Frame materials - Steel vs CF vs Alu

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Frame materials - Steel vs CF vs Alu

Postby simon.young » Sun Jul 27, 2014 11:59 am

Obviously there are many variables, such as use, storage, gas pipe vs prestige, price etc but are there any guidelines when looking at 20yo + frames?

CF look for delamination?

Steel has rust issues, welds etc. Look internal as well.

What about Aluminium? Stress? Cracked welds?

Any tips without going to stress test the frame?

Particularly interested in comment on aluminium, I like some of the 80s/90s cannondales, but their nickname scares me. I've stayed away from CF, but QV has a few, so is 20+ yo carbon ok? I've mainly stuck to steel, I guess I've felt is easier to visually inspect?
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by BNA » Sun Jul 27, 2014 5:40 pm

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Re: Frame materials - Steel vs CF vs Alu

Postby yugyug » Sun Jul 27, 2014 5:40 pm

Interested in this too. I know the problem with carbonfibre compared to steel is that any failure, when it comes, can be catastrophic - steel can fail more slowly giving enough time for cracks to become visible. I'm sure others here can explain it better than that and yeah sorry I know thats not as answer to your questions. Personally I'd be really interested in buying a vintage carbon fibre, especially those cool ones with glued alu lugs, but I won't until I learn a lot more about what to look for. I guess knowing the bike's history and how its been ridden is important to start.
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Frame materials - Steel vs CF vs Alu

Postby RonK » Sun Jul 27, 2014 5:48 pm

20 yo steel - rust, fatigue

20 yo alloy - corrosion, fatigue

20 yo carbon - bonding failure at the lugs.

Obviously, these problems may be quite difficult to detect.
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Re: Frame materials - Steel vs CF vs Alu

Postby morini » Sun Jul 27, 2014 6:06 pm

Good topic. Here's my simple three golden rules after breaking my frame a month or two ago:

Only buy brand new aluminium and then recycle it when it breaks. There are a number of options for very reasonably priced frames but I wonder how long this situation will last.
Buy carbon if you need to have the latest lightweight technology, a more supple ride (apparently) but I've no idea what you do with it when it snaps in half.
......and buy steel if you want to give it to your grand kids' kids.

I've never had a carbon frame but I know from owning a number of kevlar/carbon honeycomb (Nomex) rowing boats that they're holding up well after 20 years and there seems to be no obvious signs of degradation apart from the gel coat. Kevlar is very forgiving compared to carbon fibre so I wonder how a pure carbon bike frame will go after the same time?
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Re: Frame materials - Steel vs CF vs Alu

Postby simon.young » Sun Jul 27, 2014 7:41 pm

RonK wrote:20 yo steel - rust, fatigue

20 yo alloy - corrosion, fatigue

20 yo carbon - bonding failure at the lugs.

Obviously, these problems may be quite difficult to detect.


Please feel free to correct me... I've been doing some reading online re alloy

So rust in steel, orangy in colour, can notice it pretty easily. And the oxidation penetrates the base metal, weakening it. Obviously flaking / bubbling is really bad.

In Alloy, the corrosion is aluminum oxide, a very hard material that actually protects the aluminum from further corrosion. And unlike steel doesn't penetrate the base metal very much at all. Anodizing is "colored" oxidation for aluminum. you actually intentionally oxidize the part to protect it.

If seems that CF unless fractured is ok, its the lugs, the gluing etc that let the frame down
Last edited by simon.young on Sun Jul 27, 2014 7:58 pm, edited 1 time in total.
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Re: Frame materials - Steel vs CF vs Alu

Postby simon.young » Sun Jul 27, 2014 7:57 pm

Image

From MTBR

I won't go into the restoration suggestions, but apparently this corrosion isn't anything to worry about. Maybe caused from scratching the clear coat, banging a wrench etc, prolonged exposure to salt spray or more interestingly from dissimilar metal corrosion from chrome plated bolts.

Another post goes into say "Fatigue related to heat treat and weld penetration is a MUCH bigger concern for Aluminum than oxidization."

I guess paint cracking around joints would be sign for alloy? and if so, with steel being more flexible than alloy, would you expect some cracking in joint paintwork and potentially not as much fatigue? just flex?

Both options I'd steer clear of at this stage, but steel is repairable, alloy would be throw away.
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Re: Frame materials - Steel vs CF vs Alu

Postby RonK » Sun Jul 27, 2014 8:06 pm

The corrosion risk to alloy frames is from electrolysis. Seat posts/seat tubes are prime sites.
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Re: Frame materials - Steel vs CF vs Alu

Postby ldrcycles » Sun Jul 27, 2014 8:15 pm

In my job repairing pool pumps i see extreme aluminium corrosion, to the point where there are whopping great chunks missing. Corrosion such as in that photo is not an indication that the frame is about to snap in two, but it should be made very clear that not removing it WILL lead to trouble, as the corrosion makes it easier for moisture to hang about, accelerating the corrosion.

As far as steel frames go, unless you're talking very thin walled Reynolds/Columbus/whatever, rust needs to get to quite an advanced stage to compromise the frame. Just a bit of orange i wouldn't care in the slightest, bubbling/flaking is usually no problem either (although obviously if you were to just leave it to keep going there will eventually be trouble).

EDIT: This is a good example of what can be rescued, rebilda did this one and even managed to salvage the crank arms.

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Re: Frame materials - Steel vs CF vs Alu

Postby Drizt » Sun Jul 27, 2014 8:25 pm

Titanium for the win!
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Re: Frame materials - Steel vs CF vs Alu

Postby bog1953 » Sun Jul 27, 2014 8:56 pm

What you must determine is what is the bike being used for. If I was a pro rider who was factory backed, give me carbon any day.... a new bike every time I wanted one, free. Also carbon, if I was a serious sunday warrior with a lot of money who wants a fast machine for short to medium rides, time wise. Steel frames for long rides where comfort is a priority. Because both carbon and aluminum frames transfer road noise, they cause fatigue in the rider. As far as reliability goes aluminum frames rarely fail, steel shows signs of imminent failure. As long as you buy a bike that hasn't been tampered with and use preventive measures most steel frames are the most reliable. I've seen quite a few carbon frames that have failed and as far as a long term prospect I'd be very wary. Carbon is a form of plastic and eventually all plastics are subject to deterioration. As far as bonded frames logic tells you, all glues become brittle over time, so a frame may appear to be strong , but given the right circumstances fail dramatically . The next big development in frame tech. is extruded aluminum frames, !0X stronger than carbon, and lighter. The greatest development in bikes in the last 20yrs hasn't been in frames, it's wheels. A modern wheel is light years ahead of those heavy things we put on period correct bikes. A modern wheel seems to spin forever without any effort , and so light.
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Re: Frame materials - Steel vs CF vs Alu

Postby yugyug » Sun Jul 27, 2014 9:14 pm

bog1953 wrote:The greatest development in bikes in the last 20yrs hasn't been in frames, it's wheels. A modern wheel is light years ahead of those heavy things we put on period correct bikes. A modern wheel seems to spin forever without any effort , and so light.


Sorry off topic but where is the greatest development within the wheel? Hubs mainly? Or is this also true for rims and spokes?
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Re: Frame materials - Steel vs CF vs Alu

Postby bog1953 » Sun Jul 27, 2014 10:10 pm

Well I was shown a set of wheels recently that if you saw them at Kmart you would have thought that they were beneath even them. They looked cheap and flimsy, price $8,000.00. They were one piece of carbon, hubs spokes and rim. They weighed less than a kilo the pair, and spun if you breathed on them [ figuratively ]. The problem of course was that if you broke a spoke they were unrepairable. I have a pair of Mavic cosmics first gen. which in comparison are dinosaurs, but in their time state of art.
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Re: Frame materials - Steel vs CF vs Alu

Postby simon.young » Sun Jul 27, 2014 10:35 pm

ldrcycles wrote:In my job repairing pool pumps i see extreme aluminium corrosion, to the point where there are whopping great chunks missing. Corrosion such as in that photo is not an indication that the frame is about to snap in two, but it should be made very clear that not removing it WILL lead to trouble, as the corrosion makes it easier for moisture to hang about, accelerating the corrosion.

As far as steel frames go, unless you're talking very thin walled Reynolds/Columbus/whatever, rust needs to get to quite an advanced stage to compromise the frame. Just a bit of orange i wouldn't care in the slightest, bubbling/flaking is usually no problem either (although obviously if you were to just leave it to keep going there will eventually be trouble).

EDIT: This is a good example of what can be rescued, rebilda did this one and even managed to salvage the crank arms.

Image


Awesome. Exactly what I'm after re alloy and removing corrosion. And the level of rust in steel. Can't believe that pic and even some was recovered..

RonK wrote:The corrosion risk to alloy frames is from electrolysis. Seat posts/seat tubes are prime sites.


Another great point, I've heard / seen stuck seat posts, but just moved on. Quickly. Never thought too much about it, but really should check.
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Re: Frame materials - Steel vs CF vs Alu

Postby QuangVuong » Mon Jul 28, 2014 4:47 pm

RonK wrote:20 yo carbon - bonding failure at the lugs.

Obviously, these problems may be quite difficult to detect.


20 year old carbon is also about 3mm + thick. It is not the coke can thickness of modern carbon. Its unlikely that the carbon will be the one breaking from fatigue, unless it has been struck by something. The lugged frames would fail at the lugs first, mainly due to the galvanic attack between the different materials. The aluminium lug rusts white aluminium oxide powder which essentially expands in size, and the glued joint could crack and not be hold the carbon tube anymore. Some of the newer frames had some sort of sleeve in between the lugs so that debonding was not as great an issue.

Even the 20 year old monocoque frames were built thick back then. This is a Kestrel 200 chopped in half. Quite thick along the tubes, and even thicker at joints.
Image

Cracks in the carbon are easy to spot. It will be softer in that area, and you should be able to see the crack. Best to watch out for aluminium oxide(whitish powder) around the lugs, and cracks around the lug joints too. If they arent visible, then you should be good.
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Re: Frame materials - Steel vs CF vs Alu

Postby yugyug » Tue Jul 29, 2014 12:44 am

QuangVuong wrote:
RonK wrote:20 yo carbon - bonding failure at the lugs.

Obviously, these problems may be quite difficult to detect.


20 year old carbon is also about 3mm + thick. It is not the coke can thickness of modern carbon. Its unlikely that the carbon will be the one breaking from fatigue, unless it has been struck by something. The lugged frames would fail at the lugs first, mainly due to the galvanic attack between the different materials. The aluminium lug rusts white aluminium oxide powder which essentially expands in size, and the glued joint could crack and not be hold the carbon tube anymore. Some of the newer frames had some sort of sleeve in between the lugs so that debonding was not as great an issue.

Even the 20 year old monocoque frames were built thick back then. This is a Kestrel 200 chopped in half. Quite thick along the tubes, and even thicker at joints.
Image

Cracks in the carbon are easy to spot. It will be softer in that area, and you should be able to see the crack. Best to watch out for aluminium oxide(whitish powder) around the lugs, and cracks around the lug joints too. If they arent visible, then you should be good.


Good info, thanks. I'm guessing that Kestral frame failed in some way before it was bisected?
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Re: Frame materials - Steel vs CF vs Alu

Postby QuangVuong » Tue Jul 29, 2014 9:28 pm

I dunno about that. Someone posted this photo on the Retro Classic Bikes FB page, and said they just saved the pic when they saw it. It would be good to know why it was chopped in half.
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Re: Frame materials - Steel vs CF vs Alu

Postby singlespeedscott » Wed Jul 30, 2014 2:45 am

For Long term reliability and long distance comfort you can't beat a good quality steel frame. If you want to race, carbon and aluminium are the go. Carbon is probably a better choice if you want to race on rough roads. Titanium is another option, but it's expensive and I have seen just as many cracked ti frames as carbon and aluminium ones.
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Re: Frame materials - Steel vs CF vs Alu

Postby clackers » Wed Jul 30, 2014 2:16 pm

yugyug wrote:
Good info, thanks. I'm guessing that Kestral frame failed in some way before it was bisected?


It may have failed by finishing second in a sprint ... high price for disappointing its owner!
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Re: Frame materials - Steel vs CF vs Alu

Postby rkelsen » Wed Jul 30, 2014 2:34 pm

^ cycling equivalent of the glue factory!

I guess you can't make mortadella from a bike... :lol:
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Re: Frame materials - Steel vs CF vs Alu

Postby simon.young » Wed Jul 30, 2014 6:52 pm

QuangVuong wrote:
20 year old carbon is also about 3mm + thick. It is not the coke can thickness of modern carbon. Its unlikely that the carbon will be the one breaking from fatigue, unless it has been struck by something. The lugged frames would fail at the lugs first, mainly due to the galvanic attack between the different materials. The aluminium lug rusts white aluminium oxide powder which essentially expands in size, and the glued joint could crack and not be hold the carbon tube anymore. Some of the newer frames had some sort of sleeve in between the lugs so that debonding was not as great an issue.

Cracks in the carbon are easy to spot. It will be softer in that area, and you should be able to see the crack. Best to watch out for aluminium oxide(whitish powder) around the lugs, and cracks around the lug joints too. If they arent visible, then you should be good.


Thanks. really good tips on older carbon frames.

Been looking at Kestrel MTB's.... maybe I've shouldn't have!

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