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LMR SVE SP2 Wheels Cracking

Ewheels

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CRACKED!!!

I purchased these wheels awhile back as my track-only set and used them for the first time this past weekend at Buttonwillow and one of them cracked.
I contacted LMR and they sent out a replacement the same day. (Their customer service is incredible - thank you LMR)

My concern is, is this going to happen again?? I seriously doubt the crack was caused by driving too hard. A friend of mine suggested that it was either a defective wheel or it was caused from over-tightening the lug nuts. The owner's manual says 150 lb-ft which is what I was doing. Though he mentioned that 150 lb-ft may be required for factory lug nuts but using forged steel lug nuts (like I have) may be too much for the wheel. Does this sound accurate? Are these wheels prone to cracking? Should I lower my lug nut torque? Please advise.

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Bybcous

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, i was waiting doe these too come back in stock but this post maybe i should look at somrthing else
 
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Ewheels

Ewheels

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I mean, this crack could have been there since day 1 and I just happened to notice it at the track but who knows. I hope its just a defective wheel but it makes me wonder
 

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, i was waiting doe these too come back in stock but this post maybe i should look at something else
To be fair, it's 1 wheel, and they replaced it very quickly from the sounds of it. Other makes have had wheels crack before. I'd personally wait to see if any other wheels end up with the problem before writing them off.
 
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Ewheels

Ewheels

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I was talking with a guy from LMR and he said the lug nut torque could definitely be a possibility. 150 is required for factory nuts but stronger aftermarket ones "should not be tightened to those specs." He recommended 110 lb-ft and adjust from there as needed.
 

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1 old racer

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Just my opinion. I dont know it the LMR SVE SP2 wheel is a cast or forged wheel but I strongly recommend only a forged wheel be used on any track event. A cast or formed casting is great for daily driving. Just google the difference and it will become clear why. I love those wheels and when they are back In stock I am buying a set for daily use. I am very happy to see that LMR stands behind their product.
 
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Ewheels

Ewheels

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Just my opinion. I dont know it the LMR SVE SP2 wheel is a cast or forged wheel but I strongly recommend only a forged wheel be used on any track event. A cast or formed casting is great for daily driving. Just google the difference and it will become clear why. I love those wheels and when they are back In stock I am buying a set for daily use. I am very happy to see that LMR stands behind their product.
The SVE SP2 wheels are rotary forged (cast face and forged barrel). I would love to use fully forged wheels but I don't have that kind of budget. I know plenty of people who track with partially forged wheels without issue. Hell, most spec groups in NASA use partially forged wheels. (The spec E36 group from this last weekend were all using Apex wheels which are rotary forged.)
 

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Thats the risk when chasing the coolest new wheel designs. You don’t really know how good the structural engineering is behind them. Only time will tell. Thanks for beta testing them for the rest of us tho :)

My understanding is that the 150 lug nut torque is required to meet the clamping force when on a wheel stud as large as it is on our cars. It seems high, but its a massive lug nut so the clamping force is normal and not as high as it would seem to a lay person. But... I wouldn’t trust what the LMR customer service guy says (or even what I’m saying) unless one of us has an applicable engineering degree (we don’t).

i went with Apex for my track wheels, but because their latest SM-10 design was a sure thing, but at least they as a company have a good track record (pun intended) with wheels used on the racetrack.
 
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Ewheels

Ewheels

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Thats the risk when chasing the coolest new wheel designs. You don’t really know how good the structural engineering is behind them. Only time will tell. Thanks for beta testing them for the rest of us tho :)

My understanding is that the 150 lug nut torque is required to meet the clamping force when on a wheel stud as large as it is on our cars. It seems high, but its a massive lug nut so the clamping force is normal and not as high as it would seem to a lay person. But... I wouldn’t trust what the LMR customer service guy says (or even what I’m saying) unless one of us has an applicable engineering degree (we don’t).

i went with Apex for my track wheels, but because their latest SM-10 design was a sure thing, but at least they as a company have a good track record (pun intended) with wheels used on the racetrack.
I can be the community test mule, that's fine. I'll report my findings as I go.
Are you then torquing your lug nuts to 150 lb-ft on your SM-10s?
I may end up selling this wheel set for EC-7s in an 18" size. Trusted brand and cheaper tires
 

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I was talking with a guy from LMR and he said the lug nut torque could definitely be a possibility. 150 is required for factory nuts but stronger aftermarket ones "should not be tightened to those specs." He recommended 110 lb-ft and adjust from there as needed.
That's odd, because the strength of lugnuts should have no impact on the torque value. A forged lugnut is not going to produce a stronger clamp than a cast lugnut at the same torque value.

The stud is what drives the torque value necessary, and you didn't change that. IMO, the LMR guy probably said that to avoid any issues going forward with the wheel integrity, but that's a bandaid fix meant to swing the liability from them to you.

I personally have done 150lbs on my SVE track wheels since I got the car back in 2016, and have done countless track days with no issues (and this is with badass aftermarket lugs not the stock ones). My guess is this was a bad wheel or just bad luck. Take the new wheel and go on about your day without changing anything. If you keep noticing this, maybe there's an issue. But one off like that I wouldn't worry.
 

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I was talking with a guy from LMR and he said the lug nut torque could definitely be a possibility. 150 is required for factory nuts but stronger aftermarket ones "should not be tightened to those specs." He recommended 110 lb-ft and adjust from there as needed.
100% bullsh!t. Call people on that the next time they say something like this. For a 60 deg conical seat lug, and the M14 studs that the S550 has, 150 is the required torque for proper clamp load.

I have used 150 for 3 years on my two sets of SVE wheels with no cracking or issues, with >40k miles of driving and much track use.
 

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Also that crack looks like it initiated from porosity at a stress riser in the wheel design. I would seek replacement from LMR.

upload_2019-10-23_9-19-21.png
 
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Ewheels

Ewheels

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I had to take a minute for myself and think back to my college days to understand what's going on.

You tighten the nut to the specified amount (150 lb-ft in this case) and in doing so, the portion of the wheel between the 60° nut interface and the hub is under a certain amount of compressive loading and the wheel studs are under an equal and opposite amount of tensile loading. These loads are already calculated and accounted for by the Ford engineers.
Now if we change the material strength/hardness of the nut, does the loading on the wheel or the studs change? No. The same forces are still in place. The only reason the wheel would crack in this location under these conditions is if the wheel is in fact defective or the wheel was not designed to handle this loading, in which case it would be an insufficient design for this car. Therefore, the wheel was either defective or I do indeed need to look into other wheels.

Correct me if my train of thought is off here.
 

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I had to take a minute for myself and think back to my college days to understand what's going on.

You tighten the nut to the specified amount (150 lb-ft in this case) and in doing so, the portion of the wheel between the 60° nut interface and the hub is under a certain amount of compressive loading and the wheel studs are under an equal and opposite amount of tensile loading. These loads are already calculated and accounted for by the Ford engineers.
Now if we change the material strength/hardness of the nut, does the loading on the wheel or the studs change? No. The same forces are still in place. The only reason the wheel would crack in this location under these conditions is if the wheel is in fact defective or the wheel was not designed to handle this loading, in which case it would be an insufficient design for this car. Therefore, the wheel was either defective or I do indeed need to look into other wheels.

Correct me if my train of thought is off here.
It wouldn't crack like this or there if it was related to lug nut torque. The wheel had a defect and the loading of the wheel on the road/road course propagated a crack from the defect (probably porosity).
 
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Ewheels

Ewheels

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It wouldn't crack like this or there if it was related to lug nut torque. The wheel had a defect and the loading of the wheel on the road/road course propagated a crack from the defect (probably porosity).
Thank you for the correction. I'm glad to have ruled out the incorrect lug nut theory though.
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