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  1. #1
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    Ever had this happen?

    Yesterday we had a blowout in the front tyre while going downhill - pretty scary resulting in a few grazes. Luckily our son, who was in his seat at the back, was unscathed (a recommendation for Rhode Gear Limo).

    The sidewall of the tyre, just where it touched the rim was ripped to shreds, like the brake pad was rubbing. However, I didn't see how that could be happening. I've just been to the bike shop to have everything checked over and the mechanic reckons that sometimes under braking the tyre can stop rotating while the rim is still going round, ripping the tyre to shreds. This is the first time in four years of tandeming that we've had this happen. Has anyone had this happen to them and, more importantly, are there any tricks to stop it happening again?

    Ian

  2. #2
    hors category TandemGeek's Avatar
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    Whenever I've seen a tire that has "blown out" to the extent that the bead came apart it has been a wire-beaded tire where the tube was pinched under the rim when it was installed, or where the tube lifted the tire's bead strip away from the rim seat under heavy braking due to rim overheating, or where the tire was just old and dried out and the bead tape came apart from the tire.

    In the second scenario, as the rim/tire/ tube heated up and the air pressure in the tube increased the tube worked its way under the bead and either blew when it was pinched on a subsequent rotation or when it nicked the brake blocks. In any of these scenarios, the blow-outs (kaboom!!) were dramatic enough to shred the cloth bead strip and tire adjacent to the tube blow-out point and in one case it even knocked the cantilever brake arm that clipped it out of whack. The only other thing I've seen that replicates the blow-off is where a misaligned brake block is rubbing against the tire and wears it thin enough for the tube to push through and blow.

    The tricks to preventing it are to make sure you have good tires that have a nice, tight fit between the bead and the bead seat. If they're too easy to remove and install, it's not a good fit. Secondly, make sure your tubes are seated in the tire and not pinched between it and the rim. Thirdly, make sure your brake blocks are aligned to fall on the braking surface and remain well away from the tire's sidewall. Fourth, be mindful of how hard you are using your brakes on steep descents. Brake loads should be alternated between front and rear brakes on long descents so that the rims get a chance to cool off a bit between brake applications. Riding the brakes will heat many wheel/tire combinations to a point where blow-offs can occur.

    If you know that you will encounter steep descents where extensive use of the brakes on your tandem are required an auxiliary rear drum drag brake would be a good addition. If you don't have a drag brake and find yourself on long descents that demand a lot of heavy brake use keep your speed down from the start of the descent and consider making several stops along the descent to allow your rims to cool.

  3. #3
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    I'm not sure quite what happened. It's a short hill that we ride 3 to 5 times a week, and have never had a problem before. So I don't see overheating being the cause. Having said that I have got an Arai drum brake on order.

    I had just mended a puncture the night before and may not have seated the tyre properly. Also, although not worn out, the tyre is a bit older and it just may have been the last straw for it.

    Who knows, but I don't want to experience it again!

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    We had the cable on our Arai Drum brake snap while going pretty fast in the French Alps. The rear tire blew about 20 seconds later. Mind you this was a Bike Friday, so a smaller wheel, less rim surface area to disperse heat and we had panniers fore and aft.

  5. #5
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    Today was the first day back on the tandem after our crash. We have a new front tyre and tube and the bike was checked out at our local shop. We walked down the hill from home (I'm a bit nervous of it now) and then rode in.

    One thing I did notice though was that the front brake was "snatching" on the rim. When applying the brakes they seem to start to grip, then suddenly grip hard before releasing, causing a lot of juddering. It also seems that the calipers flex (but probably not enough to push the pads into the tyre).
    Has anyone got any suggestions how to cure this? I was thinking of trying another type of brake block (I currently use Kool Stop, grey ones on the front and Kool Stop Mountian pads on the back) - any suggestions? Otherwise, what about Magura HS33 hydraulic rim brakes - does anyone have experience of these? My only other thought was my headset needs replacing.

    I would really appreciate any advice you could give, as this is starting to affect my enjoyment of tandem cycling.
    Ian

  6. #6
    Time for a change. stapfam's Avatar
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    Quote Originally Posted by simsi
    Yesterday we had a blowout in the front tyre while going downhill - pretty scary resulting in a few grazes. Luckily our son, who was in his seat at the back, was unscathed (a recommendation for Rhode Gear Limo).

    The sidewall of the tyre, just where it touched the rim was ripped to shreds, like the brake pad was rubbing. However, I didn't see how that could be happening. I've just been to the bike shop to have everything checked over and the mechanic reckons that sometimes under braking the tyre can stop rotating while the rim is still going round, ripping the tyre to shreds. This is the first time in four years of tandeming that we've had this happen. Has anyone had this happen to them and, more importantly, are there any tricks to stop it happening again?

    Ian
    Been out tonight and had our first big off. Off road, downhill at around 35mph. Took a "Jump" and caught a snakebite on the front tyre. It wasn't long before we were off and it looks as though the only injury is a bloody nose on the pilot. However the front tyre has had it for future use. Running on a flat tyre for no more than 20yards before we were over put enough cuts and grazes into the sidewall to scrap the tyre. Sods law but we did not have the spare folder with us, that we always carry for this eventuality, so 16 large tyre repair patches on the side wall and we limped to the nearest pub, about 1 mile away, and had a couple of pints of guinness awaiting the wife with the car for recovery. In that mile or so, the tube had started to push the patches through the tyre so we would not have got much further. Thank goodness that the pub was handy enough for us to replenish our thirst that we had got on the slow ride to it.

    The tyre looks exactly as yours sounds. Enough sidewall damage to think that the tyre has failed, wheras it was the sudden deflation and running on a flat tyre that has ruined it. Incidentally it was a new tyre, no more than 100 miles on it, and the pressure was correct at 60 psi.(Checked before the ride)

  7. #7
    hors category TandemGeek's Avatar
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    Quote Originally Posted by simsi
    I had just mended a puncture the night before and may not have seated the tyre properly. Also, although not worn out, the tyre is a bit older and it just may have been the last straw for it.
    I suspect the tube was pinched and it's very common. In fact, we were riding with friends a couple weeks ago and they had just moved their tires/tubes over to a back-up set of wheels the night before and blew the rear tire with a resounding BOOM right at the bottom of a fast descent when the light changed to red and required an aggressive stop. It had the classic unseated tire bead with the tube splayed wide open with an 8" gash.

    Best trick for installing tubes so that they don't get pinched is to put enough air in them to give them full shape, stuff them into the tire casing, and then mount the tire. As you get close to seating the last bit of the tire bead you may find that the tube needs to be deflated a bit but that's about it. Also, be careful using your tire levers so as not to unintentionally "nick" the tube such that a weak spot is created.

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