Can Alu frames ever feel like Steel frames?

[pileyk]

I'm talking regular fully rigid normal/hybrid bikes, not the extremes of MTB or road bikes. I've read people claiming that frame material itself does not affect stiffness rather how the tubing is selected and put together, etc. By their logic the saying is that ALU is lighter than STEEL for a given stiffness, i.e if you wanted a steel bike as stiff as alu then it would be much heavier.

But the few alu bikes I've ridden (with no susp) all feel horrible and harsh with vibrations on rough terrain vs steel. So if it's not the frame material causing it, why can't manufacturer build an aluminum frame that way less stiff, similar to steel (even if it's more "noodley") that has the same comfort but it just lighter??! Most people who aren't riding serious would prefer an absorbent comfier ride at the expense of some flex surely...

Do such frames exist? I'm 200lbs so it can't be too delicately built but it annoys me when folks say "it's not the frame material" or "alu can be just as smooth riding as steel" because in my (limited) experience all alu frames so far feel quite harsh in comparison! If it was possible to make them less stiff with same flex as steel but just lighter, then surely that would be a very popular thing to sell.... Thoughts?

 

[winjohn]

I have also read that it is not the frame material alone that affects the ride quality. IMHO the Cannondale CAAD frames seem to have a very pleasant ride quality.

John

 

[BiketoBasics]

Someone once suggested the analogy between steel and aluminum (or, Al-You-Min-Ium as the Brits say) frames is like the difference in feel between batting with an Ash tree bat or an aluminum bat in baseball. I always seek out steel frames. An aluminum frame might ride nicely if it was designed properly, had a long wheelbase and could fit large diameter tires.

 

[hamster]

The stiffness issue is that indeed you could make an alu frame as flexy as a steel one - the problem is the different fatigue characteristics. Aluminium is entirely unlike steel in that it has a finite fatigue life regardless of the load. Steel has a limit below which it is effectively infinite. As a result a nice flexy alu frame will have a short life. To engineer them for acceptable durability they ended up as stiff as jackhammers, unlike steel frames.

 

[CassidyAce]

You're not going to make an aluminium frame feel like a good steel frame, but there are ways to take the harshness out of the ride: wider tyres at lower pressures; more supple, better quality tyres; latex instead of butyl inner tubes; good quality carbon seatpost...

 

[hamster]

You're not going to make an aluminium frame feel like a good steel frame, but there are ways to take the harshness out of the ride: wider tyres at lower pressures; more supple, better quality tyres; latex instead of butyl inner tubes; good quality carbon seatpost...

Well said. The tyres have much more effect than even the frame...starting with tyre pressure!

 

[PanoIgano]

Nice convo and very interesting points so far.

As already said, it's very hard to make a durable MTB frame in alu that is already flexible enough to be comfortable for long rides.

I think alu frames are best when they are made for full suspensions or at least hardails with long travel front sus. They can be made super stiff and chunky to take all abuse but then having the front and rear suspension will go a long way to take out the edge from alu itself. Even then, once alu frame reach or overpass their lifecycles they will start cracking. Many MTB brands have taken this approach and the one I am liking a lot is Ventana.

I have tried a few alu frames in rigid and no matter how much I played with the type of tyres and airpressure I never managed to overcome the dead feel I was getting from the frame. But I am a light rider and very sensitive to small changes on frame material, overall wait of the frame and certain parts. I guess for a bigger rider this wouldn't be much of an issue.

 

[7Speed]

The idea that shape and other engineered characteristics can change the fundamental nature of a material feels a little misguided?
I always thought you can build in engineered changes to frame characteristics that way, but there is a limit beyond which you can’t go defined by the material itself. If you want a specific characteristic - like the spring and whip of a well made steel frame - you will be much more successful using steel that any selection of Al alloys/tubes/designs. happy to be wrong here!
I am now holding my breath pending feedback from the many engineers on the site!

 

[hamster]

I'd say you are basically right - there are a combination of characteristics that give a kind of box of limitations for any material. After all, you could make a frame from pasta, it's just that you would need very thick tubing. Each material has a different box, but they definitely overlap.

Part of the discussion is also marketing and manufacturability - alu frames came in because they were cheap to make, especially for machining costs. As they had to be super-stiff (see above) the marketing story was then that you needed a really stiff frame.

 

[pileyk]

Good to hear all your thoughts! So the people who say the frame material doesn't matter, "it's all about the construction and tube specs" are full of BS... because if alu frames could be safely/durably constructed to give a steel feel with less weight, then obviously manufacturers would do it!

As panolgano says I also like alu frames with front sus... but I just can't deal with rigid bikes made from alu when riding on trails or light off-road. I picked up a cheapo early 00s Claud Butler Ravana for £25, but even with a steel fork it just transmitted every undulation through your arms and arse! I've gone back to my trusty (dreadful looking) 80s Emmelle touring/ATB bike, it has standard carbon steel tubes but it's way smoother and comfy on gravel trails even with 26 x 1.6" tyres than the CB alu bike that has 1.9" tyres at a lower relative pressure.

I wonder if a decent cro-mo frame will ride much better than my gas pipe tubing that I'm quite happy with?

As for the comment about rider weight, I think it makes virtually no difference. I'm 200lbs and however much I make the alu frame flex a tiny amount more than you; I probably make the steel frame flex much more in relative terms!