When are Open Pro rims worn out?

bdm
bdm Posts: 112
edited December 2009 in Workshop
I've had about 20,000 miles so far from my Open Pro rims. The walls of new Open Pro rims are about 1.2mm when new; mine are now down to about 0.6-0.7mm.

Anyone suggest a minimum safe thickness for the rims? Somewhere Brandt writes of using 0.5mm: is that a bit risky - or maybe it's possible to go thinner still. Any experience with Open Pro failure thickness out there?

BDM
Bernard

Welcome!

It looks like you're new here. Sign in or register to get started.
«1

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    As well as measuring thickness, the rim wall starts to noticeably 'bow' outwards due to pressure from the tyre i.e. the brake track feels convex. Catastrophic rim failure can be very hazardous, particularly when going fast.
    Make mine an Italian, with Campagnolo on the side..
  • balthazar
    balthazar Posts: 1,565
    I've always replaced rims before they reached .5mm. There's no basis to it, I just chicken out. 0.6 – .7mm and 20k miles is the sort of life a rim should be proud of: let it out to pasture, I say.
  • normanp
    normanp Posts: 279
    How do you mesaure the thickness?
  • jonmack
    jonmack Posts: 522
    I'd imagine a set of digital vernier calipers.
  • geoff_ss
    geoff_ss Posts: 1,201
    normanp wrote:
    How do you mesaure the thickness?

    As mentioned, with a vernier gauge but it's difficult to get it into the rim. A method I've used is to fashion a caliper from a spoke to put round the rim and measure outside that. Not my idea, Chris Juden's of the CTC.

    A standard 14 gauge spoke is 2mm diameter so you just subtract 4mm from the reading. If you're going to be really anal you could measure the rim when new and make a note of it, then if you check each time you replace a tyre you'll get an idea of how the rim's wearing. I don't bother, but my wife does :) She tends to use the brakes more than I do.

    Geoff
    Old cyclists never die; they just fit smaller chainrings ... and pedal faster
  • gundersen
    gundersen Posts: 586
    I have never measured thickness - but from experience I can tell its one hell of a bang when they go. Last time it happened I rode 12 km home on the wheel as it was buggered anyway. Changed rim when I got home. Broke a piece about 10 - 15 cm long off if my memory serves me well.

    Usually you can feel the rim rub against the brake shoes before it goes.
  • gundersen
    gundersen Posts: 586
    I have never measured thickness - but from experience I can tell its one hell of a bang when they go. Last time it happened I rode 12 km home on the wheel as it was buggered anyway. Changed rim when I got home. Broke a piece about 10 - 15 cm long off if my memory serves me well.

    Usually you can feel the rim rub against the brake shoes before it goes.
  • Monty Dog
    Monty Dog Posts: 20,614
    A telling sign is when your braking starts to 'pulse' as if you have a buckled wheel and yet the wheel is still true.
    Make mine an Italian, with Campagnolo on the side..
  • Nigel Bennett
    Nigel Bennett Posts: 653
    I have a collection of well-worn rim sections from Rigida DP18s. They were down to about 0,6mm. I modified a micrometer with a ball on each anvil to measure the overall rim width (still with the tyre on) and I knew what the scrapping size was. When it started to get a bit dodgy, I'd pump up the tyre to 150psi and check to see if the rim bulged out anywhere.

    As peeps have said, bursting a rim out on the road isn't funny.
  • jhop
    jhop Posts: 369
    gundersen wrote:
    I have never measured thickness - but from experience I can tell its one hell of a bang when they go. Last time it happened I rode 12 km home on the wheel as it was buggered anyway. Changed rim when I got home. Broke a piece about 10 - 15 cm long off if my memory serves me well.

    Usually you can feel the rim rub against the brake shoes before it goes.

    My Open Pro front rim went exactly as described above on a 200k Audax fairly recently after 150k and left me in the middle of nowhere and with a long walk to civilisation, no chance of riding it at all.

    It was scary so if there is a way of checking then do it!!!!
  • andrew_s
    andrew_s Posts: 2,511
    This is the style of gauge you need for measuring rim thickness
  • balthazar
    balthazar Posts: 1,565
    andrew_s wrote:
    This is the style of gauge you need for measuring rim thickness

    Great little tool, I've never seen them before. For those like me who couldn't see how it works, this picture makes it clearer:

    G8869_cmyk.jpg
  • pieinthesky
    pieinthesky Posts: 417
    Firstly if you got 20 000 miles out of an open pro you have done very well, do you live in Norfolk? It owes you nothing so unless sure it is Ok get it replaced.

    I have gone through a few open pros and have sectioned them in various places out of interest before binning them.

    I didnt measure the wall thicknesses accurately but it was noticeable that they did not wear evenly all the way round. So if measuring the thickness, check in as many places as possible.

    Also as posters have already said, as soon as you feel any uneven braking, rubbing or vibration, check your rim. In my experience cracks appear or the rim bulges before catastrophic failure occurs. But dont rely on this as your life might depend on it.
  • NervexProf
    NervexProf Posts: 4,202
    A much better buy - measures in metric and imperial too.


    http://cgi.ebay.co.uk/6-inch-LCD-Digita ... 7C294%3A50
    Common sense in an uncommon degree is what the world calls wisdom
  • Chris Juden of the CTC recommends a simple proof test: inflate the tyre to twice its rated pressure. That will load the sidewall enough to break it if it's getting close.
    John Stevenson
  • sicknote
    sicknote Posts: 901
    NervexProf wrote:
    A much better buy - measures in metric and imperial too.


    http://cgi.ebay.co.uk/6-inch-LCD-Digita ... 7C294%3A50

    If you have a lidli's or Aldi's near you, have a look as they still have them near me for under £8 :D
  • alfablue
    alfablue Posts: 8,497
    I got a Lildl one - its great but it doesn't do this job because of the lip on the inside of the wheel rim. You can insert a spacer of some kind but then it gets a bit hit and miss. That's why the dedicated instruments are a better idea (and cheaper, though the digital calliper has been very useful for loads of other things).
  • sicknote
    sicknote Posts: 901
    On the one I have you can set it to zero at any point so if you taped a small spacer to one side, it would not be a problem at all.
    Plus it would be stop on to what thickness the rim is.
  • Dave Loasby
    Dave Loasby Posts: 32
    you all have me worried now. think i need to get the vernier out.
    Former employee of Ray Inkley cycles 1989-1991

    ex Lincoln Wheelers 1981-1990 iirc. TT + U12 CX
  • sicknote
    sicknote Posts: 901
    Think I will be checking mine too.
  • Kléber
    Kléber Posts: 6,842
    Chris Juden of the CTC recommends a simple proof test: inflate the tyre to twice its rated pressure. That will load the sidewall enough to break it if it's getting close.
    Good idea. Because the rim is likely to blow when you are braking and heating up the rim, increasing the pressure. Visual inspection works, check the surface for wear and to see if it looks worn. Remember the rim is part of the braking system, it is inevitable that it will wear.
  • balthazar
    balthazar Posts: 1,565
    Chris Juden of the CTC recommends a simple proof test: inflate the tyre to twice its rated pressure. That will load the sidewall enough to break it if it's getting close.
    Twice its rated pressure may well blow a tyre off a healthy rim, resulting in a bang nobody nearby will forget for a while. For the tyres commonly used by road riders that could be 240 psi, not easy to achieve with an ordinary track pump. I suggest keeping away from the dramatics and just measure the rim by any of the methods mentioned.
  • andrew_s
    andrew_s Posts: 2,511
    I'd call a rim OK at 160 psi myself. I normally stop pumping at 100-105, so that's about 50% over pressure.
    The advantage of a pressure test is that it's actually related to the failure mode.
    If you measure, whose recommended thickness do you take as the thickness at which you should replace the rim? How cautious were they being? Also if you measure, you could measure in the wrong locations for the actual weak point in your specific rim.

    If pressure testing, leave the rim at pressure for an hour or two before you let the tyre down to normal.
    Also make use of the track pump hose to stand clear of the wheel. Sometimes bits of broken rim can flail about and it would be annoying to get a gashed leg.
  • balthazar
    balthazar Posts: 1,565
    andrew_s wrote:
    I'd call a rim OK at 160 psi myself. I normally stop pumping at 100-105, so that's about 50% over pressure.
    The advantage of a pressure test is that it's actually related to the failure mode.
    If you measure, whose recommended thickness do you take as the thickness at which you should replace the rim? How cautious were they being? Also if you measure, you could measure in the wrong locations for the actual weak point in your specific rim.

    If pressure testing, leave the rim at pressure for an hour or two before you let the tyre down to normal.
    Also make use of the track pump hose to stand clear of the wheel. Sometimes bits of broken rim can flail about and it would be annoying to get a gashed leg.

    There are vagaries with both methods: the lack of consensus over minimum wall thickness, and the lack of consensus over a maximum pressure that testifies for rim safety.

    I'd prefer not to pump my tyre up so hard that I approach the point that it blows off - I've been in the room when that happened before, and it isn't fun. Given how few rims make it to this stage, I'd happily retire a rim at 0.6 - 0.7 mm, which is a tenth or two more cautious than the rough consensus. The extra miles I might have had won't worry me.
  • Chaz.Harding
    Chaz.Harding Posts: 3,144
    I'm with you on that balthazar! If you've had that many miles out of the rim, leave it be, and build up a new one.

    It's 'only' and Open Pro, so not mega super expensive! Can't say it's done you wrong either!
    Boo-yah mofo
    Sick to the power of rad
    Fix it 'till it's broke
  • andrew_s
    andrew_s Posts: 2,511
    I've now acquired one of the Tenth Gauges illustrated up thread, and measured the bits of dead rim I've got lying around. It seems like 0.6mm is indeed the point at which the rim is likely to start to fail. That's for wear into the tyre well. You can go thinner into the rim cavity, not that there's any way to measure it short of chopping the rim up.
    I'm probably still going to use the pump it up method though. It's quicker to pump the tyre up to 160 than it is to take the tyre off so you can measure the rim properly, so I'm more likely to check often enough.
  • TomF
    TomF Posts: 494
    I think I may acquire a guage and a more regular maintenance habit.

    This exploded in the dining room as I was eating my porridge before heading out on a club run...

    3395163379_c9ef3435a7.jpg
  • freehub
    freehub Posts: 4,257
    I wish I got 20,000 from mine, only got 3000.
  • don key
    don key Posts: 494
    I was at the lights last year about a mile and a half from Hillingdon with a guy I never met before, his wheel exploded just as he stopped and as I was not racing I gave him my wheel and walked the rest of the way, if it had happened mid race it would have caused car(bike)nage. The more I race the less fond I am of old /cheap/shoddy gear.
  • redddraggon
    redddraggon Posts: 10,862
    TomF wrote:
    I think I may acquire a guage and a more regular maintenance habit.

    This exploded in the dining room as I was eating my porridge before heading out on a club run...

    3395163379_c9ef3435a7.jpg

    Did you not snap a chain that weekend too?
    I like bikes...

    Twitter
    Flickr

Welcome!

It looks like you're new here. Sign in or register to get started.