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Tire Pressure Question(28 posts)

Tire Pressure QuestionJuniorgriff
May 15, 2003 12:51 PM
I just recently got into cycling and I went to my LBS and had the pressure in my tires checked because they felt squishy. The mechanic at the LBS told me that road tires usually lose pressure after a week or so and they need to be constantly checked. I am still learning about cycling, but is this true? Do I need to check the pressure in my tires that often? What kind of floor pump is a good value for the money? Any feedback is greatly appreciated.
it's not that hardmohair_chair
May 15, 2003 1:04 PM
How much pressure you lose depends a lot on what kind of tubes you are using. Lightweight tubes will lose air more than the thick ones.

But really, putting air in your tires should be part of your pre-ride ritual. You probably won't have to add air everyday, but at least once a week. Always check pressure before any long ride, too. It's not hard, and takes almost no time to do if you have a good floor pump. If all you have is a mini-pump, go buy a floor pump immediately. You can get the Joe Blow pump, one of the best out there, at Performance on sale for around $20.
It can happen ...Humma Hah
May 15, 2003 1:06 PM
... you lose pressure faster with higher-performance tires/tubes, which are thinner. Latex tubes can go flat overnight.

I put air in my cruiser's tires (which has super-thick thorn-resistant tubes) every 6 months or so.

Assuming you have a roadbike with those skinny-little Presta valve stems, you'll need a special bicycle pump intended for high pressure and Presta stems. A good start is a small "double-acting" pump intended for carrying on the bike or in a toolbag. I bought a decent one recently at a clearance sale for about $15. Most of these will fill either Presta or Schrader.

I use a floor pump with a built-in gage that cost something like $30, and fills both Presta and Schrader valves. Faster than the little pump, but you can't take it with you on a ride.

Department stores rarely carry pumps that will fill Presta valves, and auto parts stores NEVER do.
I do it every single rideDougSloan
May 15, 2003 1:22 PM
With a good floor pump with a built in guage, it doesn't take but an extra 60 seconds to pump up and at the same time check both tires before you ride. No reason not to. I've occasionally discovered problems before heading out doing this. If one tire starts at 100 psi and the other is 60, I know I have a concern. If you want the bike to handle and perform consistently, you should do it every ride, assuming you don't have the really thick thorn proof tubes, as HH does.

Doug
This just plain confuses me!!!Kerry
May 15, 2003 3:52 PM
I use Michelin ultralight tubes, 23mm tires, pumped to 8 bar (ca. 115 psi). I only need to pump them up once per week, during which I see less than 1 bar pressure loss. This takes about 5 strokes from my Silca Super Pista pump. If I pumped every day, it would take only one stroke of the pump. So what is the deal with pumping every day? I do check the tires by squeeze, so I can tell very easily if there's a problem. For me, pumping twice a week would seem extreme, but every day?
1 bar is huge, to meDougSloan
May 15, 2003 4:01 PM
1 bar = about 15 psi, right?

I want mine exactly the same every time. If I'm going to the trouble of putting a guage on them, then I might was well pump a stroke or two while I'm at it.

Also, I frequently ride different bikes, maybe 3 different ones each week (Pista, EV2, Alloro). I can't keep track of when I pumped up each bike. Better safe than sorry.

Maybe it's irrational anality. It's what I do and what I recommend, though.

Doug
I don't do that myself, but ...Humma Hah
May 15, 2003 4:52 PM
... If I ever need to hire a lawyer, it would be nice to get one who's that conscientions and such a stickler for details.

Being AR is not entirly a BAD thing.
I share your anality.KG 361
May 15, 2003 5:13 PM
Got to check them. Every ride. Only takes a couple of seconds. If it is my beater/commuter, I may let it go a day or 2, but then, it has thicker tubes and I really don't care too much how it rides.
1 bar is huge, to mepina
May 15, 2003 6:27 PM
Same here, i pump to same pressure before every ride. It's a pre-ride ritual with me.
Kinda like-KG 361
May 15, 2003 7:12 PM
the pre-ride piss. No matter how many times I've gone in the hr preceeding the ride, I still have to "go" right before I leave. Never fails.
Me too. nmMel Erickson
May 15, 2003 7:45 PM
The deal is the belief...micha
May 15, 2003 4:23 PM
... that if 8 bar is good, 10 bar must be better.

In many crits I did (years ago) there was a 12-bar POW! after the first few laps, telling me that some poor sop got flatted out of the race because of a meaningless minus 0.00000001 F small r reduction in rolling resistance.

If it's hard to the thumb, you're fine.
consistency is the issue for meDougSloan
May 15, 2003 4:41 PM
The are some tires I only run 100 psi in. However, I want them to be 100 psi every time. Some I run at 120 or 130. I've stopped running tubulars at 180 any more, as the grip really sucks.

Doug
Yeah, me too.dzrider
May 16, 2003 5:32 AM
On my commuter bike with bigger tires, I inflate them a few pounds above the ideal and let them go for a while before re-inflating. On my road ride I pump 'em up every time I take it out, in part because I'm not disciplined enough to remember if I did it the last ride much less the ride before. It's also, like watching my wheels spin through the brake pads after every ride, part of knowing that my bike is just how I want it to be.
Most important: Note the pressure brfore pumping...TFerguson
May 15, 2003 5:31 PM
I find this the most valuable part of the pre-ride pump up. If you find that the tire is 20 lb less than normal, it will probably be flat before the end of the ride.
TF
remove some pressure first...Bruno S
May 15, 2003 7:08 PM
I also find that tires loose about 10psi a week at the most. I pump once a week and sometimes it's difficult to get the pump started so I remove some pressure (to about 80) then I pump to 110.
re: Tire Pressure QuestionBarnyard
May 15, 2003 1:29 PM
I'm a big fan of the zefal hpx. If your frame is set for a frame fitting pump, it's a great way to go. It's always near by and it's a very reliable pump. Indy fab has a pump peg on their frames that is so dialed into the Zefal pump, it's wonderful combination, very secure fit. Little pumps don't give me much confidence. Though I do carry a Crank Brothers pump that has gotten me out of jam on occasion. Hopefully you can give your tires a squeeze once in a while and figure out when your dangerously low. Finally it's nice riding on hard tires, but it's also nice riding on tires that are not fully inflated.
re: Tire Pressure QuestionBaadDawg
May 15, 2003 6:34 PM
I have an zefal hpx and never use it. Its heavy, rattles on the bike and is just as hard to pump a tire as a minipump (for me at least)

I now use a Topeak pocket master blaster attached to the water bottle bracket and a floor pump and even though my floor pump has a guage I also use a seperate presta tire pressure guage.
I pump 'em up every ride..coonass
May 15, 2003 3:55 PM
since my hands aren't sensitive enough to distinguish between 110# and 85#...if you ride on low pressures tires, not only are you risking damage to the tire & tube (i.e., hit a rut), but you're also having to work harder to maintain your cadence and speed. There are a lot of good floor pumps on the market; I have a Silca floor pump which I bought in 1980, and only had to replace the diaphram twice (~$1/ea.) and I did change out the hose/head to a SmartHead setup. If self-servicing the pump is an issue, ask before you purchase. Don't skimp on the price....it's going to be with you a lonnnnnng time.
The difference in rolling resistance between 85 & 110Mel Erickson
May 15, 2003 7:53 PM
is almost nothing. You won't be working any harder to maintain you cadence and speed. If you don't believe me how 'bout Uncle Al?

2. UNCLE AL'S RANT: Rolling Resistance

DEAR UNCLE AL: It's obvious that low rolling resistance is
a good thing. Yet trying to find solid information about the
rolling resistance of different tires is a problem. Do you
have a cluestick to point the way to some clarity on this
issue? -- Michael R.

UNCLE AL FIRES BACK: When I opened your e-mail,
I cringed at the thought of the negative reactions I might
get after answering your question.

I know some of you won't agree with me, and I pretty much
know your reasons. You don't need to send long e-mails to
dispute the way I look at this issue. Hey, it was Mike who
asked, not you!

Rolling resistance is one of the most misunderstood elements
of the bike. There will be those who insist that reducing it
is all about running super-high tire pressure. That is simply
not the case.

Rolling resistance is dictated by several factors, one
being tire construction. A top-quality clincher tire will
have a threads-per-inch count ranging from 125 tpi to an
astounding 440 tpi. Most companies use nylon for casing
threads, going by names such as Aramid or Polyamide.

There will be 3-5 overlapping casing layers to give the tire
strength, puncture resistance and good handling
characteristics. The suppleness of the casing material is
key to performance and reducing rolling resistance.

Another factor is the tread material. Most top-end clinchers
are now using some form of silica compound, which lowers
rolling resistance while increasing cornering traction.
Sounds like magic, doesn't it?

Understand that the designers and engineers behind quality
tires are some of the brightest lights involved with the
bike industry. We are spoiled riding tires that are as good
as the stuff used in auto and motorcycle racing, yet we can
buy them for just $50.

Remember this: The best tires cost what they do because of
the technology and materials that go into making them. We
are the lucky beneficiaries of this high science.

The last factor affecting rolling resistance, obviously, is
tire pressure. If a tire is flat, it has a whole bunch of
resistance and really doesn't handle very well.

A properly inflated road tire (700x23C) at 6bar/87 psi has
about the same rolling resistance as the same tire at
8bar/115 psi. But at the higher pressure, the rider gives up
some of the cornering traction and comfort so necessary to
cycling.

There's a perception that running tires at 115-140 psi
somehow makes a rider faster. What those maximum pressures
really do is accelerate wear, compromise handling and give an
extremely harsh and skittish ride.

Super-high pressure also compromises the integrity of your
wheels and, in the case of a high-speed blowout, can assure
you of a visit with the pavement. Heavy braking while
descending will heat the rims and increase pressures well
beyond the danger zone.

I've talked to pros about tire pressure. They universally
agree that inflation to 85-100 psi is plenty, depending on
road conditions. Pressures up to 110-115 psi are fine on a
smooth time trial course without many corners.

Most riders who run super-high pressure will remain
unconvinced about the benefits of lower pressure. I think
it's their placebo.
I've learned from years of MTBing....Stinky Hippie
May 16, 2003 4:22 AM
...and even rollerblading that rough surfaces require lower pressures and smooth surfaces require higher pressures ( or, in the case of rollerblading, wheels with higher durometer compounds are good for smooth pavement; lower durometer for rough conditions)

I'm running 110psi on conti gp3000 and found it to be the sweetspot (I weigh 160 pounds): I tried the 120 psi thing, thinking I'd be faster, but the loss of traction in the rough stuff meant that my wheel wasn't keeping contact with the the pavement and was therefore slowing me down. This is why I'm usually faster running lower air pressures in my MTB.

Good post. thanks

Feel the gin
Lots of good deals on floor pumps.DERICK
May 15, 2003 4:48 PM
Just check some of the websites featured on this site. Pumps are always on sale or clearance.
I pump before every ridebianchi boy
May 15, 2003 7:15 PM
Since I rarely ever get flats, it must be doing something right -- or I'm just lucky. Pumping up your tires with a good floor pump takes about 30 seconds. Well worth the time to me. When I connect the pump head, the pressure generally reads about 85 psi, even if I rode the day before and pumped to 110 psi before the ride. I don't know if it's losing that much pressure overnight, since some air probably escapes when connecting the head, but it appears to be losing something.
Rolling resistance & PSIcoonass
May 15, 2003 7:32 PM
http://www.terrymorse.com/bike/rolres.html
Agree with Uncle Al but... as far as why they cost...Old_school_nik
May 16, 2003 5:24 AM
I mostly agree with Uncle Al's response but.. one claim he made is just a load of Horse S**T - "tires cost so much becuse of al the technology that goes intot them? - no they cost so much because they market them that way.Overseas shops sll them for 50% less than they sell them for here. They can't sell them for that here becuase the one distributor in the US basically price fixes the cost of their brand high end tires to keep prices high - if some catalog sells them too cheap they get shut out in a variety of ways so as not to break the law.... of course I am getting off the topic - but it just erks me when someone says all the r & d and everything and materials make the tires expensive.

-Jas
What about rider weight?oldschool
May 16, 2003 6:37 AM
My car manual states that proper tire pressure depends on tire size and total load. This dicussion seems to ignore the fact that some folks use wider tires (which require less pressure per square inch to support the load) and that we don't all weight 160lbs. I'm quite certain that the appropriate pressure for a tire of given width should be different for a 130lb rider versus a 200lb rider.
I'm with youcoonass
May 16, 2003 8:37 AM
Automobile tire pressure should be taken when the tires are cold (haven't been driven for a minimum 2 hours), and if you're loading the car up for a trip, you HAVE to check the tire pressure AFTER the car is loaded...I typically put ~100-110# in the front, and ~120-130# on the rear tire, due to the additional body weight....(Don't get too technical guys/gals, yes I know my body weight will also distribute to the front wheel) and obviously I'm not going to go through the trouble to sit on the bike, and read the gauge....just a compromise of oldschool's & my philosophy.
"loaded" pressure?micha
May 16, 2003 5:15 PM
Tire pressure, bike or car, is overpressure above current atmospheric pressure. No amount of load, in trunk or on saddle, will change a tire pressure reading.

Tire deflection will change under load - yes. And increased tire deflection under load is why you add a few bars to the rear(s).