Seeking engineering widsom - tires scrubbing after mild lift but alignment good?

[DesertDoc]

Hello All,
I have a problem of excessive tire wear after a mild spacer lift & spider trax install on a 2017 otherwise stock 200-series. Wondered if anyone might be able to shed some light as to what is wrong.

Our off-road usage is primarily desert tracks and dunes. Achilles heel of the stock 200 series in the dunes is its low approach and departure angles, necessitating occasional trips to Toyota to re-fasten the front/rear stock bumpers. I looked for a solution via a small lift rather than steel bumpers.

Max angle of LC200 lateral stability is 42˚. Max angle of repose of dry sand dune is 34˚. But the 8˚ margin of safety can be significantly eroded by passengers/cargo, downhill wheels digging into soft sand etc. Raising the CoG with a bigger lift might lead to a roll over if caught side-sloped, which shouldn't but can happen. So went with a smaller spacer lift rather than a OME 2”lift. Installed OME nitrochargers, 20mm (8/10”) front and rear spacers on the stock coils, remained with stock UCA’s, and added spidertrax 1.25”wheel spacers to widen the track and offset the raised CoG. Alignment after install reported everything back in the normal range. Steering and braking were neutral but noted a pull to the right under harsh braking that was not there before. The 1” of lift seems only little on paper but was just right for the dunes.

Stock tires were 30k miles run at time of install with even wear. Now 70 days later the inner edges on both front tires are becoming very scrubbed, in a pattern that indicates toe wear and or exaggerated camber wear. I had the alignment rechecked yesterday at another shop and they found everything correctly aligned, including caster and camber. They asked if the wheel spacers might be a cause and suggested to remove them which of course I can do. But I see a lot of people on mud running the spidertrax and see no reports of any tire wear or other problems.

Is there is a different caster/camber combination from stock required once wheel spacers are added?

Garage installed front spacers as ring under the shock (photos below). I have since ordered and received yesterday the toyota OEM spacers (which install above the shock) and wonder if swapping them over would change the geometry?

Appreciate any wisdom that anyone who has been through this before could share. Otherwise it would seem I need to go with a 2" OME coil / shock combo or just return the vehicle to stock and add the OEM toyota spacers and see if that does the job. Many thanks if you took the time to read all this and for any insights.

 

[TimCFJ40]

With stock tires at 30k miles, are you sure you didn't just notice uneven wear that was already starting? The pic of tire wear doesn't look abnormal for stock tires at 30k+ of usage, especially if you didn't rotate them regularly. Your spacers and spacer lift should make minimal difference, assuming the alignment is indeed correct, which two shops have confirmed.

BTW, I haven't seen that sort of spacer lift before. It seems like a pretty thin piece of metal to take all of that side load from the spring perch, but that's not why your tires would wear unevenly.

 

[linuxgod]

Do you have a printout of your alignment specs?

It looks to me like both the inner and outer edges are wearing, not just the inner edge. If that's the case I'd suspect either:

1. Excessive caster. More caster causes more tire lean when turning, wearing the edges more
2. Low tire pressure, which can cause tire edge wear.

 

[TeCKis300]

Are you on stock sized tires? (31.2" tires) And Spidertrax 1.25" spacers? (effective offset +28mm).

It's indeed a symptom of incorrect with scrub radius. I mention it often as it's not an easy concept to understand, but still important. Wheel offset is integral to the steering geometry of the suspension, which itself is also tied to the overall diameter of the tire. Many can get away with more aggressive offsets when paired with larger diameter tires. Suspension lift doesn't really have much to do with this geometry.

If scrub radius is not right, when turning, the 2 front tires effectively point at slightly different directions. Instead of working together and turning the car towards the same point, they will fight each other and point in slightly different directions - hence the term scrub radius. That is why you're seeing wear and scrub on the tire shoulders. There are other symptoms too that you might notice: steering pulling on aggressive acceleration or decel and reduced traction in turns.

31.2" tires need a stock offset of 60mm. 28mm is way off. Conversely, if you were to put say 34" tires, the optimal offset is ~40mm. Much closer with less impact.

 

[DesertDoc]

Many thanks for all your considered replies.

@TimCFJ40: I am pretty sure the uneven wear is only post install, I have been watching out for it as I wasn't quite comfortable with the whole set-up. Agree with you on the coil spacer, seems small for the forces it has to sustain. I did order the OEM spacer which arrived yesterday and will swap it out.

@linuxgod: unfortunately didn't ask for a print out which would have been smarter, just looked at it on the screen. Will remember for next time.

@TeCKis300: yes to stock tires and 1.25" spydertrax. And yes to the scrub radius problem, that logic makes good sense to me. Everyone else is using the wheel spacers to accommodate a larger diameter tire which will in itself bring the steering geometry closer to the original neutral point. I was trying to use it to bring down the CoG. By retaining the stock tires I am too far out. I can feel it too as you suggest with a pull under hard braking and in a public car park environment where the concrete floors are smooth or painted I can feel the traction breaking away slightly in tight turns even though speed is only 2-3 mph. Thank you for your insight. I will take out the spydertrax now while on stock size tires.

Following the same logic if we increase tire size then the stock wheels won't be optimal. I presume this is why I see many people with aftermarket rims on Mud. Is that likely necessary for a 1 size increase up to 285/65/R18 (31.5 to 32.6 inch) do you think?

Many thanks for all your replies.

 

[TeCKis300]

The parking garage test with squealing tires is a sure giveaway that the tires aren't exactly working together, and often what people notice the most.

You're right that as we change tire size, that it's necessary to adjust offset - either with wheels or spacers. Most do it out of style or clearance. Sometimes they get scrub radius accidently right, or right enough. Other times, way wrong, but the symptom may be hard to comprehend and they live with it. The symptoms are magnified depending on the severity of the offset to scrub radius discrepancy.

For a 285/65R18 (32.6") tire, optimal offset is ~50mm. We know this from factory approved Rock Warrior (+50mm) wheel fitments of a 285/70R17 (32.7") tire.

IMO, a scrub offset discrepancy of about 10mm is okay. It really depends on the individuals tolerance and performance expectation.

 

[DesertDoc]

To close the story on this for anyone who might read it in the future and for those who kindly contributed their wisdom:

I removed the spidertrax, replaced the tires with new stock sizes 285/60/R18 and was quite surprised by how much the ride and handling immediately improved. At the time i had installed the spacers I also had installed OME Nitrocharger shocks. The ride felt off after that, the vehicle seemed to constantly micro-rock from side to side picking up the slightest imperfection in the road surface and I had assumed the shocks were not matched to OE springs. But it turned out not to be. The issue was the wheel spacers and once removed the the ride was excellent on the nitrochargers. Clearly evidencing the offset need to be within the correct parameters for an optimum ride quality.

I changed out the 20mm (1") under shock spacer for the Toyota 10mm (1/2") OE front suspension top of mount spacer. Surprised to see I gained 10mm (1/2") in additional lift. If you are not climbing over boulders I think this is a good amount of lift for most people and is simple and inexpensive and does not change the suspension geometry. For my use in desert and dune environments it is sufficient. My experience from this is if a mild lift might suit you this is something to try first before looking at new shocks and springs.