Is this an unusual rim crack?

[bambam]

Changing a flat this weekend I noticed this.


Velocity aerohead OC
built in november of 2009

[Charles M]

"unusual" is relative... But that's all done.

[David Kirk]

yep - stick a fork in it.

dave

[thwart]

I wanna hear more about that flat... ouch.

[jr59]

ouch!

[sirroada]

Is there a crack present on the inner part of the wheel surface? That definitely is a strange one. Did you hit something? If not, I do know that stress risers can occur in aluminum when the edges of drilled holes are not dressed properly (deburred). If you didn't hit anything I would say that is what happened. (just my 2 cents).

[ultraman6970]

Rip

[RPS]

What size tire and pressure? Just curious.

[dekindy]

I am 200 pounds and my OC rim cracked maybe due to only having 28 spokes and I needed 32. Replaced it with a Deep V which is what I should probably have went with anyway. The Aeroheads rode very nicely though so I wish that I could have kept them.

[bambam]

The cracks are only under the the rimstrip.
The outer wall of the rim looks perfectly fine.

Luckily the flat was a slow leak. The tubes hole was on the inside by the valve stem. It wasn't till today I noticed the extent of the damage. When I puled off the rim strip. 24 of the 34 remaining spoke holes had hairline cracks.

Oh yea, the rims done. I hope to get one this week.

I run 25mm Conti's GP at 110 to 120 psi.

I built the wheels myself but could not find the proper force needed for the spokes. according to the chart with the park tool tensiometer I was at about the 75% mark on the drive side, Less on the non-drive. If that makes any sense.

Does anybody know what the proper spoke tension should be?

[bambam]

I am 200 pounds and my OC rim cracked maybe due to only having 28 spokes and I needed 32. Replaced it with a Deep V which is what I should probably have went with anyway. The Aeroheads rode very nicely though so I wish that I could have kept them.

I am about 170 on 36 holes but carry 5-20lbs of stuff.

[bambam]

Is there a crack present on the inner part of the wheel surface? That definitely is a strange one. Did you hit something? If not, I do know that stress risers can occur in aluminum when the edges of drilled holes are not dressed properly (deburred). If you didn't hit anything I would say that is what happened. (just my 2 cents).

I didn't hit anything to warrant this. I noticed something was odd with a bump on the rim during breaking late in the ride. I pedaled the remaining 45 miles using as little torque as possible. I could only see the damage around the valve. Thanks for the hint about the deburring. I'll definately do that on the next wheel.

[Pete Serotta]

It is done,,,,


It is probably a cumulation of events and not a single item that caused it.


We will never know :crap:


Pete

[mschol17]

My rear Aerohead cracked in the same spot. The only way I noticed it was some strange pulsing in the brake and a non-true rear wheel.

[Hank Scorpio]

I had a rear Velocity A23 with multiple stress cracks around the spoke holes but not like yours. This was after less than half a season.

[bambam]

My rear Aerohead cracked in the same spot. The only way I noticed it was some strange pulsing in the brake and a non-true rear wheel.

Around the time when the flat occured I noticed the pulsing as well and knew it wasn't doing that earlier in the ride. I don't use my rear brake a lot but this day I was due to rain earlier in the ride. Oddly enough the wheel stayed pretty true. Except for the bulge on the non drive side.

[weiwentg]

I run 25mm Conti's GP at 110 to 120 psi.



that pressure sounds too high - I doubt this alone is a major contributing factor, but what's your weight?

[oldpotatoe]

The cracks are only under the the rimstrip.
The outer wall of the rim looks perfectly fine.

Luckily the flat was a slow leak. The tubes hole was on the inside by the valve stem. It wasn't till today I noticed the extent of the damage. When I puled off the rim strip. 24 of the 34 remaining spoke holes had hairline cracks.

Oh yea, the rims done. I hope to get one this week.

I run 25mm Conti's GP at 110 to 120 psi.

I built the wheels myself but could not find the proper force needed for the spokes. according to the chart with the park tool tensiometer I was at about the 75% mark on the drive side, Less on the non-drive. If that makes any sense.

Does anybody know what the proper spoke tension should be?

100-100 KGF for the RH side rear and front.

[Elefantino]

I just noticed a number of small stress cracks on my rear rim. Like the front it's a Niobium 19 w/32 spokes laced to DT240s. Maybe it's not made for 190 lbs? I can't believe they are all from the landing after I ass-ended the VW.

Going to swap it out for a stronger (but heavier) DT rim.

[RPS]

that pressure sounds too high - I doubt this alone is a major contributing factor, but what's your weight?
That’s why I asked about tire size and pressure. My initial thought was that maybe running too large a tire at too high a pressure contributed because the failure looks like the braking surfaces were pushed apart with more force than the rim could resist, leading to failure at the weakest point. But since a 25 MM tire at 120 PSI shouldn’t do that to a normal Velocity rim, out of curiosity I’d section the rim across the stem hole to see if for some reason the metal looks thinner than it should be. The rim is trash anyway so putting a hacksaw to it won’t hurt. :beer:

[weiwentg]

That’s why I asked about tire size and pressure. My initial thought was that maybe running too large a tire at too high a pressure contributed because the failure looks like the braking surfaces were pushed apart with more force than the rim could resist, leading to failure at the weakest point. But since a 25 MM tire at 120 PSI shouldn’t do that to a normal Velocity rim, out of curiosity I’d section the rim across the stem hole to see if for some reason the metal looks thinner than it should be. The rim is trash anyway so putting a hacksaw to it won’t hurt. :beer:

yeah, and I see the OP answered. oops! I stand by my comment, though - for the sake of his own butt he should run lower pressures, but that wouldn't have done the rim in.

[Velosmith]

My wife and I had three Arrowhead OC rims warranted 3 months ago for these same cracks... She's 120 and I'm 160lbs. I think they had a bad batch go out.

Our LBS took great care of us.

The new ones are doing fine. No sigs of cracking yet.

We are running 25mm and 26mm tires a 80-90lbs, so I doubt pressure was an issue.

[bambam]

that pressure sounds too high - I doubt this alone is a major contributing factor, but what's your weight?

Correction on the tires conti gp 4 seasons.

[bambam]

100-100 KGF for the RH side rear and front.

Thanks for this information.

[bambam]

that pressure sounds too high - I doubt this alone is a major contributing factor, but what's your weight?
I weight about 165-170.

My LBS has a rim on the way. I guess I'll figue out if I have to pay for it when I pick it up.

[srice]

Dave - have you looked at the front rim?

[bambam]

Dave - have you looked at the front rim?

I will be during the cleanup. I might as well check out it trueness when I build the other wheel. Has this info made you worry enough to check yours out?

[srice]

I'll go over them with a fine tooth comb before I head out on TOKYO and PBP.

[roydyates]

I'm bumping this thread since over the weekend I was 200k into a 600k ride when I got a flat caused by the rim tape sagging into the indentation where the inner wall of my aerohead O/C rim cracked. My photo is just like the first photo in this thread:
https://lh3.googleusercontent.com/-VKfnwAgLar8/Th3d_stv57I/AAAAAAAAAe4/yascFtD4P3M/s128/crack-small.JPG
Last year, I trashed an aerohead in a pothole on a dark and rainy night. The rim was replaced and this year I've been careful to avoid any incidents, but this wheel is toast after less than 2000 miles. I weigh 200 lbs and my loaded rando bike is over 25 lbs. I suspect I'm just too heavy. On the other hand, bambam, mschol17 and Velosmith all tell the same story, so maybe I ought to be seeking a warranty?

In any event, I'd like to reuse my 32h DA7700 hub, what 32h silver rim do I get instead? Maybe a Velocity Dyad? Maybe a Synergy O/C? Something else?

Finally, if you're wondering, the temporary fix was to cover the crack with a tightly folded dollar, cover the dollar with the rim tape and keep riding. The sidewall bulged but the rim stayed true and survived the 400km to the finish.

[skijoring]

I'm bumping this thread since over the weekend I was 200k into a 600k ride when I got a flat caused by the rim tape sagging into the indentation where the inner wall of my aerohead O/C rim cracked. My photo is just like the first photo in this thread:
https://lh3.googleusercontent.com/-VKfnwAgLar8/Th3d_stv57I/AAAAAAAAAe4/yascFtD4P3M/s128/crack-small.JPG
Last year, I trashed an aerohead in a pothole on a dark and rainy night. The rim was replaced and this year I've been careful to avoid any incidents, but this wheel is toast after less than 2000 miles. I weigh 200 lbs and my loaded rando bike is over 25 lbs. I suspect I'm just too heavy. On the other hand, bambam, mschol17 and Velosmith all tell the same story, so maybe I ought to be seeking a warranty?

In any event, I'd like to reuse my 32h DA7700 hub, what 32h silver rim do I get instead? Maybe a Velocity Dyad? Maybe a Synergy O/C? Something else?

Finally, if you're wondering, the temporary fix was to cover the crack with a tightly folded dollar, cover the dollar with the rim tape and keep riding. The sidewall bulged but the rim stayed true and survived the 400km to the finish.

I'd look at the DT 465 ( a little light) or the DT TK touring rim OR a CR-18 (Sun).

[Mark McM]

I don't have any photos, but just yesterday a friend showed me his Velomax Orion rear wheel, which has similar cracks on the tire bed (i.e. the rim surface under the rim strip). When he spoke to a Velomax tech. support, he was told that the Orion used a Velocity Aerohead OC rim.

On my friend's rim, cracks radiating from the valve hole on the tire bed had propogated to the sidewall, causing a section of sidewall to bow outward. It looked similar to the cracks in the photo earlier in the thread, except that they were only one side, and went further along the sidewall. His first indication of the problem was brake pulsations, which grew worse over time. After he removed the tire and rim tape, he found that there were also smaller cracks starting around about a half dozen of the spoke holes in the tire bed. The valve hole had the most jagged edges, so maybe those cracks started first/grew fastest.

In any case, it sounds like Velocity might have design or QC problem with the Aerohead OC rim. Perhaps the tire bed wall is too thin, or has gouges or ripples in the tire bed wall (causing stress concentrations where cracks may start), or one of the other rim making processes over-stresses the tire bed and initiates cracks.

[RPS]

After he removed the tire and rim tape, he found that there were also smaller cracks starting around about a half dozen of the spoke holes in the tire bed. The valve hole had the most jagged edges, so maybe those cracks started first/grew fastest.

Wouldn't you expect that as the weakest point regardless?

More holes = less material = higher stresses

If damage was initiated/caused by impact loads then I'd expect more random distribution, but if due to high stresses (whether poor design or manufacturing) then weakest point should fail more often.