Alex Reed

I know that because of the dust cap, the tire valve will not fill up with mud. But, I don't bike on mud trails.
So, do I need to use a dust cap on my tire valve? Is it necessary?

PeteHski

It depends on the valve. If Presta then no, if Schrader then yes.

rm -rf

I never use a cap on my Presta wheels.

The spare tube in my saddle bag has one, to protect the folded tube. And, I wrap the folded tube in a piece of heavy 4 mil plastic sheet or Tyvek. I've seen a two different cyclists have a second flat tire from the spare tube getting worn along a folded edge after months in the saddle bag.

noglider 

I never use dust caps. I suppose it's true that it can prevent dust from entering the valve stem, but it's also true that it keeps elephants out. I haven't had a problem with either.

PeteHski

Elephants are rarely a problem in valves. Dust and mud in a Schrader valve could potentially be a show stopper. Presta valves are not really vulnerable to dust with their screw top effectively sealing the stem. But I do tend to use caps until I eventually lose them!

noglider 

Yes, it could be a problem, but has anyone you know ever had the problem?

indyfabz

Depends on how many miles you should ride in a day.

Iride01 

I don't like the idea of dirt getting down in them. Sure presta's are a little more resistant since you can snug them up with the little nut. But I still keep the plastic cap on both presta and Schrader valves. If I happened to lose it, it wouldn't be the end of the world.

pdlamb

I've been known to blow a bit of air into a tube before installing it into a tire -- like when fixing a flat. I figure the dust cap keeps some of the common road schmuck off the part of the valve I'm blowing on.

But, you know, some people find dust caps terribly troublesome. If you're one of those, do not use them!

mstateglfr 

No you dont need them. Yes they are largely a worthless component in 99.5% of riding. But in that other .5%, the top could bend due to the bike falling over or some other odd incident and it then becomes really difficult to use the valve core.
I dont have caps on most of my bikes. I do have em on 3 bikes- 2 of the bikes have caps because the caps are anodized the same color as the frames...so its vanity. The other bike that has em is my gravel bike and the caps do help keep dust from accumulating, but the caps I use also have a built in core remover so its sort of a multitool- both vanity bling and a tool if ever needed. I have never needed the core remover for me, but I have used it during a ride to replace a valve core for someone else.

https://www.amazon.com/Muc-Off-Orang...08Y941ZG5?th=1




https://www.amazon.com/Granite-Juicy...8C0PBEE2Z&th=1

noglider 

I don't think that's the Yiddish word you're groping for. Maybe you meant to say schmutz which means dirt. Schmuck means male reproductive gland (and also jerk).

MoAlpha

It’s really ornament, adornment, or piece of jewelry in German, which is why the Yiddish euphemism is so funny.

Eric F 

I've been without caps on my presta valves, since before there were clipless pedals. This has included riding and racing road, MTB, CX, and gravel. Zero is how many times I have had a valve issue due to mud, dirt, or dust getting in the valve from the outside. These days, a more common issue is the valve getting plugged with dried sealant from the inside.

BobG

I threw them away for 59 years. Then on year 60 I started using them! Why? Last summer I had a troublesome leak to find on a tubed tire. I finally discovered the presta valve to be leaking after putting the tube under water. I replaced & tightened the valve core but just to be sure I put the caps on both tubes tightly in case they were still seeping.

datlas 

Larry, is that you?

veganbikes

I do have a custom made valve caps on my Schrader valves (I really only have 3) they are made from .40 S&W shells glued to plastic caps because they look cool and I had the equipment so why pay $10+ for someone else to do it when I can do hand made ones from ones I emptied. My presta stuff usually doesn't have a cap some do but most don't I got a couple nice anodized ones on some of my road stuff but mostly without though I probably have a bike or two that has only one valve cap because if it brakes or I forget to put it on I don't bother.

For schrader yes all the time valve caps and probably also for Woods/Dunlop valves (though my experience with them is limited and I have never not put a cap back on) but presta they are not needed at all. One could argue you don't really need them on Schrader but it is a free piece at a shop and they weigh nothing so there is really no downside plus you can make or buy some cool ones out there.

NumbersGuy

I use them mostly to protect the head on my pumps. Although dirt and grit on the outside of the valve won’t impact the valve inside, it can potentially wear the rubber seal on the pump head. Keeping it clean seems like it has no downside, unless you’re trying to follow the stupid cycling Illuminati rules of coolness, or think a couple grams makes any difference.

79pmooney

To me, presta caps are small labor devices. Labor to remove, labor to replace and very likely, labor to find that silly little thing you tool off to repair that flat. THe way to keep that labor small? Do the direct brand new tube to cap jar transfer when you take that tube out of the box. (And no small plastic bits to rattle around a bird's guts; probably not improving his life experience.)

phughes

Schrader valve? Yes. Once any dirt gets in around the valve stem, it can get in when you add air, and it can get into the valve itself causing it to leak. It happens often on cars. I have seen it many times. Is it a huge worry for me on a bicycle? No, not really, but I should probably take better care.

downtube42

I recall reading years ago on sheldon brown's site that a presta cap could be chopped and used as a presta/shrader adapter. I actually used that a few weeks ago, enabling me to mount a tubeless tire at the office using an air compressor.

Ultimately the repair failed for other reasons, but technically it's a possible reason to carry a presta cap (and a blade).

It's a hack. I like hacks.

noglider 

I asked if it has ever happened, and you told me what it would be like if it did happen. So far, the answer is no, it hasn't happened on a bike.

Cars go faster and farther, so I use valve caps there.

When I was a bike shop mechanic, I used valve caps only because customers think the job isn't done unless the caps are there. I believe they don't help anything at all. Of course, they don't hurt anything, either except, as @79pmooney points out, they are extra work.

Garfield Cat

How about in Automotive applications? Do cars have them and how about those big 18 wheelers that carry expensive cargo?

This may be a poor analogy, still...

And those pesky injury accident attorneys on major networks - advertisements. I wonder if they ever had to claim that something happened and part of the blame was the proper upkeep of the vehicle.

PeteHski

With Schrader valves, there is a real chance that you could get a slow leak with build up of dust and debris in the open valve. That’s why car tyres always have them fitted. With Presta valves you don’t have this same risk and therefore dust caps are not important.

noglider 

Oy vey.

Again, that's hypothetical.

I see I'm not succeeding at asking a question clearly.

Has anyone seen any of this happen on a bicycle?

Please answer the question I ask, not the one you want to answer. If you use words such as could, would, or should, you're not doing it right.

KerryIrons

Oh, now you want to get logical by referencing the real world?