32s & 33s - For the Love of God, Where's the Power?!

just installed 32" mud terrains. this was mainly an impulse buy - i do ALOT of off-roading, but in michigan, you just don't NEED 32s. but they looked great, sound good and i needed to write a $600 check to somebody. so i got 'em. then i tried to tow something. holy cow.

the xterra (even the 3.3) is pretty anemic whence it comes to power anyhow but with these tires, it flat out SUCKS (for lack of better vernacular). i was towing about 1000 lbs, and the thing would not hold 65 mph in overdrive. so i drove the 200 miles with OD off, resulting in an earth-warming 11 mpg. to me, this is rather pathetic for a vehicle supposedly capable of towing 5000 pounds. (even with stock tires, i would LOVE to see someone try and tow 5000 lbs). so my question is: what effect on power has bigger tires had, if you've made the switch. and, how are you mitigating the problem?

thanks

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Umm...uhh..."duh."

Those tires are pretty heavy...
So far no one has been able to regear that I've heard about--I don't know of any sources for a new r&p for the front diff (yet.) I'm running tires that are considerably heavier than stock as well and I just live with it. Don't really tow anything, though--if I did there's no way I would have a) bought an Xterra or b) bought big/heavy tires for my Xterra.

You can try some of the performance upgrades, intake/exhaust, maybe even headers...beyond that...going to have to live with it if you want the clearance & footprint of 32's. Sorry.

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Vikram/gothamist -- MAXC member
http://www.4x4LO.com

You lost lots of power going to the bigger tires. The only solution is to modify the gearing or change back to smaller tires. If you carried aq GPS you would notice that your speed is also not correct.....Your speedometer will err onm the low side, so at 65, you could very well have been doing 75+

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yes, good point, griffin. i was never sure whether the speedo would show on the low or high side with an increase in tire size. i guess i just wasn't anticipating such a big hit on power.

thanks for the tip.


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[This message has been edited by fakie99 (edited 05-10-2001).]

That is not 100 % true for every one.

My truck was off with stock tires and was exsactly right with 31 inch tires

so every ones spedometer may/IS different


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The weight of the tires isn't a huge issue. It may be an issue when accelerating, but not once you're up to speed. Though the added rolling resistance is huge. It takes a lot to overcome that. Plus, as it was mentioned, two inch bigger tires is a huge increase in overall gear size. And as Griffin said, your speedo is probably far off, at least from what it read with the stock tires.

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Eric Konarske & Lara, my X
'01 Solar Yellow XE 3 Pk. 4x4

Ok, now that we know that the speedo may be off. How does one calculate the speed if you don't have a GPS. And don't tell me to buy one because it isn't in the cards right now.

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http://www.gpxo.org

You're right. With my 31s my speedo is more accurate than it was stock, but when you're comparing power loss with stock tires the difference is what's important--not real world accuracy.

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Eric Konarske & Lara, my X
'01 Solar Yellow XE 3 Pk. 4x4

In theory...
MPH is calculated based on rotation of the tires. Now, for each rotation of the tire, the distance traveled is greater because of the larger tire circumference. Since tire circumference is linear with tire diameter, just take the difference in the tire size and divide by the old tire size.
So, assuming original tire size of 30", (32-30)/30 = .0667. So, your speedo reads 6.67 percent higher. At 65mph with the new tires and uncalibrated speedo, actual speed is 65/(1-.0667) = 69.6 mph. Actual results may vary based on true tire diameter (dependent on inflation, tread thickness, etc...).
I think this is about right.


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[This message has been edited by xterrabull (edited 05-10-2001).]

Great now I gotta go back and take a math class just to figure out how fast I am going when I get new tires.

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http://www.gpxo.org

[This message has been edited by DeFibVT (edited 05-10-2001).]

I disagree. Even if you kept the same overall tire size, weight of the tires/rims makes a very noticeable difference in actual and perceived power. The only fun thing is that now I have so much rolling inertia I don't need to give the truck any gas on the highway going downhill.

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Vikram/gothamist -- MAXC member
http://www.4x4LO.com

In perceived power only when accelerating. After that the only power loss you'll feel is from big fat squishy tires with a lot of rolling resistance.

A quick story to relate my point. Bicycle racers are huge weight geeks. Especially when it comes to wheels/tires because rotating weight is roughly 4 times more noticable than non-rotating weight. But that's only for bikes that need to be able to accelerate fast. For the cyclists who attempt what's known as the hour record, they actually put weights in their wheels to make them heavier. The hour record is just to see how far you can go in an hour on a flat track where your speed stays the same for the whole ride. I guess in a case like that, where there is no acceleration, they feel that inertia is actually an advantage. And belive me, those guy wouldn't do it if they lost even a 10th of a second.

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Eric Konarske & Lara, my X
'01 Solar Yellow XE 3 Pk. 4x4

when you drive on the highway
try to find a smoth straight spot and look at the side of the road there should be ( on most highways) mile markers

count how many mile markers you pass by while doing 50 miles per hour in 1 minute then multiply by 60 minutes and you will get roughly your true mph

or better yet drive 50 mph for 10 minutes and then mupltiply the mile markers by 6 and you should get even more acurate figure

or get GPS




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Does anyone know what the gear ratio is at at stock? If you are wanting to change your gear ratio this website:http://www.differentials.com/njfaq.htm may help determine what you will need for that power gain that you are looking for.

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Vince

who tows with 32' tires? Dude, hate to say it, but *any* vehicle is gonna lose a drastic amount of power towing with that size tire. Ever see big fullsize dodges and Chevy's on the highway towing trailers or whatever? Look at their tires, their usually faily small, skinny tires. Not 32's or 33's. The trade off to running flotation size mudders is that you are commiting yourself to driving a trail rig, not a tow rig. If you need to tow frequently then I say just get another set of all season highway tires and have them put on when you need to tow.Or leave them on and have the mudders put on only when you know you are planning an off-road trip. Just my .02

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01 SE 4x4
Silver Ice

Final drive ratio

XE (V6): 4.363

SE: 4.636

Transfer gearratio (:1) 2.020

more specs at http://www.theautolink.com/Transcripts/Xtera_info.htm

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01 SE 4x4
Silver Ice

The speedometer difference may be more than 6-7%:

I don't need no stinking math to calculate my tire ratios.

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Dan.
Exploring the Rockies

I did a little test last weekend with my 32s. 50 miles covered (by mileposts) but 48.1 miles recorded. 2.9 miles short x 2 = 5.8% difference.

Brent

The problem is simple...

You have an automatic.

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01 SE 6cyl 5spd Solar Yellow

i have an automatic with 32" BFG MTs and I can still beat people off the line if need be. i can cut people off with the best of them on the DC beltway if i have to. i have yet to tow anything though. maybe i am just not sure what you all are talking about to undestand, but this thing has plenty of power for my needs. the only thing i have swapped out is, i put a K&N air filter in.

i know Mr T has towed his camper a bunch of places with his X. it's got 32" BFG MTs as well, but it a manual.



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Synchro (aka Kirk)
2000 Alpine Green 4x4 Auto, ARB, Warn XD9000, 32" BFG MTs

I was able to hit 100mph (briefly) on I-70 on the way to Moab last month, and I have 32s. I was able to get a true speed reading from my GPS. My speedo really isn't that far off on the speed correction and they are new tires. The 5 speeds seem to have a higher correction than the ATs.

I also had about 450lbs of extra weight from sliders, bullbar, winch, skid plates, and a bunch of camping gear.

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2000 Silver Ice 4x4, SE
ARB Bullbar & air locker, 32" BFG Mud Terrains
PNWX webmaster www.pnwx.net

[This message has been edited by Mosi (edited 05-10-2001).]

I am a Police Officer, oneday I played around with the RADAR trailer and my X. With stock tires it was anywhere from 3 to 4 miles per hour off. So maybe the bigger tires would then give a better reading. Would it matter if the X had bigger rims? Does Nissan change the gears for the larger rims? Or does the smaller rims get stuck with the other ratio? Or does it even matter?

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Lawdawg
2001 XE 4x4
Cloud White

GO GATORS!!!!

Wheel size doesn't matter--just the OD of the tires.

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Eric Konarske & Lara, my X
'01 Solar Yellow XE 3 Pk. 4x4

Don't you mean 1.9 and 3.8%?





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Patto
Silver 2001 4WD XE 3 Pak
w/mods

Aren't the stock tires on the X basically 30.5 tall x 10.50 wide? Would 31" tires have much of an effect on towing/power, then?

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The tires on a stock 2001 SE (16" wheels) are only 29.05" in diameter (255/65R16).

2000 model SE's and XE's (and 2001 XE's) with Utility Packages are 29.6" in diameter (265/70R15).

A 2000 without the goodies are a measily 27.95" in diameter (235/70R15).

The 2002 SC will get 265/65R17 tires on it, which are 30.5" in diameter.

Non-Supercharged models will get 265/70R16's at 30.6", the biggest yet (same as a 31" BFG All Terrain).


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Regards,
Ian

Nope, I botched the 48.1 bit, it was 2.9 miles short, 5.8% off.

Brent

So if you put bigger tires on your X then your actual milage on the odometer would be less... yeah, thats a good thing for resale value...
That is in no way that I am every gonna sell it... not till the wheels fall off.

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[This message has been edited by arkiteqt (edited 05-11-2001).]

With my Trxus tires, I'm about +3mph than the odo.

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Denim Blue SE
4x4 3pk AT

Whats up every one?

I've got 33x12.50 pro-comp muds on my '00 x and i love em! i didn't notice much of a power loss but i've got a custom air intake and dual exhaust. my mpg has also stayed about the the same. my spedo is about 8mph off but i can live with that. i've never towed anything so i don't know how it would handle that. i've got the 5spd and it is actually pretty quick off the line.

later,

BigAssXterra



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BAX

You have a 2WD Xterra at Sea Level.
Big difference (about 500 lbs) between that and my 4WD at 5000 feet.


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Regards,
Ian

I have to think that you get some rubbing on the fender lips at the rear with those, provided you have put much flex on your rig with 'em anyway. My 32x11.50 tires barely clear the fender lip on the front half of my rear wells. I took some pics yesterday that I'll post...

Brent

OffroadX,

Wouldn't the rubbing be on the rear half of the front wells and not on the front half of the rear wells? actually i do not rub there or anywhere for that matter. i've got 3" susp, 3" body, 1 1/2" shackles and t-bar adjustments. i have done some trimming, but nothing extensive. as for flex, i have tweaked and twisted my X to the limits. just cause shes 2wd doesn't mean i don't work her hard. i hit the trails at least once a week.
is your X lifted or are you stock? did you post your pics yet, i want to see them?

See-Ya

-BAX-



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BAX

Here are the pix:





That's where I figure you can't do much more than 11.50" wide. The front fenders should be able to take it as far as pure stuffing, but there would be still more of an issue with rubbing when turning. It's about 50/50 diameter and width contributing up front.

Your lift probably doesn't let the tire stuff far enough into the wells to be an issue anymore. Do you have your rear swaybar on? I don't.

Brent

[This message has been edited by OffroadX (edited 05-22-2001).]

OffroadX, what mods (if any) have you done to your suspension? I'm thinking about going with the 32"x11.5" BFG A/T's as well...
Oh yeah, do those fit where the spare goes?
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Relax, have a homebrew,
Joe

[This message has been edited by arkiteqt (edited 05-22-2001).]

for the 32s, you will have to trim some plastic in the front wheel wells, and adjust the torsion bars a little higher. a howto is here .

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Synchro (aka Kirk)
2000 Alpine Green 4x4 Auto, ARB, Warn XD9000, 32" BFG MTs

and the other question would be, are the front sway bars on. the fronts will rub WAY more than the rears if this were the case. if the front sway bars are disconnected and the front wheels are turned and under heavy compression, this is there that would be issue.

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Synchro (aka Kirk)
2000 Alpine Green 4x4 Auto, ARB, Warn XD9000, 32" BFG MTs

No mods other than the missing rear swaybar. The only problem (after trimming and t-bar adjustment) that you will encounter with 32s is some mild rubbing inside the RR wheelwell where the plastic covers the fuel filler line when you are at max compression (like in the pic) but it's not too bad. My plastic cover is split in half but still manages to stay in place. If you keep your swaybar on I doubt you would get enough flex for it to be a problem in the first place.
As for the spare well, as I recall it will fit if you don't have a hitch, but I don't recall if it can be wrangled to fit along with a hitch.

Brent

[This message has been edited by OffroadX (edited 05-23-2001).]

So "BAX" never made it past 2 posts eh? His 2WD must be stuck in the Florida sand somewhere.

Now i remember why i don't post on this board. if your not like everyone else, you get flamed. dont worry Philosopher, i won't get past 2 posts!
-BAX-



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BAX

Now i remember why i don't post on this board. if your not like everyone else, you get flamed. dont worry Philosopher, i won't get past 2 posts!
-BAX-



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BAX