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Land of the 230+
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Discussion Starter · #1 ·
So the other day, in just the right light, I noticed the smooth glossy finish of my front rim was suddenly somewhat textured. I knew immediately what had happened.

My regular car with the roof mount rack has been at the dealership for the airbag recall. Ive been driving my wrx around with a trunk mount rack, and while the tire is a good 15 or 16 inches away from the exhaust, its obviously close enough to cause damage.

I know these pics are not the greatest, but do you think the rim has been structurally compromised? Or is the damage just superficial? The surface coat seems to have softened a bit and the carbon weave is imprinting just a bit of texture. I dont see any voids or bubbles and nothing feels soft. These are nextie i45 rims with extra thick 3.5mm hookless beads. Nobby nic 2.8s at 16 psi.

Any thoughts other than reiterating that I'm a moron?

 

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Norðwegr
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1,910 Posts
Never get gloss carbon rims, it's just an extra coating that does nothing. (stay away from 3k and 12k cf too, always go matte UD)

The melting temps of most cf would require a flame, so that is most likely just the gloss finish. Either way, contact nextie and ask them.
 

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Land of the 230+
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Discussion Starter · #3 ·
The rims were clearance so I didnt have a choice on finish. Theyre well out of warranty, so I doubt nextie will tell me anything other than hey, buy new rims from us!

My feeling is that this is only the top coat as well. There is no deflection or bowing of the bead at all, not even close. I just dont know if the heat has compromised the epoxy strength even if there is no deformity.
 

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Hitching a ride
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Never get glossy rims? lol. Get what you want. If this is the rear rim I'd go ride it and see how it turns out. If it's the front rim, you could do some lateral stiffness tests before trusting it.
 

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EAT MORE GRIME
(ノಠ益ಠ)ノ彡┻━┻
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7,803 Posts
car exhaust definitely can compromise carbon. how bad yours are is pretty much unknowable w/o xray or cutting it up and looking

probably ok but if that were me I'd chuck them out. as said it takes some serious tools to know for sure....and it is likely OK but then, there is actual visible damage, right ? .....I'd put those on a commuter bike or training bike where you aren't around trees and rocks imho
 

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Well dude, I'd say if it's a rear, ride it until it dies, if it's a front, I'd highly recommend you change it if you like your face :skep: Had a guy completely bust his SpecialED carbon rim carrying it hanging off the back of his Land Rover, exhaust about 10" away on a 5 mile trip, went off with a shotgun like bang when the tyre blew, broke the rim.
 

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The lighting is really poor in your photos so I can’t see the blemishes you’re talking about but I wouldn’t trust the rims on my primary bike.

New rim time! May as well get all new wheels while you’re at it. Safety first.
 

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Don't beat yourself up too hard over this, you aren't alone. I spoke with the guys at Ibis a while after their carbon hoops came out, they told me this is the number one failure cause they see of rims. Apparently the point the carbon becomes structurally compromised is lower than that of rubber, so it may happen and you never know it.
 

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Elitest thrill junkie
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38,860 Posts
Most decent racks lift the bike up and away from the exhaust, also for ground clearance for grade changes, so it's a rare problem, but it can definitely happen. A heat-shield may be necessary (weld or bolt to the rack) in some circumstances.
 

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since 4/10/2009
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34,375 Posts
Most decent racks lift the bike up and away from the exhaust, also for ground clearance for grade changes, so it's a rare problem, but it can definitely happen. A heat-shield may be necessary (weld or bolt to the rack) in some circumstances.
Nah. Not so rare. a hitch receiver that's particularly low, or a vehicle with exhaust that's particularly high are more likely to have problems. Seems to be a particular issue with BMW SUV's, since the exhaust can be pretty high relative to the hitch receiver.

(https://www.etrailer.com/tv-install-trailer-hitch-2012-bmw-x5-75600.aspx)

I've seen carbon rims completely delaminated because the vehicle's exhaust lined up just so with the wheels when the bike was mounted on a hitch rack. Platform rack. Hanging rack. Some combinations line up perfectly for melted wheels.

I'm not a fan of exhaust that points straight backwards for reasons like this. Point it down or off to the side to keep it away from anything you're towing or attaching to the hitch receiver.
 

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Methanol burns much hotter than gasoline. They put it in gasoline to reduce emissions in the summer at 10% -15%

If you run E85 or methanol injection (popular on boosted motors) it's hot enough to cause issues.
 

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Land of the 230+
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Discussion Starter · #17 ·
Check spoke tension in the affected area. If it didn't go slack, nothing happened.

-F
Interesting idea. Tension is spot on, checking both sides with a park TM1. But then again loss of tension was not my main concern. I was more worried about a failing rim sidewall blowing out. But the extra thick 3.5mm hookless may help here. Thanks.
 

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Land of the 230+
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Discussion Starter · #18 ·
Never get glossy rims? lol. Get what you want. If this is the rear rim I'd go ride it and see how it turns out. If it's the front rim, you could do some lateral stiffness tests before trusting it.
Sadly it is a front rim. Ive already inadvertently put about 30 miles on it so far, fast singletrack, but no drops over 2 ft, rocks or aggressive roots yet. I dont suspect lateral stiffness to be an issue. More concerned with a bead hook failing.
 

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Land of the 230+
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Discussion Starter · #19 ·
Most decent racks lift the bike up and away from the exhaust, also for ground clearance for grade changes, so it's a rare problem, but it can definitely happen. A heat-shield may be necessary (weld or bolt to the rack) in some circumstances.
I'm only using the WRX while my daily driver is at the stealership for takata airbag recall work. If I knew I'd be driving the WRX for this long, I'd have moved the roof mount rack to this car.
 

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Land of the 230+
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Discussion Starter · #20 ·
The lighting is really poor in your photos so I can't see the blemishes you're talking about but I wouldn't trust the rims on my primary bike.

New rim time! May as well get all new wheels while you're at it. Safety first.
Does your WRX have a gigantic cantaloupe launcher fart pipe on it?
Maybe it was the NOS that did it. Do you have NOS?
Damn, dude, you're really trying to hammer this one home.

Car is stock 2006. Was a daily commuter / grocery getter until the wife got a new car and I got her hand-me-downs. Anyway, all the go-fast goodies are on the camaro, but I haven't driven it since I cut my mullet and lost all my good 8-tracks.

Heres one with [marginally] better lighting:


Methanol burns much hotter than gasoline. They put it in gasoline to reduce emissions in the summer at 10% -15%

If you run E85 or methanol injection (popular on boosted motors) it's hot enough to cause issues.
No methanol, but NY has e15 year round. Regardless I stay out of the boost with a bike hanging off the back of the car!

car exhaust definitely can compromise carbon. how bad yours are is pretty much unknowable w/o xray or cutting it up and looking

probably ok but if that were me I'd chuck them out. as said it takes some serious tools to know for sure....and it is likely OK but then, there is actual visible damage, right ? .....I'd put those on a commuter bike or training bike where you aren't around trees and rocks imho
Yeah, that might be an option. Maybe I'll look to replace the rims on the full squish out of an abundance of caution, then Ill swap the compromised rims onto my single speed, with the melty one in the rear. The current rear already has a repaired spoke pull through, but that seems like less of a spontaneous blowout risk. The singlespeed wont be subjected to nearly as much speed or chop, not that I actually ride at speed or chop anyway.
 

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