Tires Thoughts on Tire Pressure

Discussion in 'Bicycle Repair' started by HoughMade, May 21, 2008.

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  1. HoughMade

    HoughMade Guest

    I've seen a lot of opinions about tire pressure in various threads- please post your peferences here and back your choice up with an anecdote or research if you have it. To aid us, please post the size and type of tire.

    I run 26x2.125 cruiser tires on steel 2.125 rims- so far I have been running at the sidewall suggested 40 psi, but I have not taken any long trips yet.

    Please share your thoughts and experiences.

  2. sjackson

    sjackson Member

    My experience thus far only lies with un-motorized bicycles. On my road bikes, I usually inflate the tires to 110psi. Skinny little 700x28 conty contacts. It says 85psi on the sidewall, but that just feels mushy to me, and I've never had a blow out at 110. I feel like I'd be more likely to get a pinch flat at 85 anyway.

    What does the conventional wisdom say in regards to motorized bikes?
  3. HoughMade

    HoughMade Guest

    I don't know- that's what I am looking for.
  4. JemmaUK

    JemmaUK Guest

    With mine I just pump the tyres until they feel firm and the bike doesnt squirrel - from what i can tell its around 30psi - I dont have a pressure tester.

    I have noticed that there is a wear area beginning to develop along the centre line of the tyre which means I could stand to drop them off a little - but then there is the fact that at the speeds the machines go it might cause problems with cornering if you go too low on pressures (rim/bead coming free and other fun experiences).

    I have been looking into helmets today amongst other things.. They are expensive - the choice is either a upper price cycle type or a lower price full face but the problem with the latter is that I have neck and shoulder problems already *sigh*

    If anyone finds a cheap supply of white tyres.. I am interested in getting a set :)

    Jemma xx
  5. I have a mountain bike with 26" X 1.75 knobby tires. I run 35psi, the tire rating is 40-65psi. It does not have suspension other than suspension seat post, so I run "low" for a smoother ride. I live in Florida and have read that friction and road heat could cause a blowout on a motored bike, prob another good reason to run low tire pressure..

    I hope this is what your looking for...
  6. srdavo

    srdavo Active Member

    I agree.....too low = pinch flats.
    motored or not..... I run within the range the tire is rated for.
    I even ran 80psi (100 max) kenda kwest 26X1.5 on my friction drive.
  7. Marktur

    Marktur Member

    Well, I'm sure some of you have seen my "Another Flat" thread... I now have a solid core tube in the front and Bell Extra-thick, super-duper, self sealing jobbie in the back (couldn't get the rear solid on correctly and gave up after 6 hours of fighting with it)....but I used 3 layers of electrical tape over the spokes...then the tube...then Mr Tuffy protectors.

    I'm running Bell Kevlar Comfort Tires, 26x1.75 at 28psi, but I felt a little squirrely so I'm going to add another 5-7 lbs when I get home. I think I've been getting blowouts from too much pressure, the speeds (20-25mph), and the heat being generated. I had it at around 50psi to start (tire sidewalls on the previous cruiser balloon tires said 45-65psi), and have had horrible luck.

    Today at the lower PSI, not only did I not get a flat, but the ride was smoother because the tire was softer. With these lower profile tires I have now, the solid front wheel felt great.

    OK, ready to try and make it home (6 miles)....I hope I don't have another flat.

    Jemma - I just posted about my new helmet...I think they're a great idea, and I don't care if I look goofy or not...I want to live to be a "dirty old man"! :)

  8. loquin

    loquin Active Member

    I'm also running a Bell kevlar comfort tire on the front, and an Innova Swiftor smooth tire on the rear, which works GREAT with a friction drive. (I just wish that Bell would come out with a smooth kevlar tire - they have a smooth cruiser non-kevlar version.) I run both at around 50 psi, but then, I'm an ex-defensive tackle & tip the scales currently at about 350 pounds.

    When the temps get over a hundred, I back off the pressure to about 45 psi.

    Followup re the Innova Swiftor tire:

    I really like the tire - it grips very well, and is really a smooth ride. However, it's made from a very soft rubber compound. Because if this, if you skid the tire, the road WILL grind the tire flat in spots. I had an emergency stop last week (with a broken front brake cable,) and the road ground right through to the fabric!.

    FYI: If that happens, a plastic water bottle, cut into a couple of "U" shaped sections three inches long or so, will make an emergency tire 'liner' to support the patched tube, to keep it from blowing out again at the same spot.
    Last edited: Jun 17, 2008
  9. sjackson

    sjackson Member

    I really think that recommended sidewall rating are there for ride comfort mainly. I always feel like it's safe to inflate a bit more. This is a discussion that serious road bikers have all the time and there are valid arguments on both sides. I know some messengers who ride at 150psi on slicks because it gives them less deformation on their tires and more speed. It wears down your center tread quickly, and is rough on your rims when you hit potholes, but pinch flats at lower pressures are a bigger risk than blow outs at slightly higher ones IMO. Also remember, the less your tires are deforming, the less they heat up. The hotter they are, the more likely they are to fail... especially at high speeds. Throw some more heat on the rim from your caliper brakes and it's almost a guarantee.
  10. Marktur

    Marktur Member

    How FAST do you normally ride? How agressive do you enter and exit turns?
    And do you ride during the summer? I see you're in and dry.
    Also, what innertubes do you use?

    I'm only 215lbs, so I shouldn't be having these flats...

  11. losenup

    losenup Member

    With bicycles I just pump till it feels good. Not to hard, because it not comfortable, but not to soft so I loose topspeed.
  12. datz510

    datz510 Member

    I'm running slime tubes in mine and so I run a lower pressure to prevent the tube from exploding.. Around 30psi front and rear. Rides really nice.
  13. HoughMade

    HoughMade Guest

    ....resist screwing up your own topic...resist...resist...fight it.....nope, can't do it...

    That's what she said !
  14. loquin

    loquin Active Member

    Marktur: I'm running 20-25 MPH, but slow down for the turns. ALL the major city streets in the Phoenix area are on a 1 mile grid, north/south, or east/west. Only in the developments do you have curved streets. Only if you get into the hills or mountains the street plans aren't so rigid.

    I currently have a slimed tub in the front, and a thorn resistant tube in the back. When the temps get over 110, I tend not to ride too much, else you feel like a big chunk o'jerky when you get there! If I do have to rode when it gets real hot, I drop about 5 psi out of the tires.
  15. JosephGarcia

    JosephGarcia Guest

    i ride those standard smooth tread whitewalls. i dont know the brand. i always keep them between 40 and 50 PSI, i only get flats when i use standard tubes.

    Target sells 26x2.2ish tubes with sealant inside that fixes holes as they happen. they are made by Schwinn and they have never failed me, the only time they have not kept air is when it was slashed. i ran a pair on my motorbike for two years, the engine failed before the tubes.

    when you get a puncture, the air pressure drops, but once the sealant seals the hole no more air escapes, and you can fill it back to regular PSI, rotating the tire or riding on it helps seal it quicker as well, gets the fluid sloshing
  16. srdavo

    srdavo Active Member

  17. If you have SLIME you should decrease your pressure when your motoring on your bicycle. From what I have experienced,slime will generate excessive heat and will BLOW that tube to NOTHING.
    Last year riding MOOP my happy time I was doing a 70 miler when at about 60 miles of mostly continuous 15 mph riding and it was like 85 degrees out my tire went It went BANG!!
    Upon checking my tire my tube was in shreds. I had it inflated to 40 psi.
    I blame the slime,man. But slime is your friend. I replaced my front stock tube on cronus with a slime tube in my tool pouch that I know for a fact has a hole from it being pinched. And guess what. It's still there.
    I think if you don't do the slime maybe you can get by with the higher pressures. But remember that higher pressures benefit the PEDAL biker for this gives the tire less rolling resistance. Now I suppose you can get better mileage with less resistance by giving your tires some pressure,but with your engine off,high pressure or not it's pretty much a dog to pedal (Cronus not so much actually,but that's another topic).
    And then there's that other theory that with lower pressures your tire will wear down from all the flexing because your weight brought that rear tire lower. But it hasn't happened to me yet.
    I run 30 psi. It's measured on my Bell foot pump so I would only guess that's it's fairly accurate. I do know that 30 psi inflates my fat cruiser tire enough that when I squeeze the sides I can only squeeze about 1 or 2 millimeters. It also has some shock absorption.
    My front tube has been replaced recently but my rear slime tube was replaced before Cronus got the Titan. And with todays riding it has about 650 miles on it.
    It works for me. I know the last time I had more pressure.
    I simply don't want another BOOM happening,but I'm very prepared if and when it happens again.
    Btw,those frame pumps are malarky. I got a foot pump and it fits in my tool pouch.
    And for reference,back when I busted tires for a living,our major law when it came to passenger car tire pressures was 32 psi.
    So 30 psi is quite a bit when you look at it that way.
    Last edited by a moderator: May 22, 2008
  18. dbigkahunna

    dbigkahunna Guest

    Running a DE scrubber I keep them at max. 70 psi on a 700 tire. And I aint no little feller.
    The tires seem to wear less and ride comfort is not too bad. I run 20-25 MPH with occasional blast over 30.
    Last edited by a moderator: May 22, 2008
  19. Marktur

    Marktur Member

    Well...I'm feeling confident enough to feel more confident in my setup...rode home from work today doing 23mph...couple of blasts to 26-27....motor had a lot more to give, too.

    If I kept the bike, I'd lower the gearing a bit, because 15mph is a rough ride on mine...maybe because I still have only about 80 miles on it, but the low-end to mid range seems really rich and bogged down. Once I'm doing about 17-18 it gets on the pipe, then I have to back off.

    Since there's no mixture adjustment available, lower gearing will let the motor run a bit faster, but still allow me to ride at 25 or less. Thoughts?

    PS. Now that it's sold, I'm missing it :( But I'll make a nicer bike this time.
  20. lennyharp

    lennyharp Member

    Tires should be kept inflated in the range recommended on the tires. Most tires are tested and fail more above and below recommended air pressures. I have generally kept tires inflated to the maximum because I rode with my own horsepower, make that a little less than 1/2 a horse power. You will produce more heat at lower air pressure because you have more resistance which creates heat and work. Too low a pressure also allows the tire to slip under hard braking and may cut the stem.

    In racing we would use sew up tires and over inflate at times to lessen rolling resistance. This is not a good idea to keep from having flats but will allow you to go faster. 180 PSI is the max I have pumped 1" sew ups to. That is probably not too relevant to motorized bikes unless you have some real good suspension.

    I have ridden well over 100,000 bicycle miles since 1973. I have had a lot of flat tires. I figure that you spend as much on rubber for a bicycle as for a car or truck and maybe more. Tires are cheaper but you only get 1000 to 2500 miles per tire. Slime is the best product I have found to keep me riding and not patching. Slime works better on fat tires than skinny ones, but I have done ok with it in 27" X 1 3/8" or 700CM X 35MM tires.

    I have found several odd causes for flats that may escape attention. Thorns that cause flats need to be removed or they will re-puncture a tube. Rim strips need to be in good shape and cover spoke nipples and all rim edges need to be smooth. Any edges or sharp pokey areas will sooner or later wear thru a tube. One last thought is to use a pump with a gage built in so it is easy to tell the psi.
    Last edited: May 22, 2008