Spacers, scrub radius, etc? (1 Viewer)

[razzyrazz]

Okay so I'm moving from 18x9 +30 offset XD wheels to the Tundra TRD wheels at +60. I've read thru numerous spacer posts on here on what works and what doesn't. I have 285/70/18 tires. After doing the math and measuring I'm almost positive I won't need spacers.

I have read about scrub radius and the cons of positive scrub. I like the stance of the truck now and am tempted to at least use a spacer to keep this stance but am also thinking about going wider (2"). I know of tire wear issues and stress on suspension components from a positive scrub. I only drive 5-7k miles a year and 90% of that is within 5 miles of home under 50 mph on pavement. Wheel 5 or 6 times a year. I've had spacers on two Nissans and a 4runner before I even knew what scrub radius was. Never had any issues with suspension. Wheeled those fairly hard. Not debating positive scrub adds stress, I'm just wondering how much.

I am thinking about getting pretty large spacers for the look, since most of my driving is low stress on the suspension and remove the spacers for trips where I will be hitting trails to mitigate overall stress and also allow full wheel travel.

1. Aside from opinions on spacers, since the internet has beaten that to death, what are thoughts on the effect this would have?

2. Who is running with a positive scrub thru offset or spacers and what, if any, negative effects have you noticed.

Thanks

 

[grinchy]

Go ahead and get the 1.25 spacer and you’re back at 30 or 25mm
I run 1” spacer and don’t expect any issue with them. With my 35s the scrub is pretty unnoticed at 1/4” or less.

If you put on 2” and push out to 10mm and try to run more than 32” or so I think you’ll run into the fender.

 

[linuxgod]

Anecdotally many folks have run +20 to +30 offset for tens or possibly hundreds of thousand of miles either with wheels or spacers, and have not had any bearing issues, myself included (32k miles so far).

As far as handling goes, I get a small amount of torque steer under very hard acceleration, but I can’t say if it’s due to the lift or wheel offset or alignment setup. It’s very minor though. I suspect lift as it was greatly reduced when I added a 1” diff drop. It doesn’t bother me and my wife doesn’t notice it, which means it really is minor or I’m overly sensitive to nothing

 

[TeCKis300]

I'm particular to vehicle handling and dynamics (I use to race on tracks). Which makes scrub radius important to me. Yet practical concerns need to be balanced as well, including clearance for wider tires, and availability of spacer sizes.

I would say +30mm is in the range that is okay for the 200-series, especially when paired with larger diameter tires. Much below that, other practical concerns such as tire swing causing interference and steering pull become issues.

I run a ~35mm offset with my stock 20x8.5 +60mm wheels, 1" spacers, and 33.2" x 12.3" tires. I can feel a bit of pull and scrub, especially when fully laden and towing, with pedal to the metal climbing 7%+ grades. I'm not lifted at all, and the steering will pull in these conditions. Ideally, I would have preferred an offset of ~45mm.

The market also has .75" spacers which would have put me at a more ideal offset. Yet IMO, .75" spacer adapters are not safe, as there's simply not enough "meat" for a .75" piece of metal to carry lugs IMO. Which is why I'm using 1" spacers.

From a scrub radius and fitment perspective, a 1" spacer is preferred over a 1.25" spacer when used with stock wheels.

 

[JtFSU]

Interested in this as I have the TRD wheels. Currently have the stock 275/65r18 and they look silly to me. Too narrow coupled with being tucked in too far.

Are you running any suspension mods to get 285/75 to clear?

I had been considering 1” spacers. Would love to see some pics of yours before and after the spacers.

 

[razzyrazz]

Interested in this as I have the TRD wheels. Currently have the stock 275/65r18 and they look silly to me. Too narrow coupled with being tucked in too far.

Are you running any suspension mods to get 285/75 to clear?

I had been considering 1” spacers. Would love to see some pics of yours before and after the spacers.

I have an LX so YMMV. Only suspension mod is the AHC sensor lift. I get a slight rub at full lock in reverse, but I had that before the wheel change. I was running the plus 30 offset wheels for the whole time we've had the truck. I only drove about 20 miles today after the wheels were put on and idk if it's all in my head, but the truck seemed to drive smoother at the plus 60 offset, steered a tad easier which I dont really care about, but also seemed to eat the bumps even better. Doesn't look as good as the wider stance, but I'm now debating whether to get the spacers at all. Will have to put some more miles on to see if the difference is really there and parting with 200-300 dollars, dealing with spacers and perhaps sacrificing driving characteristics is worth the visual improvement.

 

[JtFSU]

I have an LX so YMMV. Only suspension mod is the AHC sensor lift. I get a slight rub at full lock in reverse, but I had that before the wheel change. I was running the plus 30 offset wheels for the whole time we've had the truck. I only drove about 20 miles today after the wheels were put on and idk if it's all in my head, but the truck seemed to drive smoother at the plus 60 offset, steered a tad easier which I dont really care about, but also seemed to eat the bumps even better. Doesn't look as good as the wider stance, but I'm now debating whether to get the spacers at all. Will have to put some more miles on to see if the difference is really there and parting with 200-300 dollars, dealing with spacers and perhaps sacrificing driving characteristics is worth the visual improvement.

What tires were you running previously vs on the TRD wheels? This could be a major factor in the improvement.

 

[razzyrazz]

What tires were you running previously vs on the TRD wheels? This could be a major factor in the improvement.

No change in tires, still 275 70 18 LT Falken Rubitrek.

 

[Pskhaat]

Tundra TRD wheels at +60. I've read thru numerous spacer posts on here on what works and what doesn't. I have 285/75/18 tires. After doing the math and measuring I'm almost positive I won't need spacers.

That puts you at a negative-to-stock scrub of ~14mm. Ain't significant but you can feel that, maybe a set of 7mm spacers to help correct?

use a spacer to keep this stance

What utility does this stance provide?

Not debating positive scrub adds stress, I'm just wondering how much...I am thinking about getting pretty large spacers for the look,

I'd be more upset at the steering compliance and geometry change than simply stress on the components. And sincere question, but when did the really wide stance/look thing come into vogue?

 

[Pskhaat]

Currently have the stock 275/65r18 and they look silly to me. Too narrow coupled with being tucked in too far.

¿Wasn't stock actually 285/60r18? 100s had 275/60r18?

All personal opinion here but I think 275 width is the perfect width for these trucks. I'm just frustrated there is no 275/85r16 nor 275/75r18 sizes available.

 

[TeCKis300]

I'd be more upset at the steering compliance and geometry change than simply stress on the components. And sincere question, but when did the really wide stance/look thing come into vogue?

All personal opinion here but I think 275 width is the perfect width for these trucks. I'm just frustrated there is no 275/85r16 nor 275/75r18 sizes available.

While I don't like calling it stance, there is some legitimacy to spacing out the tires.

As mentioned, taller tires should run lower offset to keep optimal scrub radius and steering geometry.
Lifting the vehicle via a tire lift raises its center of gravity. To regain lateral stability, it should intuitively make sense to increase the track width, in order to maintain handling and reduce the potential for rollover.

I respectfully disagree on 275s. The vehicle came stock with 285s. Tire width is important for braking and cornering traction. By lifting, narrowing the contact patch, and going with an AT tread/compound - that can only result in objective dynamic performance that will be worse than stock. Significantly. I'll reach for the safety argument here as that's important when I transport my family to ensure the vehicle can still stop and perform evasive maneuvers.

While people make the argument for better traction off-road, I'll descent again on the basis that a 275 exposes the wheel face as it sits practically flush without any bulge. In pinch situations off-road where the sidewall of the tire is against terrain, I want rubber against the terrain rather than my wheel face. Classic off-roaders do a smaller and narrower wheel. In lieu of the wheel, I say wider tire.

I've found the wider and spaced out wheel/tire to be a benefit to protecting the body of my vehicle too. The side terrain is in contact with the side of the tire that is flush with my bodywork., rather than the steps or body. The stock inset and narrow tire would have me rubbing my stock steps on several occasions. Best would be to have sliders, but even in that scenario, I'd rather the tire be the wider contact point.

 

[razzyrazz]

FWIW I corrected my tire size. I was confused with the size on my last 2 trucks. Correct size is 275/70/18 which is a 33.4 x 11 tire. Sorry.

 

[tincan45]

@TeCKis300 is right. I'm re-posting something he mentioned on another thread that opened my eyes to the whole offset/scrub debate. I think this should be converted into reference diagram for anyone deciding on wheels and tires.

Wheel	0 Offset Point (Estimated)
31.2 " (Stock)	60mm
32.7" (RW)	50mm
33"	48mm
34"	40mm

Using this as a reference, you can decide what compromises you want to make with regard to positive or negative scrub.

 

[Pskhaat]

Wheel	0 Offset Point (Estimated)
31.2 " (Stock)	60mm
32.7" (RW)	50mm
33"	48mm
34"	40mm

That seems off So on my 100 (though the calculations are the same) I run 295/70R18s (nominal 34.3") on +60 OEM steel wheels. The offset required to meet factory scrub is -13mm. So that table doesn't seem to be consistent, as that would mean I need more than -20mm. Are my own calculations incorrect?

Unfortunately on the semi-float rear in order to maintain hub-centricity with the steelies I can't space more than 7mm, which I've done. I could use maybe another 5-6mm, but I've called it good being a bit negative-to-factory scrub.

 

[luke27617]

I am running OEM wheels with 33" tire and in process of ordering .75" spacers. Want wider stance but don't want wheels going too far out and having debris from tires cause corrosion to fenders. 1" seems flash which may cause problems with time. .75 seems like a safe bet.

 

[Pskhaat]

I respectfully disagree on 275s. The vehicle came stock with 285s.

It did spec 285s. Even in other markets.

to ensure the vehicle can still stop and perform evasive maneuvers.

The US Army did a study on this maybe 10+ years ago or so (and of course...for the life of me I can't find the link) discussing numerous things but inclusive of tire aspect and safety considerations in-theater. A lot was discussed for high speed pavement and evasive maneuvering.

The higher aspect tire increased total surface area in comparison to wider (or in the military, dual wheels) under braking and thus deformation of the tire. Deformation is more elongated. Though roughly the nominal force defines this, more contact area would allow for greater friction.

I'd love to see even do a modern test here. I'd do that myself alas that pesky job thing taking up my entire life...

I'll descent again on the basis that a 275 exposes the wheel face as it sits practically flush without any bulge

agree. Would love a 7" OEM steelie. Hard to find, these. And I want them for the very same reason you just stated.

 

[TeCKis300]

As a point of reference, my stock 20x8.5" 60mm offset wheel, with 1" spacer (~34mm effective offset), and 305/55/20 (33.2"x12.3") tires. Pretty flush with the side of the body and I've not had any issue with rocks kicking up damaging the paint on the vehicle. Or the trailer I tow.

You can also see where it's helped keep terrain off my side steps in particular, because the tire is the widest point by a tad. I would have sustained more significant damage if my tires were inset in a pinch or side sliding situation.

The US Army did a study on this maybe 10+ years ago or so (and of course...for the life of me I can't find the link) discussing numerous things but inclusive of tire aspect and safety considerations in-theater. A lot was discussed for high speed pavement and evasive maneuvering.

The higher aspect tire increased total surface area in comparison to wider (or in the military, dual wheels) under braking and thus deformation of the tire. Deformation is more elongated. Though roughly the nominal force defines this, more contact area would allow for greater friction.

I'd love to see even do a modern test here. I'd do that myself alas that pesky job thing taking up my entire life...

The takeaway isn't just taller. Many times the compromise in fitting a larger tire is that one can go taller if compromising some width. In the 200-series, one can go taller and wider, up to 34s rather easily. Definitely without a need to downsize any dimension. My objective is to have the rig do everything better. Not to trade better off-road performance for significantly compromised road performance. Especially as that's where I do 99% of my driving.

 

[Pskhaat]

@TeCKis300 is right. I'm re-posting something he mentioned on another thread that opened my eyes to the whole offset/scrub debate.

Do we know what the kingpin angle KPI is?

 

[TeCKis300]

Do we know what the kingpin angle KPI is?

Kingpin angle, aka steering inclination angle, is the black line in this graphic. Critically, note how it intersects the mid-point of the tire at the contact patch. That is the "hinge point" of the tire as it steers.

Here's what scrub radius looks like when KPI doesn't intersect that point. The resulting effect is that the tire will scrub and lose traction as it turns. Potentially causing a loss of traction in low grip slick road scenarios. You'll notice it in tight turns in a parking structure for example with the tires squealing. It will pull on the steering as significant acceleration or braking force is applied. Steering effort will increase.

Sure, all this can be dismissed. It does matter however slight one imagines the impact to be.

This video really helps explain things:

 

[Pskhaat]

Kingpin angle, aka steering inclination angle, is the black line in this graphic.

Right...but do we know the actual value of the angle is? Asking because my own KPI constant might be off and is critical for proper scrub offset calculations.