Wider track vs scrub radius - JeepForum.com
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post #1 of 7 Old 07-12-2020, 03:46 PM Thread Starter
Galligher
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Wider track vs scrub radius

I have a question concerning height vs track vs scrub radius. I have a 95 with a 330hp GM crate engine, Holley Sniper FI system, and Corvette ram-horn exhaust manifolds (exhaust sound is actually somewhat tame). My build is to make a vehicle enjoyable to drive (can actually go uphill against the wind), with decent street manners, can do some off-roading, and my daughters/wife can drive. I currently have 31x10.5015 BFG KO2’s on TJ Canyon rims, 2.5” lift OME springs, and a 2” body lift. I have been trying to keep COG lower with the sbc but still looking like a Jeep. I have TJ flares and will be adding a tummy tuck, homebuilt skid, and 8.8 this winter. In starting to look at local clubs and trails as I am completing the beginnings of the jeep, looks like I may need to go to 33’s for many of the trails as a suggestion. My concern is that with 33’s I will be 2” higher of close to 100% of the total vehicle weight over stock, 2.5” higher for about 80-90% of the weight for my OME springs, and 2” higher for 20-30% of the weight due to the body lift. So I am calling it 4” of total weight. I am a little over an inch wider due to the 10.5 tires vs stock 235’s. If you go by the rule of thumb to go an inch wide for every inch up, I will need another 3” with 33’s and my current mods. If I go wider, I will change the scrub radius almost 2”. I also don’t want to go with 12.5” tires over the 10.5” due to steering/rain/wandering issues.

The question to keep the compromises, is it better to go wider for the stability or stay close to the stock scrub radius to keep steering, braking, and hitting a puddle well (vice positive scrub radius issues from less backspacing). If a deer runs in front of me in the evening, which one is saving my butt as the two dynamics are fighting each other?


1995 Wrangler - 330hp sbc crate engine, 700r4; OME springs, soon an 8.8
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post #2 of 7 Old 07-12-2020, 05:06 PM
jsawduste
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Factory scrub is always the ideal situation. Keeping the handling properties would far outweigh any desire for extra width.


You're not going high or large enough where the extra width would be a necessity or even desirable. You may have to adjust the steering stops on the knuckles a tad.to keep the tire off the spring. The minor loss of steering radius wont be noticeable.
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post #3 of 7 Old 07-12-2020, 05:38 PM
92 Green YJ
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You are seriously over thinking this.

12.50 wide tires are the norm for 33s and 35s. For an Offroad rig you generally want the wider tire because you get more contact area which in turn equates to more traction. The 8.8 you are planning to install is narrower than the 35 rear which In turn. Ames it narrower than the front 30. This is good for your turning radius. As a general rule of thumb you want the rear to be narrower for better turning.

Personally, I am on full width 1 ton axles with 13.50 wide tires. I am 83”s wide outside of tire to outside of tire. That width means more stability overall.

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post #4 of 7 Old 07-13-2020, 06:10 AM
Waternut
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Not to say scrub radius isn't an important thing but realistically, it's not saving your butt if a deer jumps out in front of you any way you look at it. If you're in a lifted Jeep and you swerve heavily, better start praying. If you slam on the brakes to avoid the deer, more rubber on the road will always give you better braking provided your brakes are strong enough to overcome the rotational mass of the tire (yes a wider tire has more rotational mass but we aren't talking about a lot).

IMO having driven several different setups, you'll notice that your steering will feel a little different if you go to a bigger tire but probably not if you go to a wider tire. If you run the same tires on stock wheels and a wheel with less backspacing, the thing you'll notice more than anything is the tire rubbing or not rubbing the leaf springs at full lock. The way the different wheels handle when driving around town will be pretty trivial and I think you'd be hard pressed to tell a difference given the sloppy nature of a lifted Jeeps steering geometry and 30+ years of wear and tear on the steering components.
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post #5 of 7 Old 07-13-2020, 04:58 PM Thread Starter
Galligher
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Thanks everyone, copy on it all. This is my first 4WD vehicle, but have owned it several years now as it seems I have been slowly replacing everything. Definately not new to vehicles or wrenching as I have been on this earth for a while, but some of my typical vehicles from my past: 69 Mustang Mach1, 76 Firebird Formula, many Mustang 5.0's (some with 351's though), T-Bird TurboCoupe, and an oddball fun one - Merkur XR4ti. Besides the Wrangler, it has been boring family vehicles the last 8 years or so while I have been paying for kid's colleges. My goal is to keep it driving "realistically" as if the family enjoys driving it, it is easier to fund all my changes without discussion... I have had some cars with really hard clutches, sidepipes, loud, smelled like fumes, fast, fun, obnoxious but not something "family freindly". Those would require a little more persuasion today.

Understand on the leaf spring clearance, I did that when I had stock springs with the 31x10.5x15's and adjusted the stops as it just barely hit. No issues with the change to OME's for clearance with tires, looks like I have another inch of clearance on a hard turn. My concern with 12.5" wide tires was the "wandering" along road grooves and the increased chance of hydroplaning, thus considering 33x10.5x15's. I bought some really neat centerline convo pro style rims (I loved these back in the late 80's and 90's) for it when I first purchased the jeep, not really understanding the difference between rims/tires on Jeeps vs musclecars. Call it an "impulse buy"... They are 15x10's with I think 3.75 BS, thus I have always had the thoughts of 12.5" tires in the back of my mind to use those rims. I just can't bring myself to sell them as I loved these rims back in the day. It would be great to use these if I knew it wouldn't make the jeep too much worse in driving.

Also copy on the brakes. I made sure those were good first thing, but are still a stock setup. We'll see how the braking system needs adjustments when I install the 8.8 with rear discs.

1995 Wrangler - 330hp sbc crate engine, 700r4; OME springs, soon an 8.8
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post #6 of 7 Old 07-14-2020, 04:17 AM
fishadventure
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The 15x10s imho are a bit wide for off road performance with a 33

Maybe locate some 15x8s new or used and offload the 10s to someone needing to get to the mall after school. If you won’t be running trails they shouldn’t matter as much, though. If you are street mostly then an AT tire won’t track the road like a lot of MTs do.
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[size=“3”]Shackles & D-rings are different things.
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post #7 of 7 Old 07-15-2020, 06:27 AM
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Hydroplaning is much more of a concern with a wide street tire like you probably would've had on all your muscle cars. Hydroplaning happens when the tire can no longer clear the amount of water that's required and the tires begin to float. With a big mud tire or even an all terrain tire, your surface area is greater but the tires can clear so much water that it's extremely unlikely.


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