I have heard claim that Al dents easier than other frame materials.
Any experience or opinion?

Yeah, I think that's pretty much accepted as fact. Although there's a range of dent-resistance based on wall thickness, aluminum tubes are generally thinner than other metal tubes used for bikes, and some aluminum tubes are thinner than other aluminum tubes.. Carbon fiber doesn't dent exactly, but it can crush in localized areas.

Multiple alloys of aluminum, wall thicknesses and diameters, lacking specifics .. check your Ouija board for the answer.

Ceteris paribus, maybe. But ceteris ain't paribus. Some steel frames dent easier than some aluminum frames.

yes, it dents, frames are normally made from pretty thin walled Alu(alloy) I dented an MTB frame by leaning it (maybe dropping a little) against at tree, still ride the same after a few years, have seen road bike with big dents, and the owners riding them for a long time with no issues.

Really?

As mentioned, one runs the full gambit of bike frames...

Some aluminum frames are mighty heavy.
Some steel frames are paper thin.

Carbon Fiber doesn't dent Of course, what might dent a steel frame could crack the Carbon. Even so, road bikes are intended to be ridden on the road. MTBs are intended to take abuse and are built stronger throughout.

The claim that aluminum frames dent more easily is just another generalization that doesn't always hold up in specific cases.

All things being equal the tubing of an aluminum frame will have more than twice the thickness than a steel frame. However things are never equal. In order to improve stiffness, a typical aluminum frame will have larger diameter tubes spreading the same volume of material thinner.

So modern aluminum frames have large diameter fairly thin walled down tubes, but a modern high end steel tube, ie. 531 or better will be even thinner. So a high end aluminum frame may dent easier than a low end steel, or aluminum, frame. But a high end steel frame will dent just as easily if not more so.

So, don't crash and let your handlebar swing into your frame, or drop your bike against a parking meter.

Steel, aluminum, Ti or carbon fiber, a high end bike is like a good sports car, simply not built to handle the abuse of a F-150 pickup. Treat it accordingly.

Thinner walls, not smaller diameter.


You mean twice the diameter of course.

No, I meant wall thickness. I prefaced it with all things equal, so diameter equal, the wall needs to be thicker to make up the difference in material strength. Then I continued, by explaining that that added material would be spread thinner in a larger diameter tube.

So it pays to read an entire thougt before assuming you know the writer's intent.

I'm calling "B.S." on this over-generalization. While it may be true that 'fat tube' aluminum frames like Cannondales or Kleins might be thinner than steel (not certain, I've never cut an aluminum frame apart), that is only because of the larger tubing diameter. If you take the tubing from one of those Trek bonded aluminum frames, however, you would be wrong (probably).

To make a long story short, all aluminum has a higher ductility modulus than any steel does. However, since the strength modulus is roughly 1/3 that of steel, you need roughly 3x the thickness at any given point to have the same strength. If this is achieved by enlarging the tubing diameter, then, yeah, it's easier to dent, guaranteed.

And CF does not 'dent' at all, it will eventually fracture, though.

Anyone wondering about wall thickness might compare seat tube ODs which are generally knowable, to the ID as known by the post it fits.

As I said earlier, typical aluminum tubes are thicker walled than their steel counterparts, however the very large diameter or super large box sections may be thinner, or even if thicker, the shape and lower strength make them easier to dent.

As I post so often in various contexts ---- There are no rules, only situations.

Hey sorry to step on your toes buddy - Grand Bois misunderstood something I wrote and I did too much correcting. I didn't think "all things being equal" included diameter.



I have a Klein and that's where my perception comes from. I'm hearing here that there are aluminum tubes with thickass walls and if that's true then yeah, they're not likely to dent.

I also have a Trek commuter with Alpha aluminum - the tubing isn't as big as the Klein's but it's way bigger than standard steel tubing. I'd be surprised if it had much dent resistance.

It's not true. All the nonsense above about Al tubes having thinner walls are BS. Even with oversized tubes, the aluminum is two or three times thicker than a light steel tube, as well as having double the diameter. Super lightweight steel (when it was common) was much easier to dent with its 0.3 or 0.4mm thick walls than modern oversized aluminum is with 0.9 or 1.1 mm thick walls. Conventional wisdom has always been that steel bikes could be made much lighter by making even thinner tube walls, but they would be too easy to dent even though the frames could theoretically be strong enough for regular riding.

My understanding of Reynolds 853 is that the alloy was originally used for car body panels because of its dent resistance compared to other steels, so modern lightweight steel frames are likely better than the fragile and dentable steel frames of yore, and likely as dent-resistant as aluminum.
Source: Lightweight steel racing bikes in the past were much more commonly dented than aluminum lightweight bikes are today.

Not sure where you got this idea. Aluminum tubes have thicker walls than lightweight steel tubes in every bicycle application I have seen. Need proof? Most tubing manufacturers publish tube dimensions - see if you can find a lightweight steel tube with a thicker wall than any aluminum tube. Failing the time to do research, cut the down tube in half on any aluminum and any steel bike... the steel tube will have walls thin enough that you could use to give youself a punch biopsy of one of your nipples, but the aluminum will have thick walls that you wold have trouble using as a cookie cutter.

Grand Bois did not misunderstand what DiabloScott said. He just couldn't believe he said it.

I'm concerned about the purpose of this thread. It's been well publicized that Squeeze's family has purchased a Trek 920. For obvious reasons, it should still be in pristine condition. Now I'm worried. Has it tipped over and fallen on the nightstand? Hope all is well!

Hey I'm happy to apologize and be corrected if I'm wrong; because I want to be right as much as possible. Especially about something I may have been wrong about for so many years. I just accepted it and never looked up actual numbers.

"Aluminum bikes dent easier because thin walls" was in all the bike reviews in all the magazines; where did that come from?

"Don't clamp your aluminum bike in the workstand because it'll crush the thin tubing." Wrong, or different problem?

"The tubing is so thin on <x brand> bike that you can feel it give with just thumb pressure." Baloney?


Thinnest area of tubing on my Klein is apparently 0.8 mm thick, up to 2mm at the BB joint. Conventional steel tubing ranges from 0.7 to 1.0 mm.

A few years ago, I had a chance at a great deal on an aluminum frame Commencal mountain bike that had a big dent on the downtube when we received it at our warehouse. It was a sample, so it was never really intended for sale, more so that we could show it to dealers. Eventually, we lost the distributorship and had to sell off remaining stock, so I bought it. It turned out that the dent wasn't the problem, the frame had at least 2 major flaws in both the front and rear triangles, neither of which really had much to do with welding but more to do with poor quality control and testing. A dent may not kill your frame, but poor quality control and insufficient testing can be a killer

This is a problem of comparing apples to oranges, while forgetting that there are a number of varieties of both oranges and apples.

Gauges and diameters vary in every material, and in the case of aluminum they vary greatly. Talking about "dentability" based on coarse generalities is meaningless. In fact, even the same material in the same gauge will have varying "dentability" based on shape.

You can see this if you look at auto bodies. Any single body panel is of uniform thickness and material, but resistance to denting varies. Go to any car (preferably your own), and press on a fender or door panel where it's relatively flat and it'll yield easily. Now look for an area of greater curvature, and press with equal force and you'll note greater resistance.

If you don't have a car to play with you can do the same experiment with a hard boiled egg (or raw if you prefer) tap the blunt (flat) end and it cracks easily, but it'll take noticeably harder tapping to break the pointy end.

This is to show that dentability is a complex consideration, which depends on multiple factors, and generalization is useless.

BTW - in all fairness to those with previous mythconceptions on this subject, I should note that at identical thickness and curvature an aluminum frame will dent easier than a steel one.

The only conclusion we can accurately draw on this subject is that there are no conclusions because of the range of variables.

Can o worms here. As some have said. With steel there's a rule of thumb of a 50:1 ratio of diameter to wall thickness before "beer canning' (haven't read that term yet). is more likely to happen.


But with all generalizations and real life the devil is in the details and the actual incidents. The advent of higher strength metals have shifted this rule some. But also have induced fatigue concerns as a steel with greater strength usually has more brittleness.


With AL the long term concern is usually fatigue and the welds are especially exposed to this what with undercutting and poor heat treating after construction. Of course thinner walls only make this more likely. But also as frame weight has been pushed to the limits mid tube denting, like with ultra thin steel tubes, becomes a problem.


In the end a dent is more about an incident then anything else. Andy.

Word of the day !