Hairy Posted August 13, 2012 Share So just how liable is an LBS here if they sell a bike with rims, that they "Should" know the specific specs and limitations of , to a rider that is clearly over the weight limit. Should they not advise the client up front before his/her purchase RE this? I am not wanting to start a witch hunt here, but I do feel a decent LBS would know there products and steer a client in the right direction when discussing the purchase. H Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted August 13, 2012 Share Counter-intuitively, drop-offs and rocky sections don't increase stress on a rim but reduces it. The examples you cite are not good ones unless the bump is a sharp one and the rim bottoms out through the tyre. Only then does rim strength come into play in "rough riding". Johan, in this example, surely the stresses on one area would be in compression whereas the other side would be in extension? EG - if I hit a 4ft dropoff to flat ground, and hard... would the bottom most spokes not experience forces in compression (ad yes, therefore be under less tension, but only due to the compressive force experienced when landing) and would the top most spokes not experience MORE tension (as a result of the downward gravitational force of the bike and rider)? Link to comment Share on other sites More sharing options...
Hairy Posted August 13, 2012 Share Counter-intuitively, drop-offs and rocky sections don't increase stress on a rim but reduces it. The examples you cite are not good ones unless the bump is a sharp one and the rim bottoms out through the tyre. Only then does rim strength come into play in "rough riding". i.e, nice square edged type rock gardens? Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted August 13, 2012 Share So just how liable is an LBS here if they sell a bike with rims, that they "Should" know the specific specs and limitations of , to a rider that is clearly over the weight limit. Should they not advise the client up front before his/her purchase RE this? I am not wanting to start a witch hunt here, but I do feel a decent LBS would know there products and steer a client in the right direction when discussing the purchase. H Send them to Enticement. He'll know what to do. Pfft. Thing is, you're right. But also, certain bikes are sold with a certain expectation of the type of rider that is going to be riding them (weight etc) and therefore are specced with certain wheels. It is the LBS's responsibility to ensure that, as the provider, the correct bike is being sold to the client. That includes the wheels / tyres that are fitted as well. That is if the guy doesn't come in and say (a la Little Britain) - I want THAT one! Link to comment Share on other sites More sharing options...
Hairy Posted August 13, 2012 Share Send them to Enticement. He'll know what to do. Pfft. Thing is, you're right. But also, certain bikes are sold with a certain expectation of the type of rider that is going to be riding them (weight etc) and therefore are specced with certain wheels. It is the LBS's responsibility to ensure that, as the provider, the correct bike is being sold to the client. That includes the wheels / tyres that are fitted as well. That is if the guy doesn't come in and say (a la Little Britain) - I want THAT one! Should a drama student client come in and demand a certain bike that is waaaayyyy to fragile for say person then I do feel the LBS should ensure that the client is aware of this. Now without becoming like the USA where you have to cover your ass for everything, should the LBS not also get the Client to sign an indemnity form RE the purchase as there will be chop who will take an issue as per the hypothetical drama student above, who will try their luck at the Consumer Protection Act. Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted August 13, 2012 Share Should a drama student client come in and demand a certain bike that is waaaayyyy to fragile for say person then I do feel the LBS should ensure that the client is aware of this. Now without becoming like the USA where you have to cover your ass for everything, should the LBS not also get the Client to sign an indemnity form RE the purchase as there will be chop who will take an issue as per the hypothetical drama student above, who will try their luck at the Consumer Protection Act. Yeah, it's a sad sad situation. But seriously - the average Joe doesn't know that there may be weight limits on wheels etc. But if you go to an LBS to buy a bike, and ask their advice, they shouldn't just tell you to buy the pink sparkly one 'cos it's pink and it sparkles. More should be asked about what type of riding they do, and what they plan on doing with it. Sadly, this isn't done as much any more. Link to comment Share on other sites More sharing options...
Johan Bornman Posted August 13, 2012 Share Johan, in this example, surely the stresses on one area would be in compression whereas the other side would be in extension? EG - if I hit a 4ft dropoff to flat ground, and hard... would the bottom most spokes not experience forces in compression (ad yes, therefore be under less tension, but only due to the compressive force experienced when landing) and would the top most spokes not experience MORE tension (as a result of the downward gravitational force of the bike and rider)?No. This has been debated here ad-infinitum. It always causes a huge barney so I suggest you do a search. Use keywords like "stand on bottom sokes" and "reduce tension" in my posts. You'll find it. Link to comment Share on other sites More sharing options...
Johan Bornman Posted August 13, 2012 Share i.e, nice square edged type rock gardens? i.e, nice square edged type rock gardens? Correct Link to comment Share on other sites More sharing options...
Hairy Posted August 13, 2012 Share Yeah, it's a sad sad situation. But seriously - the average Joe doesn't know that there may be weight limits on wheels etc. But if you go to an LBS to buy a bike, and ask their advice, they shouldn't just tell you to buy the pink sparkly one 'cos it's pink and it sparkles. More should be asked about what type of riding they do, and what they plan on doing with it. Sadly, this isn't done as much any more. I like and agree with what you are saying Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted August 13, 2012 Share No. This has been debated here ad-infinitum. It always causes a huge barney so I suggest you do a search. Use keywords like "stand on bottom sokes" and "reduce tension" in my posts. You'll find it. okay - I don't know enough on the subject of wheels to go further on that, but in a nutshell is it due to the overall tensioning role that the spokes perform on the circular construct of the wheel? Link to comment Share on other sites More sharing options...
Hairy Posted August 13, 2012 Share While we are on the wheel strength subject, and sorry OP for the hi-jack, if you want a strong wheel build should you go with butted or straight gauge spokes? Link to comment Share on other sites More sharing options...
Johan Bornman Posted August 13, 2012 Share okay - I don't know enough on the subject of wheels to go further on that, but in a nutshell is it due to the overall tensioning role that the spokes perform on the circular construct of the wheel? Sort of. A tensioned bicycle wheel is a pre-stressed structure and pre-stress allows strange things, like concrete to not crack under tension and bicycle wheels to never increase tension anywhere on the wheel when in compression. Edited August 13, 2012 by Johan Bornman Link to comment Share on other sites More sharing options...
Captain Fastbastard Mayhem Posted August 13, 2012 Share Sort of. A tensioned bicycle wheel is a pre-stressed structure and pre-stress allows strange things, like concrete to not crack under tension and bicycle wheels to never increase tension anywhere on the wheel when in compression. in other words, hocus pocus... Got ya. Link to comment Share on other sites More sharing options...
Johan Bornman Posted August 13, 2012 Share While we are on the wheel strength subject, and sorry OP for the hi-jack, if you want a strong wheel build should you go with butted or straight gauge spokes?While we are on the wheel strength subject, and sorry OP for the hi-jack, if you want a strong wheel build should you go with butted or straight gauge spokes? I prefer not to use "strong" in the context of wheels. It has strange connotations. Straight-gauge spokes are strong enough but not durable enough. Double butted spokes are not as strong as straight gauge, but strong enough. They are infinitely more durable though and therefore you always build a quality wheel with double-butted. I have explained the concept of strength and durability in the context of wheels here often enough and a search should produce the results. Link to comment Share on other sites More sharing options...
Johan Bornman Posted August 13, 2012 Share in other words, hocus pocus... Got ya. To the contrary.It is a well developed and easily demonstrable science. Without pre-stress science, buildings will still have arched doorways and windows, we won't have long-span concrete bridges and wheels will have wooden spokes like ox wagons. Go buy yourself a copy of Structures (And why things don't fall down) by GE Gordon. It is an easy read and gives you insight into these sort of structural anomilies. Edited August 13, 2012 by Johan Bornman Link to comment Share on other sites More sharing options...
arendoog Posted August 13, 2012 Share Anyway .I will swop your wheels for a good set of giant wheelset from a xtc bike that my daughter 60kg rides .That way both will win Link to comment Share on other sites More sharing options...
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