Tandemonium 2 Posted June 19, 2016 Posted June 19, 2016 I have a cannondale tandem , mountain bike 29 , with dt swiss rims . The max rim pressure is 4 bar . For road use I want to put on a set of 32 mm gator skins which I probably will have to push to 6 bar . Is this recommended to exceed the rim pressure with so much .
porqui Posted June 19, 2016 Posted June 19, 2016 I think you answered your own question. I especially would play it safe when it comes to tandem wheels as failure would be more catastrophic.
Showtime Posted June 19, 2016 Posted June 19, 2016 Force = Pressure x Area So 6 bar from a high volume mountain bike tyre is allot more force on the rim than 6 bar from a road tyre.
Tandemonium 2 Posted June 19, 2016 Author Posted June 19, 2016 Why so high a pressure??????I was under the impression that was the pressure to go for on road slicks with tubes. were a tandem couple of about 160 kg
Tandemonium 2 Posted June 19, 2016 Author Posted June 19, 2016 Force = Pressure x Area So 6 bar from a high volume mountain bike tyre is allot more force on the rim than 6 bar from a road tyre.Showtime please explain in lay mans terms . Are you telling me that 6 bar from a road tyre would not be to bad .
BaGearA Posted June 19, 2016 Posted June 19, 2016 Showtime please explain in lay mans terms . Are you telling me that 6 bar from a road tyre would not be to bad .Yes but not because the rim won't fail but because there is less air to intensify the failure i.e. if it fails it may blow a spoke or break them rim joint (using the road tire ) If using there mountain bike tire there is so much more air still at the same pressure but when it fails it will push that massive amount of air through a small hole with all the possibility of causing a catastrophic failure , ex: it starts by breaking the rim joint but all theair can't escape fast enough so eventually it rips the whole rim apart . I am not saying 6 Bar from a road tire won't be bad for the rim , I am just saying 6 bar from a mtb tire will be FAR worse
porqui Posted June 19, 2016 Posted June 19, 2016 6 bars of pressure is the same no matter what type or size tyre or rim you have.The rim joint won't fail nor will a spoke blow out - it is more the seating of the bead of the tyre on the rim failing or the edge of the rim where the bead is not being able to hold the 6 bars of pressure. The pressure exerts the same force evenly on all "sides" of the tyre and rim. Having 160kg or 80kg on the bike will not significantly change the pressure in the tyre but it will have a serious effect on the mechanics of the wheel.
JXV Posted June 19, 2016 Posted June 19, 2016 I have a cannondale tandem , mountain bike 29 , with dt swiss rims . The max rim pressure is 4 bar . For road use I want to put on a set of 32 mm gator skins which I probably will have to push to 6 bar . Is this recommended to exceed the rim pressure with so much .The pressure rating of the rim relates to the strength of the flanges. The designer would have built some fat built into that 4 bar rating so that it can withstand 4bar plus overpressure due to normal dynamic events like hitting a stone or root or a pothole at good pace. Pumping to 6bar it could blow up in your face but if it doesn't then abovementioned dynamic events might rip a flange off while you're riding. Sent from my SM-G900F using Tapatalk
Capricorn Posted June 19, 2016 Posted June 19, 2016 P = F/A pound force (lbf) <> pound mass (lb) F = ma or F = mg in under gravitational acceleration The larger the area, the larger the force. Showtime has a point there somewhere.
JXV Posted June 19, 2016 Posted June 19, 2016 Yes but not because the rim won't fail but because there is less air to intensify the failure i.e. if it fails it may blow a spoke or break them rim joint (using the road tire ) If using there mountain bike tire there is so much more air still at the same pressure but when it fails it will push that massive amount of air through a small hole with all the possibility of causing a catastrophic failure , ex: it starts by breaking the rim joint but all theair can't escape fast enough so eventually it rips the whole rim apart . I am not saying 6 Bar from a road tire won't be bad for the rim , I am just saying 6 bar from a mtb tire will be FAR worseThat's not how pressure breaks a rim and the volume of air is not really a big issue. The issue is the outward force on the rim flanges..... Sent from my SM-G900F using Tapatalk
Captain Fastbastard Mayhem Posted June 19, 2016 Posted June 19, 2016 Now why you delete that.. it was a gem!Because it was full of dumbass. Lol.
Showtime Posted June 19, 2016 Posted June 19, 2016 Showtime please explain in lay mans terms . Are you telling me that 6 bar from a road tyre would not be to bad . I see this point is contested wherever it is discussed. Look at the tyre inflation section of the notubes rim specification below. http://www.notubes.com/literature/ztr_rim_specifications.pdf From my understanding a wider tyre will apply a larger pulling force to the rim bead at the same pressure than a narrow tyre and I would definitely run a road tyre at 6 bar. But I have been wrong before and stand to be corrected.
Tandemonium 2 Posted June 20, 2016 Author Posted June 20, 2016 Hi thanks for all the replys. Got hold of dt swiss tech that confirmed there should be no problem. Their pressure chart shows for the particular rim and tyre size i can go up to 7.2
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