Properties of Aluminum and Carbon Frames?

[Bethany1]

I finally made a few more miles out with my Sirrus and realize that every bump, rock, and crack makes my bones jar. It's like riding on a metal roller coaster (not the smooth ones) that is stiff and rattling. It's aluminum with a carbon fork. The faster I went, the more stiff the bike became and even seemed to shimmy from side to side.

Is this a normal ride for aluminum/carbon fork frame and anything similiar to it will have the same riding properties?

While a carbon frame is lighter, will every bump be felt that much more?

I made 13 miles yesterday which is the most I've ever done and probably hit 25-30 miles going down a hill causing the bike to feel like it was vibrating from side to side. My computer went out a few miles after going..probably from all the rattling. I was doing regular highway roads, the ones I would be riding and if there's a better solution, it would be helpful.

I'm riding on ashpalt and concrete roads.

Now I know why you need cycling shorts. LOL. Glad I invested in a pair. Riding a couple of miles around the neighborhood is completely different than doing a 13 mile trip.

[indysteel]

AL bikes are not generally known for their velvety smoothness. But if I had a bike that was that unstable, especially on descents, I'd take it in to my LBS to have it--especially the fork and headset--checked.

But, yes, carbon typcially will ride a lot nicer than AL. So will steel.

[Catrin]

Yeah, aluminum frames even with a carbon fork can be quite uncomfortable - at least that was my experience. My first bike was a Trek that had a carbon fork and "Isozone"? stabilizer in the seat stays that was supposed to help that. It may have, it just shook me to death but your experience sounds even worse than mine was.

I moved to steel frames and haven't looked back. The steel evens out the vibration and bumps and is just so much more comfortable and provides a much more smooth ride. A steel frame doesn't have to be heavy - and I think that even the heavier steel frames aren't like they were 25 years ago weight-wise.

Others will need to speak on carbon frames. I've no experience with carbon but I dearly love my steel bikes and had to speak up for steel

[Veronica]

I have both a steel bike and a carbon fiber bike. I honestly don't believe one has a comfort advantage over the other. My carbon fiber bike is truly a race bike and is much faster, not just because of the material but also because of the way it's shaped. It's what I ride most of the time.

My steel bike is fairly light, just under twenty pounds. It's the bike I take touring or on a self supported out in the middle of nowhere ride.

Veronica

[Owlie]

Aluminum is light and cheap, but since it doesn't flex like carbon or steel (it's a property of the material), every bump will be transferred to you. Even with a carbon fork. Higher quality aluminum tubing may be less susceptible to this--DBF says that when he switched from an OCR3 (the old version of Giant's Defy) to his Cannondale R2000, the quality of the ride improved a lot. My next bike will be either carbon or steel.

Do what Indy says and get the bike checked out if it feels that wobbly on descents. That's not a frame material problem. That's either you (you're not used to going that fast), or a problem that really does need to be checked!

[ultraviolet]

I finally made a few more miles out with my Sirrus and realize that every bump, rock, and crack makes my bones jar. It's like riding on a metal roller coaster (not the smooth ones) that is stiff and rattling. It's aluminum with a carbon fork. The faster I went, the more stiff the bike became and even seemed to shimmy from side to side.

Is this a normal ride for aluminum/carbon fork frame and anything similiar to it will have the same riding properties?

While aluminum has a reputation for being more buzzy ride, the shimmy you're experiencing is not something that should be expected just because a bike is made from aluminum.

It's also worth noting that not all aluminum frames are created equal. And people have varying levels of sensitivity to "road buzz."

I've owned several aluminum-frames bikes with carbon forks and seatposts--my BMC also has carbon seat stays. Two (the LeMond and the BMC I currently still have around) are ridiculously comfortable for as long as I want to ride them, including doing back-to-back centuries. A cheaper aluminum Leader frame that I built up on my own as an experiment was extremely stiff and harsh...it didn't last long in my collection.

I've also had two bikes that had aluminum frames with steel forks. Both of those were fine (and fun) for short rides and errand running, but I probably wouldn't have taken them for any century rides. And I'll note that neither of them are currently in my stable.

Even within steel frames there are various levels of smoothness and comfort. The heaviest of my steel bikes also happens to be the stiffest of them. It's great for bombing around town, and I can stand up and hammer up a hill without feeling too much squish in the bottom bracket, but I can't say that about my other two steel bikes. The other two are more "comfy" rides, but I can definitely feel the torque in the frame on hard efforts. (FWIW, I am not a spinner. It took me a while to accept that, but I finally have. Spinning a low gear is way more uncomfortable for me than mashing a big one.)

My favorite bike as far as ride quality goes was a titanium Litespeed with carbon fork. Sadly, we could never quite get the fit dialed in on that one, so I let it go. But I've heard plenty of complaints from people who bought titanium frames who felt like they were trying to pedal on a wet noodle. *shrug*

All of that to say that before you assign bike problems to the frame material, investigate if it's something specific to your bike, the bike setup, or the frame geometry.

[Bethany1]

I figure some of it is me, being a newbie, but I'm taking the bike in today and seeing if he can tweak it some or have better ideas. They've been great to work with. My son was having the same issues on his Specialized Allez. I'll get used to the ride if that's the norm. I just wasn't expecting the huge difference when I got further out and went faster down a hill.

I would hate to invest in a full carbon frame and have similiar issues especially if it's the same issues between different lines of the same brand. LBS sells Trek and Specialized.

For example, I'd hate to buy a Specialized Dolce if I'd have the same problems with my Sirrus. Or go up to a carbon Ruby.

I don't have a problem with steel. Would I need more of a touring bike instead of a lightweight racing style for highways?

[Veronica]

Would I need more of a touring bike instead of a lightweight racing style for highways?

No, not really. My steel bike that I use for touring and unsupported rides is actually a cross bike. I use that bike when I want/need to carry more stuff. Mostly because I think my Cervelo would look ridiculous with a big bag on it.

Veronica

[Owlie]

I don't have a problem with steel. Would I need more of a touring bike instead of a lightweight racing style for highways?

What Veronica says. It depends on what you want to do--touring bikes are designed for carrying loads as well as you, and over distance. If you're not going to be carrying tons of stuff, a regular old road bike (or a cross bike) will be perfectly fine.

[pll]

I wonder if the vibration you felt was what people refer to as "speed wobble" or "shimmy". Some references to it:

• On Sheldon Brown's web site
• Wikipedia
  
• Bike Radar
• Discussion in Cycling Tips (with a video)

I would have your LBS rule out any equipment problem, but it appears that the wobble can happen on any bike. Luckily, I have never felt it. From the articles, some things that appear to help: unweighting the saddle, perhaps by standing on the pedals, pressing a knee against the top tube, keep the cranks horizontal and not vertical if you are coasting down, not having a 'death grip' on the handlebar.

[Catrin]

What Veronica says. It depends on what you want to do-touring bikes are designed for carrying loads as well as you, and over distance. If you're not going to be carrying tons of stuff, a regular old road bike (or a cross bike) will be perfectly fine.

This. A lot of people do use cross bikes for pretty much everything - they are a good general all-around bike. Touring bikes also have a different geometry and aren't really made for speed but for all-day-long comfort and loaded riding.

Let us know what the LBS says about your bike. I am pretty susceptible to road buzz but that doesn't sound like what you are experiencing on descents.

[Kiwi Stoker]

Just to chuck in my experiences. I and DH don't like steel forks. My flat bar has a steel fork and so did our tandem. I hate the way the steel seemed to make the road even worse tham it was. We changed the steel fork on the tandem to carbon and DH has said it was the best ever decision. So if you go down the steel route I wonder if they do bikes with carbon forks?

[Owlie]

If I recall correctly, the Jamis steel road bikes have carbon forks.

[indysteel]

My steel Bianchi has a carbon fork.

[Cataboo]

I found aluminum a harsh ride - even with carbon seatstays, handlebars, fork, and seatpost. My hands went numb really easily


I switched to carbon to get rid of the harsh ride - and yeah, unless I hit a big bump, my carbon bike is really smooth. I then got a titanium bike that i love to death, it makes all the vibrations pleasant.