ALU- Frames - How long...

[Smokin Joe]

What are the bolts holding the caliper to the frame made of?!

steel, as are most bolts because the softer alu would stip the threads at high torque settings. The calipers still have to absorb the stress on them under braking.

 

[mickle]

If nothing goes wrong, aluminium will last longer than steel as it won't corrode to the same extent. However aluminium is also more prone to sudden failure and you won't get any warning if it does go. It is worth adding that steel can be repaired by any blacksmith, so it would make more sense if you were touring in a remote and undeveloped area. This isn't most of us however...

I regularly ride a steel frame which dates from about 1890. Good quality steel alloys corrode slower than some aluminum alloys.

Prone to sudden failure? Really? Evidence?

'Blacksmiths' beat hot iron. The skills of a third world blacksmith are unlikely to include MIG and TIG welding and brass brazing.

 

[Chris James]

Good quality steel alloys corrode slower than some aluminum alloys.

Much as I like steel frames, this isn't true. Typical bike frame steels such as Cr-Mo don't have sufficient chroimium in the alloy to form a passive layer on the surface, unlike aluminium alloys (which form aluminium oxide ). Although I believe 953 is supposed be a 'stainless' so in that case it will have enough chromium.

However, given that steel frames are painted and the internals can be treated with waxoyl or similar then a steel frame that is looked after should not corrode away.

Likewise, aluminium frames needs washing as build up of road salts and sweat can lead to conditions where localised corrosion can set in.

 

[User482]

steel, as are most bolts because the softer alu would stip the threads at high torque settings. The calipers still have to absorb the stress on them under braking.

The braking force by the front caliper is taken by the bolt - the wheel rotation is trying to move the caliper forward. It's steel because an alu one would break.

 

[Smokin Joe]

The braking force by the front caliper is taken by the bolt - the wheel rotation is trying to move the caliper forward. It's steel because an alu one would break.

Well, as one metallurgist to another, I put it to you that as the caliper is securely held to the fork by the said bolt, that is also having a considerable amont of stress put through it's arms.

 

[LLB]

Much as I like steel frames, this isn't true. Typical bike frame steels such as Cr-Mo don't have sufficient chroimium in the alloy to form a passive layer on the surface, unlike aluminium alloys (which form aluminium oxide ). Although I believe 953 is supposed be a 'stainless' so in that case it will have enough chromium.

However, given that steel frames are painted and the internals can be treated with waxoyl or similar then a steel frame that is looked after should not corrode away.

Likewise, aluminium frames needs washing as build up of road salts and sweat can lead to conditions where localised corrosion can set in.

They are also butting the weld areas much more substantially nowadays to increase the thickness around the weld. One thing of note is also whether the finished frames are sent off for post welding heat treatment as failure to do this will knock off up to 40% of the post extruded/aged strength

 

[Chris James]

Well, as one metallurgist to another, I put it to you that as the caliper is securely held to the fork by the said bolt, that is also having a considerable amont of stress put through it's arms.

At the risk of labouring the point about distinguishing between force and stress, the amount of stress being applied to the caliper is related to the cross sectional area of both arms and not just the braking force. The area of TWO caliper arms, I would suggest, is considerably more than the cross sectional area of one bolt. So the bolt will see proportionately higher stress than the calipers.

 

[LLB]

At the risk of labouring the point about distinguishing between force and stress, the amount of stress being applied to the caliper is related to the cross sectional area of both arms and not just the braking force. The area of TWO caliper arms, I would suggest, is considerably more than the cross sectional area of one bolt. So the bolt will see proportionately higher stress than the calipers.

That would depend on whether they also dowel it

 

[lastpubrunner]

So how many fifty year old steel frames do you see around now? Or even twenty year old, come to that.

They have got a "bad reputation" because people who hate progress and can't see why the rest of us are not happy riding round on a 1955 Curly Hetchins with a four-speed block and toe clips and straps keep telling us that Aluminium will melt after two years and carbon fibre will explode in sunlight.

This is some truth in what you say; but I've seen many quite portly cyclists on bikes (aluminium, carbon fibre/titanium) costing upwards of £1,000, purely because they have been told that such bikes are what they 'need' to have. They have expensive bikes with aerodynamic wheels, the latest groupsets etc., etc, - all designed to make them go faster. How many of us are top cyclists and really do benefit from the latest materials ? Surely, for recreational cycling, a good 531 frame is perfectly adequate ?

Recently, I went out on a Reliability Run for the first time; only one other cyclist had a steel frame. An elderly chap told me that my FW Evans was very similar to one on which he used to race in the 1980s. If it was good enough for racing back then, it is certainly good enough for me to trundle around on today.

I believe that it is largely down to fashion - many cyclists (and those starting out) want to be seen on the latest thing - which steel certainly isn't; however, that doesn't mean that it isn't more than adequate for the needs of most people. I think that it is important not to confuse 'progress' with 'fashion'. I suggest that that is the reason why old steel framed bikes are hardly seen nowadays.

 

[Chris James]

I dunno, I have a 1986 531c frame (amongst other bikes). It looks rather nice with it's lugs.

No rust problems either.

 

[actingskint]

I had a nice scott P1,which until it hit a pot hole in the road was fine.But that one incident cracked the frame by the crank.My mate who ran the shop near me said he had never seen a scott with a break like it.So I guess a bikes made of alu,or steel or carbon have their own weaknesses.Anybody know if titanium has problems as Ive just got hold of a 1996 litespeed frame.So far so good for it.
Im riding on the original carbon forks,complete with carbon steerer.Im worried about using carbon for something Im relying on for my life.Ive heard splitting and snapping stories about it.
Has it got a shelf life? I not known for my delicate riding style,and at 16 stone every pot hole in the road could be a two ton shock wave for anything Im riding.

 

[Mr Pig]

I was talking to a guy in Dales bike shop in Glasgow yesterday about frame materials. He expects Specialized to be making their mainstream off-road bikes out of carbon fibre within a few years. They've invested heavily in the technology and according to him Carbon Fibre is fine provided it is applied in the correct way for the given application.

Obviously this technology is advancing all the time, the carbon frames being built today will be a heck of a lot better than the ones made in the material's infancy, and I'm sure there will come a time when all of the problems with carbon fibre will either be solved or worked around.

He did say however that there was vast variation in the quality of carbon fibre products and he wouldn't ride on a non-branded/cheaper-manufacturer carbon part.

For me it's a matter of confidence. I'm buying a steel-framed MTB and one of the reasons is that frame failure is not something I want to have on my mind at thirty-miles-an-hour. Simply being worried about a component is enough to justify not using it in my book, even if the fear is not totally rational.

 

[actingskint]

You mention 30 miles an hour reminded me I had a quick watch of the tour de france,the guys there were desending from the mountains at 50-55 miles an hour.All I could think was fu'''''''''''g hell.Id be coming down the mountain shouting aaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhh.

 

[Mr Pig]

It's quite scary. I fell off one of the kid's bikes in the back garden last week. Hardly moving but I skint both knees and knocked the wind out of me. If you hit the road at fifty you're going to hospital for quite some time!

Motorcyclists wear thick leather with crash pads underneath and a massive helmet. Cyclists seem to reckon that Lycra will do the job! ;0)

 

[mickle]

This is some truth in what you say; but I've seen many quite portly cyclists on bikes (aluminium, carbon fibre/titanium) costing upwards of £1,000, purely because they have been told that such bikes are what they 'need' to have. They have expensive bikes with aerodynamic wheels, the latest groupsets etc., etc, - all designed to make them go faster. How many of us are top cyclists and really do benefit from the latest materials ? Surely, for recreational cycling, a good 531 frame is perfectly adequate ?

Recently, I went out on a Reliability Run for the first time; only one other cyclist had a steel frame. An elderly chap told me that my FW Evans was very similar to one on which he used to race in the 1980s. If it was good enough for racing back then, it is certainly good enough for me to trundle around on today.

I believe that it is largely down to fashion - many cyclists (and those starting out) want to be seen on the latest thing - which steel certainly isn't; however, that doesn't mean that it isn't more than adequate for the needs of most people. I think that it is important not to confuse 'progress' with 'fashion'. I suggest that that is the reason why old steel framed bikes are hardly seen nowadays.

Jeez, what's your problem? Can't you comprehend that some people like riding nice bikes simply because they enjoy riding nice bikes? My bikes are worth a great deal of money but the likelyhood of me ever entering a race, let alone winning one is precisely zero. There's nothing wrong with steel but you cannot hold back the march of technological development like some wool clad Canute. Your lack of desire to engage with the modern world does not entitle you to accuse those who do as mere fashion victims. Would you have us huddle around coal fires and drive Austin Allegros. If you could open your mind for long enough to take a spin on a cycle made from a material which doesn't date from the 1930s you might learn something.