riotboy

so i got these wheels

and so far i have checked my tubes, tire and rim (rear) and the rear wont hold enough air. i have checked every tube ive put in so far (ive used 3 different tubes) and none of them hold enough air for me to ride safely. WTF?! i used my friends pump and it said the psi was 95-100 but when i got on the bike it looked like it was going flat. air remained in the tire it just looked like it was half pumped or something. am i doing something wrong?! i have cloth rim tape and all

trons

are the tubes popping or what? try a different pump

riotboy

nope! tubes have come out intact and without holes/leaks
ive actually used 3 different pumps as well
this is just getting frustrating for me

dkb

Have you checked the inserts in the valve stems? Schrader valves have inserts that thread into the body of the valve stem. Ever notice some valve caps have a sort of two pronged top to them? these are used to tighten or unscrew the valve stem insert. Maybe they're in there tight enough to hold air when the tube is inflated outside of the tire but when under higher pressure mounted in the tire, they leak. I doubt your wheels have anything to do with it. If you don't have this "special" valve cap try a pair of skinny needle nose pliers or go to a gas station, they probably got a couple laying around.

sr20det

+1 find out the diff between presta and schrader and make sure you find out how they work.

teiaperigosa

what do you mean "won't hold enough air"?

riotboy

"none of them hold enough air for me to ride safely"
they just end up looking flat when im riding around
hitting bumps could damage the rims or give me snake bites in the tubes

riotboy

nothing is wrong with any of the inserts or valves. the first tube i used in this wheel came right off my old one. i havent had this problem EVER with my other wheels. and this isnt a problem with the front wheel/tube. the front is fine.

riotboy

i use presta
and i know how they work

borrachobandito

do you have a good rim strip in your rim?

do you have a good way to measure air pressure?(besides a pump gauge?)

is your tire worn?

i mean, c'mon man, there are just basic things that you check.

riotboy

do you have a good rim strip in your rim?

yes theyre brand new, i bought some when i got the wheels in



do you have a good way to measure air pressure?(besides a pump gauge?)

define "good way". i used a pump specific to presta valves
and it had a psi guage intigrated into the pump. its a specialized
pump but i dunno the exact model



is your tire worn?

NOPE! i dont skid or skip nor do i ride more than 4 miles a day
have had the tires since a little before christmas. the back is a 700c x 25
shows hardly any wear and i checked the tire inside and out for any defects



i mean, c'mon man, there are just basic things that you check.

yeah no ****. i checked everything i could think of.

Ill Mitch

Maybe just ignore the pressure guage and pump it up until the tire feels nice and hard when you squeeze it

riotboy

i tried that as well on the second tube and it still did the same thing
i even bounced the wheel and it bounced pretty good but when i got
on it and rode around it looked a little flat again. after trying two tubes
that have been used before i decided to get a new tube this morning

also the first tube on the wheel was pumped up by an LBS. my friend and
i drove in his van to the LBS to have them tighten my cog and lockring and
they decided to pump the tire too but after we drove home the tire was
completely flat. this was the tube that was on my previous wheel. i checked
everything and found nothing wrong. not even with the tube. after that i
decided to go on to tube #2. still didnt pump up right. bought tube #3 and
still having the same issue. this is so lame. i just want to ride.

endform

I thought this thread was going to be about being irritated by the seemingly violent and irrational nature of skin culture, but that's just me.

mrbertfixy

the main question is: do the tubes hold air when they are not on the rim?

take the tubes that seem to be flat off the rim and pump them up to 10-20 psi or so and see if there any leaks (if you can't hear leaks, use water, or leave them alone for a little while and see if they end up flat). if there are, there is something wrong with the rim or tire. burrs on the rim perhaps, improperly installed rim strip, i'm not really sure.

if the tubes hold air, but always seems flat, maybe the valves are defective.

there are only so many problems there could be, and all are easy to check individually.

(1) bad valves, highly unlikely on three tubes.
(2) bad rim/strips. rim strips leaves spoke holes exposed, puncturing tubes, or some sort of burr on the rim.
(3) very small foreign object in the tire.
(4) bad pumps, also highly unlikely.

if your LBS can't figure this out, i don't have much faith in them.

shants

i'm half-tempted to say that this is a good ole case of bike hypochondria. you do, of course, realize, that the rear tire is always going to compress a little bit when you are riding it -- especially relative to the front, which doesn't have as much weight on it -- right? 95-100psi on many road tires will look pretty compressed when you sit on the saddle and put weight on the rear. even on insane ass tires running 140psi, you'll see some. some tires, too, are softer and will display this behavior more than others.

pump the up the tire to pressure (say, ~115-120 on a decent 23c road tire), get on it, ride it for a sec, and then check the pressure (you can often do this just by putting a pump with a gauge back on it). if it's more than ~10-15psi off from the pressure reading that you had when you initially pumped the tube, then there may actually be something afoot.

sloppy robot

you need a real pump...end of story

riotboy

dont assume that i dont have one

riotboy

maybe i am just being paranoid. i did pump the new one up to 120psi but im afraid of pumping it higher then that.

riotboy

"the main question is: do the tubes hold air when they are not on the rim?"

yes they do. ive pumped up all three and held em under water. no leaks


"if the tubes hold air, but always seems flat, maybe the valves are defective."

i was thinking that too but i doubt it.


"if your LBS can't figure this out, i don't have much faith in them"

im just gonna take this in on monday no riding for me tomorrow

Terror_in_pink

oi vey, seems like a slow leak....

check the hole where the inflation valve is passed through the rim. if it's sharp maybe you can sand it? This could very well be giving you consistent flats.

take the tube out and run your fingers along the the inside of the tire and the beading. Then move on to the rim and the walls feeling for anything that can be puncturing it. Sometimes you can't even see them.

Hey, maybe your friend who sold you the tubes is getting you back for eating his pizza.

Nothing worse than consistent flats, something is definitely wrong.

you either have something sharp puncturing it or the valve thingie is too sharp. cant really think of aything else other than defective tubes. did you switch out tube brands?

kensmerlin

From your description, it sounds like the tube might be undersized for the tire. Your tube pressure is fine but it's too small for the tire volume. Is your front wheel also mounting a 25mm tire? Are you using the same brand of tube for both wheels? If you are using different tubes, don't assume that all 700c tube will hold enough air for a 25mm tire. Some tubes are rated up to 23mm (like Michelins) while others are suitable for up to 25mm. If you have a Conti tube, stick that in there as they are supposed to go from 19-25mm tires. The other option would be to slap a 23mm tire on back with the tubes that you've tried. If either of these options work then you have your diagnosis.

Good luck!

YoKev

**popcorn**

babetski

Ever blown up a tube outside a tire? They all expand quite a lot, the constricting surface is the tire.

I think Shants is on the ball here. The tire is depressing to the point that it is creating a contact patch of a specific size. Lots of people don't understand this, so I'll give you an example.

A rider has two bikes, the sum total of the rider and bike weight for both configurations is 200 pounds. Each tire is pumped to 100psi and rather impressively, the rider is able to distribute his weight evenly over both wheels. The difference is that one bike has 700x23 and the other 26x2.1 tires. How big is the contact patch on each wheel?

Answer: 1in^2, 2 wheels x 1in^2 x 100 pounds/in^2 = 200 pounds

There are some slight variations, such as how supple the tire is, etc. but they make for very small variations. The tire will deform until it has created the appropriate contact patch size and on some tires, this may appear that the tire is more deformed than others.

jacobpriest

why would you only pump your tires to 95 psi
thats why it looks flat

get decent tire pressure then it will be fine.