Frame Load Carrying Capacity

A shy person asked:

Quoted message said:

I am interested to know if there is any information available on the load carrying capacity/rating
for bicycle frames. I expect this will vary based upon the type of bicycle eg Road, MTB,
Touring...

When bicycles are overloaded, it isn't the frames that fail, it's the wheels. With the exception of
a few exotic racing frames, any frame will be strong enough to carry any load that won't cause
wheel problems.

Quoted message said:

Are frames built to a minimum standard eg designed to carry XX kilograms and stress tested X
number of cycles without failure etc. prior to their release to the public?

No, generally not. Bicycle frames have developed by an evolutionary process of trial and error over
the last 110 years.

It is very difficult to make a good computer model of the varied stresses a bike frame will be
subjected to in the real world.

Sheldon "Survival Of The Fittest" Brown +-------------------------------------------+
| It's easier to be original and foolish | than original and wise. | --Gottfried Wilhelm Leibniz |
+-------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

I know that some manufacturers specify a maximum rider weight for their frames. For example, DeRosa
does. Some info may be available on manufacturers' websites or by email with them. Z

Sheldon Brown <[email hidden]> wrote:
: A shy person asked:

:> I am interested to know if there is any information available on the load carrying
:> capacity/rating for bicycle frames. I expect this will vary based upon the type of bicycle eg
:> Road, MTB, Touring...

: When bicycles are overloaded, it isn't the frames that fail, it's the wheels. With the exception
: of a few exotic racing frames, any frame will be strong enough to carry any load that won't cause
: wheel problems.

A strong carriage is required as well. Some sports recumbents can't take that much load, for example
see the ratings that Challenge provide for their bikes.

Some recumbent trikes are available in different frame strenghts. (For example Greenspeed and
Steintrikes.) I gather this basically just means how much metal (extra kilograms) there is on the
frame. The wheels could be just the same. Are trike makers sensible at all? :-) I guess three
well-built little wheels can take up quite a load, but you must count the rider in the load too :-)

--
Risto Varanka | helsinki.fihpv.htmlOpen ↗ varis at no spam please iki fi

the frame load question iza good one to search back about hmmmm ayear or more maybe two. I have a
Tiwainese Raleigh street carbon steel and lugge: reliable sources say the frame was intended for
300lbs max but the rims and wheels as S.Brown writes are the examinable suspension links for weakest
link under load. In "spoke nipples" a few doors away, a unsolvable discussion goes mostly nowhere
under the auspices of-too much weight-for the available materials as I ride a "hi speed" loaded
commuter. and frankly tho i can strees relieve til I'm... the expletive deleted nipples are gonna
wear out beyond spokey to the Parks six way in no time uh flat and duh that was once the problem
with spoke breakage-now solved with lube and quality spokes-but nipples?? expletive deleted.
roundout!!! Harris has a cr-18 rim that is excellent for loaded touring. I keep watch on the frame
but no problems. The rear seat stays and chainstays flex to the point of wrinkling inadequate paint
over 12 mile rides at 23 mph on a smooth path with 35-40 pounds or more on the rack.

A shy person asked:

Quoted message said:

:> I am interested to know if there is any information available on the load carrying
:> capacity/rating for bicycle frames. I expect this will vary based upon the type of bicycle eg
:> Road, MTB, Touring...

I replied:

Quoted message said:

: When bicycles are overloaded, it isn't the frames that fail, it's the wheels. With the exception
: of a few exotic racing frames, any frame will be strong enough to carry any load that won't
: cause wheel problems.

Risto Varanka said:

A strong carriage is required as well. Some sports recumbents can't take that much load, for
example see the ratings that Challenge provide for their bikes.

Some recumbent trikes are available in different frame strenghts. (For example Greenspeed and
Steintrikes.) I gather this basically just means how much metal (extra kilograms) there is on
the frame.

The original question was about _bicycles_ not trikes, which are an entirely different beast. Trike
design is much less mature than bicycle design.

Quoted message said:

The wheels could be just the same. Are trike makers sensible at all? :-) I guess three well-built
little wheels can take up quite a load, but you must count the rider in the load too :-)

Actually, _fast_ trikes, such as Greenspeeds are highly stressful to wheels, much more so than
bicycles. This is because a trike doesn't lean in the corners, so there are _much_ higher lateral
stresses on a trike that is ridden above boardwalk speed.

Fortunately, most fast trikes use 406 mm (20 inch) wheels, which are much stronger laterally than
full-sized wheels.

Sheldon "Greenspeed Lust" Brown +-------------------------------------------------+
| There is something fascinating about science. | One gets such wholesale returns of conjecture |
| out of such a trifling investment of fact. | --Mark Twain |
+-------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

the sun boiled into the gulf as i hoisted the evening cup of hemlock triangulating the thought that
factory paint applied to a HD commuter is not the desirable paint for this application. like, whats
reallly neede here is a temp cone application paint for the stresses involved at the
headset-downtube/toptube and the four stays and for some the departure of axle mounts.

what i stumbled on was the result of several failing experiments with hexane flourescent paints
which are NOT GOOD as the hexanes fade even in the antartic summer. at the stressed chain and seat
stays the rusto hexanes did a dry lake natural 90 degree mosiac wrinkle. such a guage paint wud be a
good idea before the failure of metal. "oh look, itsa gonna blow." is more comforting that "oh look
itsa blown."