will 31x10.50-15's kill my power? [Archive] - FSB Forums

: will 31x10.50-15's kill my power?


KrautBurner
10-05-2007, 05:12 AM
ok,

I just picked up a 1990 302 bronco AOD
it runs good (not a monster as far as power goes:doh0715:)

it's got stock size "touring tires" 235/75-15 (28.8"x9.2")
I wanna go a little bigger (mostly wider)
but I don't wanna lift it
I want something that's decent on the highway, not super loud, but is gonna get me up the mountains for snowboarding:toothless


how much will going to 31x10.50's kill me for highway power?
as well as my spedo?


or should I just be looking at 30x9.50-15's? :banghead




Thanks in advance...

Russ

stan the man
10-05-2007, 05:30 AM
ok,

I just picked up a 1990 302 bronco AOD
it runs good (not a monster as far as power goes:doh0715:)

it's got stock size "touring tires" 235/75-15 (28.8"x9.2")
I wanna go a little bigger (mostly wider)
but I don't wanna lift it
I want something that's decent on the highway, not super loud, but is gonna get me up the mountains for snowboarding:toothless


how much will going to 31x10.50's kill me for highway power?
as well as my spedo?


or should I just be looking at 30x9.50-15's? :banghead




Thanks in advance...

Russ

:doh0715:

Well first and foremost i would like to say Welcome to the forum. Secondly, the search button is your FRIEND. Thirdly, you can run up to a 33x12.5 on a stock bronco. Since you have a 302, if you decide to jump up to 33s, you probably will notice a slight power loss. Since youre looking for something quiet and will get you trough the snow, go with either a 31x10.5 or 32x11.5 BFG AllTerrain. BFG has the most agressive all terrain you can find, not to mention they are great highway tires and awesome in the snow.


Goodluck:beer

84broncorig
10-05-2007, 05:36 AM
Well with a 302 your power sux. But by putting 31's on, you won't make it any worse. I have 33's on with out a lift, and its a dawg!!!!

gildedseat
10-05-2007, 05:40 AM
Anyone have pictures of a 93ish bronco unlifted with 32's or 33's?

Bronco4Life
10-05-2007, 06:33 AM
You'll be fine with the stock gears and 31" tires. My 200+ thousand mile 302 is still quick as shit with 31's on it.


Anyone have pictures of a 93ish bronco unlifted with 32's or 33's?

Have you tried looking in the "Post a pic of your Bronco" thread? I would guess there's probably a few of them in there.

KrautBurner
10-05-2007, 06:43 AM
I have used the search,
I've found several things saying what "will" fit,
that's not really the issue,

it's more about power loss (due to changing the effective gearing)

if I come across a set of 16" wheels,
I may go with Nitto Terra Graplers

96GreenMonster
10-05-2007, 08:22 AM
Well with a 302 your power sux. But by putting 31's on, you won't make it any worse. I have 33's on with out a lift, and its a dawg!!!!

not necessarily true. i have a 302 with 35s and 3.55 and my truck is still fairly quick off the line, and it gets up to 70 just fine. however it doesnt do 90 like it use to...but why do i wanna do 90?

only downside is the tires put my spedo off around 5mph.

KrautBurner
10-05-2007, 09:31 AM
not necessarily true. i have a 302 with 35s and 3.55 and my truck is still fairly quick off the line, and it gets up to 70 just fine. however it doesnt do 90 like it use to...but why do i wanna do 90?

only downside is the tires put my spedo off around 5mph.

is 3.55:1 the stock rear end?

"the tires put my spedo off around 5mph" at what speed?

MajSuckelton
10-05-2007, 09:48 AM
Let's put it this way, 31's were stock on a lot of broncos. The difference in power will be very slight.

Bronco4Life
10-05-2007, 09:57 AM
:stupid

Also, 96GM why haven't you re-cal'd your speedo yet? It's simple as cake to do.

Yes. 3.55:1's were the stock gears for 99% of the broncos out there.

deadeyedick
10-05-2007, 10:41 AM
the search button is your FRIEND.

Search may be useful and necessary, but it is NOT your friend. :goodfinge

Since youre looking for something quiet and will get you trough the snow, go with either a 31x10.5 or 32x11.5 BFG AllTerrain. BFG has the most agressive all terrain you can find, not to mention they are great highway tires and awesome in the snow.

:stupid

Anyone have pictures of a 93ish bronco unlifted with 32's or 33's?

http://www.fullsizebronco.com/forum/showthread.php?t=105442

only downside is the tires put my spedo off around 5mph.

Actually, it throws your speedometer off by a percentage at all speeds. With 32"s, mine is off by about 11-12% (e.g., speedo reads 70 mph = actual speed 78 mph)

:stupid

Also, 96GM why haven't you re-cal'd your speedo yet? It's simple as cake to do.

Please elaborate...the only shop around here that can do it wants $300. :shocked

DaveG
10-05-2007, 10:45 AM
The power difference is slight but nonetheless, to me, I felt it. Back in the day, I ordered my 95 with a 5.8 and P235s. Everyone made fun of the way it looked but I didn't care because I had great throttle response!

87FSBinKY
10-05-2007, 11:10 AM
I run 31x10.50's on mine with basically no noticeable difference in power. I do have the 351w, which might make some difference.

I've GPS'd the speed to compare with the speedo and I only calculate a 2-4% discrepency between actual mph and what the speedo shows, which I can live with.


http://www.supermotors.net/getfile/542589/fullsize/awesome_truck[1].jpg

http://www.supermotors.net/getfile/544903/fullsize/bronco_top1.jpg

SyntheticD
10-05-2007, 11:26 AM
maybe you can use a 31x11.50 instead of 10.50 if your looking for a wider stance, i didnt loose any power that i noticed when i put on 32s but i have a 300.

96blkbeauty
10-05-2007, 12:27 PM
I am running 31x10.50xr15's right now, and like stated many times above...not a major difference in power. I am running the BFGoodrich a/t's and they are the best tire i have owned. They do great in the snow and on the highway. Just make sure you keep them properly rotated and maintained.

http://www.supermotors.net/getfile/468097/fullsize/sevenmile11.jpg

http://www.supermotors.net/getfile/468069/fullsize/picture-003.jpg

http://www.supermotors.net/getfile/468070/fullsize/picture-004.jpg

Alejoint
10-05-2007, 01:02 PM
My '92 with 31x10.5 and a carb'd straight-six has remarkably good road manners, so I don't see why it wouldn't work for you. At least you have a couple extra cylinders...

hossman777
10-05-2007, 01:13 PM
I'm currently running the stock 3.55's with 35" tires. It's not as bad as everyone makes it out to be in my opinion. I was running 31"s, and it was fine. 35"s isn't all that bad. I do plan to upgrade to 4.88's next year, but it'll definitely get me through for a while.

You won't have any problems with torque or speed with 31"s.

tripen2
10-05-2007, 02:11 PM
Search may be useful and necessary, but it is NOT your friend. :goodfinge



:stupid



http://www.fullsizebronco.com/forum/showthread.php?t=105442



Actually, it throws your speedometer off by a percentage at all speeds. With 32"s, mine is off by about 11-12% (e.g., speedo reads 70 mph = actual speed 78 mph)



Please elaborate...the only shop around here that can do it wants $300. :shocked


Heres the link to recalibrating your speedo
http://www.fullsizebronco.com/forum/showthread.php?t=55005&highlight=calibration

Mike

Bronco4Life
10-05-2007, 05:08 PM
Please elaborate...the only shop around here that can do it wants $300. :shocked

Search noobie! :goodfinge :beer

http://www.fullsizebronco.com/forum/showthread.php?t=55005&highlight=calibration


edit: Doh, tripen2 beat me to it. :thumbup


It's friggin easy as hell to do... I kicked myself after I'd bought one of those fawkin TrueCal speedo recalibrators... good thing Summit took it back.


And now you can paypal Steve 300 bucks for showing you how to do it... :histerica

RGJ 58
10-05-2007, 08:26 PM
you really shouldnt lose any power wit 31s i have 31x10 on and it runs great and i have a 302 and have plenty power to spin the tires on the road

KrautBurner
10-06-2007, 04:07 AM
maybe you can use a 31x11.50 instead of 10.50 if your looking for a wider stance, i didnt loose any power that i noticed when i put on 32s but i have a 300.

31x11.50's would be awesome !!!

who makes those, and where can I get them?




as of right now,
I'm leaning towards 31/10.50 or maybe 32/11.50

KrautBurner
10-06-2007, 04:11 AM
you really shouldnt lose any power wit 31s i have 31x10 on and it runs great and i have a 302 and have plenty power to spin the tires on the road

mine dosn't wanna spin the tires with 235/75-15's :doh0715::duh:banghead

KrautBurner
10-08-2007, 01:46 AM
looks like I'm gonna go with 31/10.50-15's

Yokohama Geolandar A/T-S
31X10.50R-15/C1 109S

http://www.discounttire.com/product/tires/yokvl3.ang.jpg

Geolandar A/T-S all-terrain tires have an aggressive design that'll make today's trucks or SUVs stand tall. But the real beauty lies deeper. With features ranging from Multi-Stepped Grooves to Dual Interlocking Pyramid Sipes, every Geolandar A/T-S packs the absolute latest in technology to deliver long, even treadwear. Featuring an extensive size line-up, the Geolandar A/T-S, and its powerful on/off-road performance, can be experienced accross a broad range of applications.

KrautBurner
10-08-2007, 01:52 AM
here's the wheels I have....

I currently have 2 15x7 and 2 15x8
I'm trying to find 2 more 5x8's, and use one of the 5x7's for the spare

http://truck.hownd.com/product-3774-mb-motoring-mb-wheels-70.html

Edit:
sorry,
I couldn't get the pic to link
http://truck.hownd.com/product-3774-mb-motoring-mb-wheels-70.html

roman3308
10-08-2007, 08:31 AM
i am running 31 x 10.50 x 15 goodyear wranglers on mine and they do fine .....i still have lots of power with my 302 and it has 251;000 miles on it. 31's do fine. i agree with the others get the bfg all terrains...they are cheap and have a 50,000 mile warranty....plus they are great in snow and on roads....not too good in mud

96GreenMonster
10-08-2007, 09:30 AM
well i learned something new. it just always seemed like it was about 5mph off. didnt know it was a percent, ya learn something new every day.. i have been planning on recalcing my spedo, but im on the lazy side. it will happen eventully

KrautBurner
10-08-2007, 10:21 AM
well i learned something new. it just always seemed like it was about 5mph off. didnt know it was a percent, ya learn something new every day.. i have been planning on recalcing my spedo, but im on the lazy side. it will happen eventully

yeah,

if you're 5mph off at 25,
that means you're gonna be off by 10 at 50
and off by 20 at 100

(that's about how my 79 camaro was, I figure I was " movin' " when my spedo was burried at 135 :goodfinge

deadeyedick
10-08-2007, 10:57 AM
Search noobie! :goodfinge :beer

http://www.fullsizebronco.com/forum/showthread.php?t=55005&highlight=calibration

edit: Doh, tripen2 beat me to it. :thumbup

It's friggin easy as hell to do... I kicked myself after I'd bought one of those fawkin TrueCal speedo recalibrators... good thing Summit took it back.


And now you can paypal Steve 300 bucks for showing you how to do it... :histerica

Open mouth, insert foot. :doh0715:

nitrorustlerpro15
10-21-2007, 05:20 PM
it shouldn't do anything. we had small tires on our '89, and we put 31's on it, and it ran just the same. actually a bit better
sadly, my dad had to get rid of it.....couldn't afford gas...

akford
10-21-2007, 05:31 PM
31's will be fine, i had them on mine the first two years i owned my bronco and they were wonderful. If you want to read about gears and what effects different tire sizes have on engine power and what not then read here (http://www.fullsizebronco.com/forum/showthread.php?t=355)

KrautBurner
10-25-2007, 04:58 AM
well,
I picked up a set of used 31x10.50-15 mud terrain's

they did suck a little power away,
the biggest issue is that it will loose power (at highway speeds) going up hills, and the speed will drop and it will downshift pretty easily,
unless I'm doing 70-75mph (indicated) which is faster than I wanna be going when the posted speed limmit is 60

guess I'm just stuck in 3rd most of the time.

Kpate
10-25-2007, 05:29 AM
My dad put 30x9.50s on the truck before he passed away. They do fairly well. Definitely gonna put 31x10.50s in the future....

mickaila
10-25-2007, 01:06 PM
i understand you plan on driving up the mountain or in snow, if you don't stud the tires, i would suggest getting a skinny set of tires too. in my experience, they do better in snow then fat ones.
mj

BarneyGoneBad
10-25-2007, 01:30 PM
i understand you plan on driving up the mountain or in snow, if you don't stud the tires, i would suggest getting a skinny set of tires too. in my experience, they do better in snow then fat ones.
mj

for sure the fater tires will ride on top of the powder and you will lose all kinds of traction and tend to "ski" with a fat tire. A narrow tire will sink in the snow and get down to the solid ground and gain traction. Also with a fat tire you have to plow through the snow where a narrow tire will have more of a cut through the snow.

Think of the fat tires as a shovel vs. a pick. The pick goes through with little resistance where the shovel you really got to get behind. But again the most dangerous part of fat tires in snow (and take it from someone who not so much 4x4 but does back country driving to get to the primo snow machine and skiing spots with f-150) is the tendency to rid atop the snow and "ski" makeing turning and stoping going down hill or at anything more then 20 km extreamly scary.

adrianspeeder
10-25-2007, 03:17 PM
Shoot, the height difference is less than an inch depending on the rim size. The 88 right now has 31s on the rear and 235s up front. Not even a vibration due to the sightly different size in 4x4.

Adrianspeeder

KrautBurner
10-26-2007, 03:41 AM
I'm pretty sure there's closer to 2 inches difference in 235's and 31's

as far as running different sizes in the front and rear with 4x,
i've seen vehicles get "bound up" and stuck due to alot less difference in tire size

GTRider245
10-26-2007, 10:31 AM
I'm pretty sure there's closer to 2 inches difference in 235's and 31's

as far as running different sizes in the front and rear with 4x,
i've seen vehicles get "bound up" and stuck due to alot less difference in tire size

Hes right. A 235 measures right at 29 inches.

imlikeojnow
10-26-2007, 10:43 AM
Well with a 302 your power sux. But by putting 31's on, you won't make it any worse. I have 33's on with out a lift, and its a dawg!!!!

and you base this on what? the power in the 302 does not suck. You are an idiot for thinking so. I have a 302, stock gears, with some aggressive 33s on it and i can still spin the tires. so i would venture to dsay that the power does not suck

well,
I picked up a set of used 31x10.50-15 mud terrain's

they did suck a little power away,
the biggest issue is that it will loose power (at highway speeds) going up hills, and the speed will drop and it will downshift pretty easily,
unless I'm doing 70-75mph (indicated) which is faster than I wanna be going when the posted speed limmit is 60

guess I'm just stuck in 3rd most of the time.

What year is your truck? recal the speedo, also do a tune up. 31s should not have robbed power

bronc_17113
10-26-2007, 10:46 AM
and you base this on what? the power in the 302 does not suck. You are an idiot for thinking so. I have a 302, stock gears, with some aggressive 33s on it and i can still spin the tires. so i would venture to dsay that the power does not suck



What year is your truck? recal the speedo, also do a tune up. 31s should not have robbed power
I must be an idiot to bc I think the power in my 302 sucks as well compared to the other 2 but on the other hand it gets the best gas mileage. In defense of the 302 though I will say that it is adequate.

I would agree that the 31's are not going to make any difference on power though did it on mine and did not have that issue in general the only problem I find with the power in a 302 is they suck climbing steep hills on the interstate at high altitude.

adrianspeeder
10-26-2007, 12:44 PM
I'm pretty sure there's closer to 2 inches difference in 235's and 31's

as far as running different sizes in the front and rear with 4x,
i've seen vehicles get "bound up" and stuck due to alot less difference in tire size

I measured 'em up to be sure before trying to move and the Michelin LTX A/T 235-75-R15 on the stock ford wagon wheel came out to just above 30inches with weight on the wheel. Did some driving on dry pavement with even some turns and nary a bind since March...

http://www.supermotors.net/getfile/495768/fullsize/3.jpg

Adrianspeeder

BarneyGoneBad
10-26-2007, 02:14 PM
I would agree that the 31's are not going to make any difference on power though did it on mine and did not have that issue in general the only problem I find with the power in a 302 is they suck climbing steep hills on the interstate at high altitude.

Thats no the tires fault you have trouble climbing hills at high altitude thats your motor not getting enuf air. Time to clean the air filter and you will also find cleaning or replaceing your air filter will make a sucky 302 much more to your likeing.

bronc_17113
10-26-2007, 02:49 PM
never said it was the tires and if i made it sound that way I apologize. I have a clean filter it's just one or two of the big climbs out here that give me any problems and if I downshift it's ok

Sixlitre
10-26-2007, 07:48 PM
i understand you plan on driving up the mountain or in snow, if you don't stud the tires, i would suggest getting a skinny set of tires too. in my experience, they do better in snow then fat ones.
mj

You know it !

Winter time you want tall, skinny and knobby. I'm very pleased with the way the few ignition and exhaust mods have woke up the performance and mileage on my EFI'd 302.

That said, I can feel a difference (loss) in performance just going from the 235/75/15 Summers to the 235/75/15 A/Ts for Winter.

They also drop a mpg or two as well. I would expect at least as much of a drop with 31s.

Sixlitre

Bruce M
10-26-2007, 09:30 PM
Mud tires do get less mpg and performance because of the aggressive tread. If you put the same size tire on it with less aggressive tread you'll feel more power.

KrautBurner
10-27-2007, 04:38 AM
and you base this on what? the power in the 302 does not suck. You are an idiot for thinking so. I have a 302, stock gears, with some aggressive 33s on it and i can still spin the tires. so i would venture to dsay that the power does not suck



What year is your truck? recal the speedo, also do a tune up. 31s should not have robbed power


truck is a 90
I've done plugs, wires, coil, cap and rotor,
havn't played with the timing
(and a K&N Cone filter)

what else is there for a "Tune Up"



I think it came with 190-195hp (which is not much at all for a 5,500+ lb vehicle)
that's a fairly low HP-Weight Ratio (at least compared to my 500hp 4,000lb car)

KrautBurner
10-27-2007, 04:45 AM
I measured 'em up to be sure before trying to move and the Michelin LTX A/T 235-75-R15 on the stock ford wagon wheel came out to just above 30inches with weight on the wheel. Did some driving on dry pavement with even some turns and nary a bind since March...

http://www.supermotors.net/getfile/495768/fullsize/3.jpg

Adrianspeeder



odd,
you should check your measuring device....

most tire calculators list the 235/75-15 as being

28.9" Diameter
90.7" Circumference
698 revs/Mile

compared to 265/75-15 (31x10.50-15 Equivalent)
Dia 30.6"
Circ 96.3"
Revs/Mile 658

6.1% difference (3.7 mph off at 60(indicated))


as far as "binding"
I guess that's going to be dependant on how tight your drive train is (locked)