the thing is spinning

 

I=r^2*m

"r" is radius

"m" is mass

 

The second formula just states the obvious - a bigger/heavier wheel has a bigger moment of inertia than a smaller one.  What might be less obvious is the impact each variable has.  Moment of inertia increases linearly with an increase in mass but exponentially with an increase in radius.  To make it relevant, if my 35s and your 37s, including wheels, are the same total weight you have a much bigger angular momentum problem to deal with than I do.

 

You can see from this point already that accounting for angular momentum is difficult because it's based on speed.  Turning your new big, heavy wheel/tire combo gets harder as you go faster so it's very difficult to account for that stress on your drive train since it changes as you accelerate.  I would submit the bigger discussion here is the need for better brakes but that's a different topic.

 

I haven't been able to find a good calculator to account for angular momentum differences with wheel/tire combos and haven't been willing to really dig down to generate an answer.  Part of that is because of the speed variability.  Another part is because I had had a surprisingly difficult time finding the actual weight of OEM wheels and tires.  Finally, I'm not sure the difference in angular momentum makes a huge impact on the overall stress on the drive train.  While The additional weight/radius of the tires is relevant, I don't know how much it matters when those wheels are still sitting under a truck that weighs over 5,000 lbs.  This point is a bit speculative on my part and my instinct could be way off how in how much angular momentum affects the overall drive train forces.  Real engineers, feel free to chime in here if I'm way off base.

 

With all of that in mind, my conclusion is that changing gear ratios for new wheels and tires is hugely important because it allows you to match your differential ratio back to your transmission.  The "system of systems" inside the truck were designed for a specific reason and matching your gear ratio to your new tires will get you back in that "sweet spot" the GM engineers found when they designed the truck.  Using the online calculators to determine your new gear ratio based purely on the new radius or your tires is likely enough to answer the mail.  Based on those calculators, I need to go to 4.10 to get back to stock.  The guys that jump up and down saying 4.56 is the answer because they "like it" are potentially introducing new engineering problems in their truck by forcing all of the rotating internals to spin at a higher speed than originally intended for long periods of time.  I'm not saying there aren't reasons to go to 4.56 but I would argue that gearing too low can be as risky as gearing too high if your goal is to have a safe, drive-able truck that lasts a long time.

 

Again, I hope this is helpful and I welcome any feedback anyone has to make this info more useful.

Edited March 17, 2019 by Armo325
Updated title

[KARNUT]

I was going to post this as a follow-up in the 4.10 gear thread about re-calibrating the speedometer but it seemed like a bridge too far in terms of a thread jack so I thought I'd start a new thread.  I suspect I'm going to cover ground that has already been covered in a few threads so I apologize but hopefully this helps someone.  Also, if you don't want to waste your time with my nerd-ery throughout, just go to the last two paragraphs.
 
Re-gearing for different tire sizes is a topic that I have followed for some time with keen interest.  For one, I have a lifted truck with 35-inch tires (more on that later) still on the stock gears and am eagerly awaiting the moment I have enough cash to re-gear it.  I hope to do so in the next couple months.  Second, this topic is interesting to me because it seems to be loaded with opinions about the correct gear to choose, which is surprising since gear ratios and their effects are a known quantity.  Full disclosure: I have never worked in the auto industry and I am NOT a certified auto technician.  I do have a BS in Aerospace Engineering (I am NOT a practicing engineer) and a fair amount of technical experience so I consider myself at least partially qualified to discuss technical topics in general terms.  As always, there are definitely people that frequent these forums that know more than I do.  If you fit that description, please chime in and correct my errors.  Pointing out that I'm wrong won't hurt my feelings.  I will feel bad, however, if someone spends a bunch of money or makes a poor decision based on my bad information.
 
Everyone has different desires for their truck's performance so I always cringe when I see a new thread with the topic "What gear ratio should choose?"  The only thing that makes me cringe more is when someone posts in that same thread "You should get 4.56.  That's what I did and I love it.  You'll be happy."  That's great but it's also totally useless feedback in my opinion.  Without any explanation for the reasoning behind the decision and likely with no knowledge on what will make someone else happy that's a pretty big leap.  I find myself frustrated when someone's emotions drive their recommendation for a specific gear ratio based on how they feel when they drive their own truck.  I don't know anyone on this forum personally.  I respect all of you for our common love for our own trucks but I will always be skeptical when a relative stranger gives me a recommendation based on their "feelings."
 
On to my specific example: my own 2017 Silverado 1500 LT Z71.  I bought the truck from the dealer with a 6" lift, 20-inch wheels and 35-inch tires already installed.  I love my truck.  What I didn't do, largely due to a lack of experience and research was get new gears installed right away.  I wish I had.  I plan to do so soon so the natural question is "What gear ratio should I get?"  I don't tow much.  When I do, it isn't especially heavy.  I bought a 1500 for that reason.  I love the bigger, stronger trucks but at this point in my life I just don't need one.  So if you're like me and have 35-inch tires and the GM stock 3.42 differential gear (6-speed transmission), the determination on the new gear ratio now depends on what I want to do with the truck.  In my case, I want to get back to stock performance/drive-ability, or as close as possible.  To figure out how to do that, there is no opinion needed.  It's a question of geometry and its associated math.
 
If you Google the phrase "gear ratio tire size" you will be inundated with calculators that will tell you what you need.  I picked the first two that popped up.  One said my current effective gear ratio is 3.17 and I need to be a 3.98 to get back to stock.  The other said my numbers were slightly different but not by much.  The difference is likely because one calculator used a simple "tire diameter" figure and the other used actual tire sizes.  With that info alone, I will round to the next lower ratio (numerically higher) and go with 4.10 gears.
 
The common response to this line of reasoning that I see is "But, dude, what about the rolling mass of the new, bigger tires?!?"  Great point.  First off, I'm a nerd so what we should probably be referring to is "angular momentum" which is what is probably meant when people say "rolling mass."  Every wheel/tire out there is rolling mass but it's the angular momentum of that wheel and tire that we're concerned about.  Specifically accelerating when we're talking gears.  First, a few relevant formulas:
 
L=I*ω
"L" is Angular Momentum
"I" is moment of inertia
"ω" is angular speed, aka how fast the thing is spinning
 
I=r^2*m
"r" is radius
"m" is mass
 
The second formula just states the obvious - a bigger/heavier wheel has a bigger moment of inertia than a smaller one.  What might be less obvious is the impact each variable has.  Moment of inertia increases linearly with an increase in mass but exponentially with an increase in radius.  To make it relevant, if my 35s and your 37s, including wheels, are the same total weight you have a much bigger angular momentum problem to deal with than I do.
 
You can see from this point already that accounting for angular momentum is difficult because it's based on speed.  Turning your new big, heavy wheel/tire combo gets harder as you go faster so it's very difficult to account for that stress on your drive train since it changes as you accelerate.  I would submit the bigger discussion here is the need for better brakes but that's a different topic.
 
I haven't been able to find a good calculator to account for angular momentum differences with wheel/tire combos and haven't been willing to really dig down to generate an answer.  Part of that is because of the speed variability.  Another part is because I had had a surprisingly difficult time finding the actual weight of OEM wheels and tires.  Finally, I'm not sure the difference in angular momentum makes a huge impact on the overall stress on the drive train.  While The additional weight/radius of the tires is relevant, I don't know how much it matters when those wheels are still sitting under a truck that weighs over 5,000 lbs.  This point is a bit speculative on my part and my instinct could be way off how in how much angular momentum affects the overall drive train forces.  Real engineers, feel free to chime in here if I'm way off base.
 
With all of that in mind, my conclusion is that changing gear ratios for new wheels and tires is hugely important because it allows you to match your differential ratio back to your transmission.  The "system of systems" inside the truck were designed for a specific reason and matching your gear ratio to your new tires will get you back in that "sweet spot" the GM engineers found when they designed the truck.  Using the online calculators to determine your new gear ratio based purely on the new radius or your tires is likely enough to answer the mail.  Based on those calculators, I need to go to 4.10 to get back to stock.  The guys that jump up and down saying 4.56 is the answer because they "like it" are potentially introducing new engineering problems in their truck by forcing all of the rotating internals to spin at a higher speed than originally intended for long periods of time.  I'm not saying there aren't reasons to go to 4.56 but I would argue that gearing too low can be as risky as gearing too high if your goal is to have a safe, drive-able truck that lasts a long time.
 
Again, I hope this is helpful and I welcome any feedback anyone has to make this info more useful.

I spent most of my time at Hwy speeds. My calculations would address that. Depending on what the mass was, that could be rolling mas or carrying mas. In my case it was carried mas. Then transmission gears comes into play. In my working life I usually had 4. So getting up to speed comes into play. Then it a matter where you’re shooting for maximum gas mileage with the mass or more performance. Your going to need to be a little higher in the RPMs cruising depending on the mass to keep from down shifting often compared to stock. I’m more performance minded so I would be going with more gear than less. If I was worried about gas mileage I get rid of the mas.


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[Armo325]

33 minutes ago, KARNUT said:

I spent most of my time at Hwy speeds. My calculations would address that. Depending on what the mass was, that could be rolling mas or carrying mas. In my case it was carried mas. Then transmission gears comes into play. In my working life I usually had 4. So getting up to speed comes into play. Then it a matter where you’re shooting for maximum gas mileage with the mass or more performance. Your going to need to be a little higher in the RPMs cruising depending on the mass to keep from down shifting often compared to stock. I’m more performance minded so I would be going with more gear than less. If I was worried about gas mileage I get rid of the mas.

I would submit, when it comes to gears, whether the mass is "carried" or "rolling" isn't relevant.  Your differential gear (and transmission, driveshaft, etc.) doesn't know the difference.  Weight in the bed of your truck or on your wheel/tire setup is the same to the differential gear.  It is all just mass that is resisting changes in movement.  Obviously if we start talking about suspension performance, frame stress, etc. it matters where the mass is but the gears won't know the difference.

 

I agree that your desires (MPG vs. performance) should influence the decision but I get the feeling, and maybe I'm wrong here, that most people equate "performance" to a lower gear ratio.  I would submit that isn't always the case and you'll find diminishing returns (and potentially higher risk of damage) as you go lower and lower in your gearing.

 

The RPM at cruise speed is also constant regardless of mass.  That's assuming you don't change gears, of course.  That also assumes a level road and no wind.  Once you start to consider hills (gravity) and drag (both from external factors and changes in speed), things get more complicated.  I concur that a common benefit to re-gearing is so the truck isn't "hunting" for gears at highway speed.  I guess one of my other points is that going "beyond" (lower gear ratio than stock equivalent) the stock setup isn't necessarily the best fix for that.  A tune, for example, might be a better path if you're not happy with the shift points after you re-gear.  Those shift points, of course, were chosen based on the stock setup that we don't have any more.

Edited March 17, 2019 by Armo325
Grammar corrections

[KARNUT]

Changing the size of the tire changes the gearing. The tires are heavier increasing load. That's going to put a drag on stock performance. Getting back to stock performance will require a gear change, among other things such as tuning. I personally would go more gear for added performance. Yes there is a difference, done it many times as well as tuning. Getting mas rolling quicker with gearing is a no brainier. Cursing gearing is the holy grail.


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[Armo325]

28 minutes ago, KARNUT said:

Changing the size of the tire changes the gearing. The tires are heavier increasing load. That's going to put a drag on stock performance. Getting back to stock performance will require a gear change, among other things such as tuning. I personally would go more gear for added performance. Yes there is a difference, done it many times as well as tuning. Getting mas rolling quicker with gearing is a no brainier. Cursing gearing is the holy grail.


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I think we are both making the same points.  I 100% agree that re-gearing is necessary for bigger tires.  My main point was that "rolling mass" as it's commonly referred, likely isn't a huge factor and probably shouldn't drive people to a lower-than-necessary gear ratio to meet their other, more important needs.

 

More specifically, my point in writing all of this is to say when someone says "I went with 4.56 gears because I really like the performance." I get frustrated.  That statement is fine and certainly honest but it is also an opinion and falls woefully short of being useful feedback for two main reasons:

 

1.  "Performance" can mean any number of things.  What performance, exactly, are you getting from 4.56 gears that you like so much?

 

2.  You an I probably don't like the same things.  What can you tell me about the truck itself that would help make a decision?

Edited March 17, 2019 by Armo325
Added some clarity

[SierraHD17]

Hmm... lemme see.  Mechanical advantage for one lol.  It's all about working torque and quite frankly most people undergear their trucks simply adding more strain on drivetrain components based on this fear of loss of mileage... which is moot to a degree anyhow with your truck sitting way up in the air on large diameter tires... you know... something the manufacturer never intended lol.  

 

The whole spinning too fast thing is also somewhat irrelevant to a point... but what point exactly?  Gm limits the trucks based off the the tires but you will find enough threads about the driveshaft flying apart at sustained high speed.  But what is the critical speed exactly for sustained load? 100 mph, 110, 115, 120? No idea.  Of course axle ratio will get you to that critical speed sooner or later depending which direction you go but the value itself will very well change with load..  

 

But before I go anymore it boils down to preference... if someone is on the fence with something people will post their opinions on either side of the fence.  It in no way should honestly make your decision for you.  That being said I don't ask for advice on open forum or use people opinions on said open forums to actually make any sort of decisions lol.  If you do that's great but you have to weigh pros and cons... if it's already in your head based off your calculations that you have found the perfect ratio then don't ask, ignore those that don't agree and do as you please.  

Edited March 17, 2019 by SierraHD17

[KARNUT]

Hmm... lemme see.  Mechanical advantage for one lol.  It's all about working torque and quite frankly most people undergear their trucks simply adding more strain on drivetrain components based on this fear of loss of mileage... which is moot to a degree anyhow with your truck sitting way up in the air on large diameter tires... you know... something manufacturer never intended lol.  
 
The whole spinning too fast thing is also somewhat irrelevant.  Gm limits the trucks based off the the tires but  you will find enough threads about the driveshaft flying apart at sustained high speed.  But what is the critical speed exactly for sustained load? 100 mph, 110, 115, 120? No idea.  Of course axle ratio will get you to that critical speed sooner or later depending which direction you go but the value itself will very well change with load..  
 
But before I go anymore it boils down to preference... if someone is on the fence with something people will post their opinions on either side of the fence.  It in no way should honestly make your decision for you.  That being said I don't ask for advice on open forum or use people opinions on said open forums to actually make any sort of decisions lol.

I agree. I come on here for two reasons. Entertainment and I may have useful insights on some of my experiences in relation to what someone may be looking for. In my vast experience my options have been altered by what I’ve read on here, to my amazement. Iv lived in a family business bubble and my mind has been opened to a degree by this forum. Old dogs can learn new tricks.


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[Armo325]

16 minutes ago, SierraHD17 said:

Hmm... lemme see.  Mechanical advantage for one lol.  It's all about working torque and quite frankly most people undergear their trucks simply adding more strain on drivetrain components based on this fear of loss of mileage... which is moot to a degree anyhow with your truck sitting way up in the air on large diameter tires... you know... something the manufacturer never intended lol.

 

I mostly agree.  Just saying "mechanical advantage" and "working torque" doesn't really say much.  My point was choosing your new gear ratio will almost certainly account for those things as best you can.

 

I completely agree that this entire situation begins with a huge sacrifice by departing from the design GM intended by lifting the truck.  Without access to a wind tunnel, I can't account for all of those changes but arbitrarily going to lower gears beyond what the math, physics and geometry tell you likely won't help.  It won't necessarily hurt but this isn't a case of "if 4.10 is good, 4.56 has to be better."  My focus is on trying to restore stock performance.  Obviously there are those out there that are looking for something else.

 

16 minutes ago, SierraHD17 said:

The whole spinning too fast thing is also somewhat irrelevant to a point... but what point exactly?  Gm limits the trucks based off the the tires but you will find enough threads about the driveshaft flying apart at sustained high speed.  But what is the critical speed exactly for sustained load? 100 mph, 110, 115, 120? No idea.  Of course axle ratio will get you to that critical speed sooner or later depending which direction you go but the value itself will very well change with load.

 

Concur.  I also don't know what that breaking point is.  I hope to never find out.  I only brought it up to say higher RPM than designed by any amount generally isn't a good thing.  At some point, stuff will start to fail.  That breaking point, as you alluded to, is likely well past the life of other critical components but there is still an unknown failure point out there somewhere.

 

16 minutes ago, SierraHD17 said:

But before I go anymore it boils down to preference... if someone is on the fence with something people will post their opinions on either side of the fence.  It in no way should honestly make your decision for you.  That being said I don't ask for advice on open forum or use people opinions on said open forums to actually make any sort of decisions lol.  If you do that's great but you have to weigh pros and cons... if it's already in your head based off your calculations that you have found the perfect ratio then don't ask, ignore those that don't agree and do as you please.  

I completely agree.  I think you would agree there are also a lot of people out there that will just do what the masses do because they aren't willing to take the time to analyze what's actually happening inside the truck.

 

My intent of this thread was less to ask a question and more to start this exact conversation so others can benefit.  I have learned immeasurable amounts from a lot of smart, experienced people who have taken their time to post things on forums like this one.  I'm trying to do any small thing I can to return the favor.

Edited March 17, 2019 by Armo325

[SierraHD17]

Torque is just sheer mechanical advantage.  Now is there a point at which it is no longer advantageous to go deeper on the axle ratio? Yes.  However I have not found that value in a brick of a pickup truck.  My drag car has 4.56 in the rear which worked fantastic with a naturally aspirated small block that would have trapped sub 110 mph... however with the turbo LS all it does is limit my trap speed. Totally different problem there though.  I looked at what rpm my truck was happiest at prior to re-gear and that was the 2000 to 2100 rpm range in mine.  To achieve that value in 6th with my tire was 4.56.  One of my guys has half tons is the same deal..  stock 3.42 gears with 275/70/18s.  Truck is useless in 6th gear but bump it back to 5th and the mileage goes up and constant hunting gears ceases.  4.10 would be about perfect for his setup... it's just a level, no air dam and the tire. 

 

I like the added "power" of the 4.56 in my truck.  It pulls harder in every gear and sustains loads substantially better than stock which was the goal.  I didn't want "stock" performance I wanted an increase.  There would be a limit to that as I said but I haven't geared a truck deep enough yet to find it.

[Grumpy Bear]

32 minutes ago, SierraHD17 said:

I like the added "power" of the 4.56 in my truck.  It pulls harder in every gear and sustains loads substantially better than stock 

All three contributors make several excellent comments. I choose this one only because is addresses the topic all three are addressing indirectly. Stan called it moving mass and to OP angular momentum. SierraHD17 talks about how to overcome it but the idea all three of you are speaking about is 'flywheel effect'. Only SierraHD17 addresses it in it's practical state which is...………?

 

Change of velocity...more specifically the rate of change in velocity. (V2-V1 / T in part) Acceleration of mass is a much bigger deal that it's component steady state considerations or simple velocity A v B snap shots. A change in the rate of acceleration is larger still. That is where wheel/tire weight and center of mass from the axis gets to be rather huge. Once a well balanced rotating assembly is up to speed friction within the system is basically at the mercy of the bearing type friction coefficient.

 

Take 10 pounds of mass a foot and a half from the axis and try to increase rpm from say 40 to 70 in 10 seconds.  Try that equation again with 15 pounds then multiply that by 4 wheels. Or try the original setup in 8 seconds v 10 seconds. Your new gear needs to not only match the rpm within reason but supply the torque multiplication equal to or greater than the energy increase required for the mas and distance difference.

 

Adding 5 pounds of tire tread for example will have more effect than adding 5 pounds to the rim. More so if you move that tire tread increase 3 inches further from the rotational axis. 

 

Okay, I'm starting to repeat myself. 

[Jacoby]

Hey OP 4.56’s would be perfect for you 

[Armo325]

Hey OP 4.56’s would be perfect for you [emoji3]

Well played, sir.

[Donstar]

On ‎2019‎-‎03‎-‎17 at 5:44 AM, Armo325 said:

If you Google the phrase "gear ratio tire size" you will be inundated with calculators that will tell you what you need.  I picked the first two that popped up.  One said my current effective gear ratio is 3.17 and I need to be a 3.98 to get back to stock.  

GM produced many trucks with a 5.3 V8 and 3.08 gear ratio.  According to this comparison, you're better than stock!   I believe the most compelling reason to re-gear after increasing tire-size to 33" or 35" is to compensate for a perceived loss in power/performance.  That is,  you've enhanced the looks of your truck and it does everything you need but knowing power maybe compromised is bothersome. I would simply do what is necessary to make the speedometer accurate and enjoy!  

[Grumpy Bear]

29 minutes ago, Donstar said:

GM produced many trucks with a 5.3 V8 and 3.08 gear ratio.  According to this comparison, you're better than stock!   I believe the most compelling reason to re-gear after increasing tire-size to 33" or 35" is to compensate for a perceived loss in power/performance.  That is,  you've enhanced the looks of your truck and it does everything you need but knowing power maybe compromised is bothersome. I would simply do what is necessary to make the speedometer accurate and enjoy!  

Interesting choice of wording sir. Thoughtful. I like that. However I have to disagree, it is more than just a perception...from an engineering viewpoint.  Any increase in inertia moment has a corollary equivalent to an increase in the trucks weight. I.E. Power to Weight ratio = Available Power to Weight Ratio. Come to think of it, this BIG tire thing adds to both the inertia moment and gross mass of the system. Gearing will alleviate the perception but not the reality. 

 

From a practical standpoint however your well chosen words are very much on point and Sage advice. Our trucks operate with such a vast reserve of day to day untapped  power that I'll wager from observations that of the 250 or so RW horsepower I have available to me, I use less than 150,even 'under the gun'. 

[Jacoby]

5 hours ago, Donstar said:

GM produced many trucks with a 5.3 V8 and 3.08 gear ratio.  According to this comparison, you're better than stock!   I believe the most compelling reason to re-gear after increasing tire-size to 33" or 35" is to compensate for a perceived loss in power/performance.  That is,  you've enhanced the looks of your truck and it does everything you need but knowing power maybe compromised is bothersome. I would simply do what is necessary to make the speedometer accurate and enjoy!  

Assuming one does nothing with their new blingy truck accept drive it, this is sound advice.

 

But for people that tow regularly and really use there trucks the above statement is not sound advice at all.