Zipp 404 problems
Last year I used Race Day Wheels to rent a front Zipp 404 wheel for my IM event. It seemed to work well so I ended up finding a used one on eBay. I haven't been thrilled with it and I'm sure it's user error.
I'm getting an abnormal amount of flats, including "blow outs" on higher speed descents. Seems like it might be a brake issue but I can't seem to figure it out.
According to the Race Day Wheels guy, I didn't need special brakes or pads. Said what I had would be fine.
Last week, again, (the the third or fourth time), I'm speeding downhill, start to apply brakes off and on over a minute or two period and then there is a loud pop, and I'm flat. It's 45 degrees outside, so it's not that the temperature is causing the problem. My breaks appear to be lined up along the rim and not touching the tire. Tire isn't shredded and there is no gash or hole in the tire that I can see.
Any suggestions? Do brakes, brake pads matter?
Also, I hate the valve extender. Any suggestions for the best type? I tape the valve, but often I have hard time getting a reading on the pressure. Sometimes when I use the floor pump, air goes in to the tire, but then the pressure reading drops to zero, so that there is air in the tire, but I have no idea what the pressure is.
I'm about to give up on the wheel!
tom
Comments
Re; valve extenders, I use the vittoria and not the Zipp 'valve always open' type.
As David hinted, the question of the brakes matters depending on whether the wheels are clinchers or tubulars. If they are clinchers they will have an aluminum braking surface like 'normal' wheels and you should be fine to use your stock brakes. If they are tubulars, then you *do* need to use special carbon or cork brake pads.
In regards to Valve extenders, I personally dislike traditional over-the-valve extenders, even when properly installed with teflon tape. I prefer tublars or tubes that have removable valve cores. With these you just remove the core, install the extender, then re-attach the original core to the end of the extender so you end up with your normal presta valve at the buisness end and a more secure seal along the entire valve. Vittoria makes tires and tubes with removable cores, I'm sure other brands do now as well.
Here's an example of valve core extender, choose the size by adding the extender size to the length of your stock valve core as usual, I have HED Stinger 9's so I have a 60mm extender and something like a 37mm core to top me off over the 90mm mark.
http://www.tufonorthamerica.biz/ind...cts_id=285
As Nemo mentioned, start to inspect the tube after each flat to figure out exactly were the puncture is. Then check the tire, wheel, and rim tap very very carefully in that area.
On a side note ... my issue is trying to find a latex tub with a removable value core and therefore I am stuck with the over the value type extendors. Does any one know where removeable value core latex tubes are available and actually in stock?
tom keep us posted, but Matt try asking dave corso.
I'm the farthest thing from an expert....but, if you're going through the trouble of permenantly installing your value extender, can't you just buy tubes with a longer valve stem on them. I think you can buy tubes with value lengths as long 60-80mm vs the standard 32mm for a normal, non-aero aluminum wheel.
I think the reason people use a value extender is to carry it with you in the race so that your value stem can be shorter and more aero. Then you just carry an extender to screw on and fill up if you need it. If you are going to have a longer stem all the time, just buy a tube with a longer stem.
Hey Larry, thanks for the tip, but I have tons of brutyl tubes with 80mm values. You're right they are great for training and avoiding the value extenders.
The issue is I can't find long stem or removable core latex tubes for racing. I know of two compaines that make them vittoria and challenge, but I have yet to find anywhere that has them available and instock. I've even placed orders with places that have them on their website, but I always get an email a month later saying they are on back order that the order is cancelled.
I have 80mm continental tubes that work great. Haven't been able to find any 80mm latex tubes for races.
@Colleen,
I don't think there is any danger in using carbon or cork brake pads on an aluminum braking surface, higher end brake pads designed for carbon rims may very well have better heat absorption and stopping power even on aluminum. But, there should be no difference between an alumninum brake track on a carbon wheel (like a 404 clincher) vs an aluminum brake track on a set of standard training wheels, if your existing pads stop one without overheating, they should stop the other. Of course maybe you're just going that much faster on your carbon wheels.
One of the caveats that I've heard about pad selection in general is that you should never use your carbon brake pads on clinchers *then* switch to tubulars and use the same brake pad since the pads will collect small pieces of alumninum while braking on the clinchers. However, I've seen the latest SwissStop carbon pads advertise that there is no need to change their pads betweens clinchers or tubbies, just wipe them down between the wheel swap and they claim you are good to go.
@Larry,
I'm not an expert either, although people may very well only use extenders for inflation I haven't seen it. If you need vavle extenders it is because you can't access your presta valve due to the depth of the wheel. When you add an extender on it your presta valve needs to be fully open so that the air can pass through the extender and through the original valve. So if you were to only screw on an extender during inflation, the rest of the time you are riding your presta valve would be wide open since it is burried inside your rim and you can't get to it to close it. That sounds like a leaky situation.
In general I think the valve extender debate is slightly less dire when it comes to clinchers, if you find your valve extender is leaking or not to your liking it is no big deal to remove the tube and give it another shot. For my racing tubulars, I'd have to break the glue and rip my tire from the rim, fiddle with the extender, then repeat the entire glue and mount process, something that can take days, not hours. In other words, it needs to be done right the first time. I don't want to go into a whole big clincher vs tubular thing, but the only thing I'll say on the subject is had I not gotten a killer deal on these wheels slightly used, I would have never gone tubular.
thanks for all the input everyone! I've got a clincher and I'm using Continental Race 700 tubes with a 60mm stem. These still require an extender. I still had two tubes that had blown and so I checked the damage area. Both had small holes, one about 29 inches from the stem, the other 34 inches, with 39 being approximately 1/2 way. I didn't see / feel anything in the tire that would seem to puncture the tubes. I forgot to check the rim tape, so I'll do that too.
I think I'm going to do some experimenting. Definitely change out the rim tape. I'm going to order 80mm continental tubes and the Zipp brake pads. Also took a look at the site Larry linked. Much better ideas for valve extenders.
Stay tuned, I'll let you know what I find out. I'm feeling a whole lot better though!
tom
Tom - you mentioned you don't actually know what the pressure is in your tubes, due to pump issues. I've found my 404's to be real persnickity with pressure - go over 110 psi, and I start getting flats caused by the spokes poking thru intact rim tape in situations where slight increases of tubal pressure might occur, such as braking and using the trainer. New tape and attention to keeping the pressure below the critical threshold were both required to fix that.
Ordered the Zipp rim tape, tubes with 80mm stem and new Zipp brakes. All installed and officially tested. I have been a little nervous riding the brakes downhill to see if they would heat up and blowout, but no problems at all with the 404s. Looks like the problem is solved.
Thanks!
tom
Vince
But not in 650s. Thankfully at least I can get tubes with 80mm stems. I hate dealing with the valve extension dealios.
I'm loving the 80mm stems. Ditto on the valve extension stuff
Thanks Vince for the hookup on the latex tubes with removeable valve cores. That will make life a tad easier.
As for the original question it seems like almost all weird flatting issues are caused by either bad rim tape [you just can't see what it all looks like under pressure in there] or a burr on the rim.