Mountain Bike Reviews Forum banner
1 - 20 of 21 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
My Mavic XM719 rim blew apart yesterday going uphill on a graded dirt road. The rear wheel was hand-built by a very reputable smith. Shimano XTR 36 hole hub laced with 14g straight gauge spokes. It was one year old with no hard knocks - almost all dirt road and pavement. I'm 190 lbs. In other words, I believe the wheel was properly built and not abused. I am grateful to Mavic that they designed their failures to occur realtively close to home . . .
 

Attachments

·
Premium Member
Joined
·
48,238 Posts
Rim brakes or disc?
That is a typical brake wear failure. I use to go through a rear rim a year before I went to disc brakes.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #5 ·
At the time of the demise, I was riding a Schwalbe Marathon XR 2.0" @ 65 lbs. This is the tire I use the most. On trails, I usually run a Fire XC Pro 2.1 @ 35 - 40. Over the winter, Nokian Mount and Grounds (1.9 @ 40 or so). If it might be a factor, the bike is a hard tail, but I do use a Thudbuster seat post.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #7 ·
Assuming that this particular rim was not defective, that seems to be the case for the XM719. While 65lbs in a 2.0 tire is pretty firm (ok, hard), is it outrageous when riding graded dirt and pavement? Mavic targets the rim as XC/All-mountain and advertises it as "the all-around rim par excellence" and one that will "will accompany you on all your rides, from the calmest to the wildest."
Did I get too wild with my pump?
Whether it was a defective rim or I exceeded its carrying capacity, the XM719 is definitely not the rim for me. Now that I'm given the opportunity to invest in another bomb-proof build, it's back to Rhyno Lites. I'll invest the money that I save in beer and ride in confidence that the rim can handle the additional ballast.
 

·
ups and downs
Joined
·
15,599 Posts
Mavic's a bit sketchy about providing these sorts of specs (like trying to find max spoke tension specs for their rims) in any of the available languages on their website.

The XM317 is rated for a maximum of (7.7 Bar) 113PSI with a 1" tire and a max of (3.3 Bar) 48PSI with a 2.3" tire, and the V-brake XM719 and disc XC717 rims have the same max pressure ratings (having to read this off the rim labels using the image zoom on the website pics - they don't actually offer this info in the written spec).

That would put 65PSI on a 2" tire in the acceptable sort of maximum pressure range.
 

·
Spanish rider
Joined
·
311 Posts
I think that the reason why this happenned is: defective rim + high pressure.

I think that a Mavic 719 is supposed to resist 65 psi using a 2.0 tire, (probably it's the max pressure it can stand) so the rim had to be defective: a little crack on an eyelet, a bubble in the alloy, not uniform alloy...
 

·
Registered
Joined
·
17 Posts
What sort of pump do you use and do you know how accurate it is? I've never seen a bike pump that comes with a calibration certificate so there's no way of knowing what sort of tolerances you may be working with.

If you have, say, a 10% tolerance then 65 PSI could be as high as 71 or 72 PSI.

Did you pump your tyres up during the night when it was cold and then go for a ride on a warmer day? This will affect the pressure within the tyre. A few years ago I was doing the London to Brighton bike ride. While waiting at the start, along with 20,000 other cyclists, I could hear tyres exploding all around me. I suspect that a lot of people had prepared their bikes in the evening by pumping their tyres so that they were nice and hard. The next day was exceptionally hot causing the air pressure to increase and tyres/inner tubes to blow.
 

·
Unfit Norwegian
Joined
·
1,260 Posts
shiggy said:
Rim brakes or disc?
That is a typical brake wear failure.
How do you figure. The rim has clearly split right down the middle, and I see no sign of breaking surface wear.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #13 ·
I contacted the wheel builder who has contacted the Mavic rep. I'll pass along what I hear back.

The photos show the sidewall blowout and a little bit of the split immediately around it. But the center is fractured for nearly the entire circumference.

Regarding the pump / gauge, I use an older Silca floor pump. I went out this morning and pumped a tire to 60lbs on its gauge. The Park pump that I keep in the pickup read 59. My little carry-along Zefal gauge read 62. I had checked the pressure immediately before going on the ride and had ridden less than 2 miles when the rim blew.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #14 ·
Mavic issued the builder a return authorization. They'd like to see the rim before deciding where to go with this. Fair enough. Thanks for all the responses folks. I'll post Mavic's take on it when it comes through.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #15 ·
Follow up: after having the rim for 2.5 weeks, Mavic refused to warranty the failure. They claim that it was a combination of too much tire pressure (65# in a 2.0" tire) and the use of a disk brake. They say that the XM719 is NOT designed to be used with a disc brake and that the metal is too thin at the eyelet to take the pressures applied by the use of a disc brake.
Caveat emptor, eh?
 

·
Registered
Joined
·
1,908 Posts
jrk said:
.....They say that the XM719 is NOT designed to be used with a disc brake and that the metal is too thin at the eyelet to take the pressures applied by the use of a disc brake.
Caveat emptor, eh?
Wait a minute.... I didn't see anywhere in your original post where you said that this was a v-brake rim. The 719 is offered in rim and disc brake configurations. Were you running discs on a v-brake rim?
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #19 ·
The rim I had was the XM719 with the braking surface - not the disc-only version. If Mavic intended that rim to be used for rim brakes ONLY, then I sure didn't (and don't) see anything on their web site to indicate that. I just figured that having the braking surface too made it a more flexible choice. My bad?
 

·
Old man on a bike
Joined
·
12,395 Posts
If Mavic intended that rim to be used for rim brakes ONLY, then I sure didn't (and don't) see anything on their web site to indicate that. I just figured that having the braking surface too made it a more flexible choice. My bad?

What do you mean if? Yes, it's your bad. So if someone doesn't tell you something in the way of a limitation, you're able to assume whatever you want? You went to the Mavic website and saw both an Xm719 and Xm719 disc and thought what? That if the regular Xm719 was good for both, that Mavic was just obviously screwing around with you offering a disc-specific model? What other research did you do?

Braking forces are different between a rim brake and a disc brake, it does make a difference. Some have had success using old rim brake type rims vs disc specific, but if you're the one picking parts you should know that, eh?
 
1 - 20 of 21 Posts
Top