Re-gearing on 31" with eye on 33"? - Toyota FJ Cruiser Forum
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post #1 of 35 (permalink) Old 05-10-2017, 08:15 AM Thread Starter
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Re-gearing on 31" with eye on 33"?

I've started looking at upgrading my suspension beyond stock.

As my FJ is my daily driver (and I take a lot of highway road trips), I do not expect to go nuts with off-road-specific suspension - 35" tires would probably be pushing it; there is no long-travel in the foreseeable future; a 6" lift will not be happening, etc.

Reading about 33" and 35" tires, the subject of re-gearing comes up. I understand that I will certainly "want" to re-gear if I put 35" tires on.

Other places on the internet suggest a 4.65 (rather than 4.88) ratio for 33"s as a compromise between recouping power and higher RPMs.

My questions are:
  1. Will I suffer adverse mechanical side-effects or damage anything if I re-gear to 4.65 while I still have 31" tires?
  2. My FJ feels a bit sluggish on-road and up steep inclines as-is. In your opinions, will I feel a power boost that justifies the price of re-gearing if I re-gear to 4.65 while I still have 31" tires?
  3. In your opinions, will re-gearing to 4.65 be sufficient for 33" tires? (Internet says "yes," just want to double-check).
  4. If you believe I should skip 4.65 and go straight to 4.88, please answer question #1 for 4.88.

Thanks in advance!
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post #2 of 35 (permalink) Old 05-10-2017, 08:27 AM
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Re: Re-gearing on 31" with eye on 33"?

IMO no need to regear for 33's. It's 4.56 BTW. Regearing for 35's is still based on your preference. Most people with 35's don't. I would think your MPG will drop a fair amount on the 31's if you regear. (running higher RPM's)

My FJ still feels fast on 34's and alot of additional weight, it's all user preference.

Edit: Just use more skinny pedal.

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post #3 of 35 (permalink) Old 05-10-2017, 08:39 AM
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Re: Re-gearing on 31" with eye on 33"?

Quote:
101Firedog previously said: View Post
Reading about 33" and 35" tires, the subject of re-gearing comes up. I understand that I will certainly "want" to re-gear if I put 35" tires on.

Other places on the internet suggest a 4.65 (rather than 4.88) ratio for 33"s as a compromise between recouping power and higher RPMs.

My questions are:
  1. Will I suffer adverse mechanical side-effects or damage anything if I re-gear to 4.65 while I still have 31" tires?
  2. My FJ feels a bit sluggish on-road and up steep inclines as-is. In your opinions, will I feel a power boost that justifies the price of re-gearing if I re-gear to 4.65 while I still have 31" tires?
  3. In your opinions, will re-gearing to 4.65 be sufficient for 33" tires? (Internet says "yes," just want to double-check).
  4. If you believe I should skip 4.65 and go straight to 4.88, please answer question #1 for 4.88.

Thanks in advance!
Up here in Colorado, at elevation so we're losing ~20% of our horsepower over your truck breathing at close to sea level, I've never even heard of a truck on 33's regearing. 35's, yeah regear. But 33's? Nobody does it, and with all due respect our hills are a bit steeper than yours in Texas

What year is your truck, how many miles? You should figure out if the sluggishness is something else -- needs new spark plugs etc -- or if it's just the nature of driving a brick at highway speeds. In flat / level down where you live our trucks aren't great highway vehicles anyway. If your truck feels sluggish just with 31's it's either "there's another big problem here" or "that's just how our trucks drive, get used to it". Assume the first one until you prove that's not the case. Go to an FJ meet and have another FJ owner ride with you, or even better, let them drive your truck. My '99 Wrangler had no power but I just thought "it's a Wrangler" until my brother drove it, said something was wrong and we found out the catalytic converter had rusted almost shut.

If your truck is an '07-'09, it was designed to run on premium gas. If you aren't putting premium in it, it's detuning (costing you ~20-30 HP) to keep from knocking. If your truck is a '10+ the stock HP/Torque specs are for regular gas but it can take advantage of premium gas, another 20-30 HP over stock. But again, most of those HP gains are at the top of our RPM range where our trucks don't typically live anyway.

To answer your specific questions: no, regearing for such small tires won't hurt anything, but it will limit your top speed. How much? One of the more technical guys can speak to that. Will regearing give you enough of a power gain feeling to justify the cost? No, because you've got some other problem that isn't being addressed, or the problem is how you think the truck should drive. The only improvement that you can do where you'll feel a big power boost is a supercharger, which are hard to find (the TRD one) for the '07-'09 and the '10+ trucks never got one from Toyota.

Maybe I'm a bit of a purist, but the only highway miles I like on my FJ are when it's taking me to / from a trail. If you're putting a lot of highway miles on your FJ, and you love your FJ and want to keep it forever, stop doing that. Go buy a cheap efficient highway car, the MPG savings will pay for the car in a couple of years. My highway car is an '11 Lexus GS460 that gets 30 MPG highway, it's like riding in a sporty couch with a great sound system that can do triple-digit speeds all day long. But you can start at used Civic / Corolla and work your way up from there based on your price range.
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post #4 of 35 (permalink) Old 05-10-2017, 08:50 AM
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Re: Re-gearing on 31" with eye on 33"?

I've got 33's (285's) on stock gears, no issues. Would re-gear if I went any bigger though.

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post #5 of 35 (permalink) Old 05-10-2017, 08:54 AM Thread Starter
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Re: Re-gearing on 31" with eye on 33"?

Very helpful, thanks!

It's a 2013 FJ, bought certified pre-owned from a Toyota dealer with 30k miles, passed my trusted mechanic's inspection (whole family fleet has been going there for 10+ years; all their managers and most of the techs know us by name). I'm up to 52k now. I just recently learned (since my last fill-up!) that the FJ's engine actually can benefit from premium gas; I'm going to try that first. That and more skinny pedal

However,

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If you're putting a lot of highway miles on your FJ, and you love your FJ and want to keep it forever, stop doing that.
No! I like driving my FJ. I have a Camry (all 20 years of its life in the family, 12 years with me) that gets more than double the mileage of the FJ but I don't daily drive it anymore 'cause it's not the wonderful FJ! Camry made it 20 years of daily driving and still goin' strong; ain' no reason the FJ can't do the same. Especially since it's getting pampered from day 1 (whereas the poor Camry had a rough stretch of years in the middle).


@Jimmy-buffet if I had more money than sense, though, I could just find a supercharger that'd fit in the engine compartment, combine that with some willing techs in search of an adventure, and everything'd work out well, though, right?
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post #6 of 35 (permalink) Old 05-10-2017, 08:55 AM
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Re: Re-gearing on 31" with eye on 33"?

Using my FJC as an example, the stock tire size 265/75R16 is 31.6" on average (these numbers will vary some with tire manufacturer), so a little closer to 32" than 31". The 33s most people run (such as 285/75R16) are 32.8".

So the difference between the stock tire size and "33s" is only 3.7%. Not worth the substantial cost of regearing, IMO.

My other off-roader went from 29.5" tires to 35". That was an 18.6% difference, which was worth regearing...again IMO.
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post #7 of 35 (permalink) Old 05-10-2017, 09:30 AM
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Re: Re-gearing on 31" with eye on 33"?

Quote:
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No! I like driving my FJ. I have a Camry (all 20 years of its life in the family, 12 years with me) that gets more than double the mileage of the FJ but I don't daily drive it anymore 'cause it's not the wonderful FJ! Camry made it 20 years of daily driving and still goin' strong; ain' no reason the FJ can't do the same. Especially since it's getting pampered from day 1 (whereas the poor Camry had a rough stretch of years in the middle).
The FJ isn't the perfect vehicle to drive in all situations, though. I bought my S2000 after too many trips to the mountains where I never went offroad. With the top down, the S2000 is a lot more enjoyable for those drives. Admittedly, your Camry is probably a little on the boring side but there are better options out there. Will your FJ still be running in 20 years? If you take care of it, sure. Wouldn't you rather save the FJ for what it's designed for, rather than use it up on the highway? In 20 years you can have 350K of mostly highway miles or 125K of mostly offroad miles.

To each his own, just saying that's my strategy. Your post here is attempting to improve the highway characteristics of a vehicle designed for going over rocks at low speeds I understand why, for me the better fix is to drive another car.

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@Jimmy-buffet if I had more money than sense, though, I could just find a supercharger that'd fit in the engine compartment, combine that with some willing techs in search of an adventure, and everything'd work out well, though, right?
Toyota brought the FJ-S to FJ Summit in 2012, Toyota's supercharged concept 2010+ truck. When they discontinued the FJ in 2014, supposedly TRD gave their supercharger tune etc to Magnuson to finish the job. So keep an eye out. And yes, supercharging a truck running at sea level on 33's qualifies for "more money than sense" as the total kit + install would probably run you about $7-8 grand.
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post #8 of 35 (permalink) Old 05-10-2017, 10:32 AM
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Re: Re-gearing on 31" with eye on 33"?

I've got stock tires and I regeared when my diff blew out. 4.56 wakes up the truck big time and I also documented a lot better fuel economy.
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post #9 of 35 (permalink) Old 05-10-2017, 12:17 PM
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Re: Re-gearing on 31" with eye on 33"?

I run heavy 34"s and it badly needs re-gearing. Anything with hills or wind and the cruise control is worthless. I think the FJ has the wrong gears stock.
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post #10 of 35 (permalink) Old 05-10-2017, 12:45 PM
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Re: Re-gearing on 31" with eye on 33"?

Quote:
Serenity Now previously said: View Post
Using my FJC as an example, the stock tire size 265/75R16 is 31.6" on average (these numbers will vary some with tire manufacturer), so a little closer to 32" than 31". The 33s most people run (such as 285/75R16) are 32.8".

So the difference between the stock tire size and "33s" is only 3.7%. Not worth the substantial cost of regearing, IMO.

My other off-roader went from 29.5" tires to 35". That was an 18.6% difference, which was worth regearing...again IMO.
You also have to take into account the spinning weight differential created by going up in size. Even the lightest 33" MT takes a significant amount more horsepower to achieve the same centrifugal force as the stock unit, for instance I believe my Toyo 33's weigh in at over 70 pounds compared to the stock tire that's about double.

Now add the weight difference to the size differential and the percentage goes way up.
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