Advertise on Bikeforums.net



User Tag List

Results 1 to 11 of 11
  1. #1
    Senior Member
    Join Date
    Aug 2006
    Posts
    57
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    What determines maximum tyre pressure?

    My guess is that its a combination of the wheel, inner tube and the tyre, however ....

    I finally got myself a folder (cheap one at Halfords, their own brand, "Apollo"), its okay, just the one gear, but it folds small enough to fit on the train easy enough.

    The tyres were marked up as maximum pressure of 2.8 bar (whats that, about 30 psi?), which was turning out to be terrible - it couldn't take corners at any speed, bumps were a nitemare.

    I pumped the tyres up to about 4 bar, and this morning it was fantastic - massively less effort required to get up to the (low) maximum speed of the bike.

    So, back to the initial question - is the indicator on the tyre a reliable measure of the maximum pressure?

  2. #2
    Senior Member Fear&Trembling's Avatar
    Join Date
    Oct 2005
    Location
    London
    Posts
    637
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Well, I would not ride on tyres that had a max psi of 2.8 bar (approx:40 psi) for road use. You certainly can inflate them above the recommended max as there is a built in margin for over inflation. However, this is not advisable - particularly as I suspect the tyres that you are using are of the "cheap and nasty" variety. I would simply get better tyres with a higher psi rating and less rolling resistance...

  3. #3
    Senior Member
    Join Date
    Aug 2006
    Posts
    57
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Will do then, I'm sure there are a few shops in the area, get myself some better tyres.

  4. #4
    Senior Member
    Join Date
    Jul 2006
    Location
    UK
    Posts
    472
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by clonmult
    My guess is that its a combination of the wheel, inner tube and the tyre, however ....

    I finally got myself a folder (cheap one at Halfords, their own brand, "Apollo"), its okay, just the one gear, but it folds small enough to fit on the train easy enough.

    The tyres were marked up as maximum pressure of 2.8 bar (whats that, about 30 psi?), which was turning out to be terrible - it couldn't take corners at any speed, bumps were a nitemare.
    Is this it?

    http://www.halfords.com/webapp/wcs/s...egoryrn_33957#

    What markings are on the tyres?

    Any idea what the bike weighs?

  5. #5
    Senior Member
    Join Date
    Aug 2006
    Posts
    57
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yah, thats the bike, its locked up outside the office, I'll check the tyre markings at lunch.

    Not sure what it weighs - its easy enough to carry though - I cycle over tower bridge, then have to carry it down the stairs on the north side, its not too bad.

    And I went and had a puncture last night, I need a decent rear tyre and inner tube, not the cheapo nasty Halfords crud.

  6. #6
    Junior Member
    Join Date
    Aug 2007
    Posts
    9
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    A few years ago, I had an old 60's type Moulton with steel 16" x 1 3/8 wheels (sorry I don't know the modern metric sizing). I fitted it with the cheapest tubes and tyres - Halfords own brand, I think. A feature of these rims and tyres was the difficulty of fitting the beading over the rim. I broke several resin tyre levers, and generally had to resort to strong arm tactics to force the beading over the rim. However, the knock on effect of this was that I could blow the tyre's up rock hard, with no risk of forcing the tyres off the rim. Although the energy saving due to low rolling resistance was probably more than made up for by the extra work involved in trying to get the last bit of air into the tyres. IIRC, I used to get these up to around 90 to 100 psi.

  7. #7
    Senior Member
    Join Date
    Jun 2006
    Location
    New Zealand
    My Bikes
    Diamond Back Apex, Raleigh 20, Raleigh Sports
    Posts
    106
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    How do you get a tyre to 100 psi? Do you use a pump or a compressor? Sounds like a stupid question but using an air machine at a gas station it never goes above about 50.

  8. #8
    Bicycling Gnome
    Join Date
    Apr 2006
    Location
    55.0N 1.59W
    Posts
    1,877
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I use a track pump. I paid about twenty pounds for it, but I've seen far cheaper ones on ebay. They are going there for about £8 plus postage. They go up to really high pressures that you could never get near with a conventional bike carried pump - at least not without massive amounts of effort. It takes my 40x406 tyres from 80psi to 100 with about three strokes. Piece of cake.

    “Get a bicycle. You will not regret it, if you live." - Mark Twain

  9. #9
    jur
    jur is offline
    Senior Member
    Join Date
    May 2005
    Posts
    6,286
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by clonmult View Post
    My guess is that its a combination of the wheel, inner tube and the tyre, however ....

    I finally got myself a folder (cheap one at Halfords, their own brand, "Apollo"), its okay, just the one gear, but it folds small enough to fit on the train easy enough.

    The tyres were marked up as maximum pressure of 2.8 bar (whats that, about 30 psi?), which was turning out to be terrible - it couldn't take corners at any speed, bumps were a nitemare.

    I pumped the tyres up to about 4 bar, and this morning it was fantastic - massively less effort required to get up to the (low) maximum speed of the bike.

    So, back to the initial question - is the indicator on the tyre a reliable measure of the maximum pressure?
    The manufacturer will apply some margin to the tyre design and put that on the sidewall. The maximum value is determined by the strength of the carcase, ie the strength of the threads. A tyre under pressure causes tension in the threads which will have a maximum value before snapping. So a tyre with high number of threads per inch (tpi) will have a higher pressure rating.
    My folding bike photo essays www.dekter.net/

  10. #10
    The Legitimiser Sammyboy's Avatar
    Join Date
    Jul 2005
    Location
    Southampton, UK
    My Bikes
    Gazelle Trim Trophy, EG Bates Track Bike, HR Bates Cantiflex bike, Nigel Dean fixed gear conversion, Raleigh Royal, Falcon Westminster.
    Posts
    4,848
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    This is a good source for tyres of all sizes in the UK:

    http://www.sjscycles.co.uk

    Or here

    www.wiggle.co.uk

  11. #11
    Raleigh20 PugFixie, Merc LittlePixel's Avatar
    Join Date
    Sep 2004
    Location
    London UK
    My Bikes
    1982 Raleigh Twenty Hotrod Fixie; 1984 Peugeot Premier Fixie, 2007 Merc Lightweight folder
    Posts
    1,963
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Getting a track pump - off ebay just like EvilV says - was one of the best bike things I've ever done. At my old workplace someone even brought theirs in to stay as a communal resource which was a truly excellent thing for those days when you need to fix a puncture in your lunch-hour...

    One really shouldn't be trying to pump up tyres with a hand pump -they really don't cut it beyond about 30psi which in itself is a massive effort.

    Having a track pump means it's so much less effort to pump them up, which in turn means I'm so much more likely to keep tyres at their optimum pressure on a day-to-day basis, which can only be a good thing right?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •