Fixing to join the 35" tire club!!

[Dolbs4082]

Well, the day before Christmas eve, my truck took on a snow filled ditch and wound up in a tree. Had to dig her out, and then kicked it in 4 wheel drive and drove up out of the ditch. I was amazed at how well she did. But i realized at that point i needed new tires.

When i hit the tree, it busted my front bumper up some more. (it was already cracked in several places from the previous owner.) So at this point i started "trimming"...and ended up with this

I put a few custom stitches on the truck to hold the bumper together...

Now, the truck already has a 3" body lift as well as warrior shackles on back and a torsion twist up front. I've already had 33"s mounted just to see how they fit. I wouldnt have to do any trimming at all... but i think i want more...

This is how it sat with 33"s...

Now i know im going to have to order new rims, and i've read up on all the back spacings and everything needed for these rigs. I've decided a 15x8 with 3.75 backspace... And im wanting to put 35x12.5x15 bfg km2 tires.

These are the rims im planning on ordering...
http://www.summitracing.com/parts/sum-85-5865/overview/

Im fairly sure that 35x12.50 will fit on my 8" rim, but correct me if im wrong. Im planning on ordering the rims this week by the end of the week. and then ordering new tires with in the next couple weeks.

 

[Dolbs4082]

The truck has 4.10 limited slip gears already, 4.10's should do pretty good with 35"s right? Of course bigger gears would be better, but 4.10's wont be too bad...

As for the front bumper, im fixing to lop off the ends of the frame rails (where the stock bumper mounted) and start fabbing up a custom bumper that will incorperate a receiver hitch, skid plating, and some aux. lighting. The tubing bender wont be here until march ish, so i probably wont get anything done on the front bumper until then (other then going ahead and cutting the frame up and welding it solid, and mounting the receiver hitch)...

 

[LONO100]

Look into regearing. I'm running 4.10 with. 33"s and the larger tires are still putting stress on my tranny. Your Speedo will be thrown off and your shift points will be off as well.

 

[Dolbs4082]

Hadnt thought about the shift points, I knew it would strain the trans a little bit more, and the trans has had a few hick ups already. Planning on having the trans rebuilt this spring anyways - has 175xxx and feels like its getting week.

I'll look into regearing the trac as well, something like 4.56 or 4.88?

 

[LONO100]

Once you switch from the factory size wheels and upgrade, your Speedo will be thrown off. To regear to make your tranny happy and accurate again you will need to regear. To figure out the optimum gear ratio that will line everything up again use this equation:

New tire diameter (inches)/factory tire diameter X stock gear ratio = new gear ratio needed

For example, I had 29" factory diameter tires, and 4.10 factory gearing which the granny was adjusted for. Once I moved up to 33"s, my Speedo and therefore my shift points were off by 3-4 mph. So I use the equation

33/29 X 4.10 = 4.67 the new gear ratio I need. So I find the closest available ratio which is 4.56 and boom! I have my Speedo and tranny back in line. Good luck!

 

[Dolbs4082]

Only problem is, what if the current tires are already larger then stock. My truck right now has 265/70/16 which are 30.61 tall... so 31/35X4.10=4.63 gears... And im not sure what size the factory tires were, would there be a sticker in the truck stating factory tire size?

 

[LONO100]

Well I believe the factory tire size for out sport trace was 255/70 r16 which equates in inches to something near 29.5 inches, so that will be your factory tire size. You know you will be moving to 35"s, so now all you need to do is see what gearing is in your rig. Do this by looking up the axl code on the sticker in your door jamb. Then you can put that all together and you can find your new needed gear ratio.

 

[LONO100]

http://m.discounttire.com/dtcs/infoTireMath.dos

This link has a good tire size conversion tool on it. It says the stock tire size that our sport trace came equiped with equaled to 30" in diameter. So go 35/30 X your current gearing. Good luck!

 

[chad551]

If you keep the IFS I would stick 33's and regear to 4:56. I personally would not run a 35 on an 8" rim, and I had the KM2 tires and I did not like them at all. They were great when they were brand new, but after 15k miles they were useless offroad.

 

[Dolbs4082]

I've got the original build sheet from when my cousin ordered the trac, so I know it's got 4.10 with limited slip. I liked the look of the 33"s, but I've already started collecting parts to put a solid axle up front and put the spring over axle in the rear. It'll be another 6-9 months before that happens, but it will happen. Which is why I look at it as, if I'm spending 1,000 on tires now, I might as well buy the tires I'm going to want to run for the long run. This truck sees ~250 miles a month.:. Light miles... I'm not taking it out rock climbing or mid bogging..

Should I got 15x10 with a 3.75-4 back space to run the 35x12.5?

 

[Hammer Down]

Yeah bro, do what Lono said and don't ignore the gears... even if you have to wait until you have all the parts together. As you've read I just smoked my tranny trying to turn 35" meats.

The weird part is I ran 33x12.50x15 wheels/tires on my 2003 white ST for 80k hard miles... I put 1k miles on this 2001 black one and shelled the tranny. I hope it has nothing to do with my X3 tuner.

 

[LONO100]

Chad is spot on, 33" with 4.56 is the sweet spot, its why I've been hesitant to go 35" myself. Members like offtrac (hugh) have had success with their its and 35's but he doesn't drive his trac very much compared to some other members.

Hey hammer, 33"s seemed to do ok for me, but I think you going to 35"s plus the tuner may have been too much work for your tranny, especially at highway speeds. I know when I'm driving up to the mountains in the summer heat, with the thinner air at higher altitudes, I can feel my trac working its ass off just to stay around 60 mph. I'm on the verge of regearing from 4.10 to 4.56 finally, just gotta get over this flu bug!

 

[Dolbs4082]

So, i should order 33's for now, and then once i get my new front end, and everything geared properly, then swap those 33's out for 35's? Since i know it will be 6-9 months before im ready to swap axles/gears... Might even be longer if everything goes smoothly tonight (wife and i are looking at buying a new house!!)

 

[Dolbs4082]

I just read threw offtrac's km2 thread AGAIN... have read it half a dozen times front to back... im just going to order 35's... My truck never see's highway driving, and if it does its ~55 for less then 10 miles... I live in a small town, with dirt roads connecting all the other towns...

If it strains the trans too much i'll do something about it. If it strains the front end, i'll start building the solid front quicker. If it breaks something i'll fix it stronger. Thats the game we all play isnt it, if it aint broke, dont fix it!! or if it does break, its time for an upgrade!!

 

[BigGreenV10]

Nice I am regearing mine to 4.56 when I put the 33" on I got the KM2 but I rarely off road this truck is being built for a daily driver which can do light mud/snow if needed so hopefully the KM2 will be good for me. I have a truck just for mud and off road to tare up if the urge comes.