Isaiahc72

I know department store bikes are no bueno due to the fact that they are heavy and poorly assembled with mostly crappy components. But my question is, how strong are their frames? Not how much strength-to-weight. I just plainly want to know how strong they are compared to the better quality bikes? Are they likely to break under me while I'm riding?

wahoonc

Depends, some are better than others. I have had some Huffys that were pretty durable, had a Sears bike that the frame bent under normal use. Without knowing what the specific steel alloy is, tubing wall thickness, how it was manufactured, etc there is no real way to tell. The good thing is that they are cheap enough if you do trash one another one isn't going to break the bank.

Aaron

Isaiahc72

Mostly interested in knowing about the Mongoose an Roadmaster brand bikes.

downtube42

I get a fair number of these bikes donated to the bike co-op, and a fair number of people come in for help repairing theirs. I don't recall ever seeing a broken frame. Just about everything else - hubs, cranks, brake levers, pedals, chains, derailleurs, shifters, shocks - but not frames.

Then again most of these bikes see very low mileage, and components fail long before the frames see much stress. Not all mind you, but most.

Deontologist

I rode my 40 pound alu dept. store bike hard for an entire summer. Everything else broke except the frame. Nonetheless, I'd expect the frame to break eventually at the welds ... whoever welded this bike together did a horrible job.

Nonetheless sometimes I see excellent welds on dept. store bikes.

MichaelW

Even the cheapest bicycles have to comply with European safety standards.

Dan Burkhart 

One reason cheap department store bikes are so heavy is the overbuilt frames. Built to survive the apocalypse.

Kopsis

Cheap TIG welded steel frames are hard to screw up. They're usually quite durable and will easily outlast the bike's components. Welding aluminum is a more exacting process and errors will substantially weaken the weld or the tubes near the weld. Generally, the frame will either fail quickly (in terms of mileage) or it will last a long time.

The biggest exception seems to be full-suspension frames. Those frame designs often aren't well engineered and are prone to fatigue failure in the suspension linkage. One could make the case that if you're going to be riding in a way that needs a full-suspension frame, going with a low cost bike is a bad idea from both a performance and a safety standpoint.

wahoonc

Not if sold in the US...

Aaron

wahoonc

Have to see if I can find the Bicycling issue from the late 70's early 80's...

They tore down a Huffy road bike and compared it to a decent quality road bike of the same era. There was only a couple of ounces difference in the weights of the frames. The largest weight difference was in the components.

Aaron

Retro Grouch 

Strong enough. I'm sure that, if you ride one into a tree or a brick wall hard enough, it'll break just like the most expensive handmade bike frame will.

I think that lots of people get the whole strength vs. weight issue backwards. The reason why expensive bikes are made with high strength materials isn't to make them stronger. It's so the builder can use less material to make a frame that's equally strong but weighs less. Find a junk Huffy somewhere and cut through one of the frame tubes with a hacksaw. Notice how thick it is. If you try to do the same with a high end steel bike you'll have a harder time because the frame tube will be so thin that it's hard to cut with a hacksaw.

MichaelW

US Consumer Product Safety Commission
Bicycle Requirements Business Guidance

Are there strength requirements for the fork and frame?
Yes. Clamp the front fork in the test fixture so it does not move and apply force until the fork bends 2 ½ inches. The fork shall have no evidence of fracture. The deflection at a force of 350-in-lbs shall be no greater than 2½ inches. Also, when the fork is mounted on the bicycle frame, the fork and frame assembly must withstand a steady force of 200 lbf or an impact force of 350 in-lbs, whichever is more severe, without breaking, or bending in a manner that would significantly limit the steering angle over which the front wheel can turn.

wahoonc

He was quoting the EUR standards NOT the USCPSC which are a complete joke.

Aaron

wphamilton

I don't know about Mongoose and Roadmaster, but my Denali frame weighs 4.5 pounds and I think is extremely over-built. Very stiff, the frame hardly flexed at all when I wrenched a stuck BB cup off standing on a 3-foot cheater bar.

fietsbob

You can make it cheap and adequate by using a Lot More low cost Metal in the Frame materials .

StephenH

You can't always tell the strength of welds by how pretty they are. Some welding processes will just look better and smoother than others, without any improvement in quality, and what looks like a better weld may have just been ground or sanded, too.

gpsblake

Never had a department store bike frame break on me yet, including hauling 50+ pounds of gear on it on multi-state tours.

I-Like-To-Bike

The belief in the all department store bikes are the spawn of Satan reputation (i.e. "no bueno"), and conversely the fable that all LBS bikes are wonderful pieces of fine machinery assembled and fitted to the users with loving care by trained and devoted craftsman are yarns spun up by LBS personnel and its devotees as well as by believers of Internet blarney.

Isaiahc72

Isn't that bike aluminum though? Then it shouldn't flex.

wphamilton

It's aluminum and then some. But I disagree, aluminum frames do flex.

Wilfred Laurier

I agree with most of the statements above - the frames may not be pretty or light, but they very rarely fail. I don't know if this is because they are totally overbuilt with cheap materials, or if because most BSOs practically never get ridden, and if they do, the components (wheels mainly) fail before the frame can suffer much abuse.

Also as mentioned above, the full suspension frames are different kettle of fish - the linkages get sloppy or break on those more frequently than on higher cost full suspension bikes.
The moral of the story is: If you are planning on getting a box store bike, get one with a rigid frame.

2manybikes

Hard to know. My friends Roadmaster frame broke. Some are fine.

Stucky

Only when they're broken...or just about to break.

Retro Grouch 

Why that's just wrong!

Years ago Vitus and Alan made aluminum framed bikes that used the same tubing diameters as the steel framed bikes of the time. They were comparatively light and quite flexy. Along came Gary Klein who decided to make an aluminum frame bike with the same amount of material but larger diameter, thin wall tubing. The flexiness went away.

Materials do have properties but it's the total design that determines whether a bike frame will be stiff or flexy.

Stucky

I'm no metalurgist, but that sounds wrong! I'll bet those Vitus and Alan frames weren't around very long- unless they were lugged frames, and the lugs were made out of a different alloy that would allow the flex; 'cause if aluminum flexes, it breaks- aluminum [I like the way the Aussies say it: Alu-minnie-um"!] has no elasticity- that is why all extant alu-minnie-um bikes are stiff.


I agree with that. My Al. Klein rides just as nice (if not nicer) than my CF Venge- but, the thing is, with al. you HAVE to design it so that it's stiff. Any flex (unless the flex is in a non-Al. part) will result in quick fatique and failure. This is why you don't even want to repair a dent in an Al. bike- Al. will break fast with any movement at all.

EDIT: I just had to look up those Al. Vitus frames to see what the deal was. They were BONDED, lugged frames- that's what allowed the flex. Neat thing, though- I had never known about them.