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Tire pressure over time...

Started by Feanor · · Last activity · 11 posts · 2,100 views

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01 / Original postTire pressure over time...Feanor · 8 Aug 2003 02 / This pagePosts 1–11Page 1 of 1 · chronological order 03 / Latest replyPost #11BugMan · 15 Aug 2003

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Bike Cafe
Published
8 August 2003
Last activity
15 August 2003
Original author
Feanor
Posts
11
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Public discussion
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2,100
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Topics
Tyre pressureMountain bikingRim tape and valves

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  1. Original post
    Feanor
    Archived post
    #1

    Here is another real newb question for the group,

    On my mountain bike, I can pump up its off-road tires to their normal 50 PSI and even if I come back after a week, the tire pressures will still be 50 PSI...

    Being still relatively new to the sometimes insane pressures that my clincher road tires have in comparison, I was wondering what was "normal" as far as how long road tires hold their pumped pressure with use...

    I have, since getting my bike, replaced the no-name tubes with bontrager tubes (have to use long stem because of the deep dish wheels) and my normal tire pressure is approximately 110 PSI (The Bontrager Race X Lite Tires list 120PSI as their max)

    I checked the rim tape and it is sound and intact, and I make sure always that the tube is properly seated within the tire, but It appears like each day with or without use that the tire pressure drops somewhere between 5 to 10 PSI with or without use...

    I realize that because of the enormous pressures compared to Mountain Bike knobbies, the stem seal and integrity of the tire and tube are far more critical, but I was just wondering what everyone else does as far as tire pressure and keep ing it up to specs... (i.e. do you pump up the tires everyday before your ride? every other day, every week etc...)

    Just want to know if what I've been experiencing is an anomaly fixable by better quality equipment, or if its perfectly normal...

    Thanks all!

    Feanor

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  2. CycleFrog
    Archived post
    #2

    It's perfectly normal. Expect to add some pressure to your tires each ride. One of the most common sights at a roady gathering is the pump being taken out and tires being pumped up to operating pressures.

    For a newbie you have some good questions.

    CycleFrog

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  3. BugMan
    Archived post
    #3

    Feanor -- CycleFrog is right. It has to do with the relative air volume in the two tire types - road tires have much less total volume than MTB tires, thus a small amount of air leakage will be noticeable as pressure drop much earlier than with an MTB tire.

    I recommend you ride your road tires inflated to the max - you'll minimize rolling resistance (= faster), lower your risk of pinch flats, and extend tire life. Of course, special road conditions may dictate a lower pressure (maybe slightly lower with wet roads to increase traction), but normally you'll want to inflate them to max pressure every time you ride them.

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  4. Feanor
    Archived post
    #4

    Thanks for the info Bugman and Cyclefrog!

    Bugman, Inflating to as close to the rated max pressure as possible seems entirely logical. I would think that is why the print that value in the first place...

    But on tires such as Vittoria Corsa KS that are rated at 180psi, does that mean you should get close to that value as well? Is there an upper safety limit? I would imagine that a tire letting go catastropically at 180psi would be a rather epic explosion! 🙂

    Thanks again!

    Feanor

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  5. petersta
    Archived post
    #5

    As a newbie to road cycling I was amazed at how much air leaks out of the tires between each ride.
    When my riding partner suggested quite strongly that I check my pressure I thought he was joking as the tire "felt" hard enough, but it was down to 70psi. A couple of swift pumps and it was back up to 100psi and good to go.
    I don't know if supporting my 200lb frame on rides increases the amount of air escaping - yet another reason to loose weight!!!

    Peter

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  6. BugMan
    Archived post
    #6

    Feanor,

    Tires rated for 180 should be run at 180 - they're designed for that pressure. Running them lower doesn't make them safer - it just increases the risk of flats and reduces tire life. I presume your talking tubulars at those pressures, which can handle it due to their design. Don't worry about a higher rated tire having a more catastrophic blowout risk - it's not like that.

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  7. Feanor
    Archived post
    #7
    Quoted post said:

    Originally posted by BugMan
    Feanor,

    Tires rated for 180 should be run at 180 - they're designed for that pressure. Running them lower doesn't make them safer - it just increases the risk of flats and reduces tire life. I presume your talking tubulars at those pressures, which can handle it due to their design. Don't worry about a higher rated tire having a more catastrophic blowout risk - it's not like that.

    That ultimately makes the most sense, Thanks Bugman!

    Being from the low pressure (tire) world of mountain bikes, you'd probably laugh watching me pump up road bike tires to 120... The last few strokes of the pump I'm wincing and turning my head away waiting for possible tire detonation *laughing* But I'm getting more used to it slowly 🙂 When a tire finally does let go in the future, I'll probably be taken completely by surprise!

    Have a good one!

    Feanor

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  8. Snarl
    Archived post
    #8

    Interesting Thread !!

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  9. kokopuffs
    Archived post
    #9

    My mtb tires, Continental Traffic, are inflated to max pressure, 65 pounds. Yet, after 10 days passes, they've deflated approximately 10%. So they require weekly reinflation..

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  10. Insight Driver
    Archived post
    #10

    Since the proper answers have been made, all I can offer here is amplification. I am a recreational rider and pump my tires up every other day. Rolling resistance is the biggest reason for I can feel a difference with a ten pound pressure drop in my 120 psi tires.

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  11. BugMan
    Archived post
    #11

    Well, kokopuffs brought up a good point about MTB tires. My comments above about maintaining max pressure at all times referred ONLY to road tires. MTB tires is a different story - you want to adjust tire pressure for trail/weather conditions. For example, in wet conditions, fully-inflated tires are much more prone to slippage - take the pressure down to get better traction. On surfaces with lots of sharp rocks, go max to prevent flatting. These are the two extremes - go in between for intermediate conditions.

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