Stainless steel vs Aluminum on folders
 

I know from a few threads people are recommending the steel since with the additional structural breaks due to hinges, steel handles stress better... but how do these handle rust? I wouldn't keep a SS bike outside anyway especially a folder but even so, it's going to get exposed to water, salt, dirt etc. on roads. Anyone with rust problems (or with SS folders with no rust) I'd be interested to hear your experiences.

I'm sure titanium is swell and all but it's brittle, expensive, and that's not really an option... I'm looking at 1000 max in terms of pricing.. and the low end Brompton's are steel as well.

Thanks.

Typically, you should dry your bike off at the end of the day. Sometimes water might get trapped inside the frame -- at least this can happen on the big bike.

Particularly for everyday use, I would not worry much about frame material. For travel, people recommend steel because of its durability and its ability to be repaired. So if you are doing a loaded tour in #$)%#$(%*, the steel frame will be more robust with respect to finishing the tour.

It is something to consider, but I would not let it be a big deciding factor.

A material's broad susceptibility to fatigue fractures is only one factor affecting frame longevity. Others include the quality of the design and fabrication, the suitability of the particular alloy or version of the material for the task, the stress the material will be subject to, and corrosion.

Don't necessarily rule out aluminum. Birdys have an aluminum frame but are extremely long lived. The suspension protects the frame from high peak stresses when you hit a bump, the design and fabrication standards are very good and they are designed to eliminate the potential weak point of a hinge in the main frame.

There are examples of good designs that can be expected to last a long time in both steel and aluminium.

David

PS. Re: repairs in remote locations if that is a concern.
Your best defence is not to need them. The best and lightest steel frames use thin heat-treated steel alloy tubes and re-welding them successfuly in remote locations without creating a weak point may be as problematic as with aluminum.

You got me David. I don't know much about it other than what others report about 4130 chromoly ... the primary material for the Bike Fridays.

Have Bike Friday stopped using steel again? /sarcasm> ;)

Your weight and the type of riding you do are paramount in any design, though loads are conservatively estimated and designs contain safety factors. Stainless isn't used much in thin pipe configurations. Most bikes are alloys with little corrosion resistance. Alluminum corrodes also in the right environment mind you, and keeping a bike painted or clear coated is important. All in all, material is a matter of preference mostly determined by the manufacturer in terms of what they want out of the design, what they can work with, and what they can purchase. Don't worry about it and buy a bike you like. Chances are even if you left the bike in a heap for years you could recondition it and no severe damage would be evident. It's not like steel dissolves in water.

Aluminium doen't have to be coated - I have a bike that I polished, and it has held up very well. The metal polish does leave a protective film which from time to time may be renewed by polishing, but I haven't so far. It used to be my commuting bike (see sig).

Well at this point I'm thinking about souping up a Downtube and essentially build my own Jetstream. It's an aluminum frame which I'd prefer for a slight weight advantage but didn't know if the design of folders made frame material choice something to consider. Thanks for the input.

Steel bikes are painted to prevent rust. They typically have a drain hole in the bottom bracket too, so that any water which gets in the frame can get out (note that the bottom bracket may not be the lowest point on a folder). As long as the paint stays in place and the frame has a drain or is sealed closed rust is not a major issue.

It takes quite a while for 4130 (the steel used for most bicycles) to rust enough to cause a problem. I build bicycle racks and mostly ride with racks that are unfinished/unpainted. It takes a month of regular riding in the rain to have visible rust. I had a mountain bike that was missing a 2" by 1" oval of paint on the top tube and which would be parked outside. I live in Seattle where there is constant dampness for about 8 months of the year. That bike never got more than a very thin surface of rust on the top tube in the 5 or 6 years that I owned it. If you add salt to the equation (storing a bicycle next to the ocean or in a boat) then the story changes somewhat because the salt accelerates the rusting process.

Steel has nice advantages. It is stiffer and stronger for a give tubing diameter than aluminum or titanium. It is easier to weld or braze. It has nice fatigue characteristics and doesn't fail suddenly. It can be repaired.

alex

Well my old beater was a steel frame 10 speed with MTB 1" tires that I had for 20 years, and it was kept outside and it was pretty rusty superficially, but the frame never really got weak. Wasn't the lightest bike but definitely was solid. I guess my question had less to do with rust and more to do with characteristics of the folding frame... that once you create hinges and therefor increased stress points, that perhaps steel was preferably... but I think the range of opinions will pretty much lead to what folders people own. I think both steel and aluminum are strong enough to handle the folding designs, although some may be less efficient or creak more.

I think the variations in quality of manufacturing and quality of designs is much larger than the material difference of using steel or aluminum. Swift Folder has even shown us that the same design translates pretty easily between the materials. I wouldn't focus too much on the material at use.