Topic: tires sizes and gears

[norcalyoter]

i have 33 and 4:88s now and was wondering about stepping up to a 35 how bad will my power go down with the 4:88s
my truck is carbed and has a 4 speed if i get a 5 speed will that help too ?

[mr4x42u]

I think with 35's and 4.88;s is about the same as 31's and 4.10's..

[MiniSimp]

http://www.4lo.com/calc/geartable.htm

[WHITE_TRASH]

A good person to ask would be Kyota.  He's been running 35" mtr's and 4.88's now he's running 38's.    Ya think he's lost some performance onroad? 

[To The Floor]

A good person to ask would be Kyota. He's been running 35" mtr's and 4.88's now he's running 38's. Ya think he's lost some performance onroad?

Isn't that a little better than your 3.90 and 38's set up?

[WHITE_TRASH]

Yea just a tad bit.... 

[BLUCRUZ]

The way I've aways seen it done is
31's go with 4.11 or 4.10's
33's go with 4.56's
35's go with 4.88's
37's go with 5.29's
39+ go with 5.71's

Saw this on a chart somewhere but my 37's with 5.29' s put my spedo right back within 2 mph of being right on.

[Rocksurfer]

  Yup, 4.88's were just a little lower than stock with 33's, 35's on my brothers truck was just about right on the speedo.

[norcalyoter [OP]]

ok sweet i think i will move up to 35s 

[kyle_22r]

tranny alsol plays a roll.  if i had an L45 4 speed, i'd match 35s with 4.88s in a heartbeat.  reason?  there's no overdrive, so you'll want to keep it kind of highway friendly in 4th gear.  well, assuming you even make it to 70 with 35s and a 4 banger, i don't think gearing matters...my truck hits the wall around 60-70 with my foot to the flloor pretty much no matter what.  height, rolling resistance, and having a rig shaped like a brick kind of hurts your top speed.

[BigMike]

Also, you might want to measure your tires once they are loaded on the rig. You might be surprised..

My 35s only measure 33", Marlin's 37s only measure 35.5", and some old 33" Xterrains I have only measure 31".

[Makman]

Also, you might want to measure your tires once they are loaded on the rig. You might be surprised..

My 35s only measure 33", Marlin's 37s only measure 35.5", and some old 33" Xterrains I have only measure 31".

Bigmike has a valid point.  Tire diameters are rarely what the manufacturers claim them them to be.  Some get pretty close and others make you wonder why they try to sell a 33" tire as a 35 incher.

Two points:
1.  The squish of the tire will decrease the effective rolling radius.  A smaller radius results in a mild increase in torque over the nominal rolling radius since the length of the moment arm is decreased.
2.  The speed of the vehicle is not related to the rolling radius in the slightest bit.  Speed will be a function of the RPM of the tire and its circumference.  A true 35" diameter tire will have an unloaded circumference of 110" (C = pi*D).  This circumference, squished within reason for highway travel, will remain a constant perimeter value, round or otherwise.  Point being, one revolution of the tire will result in 110" of forward travel, period.  A mile equals 63360 inches so this tire would have to rotate 576 times to go one mile and these numbers are generally published by the manufacturers for wear comparisons.

My 35" Toyo M/T's measure just under 35" unloaded and new.  Installed on a '85 PU with the weight of a 4.3 V6 and winch, the front tires squish down about an inch at highway pressure, ~30 psi.  Rears squish about half that.

[germ]

Interesting this should be brought up...I just made this switch a few weeks ago.

Based on my calculations, 33" tires with 4:88 gears you are approx 17% under stock. By moving up to 35" tires, you are about 2% over stock. This is based off the stock 4runner, which came with 29" tires and 4:10 gears.

OK, enough tech-weenie stuff.

Seat of the pants dyno: There is minimal change. I noticed just a little earlier shift from 5th to 4th, and I've noted my crawl is just a tad faster. Overall, I'm very pleased with the switch, and glad I did it. I think you'll be happy with it also.

Erik

[norcalyoter [OP]]

sweet are you imjected or carbed?what kind of difference have you noticed with the gas milage

[shad]

It should be ok with 4.88's but I think the older trucks with the 4 speed transmissions used to come with 4.30 gears stock because of the lower transmission ratio.
I would change the transmission out too if you can a G54 transmission works nice if you can't find a w56 cheap.

With 5.29's and 35's with a L52 5 speed transmission I can get to almost 75 mph it's buzzing like hell though.
Also noticed a bearing whirring noise with the tranny so I may be replacing that soon as well with a g54.

[KYOTA]

someone page me? sh*t sorry I just saw this thread. 4.88's and 35's wasnt bad 70-75 tops, and like Mike said you'd be surprised at how short your 35's really are, my MTRs were only a little over 33" at 28 lbs. havent had the 38's out yet, Sundays the shake down of the new 30 splines,  38's and new trim job, gonna see if I need to cut more. and (WT) I am sh*ttcanning the double shackles also

[norcalyoter [OP]]

ok i just wanna make sure i can do 70 on the freeway and i am working on the 5 speed i know that will help i dont know what the last owner was thinking whe he swaped out the 5 for the 4    but hey it gets me around