Elusive Scrub Radius

[VA-RAM]

So...
Looking at getting some new (to me) wheels and tires on the 2017 1500 Laramie. Been doing some research and have run across a term called scrub radius. Never heard it before.

What I am looking at (KMC XD779 Badlands, 20x10 with Fuel Grippers M/T 33x12.5x20 and a -12 offset) will fit according to the wheel/tire calculators with, I believe, is enough clearance of the brakes and UCA. The calculators say that there will be a Positive 1.25" scrub radius with this set up.

https://www.wheel-size.com/calc/?wh...l=1.96875in&wcl=1.1875in&scl=1.96875in&sr=0in

The stock 20" Laramie wheel and 275/60/20 tires (19mm offset) tires show a ZERO scrub radius on the calculator. I don't mind the tires moving out about 2" (with the difference in OEM vs XD779 offsets), as I intend to do a front lift of about 2" anyway in the near future...

The question for the forum and for discussion is:

What is "too much or too little" scrub radius ?
What affect on braking and handling will the 1.25" positive scrub radius have on my Ram?
What is the prevailing "ideal set up" (if there is such a thing) for the 1500 Rams?


Ultimately, will this set up leave me pissed off at excessive tire wear and reduced ride/handling?

ready, set,...GO!

 

[kurek]

The ideal amount of scrub radius is none, a straight line from the upper ball joint through the lower ball joint to the center of your tire contact patch.

How much more than that you're willing to put up with is a bit subjective, an inch of extra radius usually won't bother anybody and you can see that people change wheel offsets to fit a bigger tire or get their visual aesthetic exactly how they want it, usually without any consideration for how that's going to affect the arc their wheel travels.

From my experience the most noticeable drawback from increasing radius is that steering and lane-holding becomes busier, the truck is influenced more by potholes and road crowns and expansion joints. I wouldn't say it becomes dangerous with an inch or two offset but at the end of a long day driving I'd expect to be a bit more exhausted driving a truck like that vs. one with ideal geometry.

 

[rod from md]

While i cant speak to scrub radius specifically,i can give my "real world" experience

bought my 14 last april, and waited until almost july for the wheels, as delays due to covid touched everything , especially from overseas.

I drove my truck for those months w brand new stock sized nittos and was super impressed w the ride and handling, except a little "wiggle" from the rear over diagonal bumps ( which i have read about and know theres a solution )

fast forward to the 35s on 10 wide wheels, and that slightly magnified the rear end issue, but otherwise, wasnt alot of big changes to ride and handling that i noticed . probably the larger/heavier wheel/tire has some real effect on braking and ride, but , again, its not a "oh my god" difference

. There will always be a tradeoff with mods, and wheel /tires are one that you def can see/feel
I accept the tradeoff, and the likely decreased lifespan of suspension/brakes etc . Mine is not a daily driver so any wear will be time extended in comparision to a daily driver.

It seems that many before me also weighed the pros/cons and moved ahead as i did

BUT the new look IS awesome.

 

[CVX20]

Too little scrub radius will cause steering to be lighter and too much will make it heavier.You'll notice too much in parking lot tight turns.Will act like it wants to push strait through.Too little as mentioned will make it harder to maintain a strait line at higher speeds.

 

[VA-RAM]

Well since this is a straight trade, can't complain too much if it isn't to my liking since it doesn't cost me anything. I would prefer the wheels with +19 offset vs the -12 but think I can live with it. Just have to make the switch and see what happens.

 

[ram1500rsm]

Nothing will happen. Go for it. You're not going with a -200 offset. Little positive or negative scrub is better than zero. I have yet to experience ill effects because of it and Ive ran fatties in my sport/muscle vehicles and bigger tires with a little more wheel in my offroad applications. Pay attention to your alignment and understand how your alignment can affect the wear in your tires and make your truck track better. More important in this context than the wheel/tire youre thinking to run. Don't worry about scrub ratio with that setup. My truck doesn't wander, never have and she has almost 98k miles. Running aggresive MT tires in 315/70/17 lifted 2.75" In the front. I can do 80mph with one hand. Same with 37x12.5x17 I had before. Zero issues with my tires wearing uneven. I run 17x9 with -12offset. Same wheel size and tire size I've run for years in many other applications.again pay attention to your Aligment and the rigth suspension parts for your application.

 

[VA-RAM]

Nothing will happen. Go for it. You're not going with a -200 offset. Little positive or negative scrub is better than zero. I have yet to experience ill effects because of it and Ive ran fatties in my sport/muscle vehicles and bigger tires with a little more wheel in my offroad applications. Pay attention to your alignment and understand how your alignment can affect the wear in your tires and make your truck track better. More important in this context than the wheel/tire youre thinking to run. Don't worry about scrub ratio with that setup. My truck doesn't wander, never have and she has almost 98k miles. Running aggresive MT tires in 315/70/17 lifted 2.75" In the front. I can do 80mph with one hand. Same with 37x12.5x17 I had before. Zero issues with my tires wearing uneven. I run 17x9 with -12offset. Same wheel size and tire size I've run for years in many other applications.again pay attention to your Aligment and the rigth suspension parts for your application.

Thanks for the input RAM1500RSM...
Its comments like this with all the others that give a good overall idea and make for a good place to make decisions.
Appreciate the forum members everyday! I'll post the pics once the deal is done (and I get the thing washed!! Geez its dirty!)