Max Weight

[Elad63]

when a folding bike manufacture mentions max weight, are they talking about just the rider or rider plus all of personal gear

[photoassign]

i always presume it is the total weight of the load.

[Elad63]

that's what I thought also,

[Mr. Smith]

when a folding bike manufacture mentions max weight, are they talking about just the rider or rider plus all of personal gear

Bike Friday quoted me a limit for me (plus backpack, etc.) and a limit for the front and rear racks to be combined. Hard to tell if there's any fat in the design...

[StephenH]

A weight limit on a bicycle has to be very very approximate. At some point, the manufacturer has to assume the equivalent of a "biggest bump" that you're going to go over, and design for that. If they assumed a bigger bump, the capacity would go down. If they assumed a smaller bump, it would go up. The likelihood of having problems with the bike goes up as the weight goes up, but it's not like a 200-lb rider can ride it anywhere with no problem, and when a 201-lb rider gets on, it breaks in half.

[Mr. Smith]

A weight limit on a bicycle has to be very very approximate. At some point, the manufacturer has to assume the equivalent of a "biggest bump" that you're going to go over, and design for that. If they assumed a bigger bump, the capacity would go down. If they assumed a smaller bump, it would go up. The likelihood of having problems with the bike goes up as the weight goes up, but it's not like a 200-lb rider can ride it anywhere with no problem, and when a 201-lb rider gets on, it breaks in half.

I'm trying to learn more about structural analysis of a bike frame and found a dated article that is interesting. The deflection diagrams and impact factors are much higher than I would have guessed would be considered. In any case, this article might be useful to those interested in some of the loads considered in design... Mechies always prototype and test anyway, but the theory is still useful. I'm starting to find some books on the subject, but haven't bought any I've found yet.

http://www.sheldonbrown.com/rinard/fea.htm

[EvilV]

A weight limit on a bicycle has to be very very approximate. At some point, the manufacturer has to assume the equivalent of a "biggest bump" that you're going to go over, and design for that. If they assumed a bigger bump, the capacity would go down. If they assumed a smaller bump, it would go up. The likelihood of having problems with the bike goes up as the weight goes up, but it's not like a 200-lb rider can ride it anywhere with no problem, and when a 201-lb rider gets on, it breaks in half.

I expect that any designer that didn't build in some 'fat' when specifying a max weight, would be lining themselves up to spend a lot of time in court. If it were me, I'd be specifying a max weight that allowed a safety factor of about 50% over what I expected the bike to tolerate long term.

OBVIOUSLY THOSE WHO DISREGARD THE LIMITS SPECIFIED TAKE THEMSELVES NEARER TO THE EDGE. it would be a horrible thing to find one's mount break in half while flying down a hill and encountering a pot hole.

[Elad63]

thanks for all the responses, I was just a little curious about all the extra weight when commuting or touring.

[jefmcg]

FWIW, from http://www.mezzobikes.com/spec.htm
The Mezzo is designed and tested for use by riders weighing up to 100kg (15 stone 10lbs). Total rider weight including clothing and luggage 110kg.

[jagatron]

I think what's more interesting are the design limits built into seat tubes, and when people extend those a bit, or pull them a little bit above the insertion line. What safety margins are there there? Can Torque calculations be made with someone at a certain weight, and see how much further they can safely extend the tube? One part of this is the amount that must remain in the seat tube - but some people are cutting off the ends and inserting faux seatposts inside. How much can safely be added, assuming the min mark is maintained, for a certain rider?

[jur]

The problem as I understand over-extending seatposts, is not the seatpost but the frame which may be damaged. The seatpost must be inserted past all welding joints because the end of the post may cause cracking in the welds through the stress exerted by the end of the post. The lever arm on the end of the post is less for a deeper inserted post.

[Elad63]

so max weight has to do with the seat post insertion more then anything

[EvilV]

so max weight has to do with the seat post insertion more then anything

I wouldn't say that, although having the post almost out of the tube would be a very bad idea. For myself, and I'm not an engineer, I wouldn't be worried about being a few pounds over the stated max weight - maybe even up to 10%, but I'd be reluctant to go to 20% 0r 25% and if I did, I'd mind where I rode the bike and how. I certainly wouldn't be bumping up and down kerbs and crashing through potholes and I wouldn't be hammering it uphill either. It is probably just common sense - designs have some safety factor built in certainly, but that's there for a reason, and part of why it is there is to cope with unexpected shock loadings like kerbs and pot- holes. I suppose you cant be over max weight AND bash the thing about.

[Elad63]

I myself am not over weight for my folder, but when adding all the racks and loaded panniers I will be over the limit.

[EvilV]

I myself am not over weight for my folder, but when adding all the racks and loaded panniers I will be over the limit.

Yes it's quite easy to pack many extra pounds onto a bike. I don't know what the maximum recommended weights are for my bikes, but I'd never get near them since I weigh about 175 pounds tops. If I were to put on another thirty pounds of baggage, I think I'd consider it over loading. Handling is always weird when you start lashing sacks of goods onto various bits of the frame. To be fair, the small wheels and low centre of gravity of my favourite bikes makes handling less awful when loaded up.