Front hubs going bad at 25k?

[CorneliusRox]

Hello guys,
I have a 2021 Model 3 Performance and recently got new tires. I went with some 355/35R20's and had a few mm's clearance to the upper control arm mounting on the knuckle.
After I let the car down off the hoist, the knuckle either deflected some or the hub deflected some and the knuckle contacted the tire. It's a very light contact, and I understand there's deflection in anything when a load is applied, but I was surprised to see any real deflection based on vehicle weight alone.

I assume the knuckles were designed with more stiffness than this, which would mean the hubs were on their way out.
I pulled the wheels and reviewed the hubs, but can't find anything wrong with them.
Has anyone had a hub go bad yet? What was the mileage? I've never had a hub go bad on such a low mileage vehicle.

Also, I'm switching back to 245/35R20's today to give some clearance. But was just surprised how much deflection happened here.

 

[The Other Dan]

I think you meant 255, not 355.
It shouldnt have changed the sidewall height by that much, if the only difference really is going from a 245 to a 255.
You sure you didn't go from a 245/30 to a 255/35?

 

[dsgerbc]

The knuckle/hub are most likely fine. Tires aren't rigid though. Any tire with >=27" claimed diameter is risky, due to slight actual size variances. Try lowering the pressures a bit and see if it helps with clearance. Although I would not want to run 20" on MI roads with less than 45psi. I run 35psi all day on 19" though.

Clearance should get better as these wear. Or have them shaved a hair, if you haven't driven on those much yet.

 

[CorneliusRox]

The knuckle/hub are most likely fine. Tires aren't rigid though. Any tire with >=27" claimed diameter is risky, due to slight actual size variances. Try lowering the pressures a bit and see if it helps with clearance. Although I would not want to run 20" on MI roads with less than 45psi. I run 35psi all day on 19" though.

Clearance should get better as these wear. Or have them shaved a hair, if you haven't driven on those much yet.

Sure, I was just surprised to see the tires get any closer on the top when set onto the ground.
I'm with you, I'm not going to run low pressure on these roads. I used to live in MN and the roads were significantly nicer there.

I'm guessing this is mostly brand to brand and model to model tire variation.

I think you meant 255, not 355.
It shouldnt have changed the sidewall height by that much, if the only difference really is going from a 245 to a 255.
You sure you didn't go from a 245/30 to a 255/35?

You're right. Fat fingers.
Stock size is 235/35R20.
I was running 255/35R20's (BFGoodrich g-Force COMP-2 A/S+). They only lasted about 15k. Pretty even wear, but there was definitely some wear from contacting the knuckle. Also, those tires gripped well and looked great, but boy were they noisy.

The new tires are 255/35R20's (MICHELIN PILOT SPORT ALL SEASON 4), but I think their physical dimensions are slightly different. A little deeper tread mostly, so I think rolling diameter and even width are slightly larger.

I had them order up 245/35R20's and 245/30R20's that I'm going to try today.

 

[dsgerbc]

Just curious, who's letting you try different sizes to see what fits?
P.S. Also lived in MN. Real winter vs a constant freeze/thaw cycle makes a lot of difference for roads.

 

[CorneliusRox]

Just curious, who's letting you try different sizes to see what fits?
P.S. Also lived in MN. Real winter vs a constant freeze/thaw cycle makes a lot of difference for roads.

On the MN comment, I agree. We'd get 3-4 weeks of actual 35deg below freezing before windchill. I like MI winters better.

And Discount Tire Co. I may have convinced them it was their fault since they recommended this tire and the last tire was the same size and fit.

 

[CorneliusRox]

I ended up with 245/35R20's.
It doesn't make sense, they should only give 3.5mm extra clearance to the knuckle, but they give about 15mm. Just goes to show that tire sizes are more of a guideline than a true measurement.

MICHELIN PILOT SPORT ALL SEASON 4 - 255/35R20 on hoist:

MICHELIN PILOT SPORT ALL SEASON 4 - 255/35R20 on the ground:

Knuckle damage:

MICHELIN PILOT SPORT ALL SEASON 4 - 245/35R20 on the ground:

 

[CorneliusRox]

I will say, these tires are very quiet for a non-acoustic mat tire.

I also did some further knuckle and hub testing. Basically I welded some large nuts to a rod I had lying around so I could put them on the hub with lug nuts holding it firmly in place and actuate the assembly with some force. The hub looks and sounds great still.
This amount of flex must be from knuckle and wheel deflection. It's significantly more than I'd expect to see out of OEM parts.

 

[dsgerbc]

I'll try to remember to measure the amount of flex of the upright next time I use my alignment hub stands. I doubt there's much.

Michelin does claim their 255/35/30 tires are of a 27.3" diameter, which is very-very borderline. Hence, it's totally not surprising to see them rub.

Those 245/35/20 do look a bit undersized though, since they should look only 1/4" shorter there.

 

[Lindenwood]

This must be tire deflection. This is more than I’d expect, but it is the same thing for folks who don’t have rubbing on the knuckle during normal driving with a tight fit, but have significant rubbing while racing. (Note: the wheel otherwise doesn’t move relative to the knuckle).

There is no way the hub or the wheel itself is deflecting 2-3mm closer to the upper ball joint without horrible noises while driving.

 

[CorneliusRox]

I'll try to remember to measure the amount of flex of the upright next time I use my alignment hub stands. I doubt there's much.

Michelin does claim their 255/35/30 tires are of a 27.3" diameter, which is very-very borderline. Hence, it's totally not surprising to see them rub.

Those 245/35/20 do look a bit undersized though, since they should look only 1/4" shorter there.

Yeah, now that's I'm looking through and reading their measurements, they have a very wide and tall 255/35R20. I wonder why.
And I agree, the 245/35R20 is surprisingly smaller.

This must be tire deflection. This is more than I’d expect, but it is the same thing for folks who don’t have rubbing on the knuckle during normal driving with a tight fit, but have significant rubbing while racing. (Note: the wheel otherwise doesn’t move relative to the knuckle).

There is no way the hub or the wheel itself is deflecting 2-3mm closer to the upper ball joint without horrible noises while driving.

How would you even know if it has horrible noise? My Model 3 is the loudest vehicle I own. ha ha
That's comparing to a 2022 GMC Sierra HD Diesel truck and a 2023 Cadillac CT5-V. I'm constantly trying to figure out how to make it quieter. Seems like the windows don't seal well enough, and the front cradle transmits a ton of noise through the chassis.

I do get what you're saying about tire deflection, but I would consider these to be more of a touring tire and be much stiffer (especially at 42psi) than a race tire.
I also completely agree that any measurable amount of flex on the wheel/hub/knuckle at ride-in height seems crazy. A large pothole event would then result in what? Something severe happening.

 

[Lindenwood]

Yeah, now that's I'm looking through and reading their measurements, they have a very wide and tall 255/35R20. I wonder why.
And I agree, the 245/35R20 is surprisingly smaller.


How would you even know if it has horrible noise? My Model 3 is the loudest vehicle I own. ha ha
That's comparing to a 2022 GMC Sierra HD Diesel truck and a 2023 Cadillac CT5-V. I'm constantly trying to figure out how to make it quieter. Seems like the windows don't seal well enough, and the front cradle transmits a ton of noise through the chassis.

I do get what you're saying about tire deflection, but I would consider these to be more of a touring tire and be much stiffer (especially at 42psi) than a race tire.
I also completely agree that any measurable amount of flex on the wheel/hub/knuckle at ride-in height seems crazy. A large pothole event would then result in what? Something severe happening.

Performance tires typically have much stiffer sidewalls and belts, actually!

It makes sense that you’d have slight bulging at the top with the bottom of the tire on the ground.

 

[CorneliusRox]

Performance tires typically have much stiffer sidewalls and belts, actually!

It makes sense that you’d have slight bulging at the top with the bottom of the tire on the ground.

Yeah, okay. That does make sense in my head.
Thanks for calming me down on the whole 'knuckle deflection' idea I was heading towards!