Tire size?

[Scott Milliken]

What is a good tire size that will fit nicly with my seven inch lift? I have 35s right now but im going to have to replace them soon

 

[miesk5]

yo,

Are you also changing gears in front diff (stock is Dana 44) and rear diff (stock is 8.8)?

This is a sticky here in the Forum; right above the questions

by ocalabronco Posted 05 March 2006 - 10:55 AM

now, this is by no means the be-all, end-all bible for bronco tire fitment. there are all sorts of variables that come into play. This post is being created in order to cut down on the repetitive questions of what size tires can i fit with X amount of lift.

31" tires: these generally come on the truck stock. no fitment issues, no rubbing

33" tires: these WILL fit with no lift. the fit will be a touch snug, but you can either trim the edges of the bumper, or use washers as shims at the bumper mount. you can run a 3" body lift if you like to clear these tires, but its not necesary. slight rub will be encountered on the radius arms,depending on the dimensions of the rims

35" tires: these will fit with a 3" body lift at bare minimum, but its not advised for wheeling. large amounts of contact will be seen between body and tires. 4" suspension lift will provide better clearance, with a 6" suspension lift providing the optimal clearance while mainting a good center of gravity

38" tires: these can be run with 6" of lift and healthy amounts of fender trimming. its better to run around 8" of lift in order sufficiently clear these tires. once you get up into this size tire, you will be seriously taxing your stock running gear and drivetrain. a built up solid Dana 44 and rear 9" can handle this setup OK. adding a stonger rear, such as a Dana 60, is a safer option. depending on your typical wheeling enviroment, a swap to one ton running gear may be necesary to minimize breakage. for more information on this, refer to the Fullsizebronco.com message board, SAS forum.

anything bigger than 38" is going to be totally custom, and you really should upgrade to one ton stuff

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Next is

Gear Ratio Guide for Larger Tires; Scroll Down or Click, Another RPM/Gear Ratio/Tire chart if site reverts to main page; MIESK5 NOTE, Rough Country® removed this same chart from their site in FEB 2011 & company rep said it isn't there anymore. Source: by Rough Country® via broncocity.com

Take time to read all Notes.

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Then compare to Jer's info that he compiled from probably above & other sources;

Updated 11/11/03

Here are some really good equations for determining what gear ratio you may want to concider.

Remember that this is reference only and is based on equasitions from simple math.

Your tire size may be listed as 33/35/37, etc. but the actual measuremnet of the tire could differ once it is mounted on your rim.

Also this write is assuming you have an E4OD, or similar auto tranni.

These are figures that I came up with, to do your own just do:

Circumference of tire divided by the gear ratio you want.

Then compare you answer to the stock forward measurement of 25.5"s and then you will know if it fall over or under.

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Stock 29" tire (235/75R15), with 3.55 gears, 90.7" is circumference of tire, thus for every turn of the drive shaft, you go forward 25.5" or so.

33" tire, 3.55 gears = 103.7" circ, forward 29.2", about 15% more than stock

33" tire, 4.10 gears = forward 25.3" basically same as stock

33" tire, 4.56 gears = forward 22.7", about 11% less than stock

35"s with 4.10s = 26.8, 5% over stock roughly.

35" tire, 4.56 gears, 110.0" circ, forward 24.1", about 5% less

37" tire, 4.56 gears, 116.2" circ, forward 25.5", identical to stock (within error)

37" tire, 4.88 gears, forward 23.8", about 9% less than stock.

38.5" tire, 4.56 gears, 121.0" circ, forward 26.5", about 4% more than stock

38.5" tire, 4.88 gears, 121.0" circ, forward 24.8", about 3% less than stock.

FYI, for those who are thinking they can run a 35" tire with 3.55 gears...

35" tire, 3.55 gears, 110.0" circ, forward 31", about 22% more than stock. That means that your motor is working (and your clutch or torque converter) quite a bit harder to move your truck. That's why it dogs so bad.

If it falls "under" your motor does not have to work as hard to turn the tires, but it does it at a higher RPM. This means that as you go more "under" you lose top end. If it's "over" you'll have a higher top end, but less grunt.

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http://www.4lo.com/4LoCalc.htm This site give easy to use calculators for the info not listed above.

\\\

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Gear Ratio Guide for Larger Tires Source: by Jeff's Bronco Graveyard via our palFred W (Rosie, Seabronc) at SuperMotors.net



Now combine all with Tire - Lift Guide, Bronco & many makes; w/ Wheel Diameter, Width & Offset Source: by Skyjacker®

 

[Scott Milliken]

so i guess 35s would be the best choice then? there is a little bit of rubbing but its not bad, like wen i turn the wheel almost to the max... but yes the gears have been redone

thanks for all the info!