Bicycle Mechanics - Well, crap. Is my bike toast?

Riding back home when I look down to find this:
293125293126

Any options besides throwing it away? :(

2008ish Trek 7.3FX, I weigh 110kg(220lb), well within limits. I might have converted it to drops and did about 2000km of loaded touring and maybe 8000km of city riding. Doesn't seem to be an unusual amount of use to me :/ but i got it second hand so no warranty.

This is how tall i set the seat post:

293131

there still was 6cm(2.4in) before the minimum insert mark!

Is this goodbye?

Worst case you can just swap everything over to another frame. Aluminum frames are pretty cheap these days.

I'd still approach the Trek dealer. Sometimes companies will extend a crash replacement discount. Andy.

I might have converted it to drops

Looking at the photos, I have to strongly agree that you might have.

Looking at the photos, I have to strongly agree that you might have.

OK, I did! I couldn't stop myself!

Also... maybe this is the signal for me to go cromoli :rolleyes:

it looks like that crack goes all the way around. if so, that chunk of metal above the seat cluster is just for show anyway. so just cut it off and reassemble. or not, it looks like that seat cluster needs a standalone seat clamp and there may not be enough room for it.

this may have been caused by a seat post that was not inserted far enough into the top tube...

If that's a crack in the seat tube above the Top tube weld,your frame is golden brown, but may not be toast yet.

First of all, understand what is causing it, which is excess stress from an unsupported seat post. The minimum insetion mark on the pot relates to the posts requirements. However, there's a second requirement that the post extend to about 1" below the top tube. On a frame with a design like yours this may mean that the minimum insertionis deeper than the mark indicates.

Also, an undersized post can cause a similar problem by rocking within the tube. If all is right, the post fully supports the seat tube where yours is cracked.

If it isn't cracked all the way around, you might extend the life with a longer, better fitted post, however the crack will probably continue to grow. If you're willing to sacrifice a post to save the frame, and you have no plans to ever adjust the saddle height, you can get a longer seat post and bond it in place with epoxy, or an anaerobic (loctite) adhesive. Once a strong post is bonded in it will hold the frame together through the cracked area.

Given your weight, it may not be a forever repair, but if done right will last a long time.

If you replace the frame, consider a careful fit for the tallest frame you can manage properly. This will shorten the unsupported post reducing stress at the base. Also a frame design with a minimum extension of the seat tube above the joint will prevent this kind of damage.

Get a Surly Long Haul Trucker frame and fork and put your components on it.

Giant warrantied some for me. Started at the weld.

If you bought the bike new before doing anything crazy go to a trek dealer and try and get them to warranty the frame for you. Trek is usually good about standing behind their products and it is not fair to assume the end user will realize their seatpost is not far enough into the frame if they are not above the min insertion line although what FB say's is spot on. Hopefully they will replace the frame for free and try to find a longer post to offer more support, especially since you need a setback post which would put a little more force on the seat tube.

3 options as I see it.


1) Contact trek, if you are original owner and can prove it

2) Buy a new Frame

3) Get a longer seatpost and do the loctite. The crack is not at a critical juncture in the frame as it is above the weld. A seatpost extending far enough downward will keep the frame together.

ya know, I saw somewhere on the Specialized webpile where they said most of their bikes were rated for max 200 lb riders. just saying... (I'm 210, down from 230).

If you bought the bike new before doing anything crazy go to a trek dealer and try and get them to warranty the frame for you. Trek is usually good about standing behind their products and it is not fair to assume the end user will realize their seatpost is not far enough into the frame if they are not above the min insertion line although what FB say's is spot on. Hopefully they will replace the frame for free and try to find a longer post to offer more support, especially since you need a setback post which would put a little more force on the seat tube.

i agree see your trek dealer.
if you are the original owner it should have a lifetime free replacement warranty.
lots of clydes have broken there frames and gotten free replacements.
someone in the 50+ threads broke his fork steer tube on a 7.6 fx and trek replaced the entire bike.

Looks like a prime candidate for a low temperature Alumi-braze or similar process(like HTS-2000) which can be used with a propane or mapp torch. For that juncture I do not think it would pose any risk if done properly in combination with a longer, tight fitting post.

I believe that frame is fornicated,

Call the Trek dealer and see what they can offer, but after riding 10000 km on a used bike, don't get your hopes up. They may offer you a discount on a new bike or frame, but you may be able to get a new or clearourt replacement frame from another manufacturer for cheaper.

Looks like a prime candidate for a low temperature Alumi-braze or similar process(like HTS-2000) which can be used with a propane or mapp torch. For that juncture I do not think it would pose any risk if done properly in combination with a longer, tight fitting post.

How low is "low temperature"? Anything using any kind of flame would have me worried about having to have the heat treatment on the frame redone to avoid weakening the alloy.

I'm using the original bontrager seat post that came with the bike, i'm possitive it's the correct size, 27.2mm. I also checked for weight limitations before buying it from the guy; this is what the website says:



Max rider weight of 300lbs:
All other bikes, including hybrids, urban, commuter, fitness, Ride+ electric assist, cyclocross, and all mountain bikes.

Things are sort of different here, most warranties will be honored for one or two years regardless of the stated duration (you will be blamed for any problems that occur after that period), dealers are not very commited to the brand; trek dealers here always deal other brands and most definitely will not honor the warranty if i'm not the original owner, which i'm not. So, that's pretty much out of the question.

Quite frankly i don't think i'll ever be riding this frame with confidence again; failure might not result in catastrophe, but i'd rather not risk it; i think i'll take the advice from FBinNY, davidad and aramis and just move all my components to a new frame that fits my height better so the weight doesn't cause so much stress on the seatpost (AND SHED SOME POUNDS! do I hear you say? hehe)

thank you all for your opinions!

Ollin already stated he bought the Trek secondhand. I don't think they'd honor any warranty here, but I suppose it's worth a shot.

Your original post said you weigh 110 kg. That's 242 lb. Maybe you meant 100 kg / 220 lb. You're still well under the 300 lb. stated limit, though.

A small voice is telling me that a drop bar conversion on an aluminum hybrid designed for hybrid bars might have resulted in you doing more pulling on the bars, thereby putting more stress on the seat tube above the top tube, especially if you hammer a lot and go up a lot of steep hills. If there wasn't enough seatpost in the seat tube as others have stated, this might be a contributing factor.

I don't know if there's ever a way of knowing where there were microcracks in the seat tube to begin with or whether drop bar + hammering caused this. Either way, I wish you the best of luck with your frame.

I suspect you raised the seat post too far for its adequate inserted length..
you should have bought a longer seatpost.

I suspect you raised the seat post too far for its adequate inserted length..
you should have bought a longer seatpost.

OP already stated that the post was 6cm from the minimum insertion line... That's hardly too far.

Hope the guy has still some warranty in the frame because that thing is toasted, specially if its aluminum. Was steel it is fixable but probably cheaper to get a new frame or something.

Good luck with the new bike dude!

Another repair option... [?]... install a collar around that exposed tube area. Glue that securely.

Or.. weld it. [?].

Or.. weld it. [?].

The frame would need to be re-heat-treated afterwards, to restore its strength in the heat-affected zone.

The frame would need to be re-heat-treated afterwards, to restore its strength in the heat-affected zone.

It's a given then that all aluminum frames are heat treated?

It's a given then that all aluminum frames are heat treated?

As far as I know, all welded aluminium frames are heat-treated after welding, as a significant amount of the strength of the aluminium alloy comes from the heat treatment.

plain aluminum is butter soft.

The frame would need to be re-heat-treated afterwards, to restore its strength in the heat-affected zone.


its a formed alloy frame, I suspect that kind of treatment is a 1 shot deal when the stuff is made. aluminum is not steel, you can't just anneal it and start over with the hardening process.

I suspect the only way to 'fix' that frame would involve MIG welding a sleeve over the failed section, and that would be ugly, and still not be reliably strong.

failures like this are undoubtably a good reason for the classic 'triangle' frame where the stays and the top tube meet the seat tube at a lug. this gives maximum strength to that joint. any frame where the seat tube sticks above the top tube / seat stay junction should undoubtably have the seatpost inserted to at least a few inches below this junction.

OP already stated that the post was 6cm from the minimum insertion line... That's hardly too far.

thats the minimum line on the SEAT POST, but the end of the seat post should probably be about 4cm or even 6cm below the junction of the top tube

my current hybrid has the same design, with the seat post sticking a couple inches above the top tube...
http://pierce.smugmug.com/By-Date/2012/2012-12-03/i-gK2t6LV/1/XL/IMG_6058-XL.jpg

I kinda worry about my 230 lbs (100kg or so) on there, too. I should verify how far my seat post goes in there.

its a formed alloy frame, I suspect that kind of treatment is a 1 shot deal when the stuff is made. aluminum is not steel, you can't just anneal it and start over with the hardening process.

I suspect the only way to 'fix' that frame would involve MIG welding a sleeve over the failed section, and that would be ugly, and still not be reliably strong.



Well, it must be possible to weld the stuff reliably, that's definitely a weld in the picture. It's not the sort of thing you could do in your shed though - aluminium has to be welded by TIG welding, which is a lot harder than MIG, and as you said, aluminium alloys don't respond to heat-treatment in the same way as steel. I'd agree that it's not really worth trying.

New frames are actually pretty cheap, and then you get the option to customize things that you didn't like about your bike as-is.

To those who are advocating a repair: Stop it! Just about any repair using heat (welding OR brazing) will remove the heat-treatment and weaken the frame. Since the frame already broke, the repair obviously needs to be stronger than the original factory construction, which simply isn't going to happen. Any repair that doesn't use heat (clamps or epoxies or whatever) is not really a repair... perhaps you could rig up some contraption to make the bike rideable for another few miles, but that's about it... it could get you to a shop to buy a frame, but not further.
Also, unless you or a friend has the correct equipment for it, a real repair will almost certainly cost as much as a similar quality replacement frame.

You could pick up one of these cheap: http://www.ebay.com/itm/56cm-Miele-Umbria-Elite-Compact-Hybrid-Touring-Road-Bike-Frame-22-Inch-/330856967846?pt=Road_Bikes&hash=item4d089caea6

I just bought one, haven't built it up yet but it looks nice.

As far as I know, all welded aluminium frames are heat-treated after welding, as a significant amount of the strength of the aluminium alloy comes from the heat treatment.

I thought 7005 al does not require heat treatment after welding, but my metallurgy knowledge/understanding is quite limited. The following from wiki:


7005 aluminium alloy

From Wikipedia, the free encyclopedia


7005 is an aluminium alloy (http://en.wikipedia.org/wiki/Alloy) used primarily for bicycle (http://en.wikipedia.org/wiki/Bicycle) frames, due to its relative ease of welding (http://en.wikipedia.org/wiki/Welding). It has similar physical properties to 6061 aluminium alloy (http://en.wikipedia.org/wiki/6061_aluminium_alloy), except it has a higher density of 2.78 g/cm³, and depending on the temper, may be slightly stronger. There is significant debate as to which is superior for bicycle frames, as both have their merits.[1] (http://en.wikipedia.org/wiki/7005_aluminium_alloy#cite_note-1)
It does not need to be precipitation hardened (http://en.wikipedia.org/wiki/Precipitation_hardened), unlike 6061, but can be cooled in air.[2] (http://en.wikipedia.org/wiki/7005_aluminium_alloy#cite_note-2)
[edit (http://en.wikipedia.org/w/index.php?title=7005_aluminium_alloy&action=edit&section=1)]Chemical composition

The alloy composition of 7005 is:


Aluminium (http://en.wikipedia.org/wiki/Aluminium) 91.0% - 94.7%
Chromium (http://en.wikipedia.org/wiki/Chromium) 0.06% - 0.20%
Copper (http://en.wikipedia.org/wiki/Copper) <=0.10 %
Iron (http://en.wikipedia.org/wiki/Iron) <=0.40 %
Magnesium (http://en.wikipedia.org/wiki/Magnesium) 1.0% - 1.80%
Manganese (http://en.wikipedia.org/wiki/Manganese) 0.20% - 0.70%
Silicon (http://en.wikipedia.org/wiki/Silicon) <=0.35%
Titanium (http://en.wikipedia.org/wiki/Titanium) 0.010% - 0.060%
Zinc (http://en.wikipedia.org/wiki/Zinc) 4.0% - 5.0%
Zirconium (http://en.wikipedia.org/wiki/Zirconium) 0.080% - 0.20%
Other, total <= 0.15%


Precipitation hardening

From Wikipedia, the free encyclopedia
(Redirected from Precipitation hardened (http://en.wikipedia.org/w/index.php?title=Precipitation_hardened&redirect=no))



http://upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png
This article needs additional citations for verification. Please help improve this article (http://en.wikipedia.org/w/index.php?title=Precipitation_hardening&action=edit) by adding citations to reliable sources (http://en.wikipedia.org/wiki/Help:Introduction_to_referencing/1). Unsourced material may be challenged (http://en.wikipedia.org/wiki/Template:Citation_needed) and removed (http://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidence). (February 2010)


Precipitation hardening, also called age hardening, is a heat treatment (http://en.wikipedia.org/wiki/Heat_treatment) technique used to increase the yield strength of malleable (http://en.wikipedia.org/wiki/Malleable) materials, including most structural alloys ofaluminium (http://en.wikipedia.org/wiki/Aluminium), magnesium (http://en.wikipedia.org/wiki/Magnesium), nickel (http://en.wikipedia.org/wiki/Nickel), titanium (http://en.wikipedia.org/wiki/Titanium), and some stainless steels (http://en.wikipedia.org/wiki/Stainless_steel). In superalloys (http://en.wikipedia.org/wiki/Superalloys), it is known to cause yield strength anomaly (http://en.wikipedia.org/wiki/Yield_strength_anomaly) providing excellent high temperature strength.
Precipitation hardening relies on changes in solid solubility (http://en.wikipedia.org/wiki/Solubility) with temperature (http://en.wikipedia.org/wiki/Temperature) to produce fine particles of an impurity phase (http://en.wikipedia.org/wiki/Phase_(matter)), which impede the movement of dislocations (http://en.wikipedia.org/wiki/Dislocation), or defects in a crystal (http://en.wikipedia.org/wiki/Crystal)'s lattice (http://en.wikipedia.org/wiki/Crystal_structure). Since dislocations are often the dominant carriers of plasticity (http://en.wikipedia.org/wiki/Plasticity_(physics)), this serves to harden the material. The impurities play the same role as the particle substances in particle-reinforced composite materials. Just as the formation of ice in air can produce clouds, snow, or hail, depending upon the thermal history of a given portion of the atmosphere, precipitation (http://en.wikipedia.org/wiki/Precipitation_(chemistry)) in solids can produce many different sizes of particles, which have radically different properties. Unlike ordinary tempering (http://en.wikipedia.org/wiki/Tempering), alloys must be kept at elevated temperature for hours to allow precipitation to take place. This time delay is called aging. Solution treatment and aging is sometimes abbreviated "STA" in metalsspecs (http://en.wikipedia.org/wiki/Specification) and certs (http://en.wikipedia.org/wiki/Product_certification).
Note that two different heat treatments involving precipitates can alter the strength of a material: solution heat treating and precipitation heat treating. Solid solution strengthening (http://en.wikipedia.org/wiki/Solid_solution_strengthening)involves formation of a single-phase solid solution via quenching. Precipitation heat treating involves the addition of impurity particles to increase a material's strength.[1] (http://en.wikipedia.org/wiki/Precipitation_hardened#cite_note-Callister-1)Precipitation hardening via precipitation heat treatment is the main topic of discussion in this article.

find really long seatpost , get the height right for you, mark that height on the post .
pull it out , clean both surfaces in the frame and on the post well,
and epoxy it, the seat post in place. then the seat collar will not have a function,

the seat post manufacturer has to guess the frame they will go into,
the marking underestimated how far the seat post collar is tall for yours
rule of thumb.. bottom of seatpost needs to be at least, below the bottom of the top tube miter..

more complicated and homely will be doubling the outside of the frame tubing
with an external sleeve. to beef up its weak spot.. epoxy again , so reheating will not occur.

Heat treatment to T-6 spec on most frame alloys of aluminum requires approaching -+900 deg F. Exceding that will precipitate the alloy elements out and produce dead soft base aluminum, but a low temp rod such as what I mentioned needs only 200-300 deg F. Not a concern for the heat treatment to be affected if done properly.

TIG and MIG welding processes on the other hand use a much much higher temperature range since they are fusing(melting) the substrates together instead of bonding with an intermediate material. Regardless of if it is 6061 or 7005 aluminum alloys I would surmise that the frame was at the very least tempered following the factory process. If it were a small crack in that junction the heat zone repair would not be an issue, but that is most of the way around so it would make me reluctant to reccomend such a large area in addition to making the seat tube insertion a possible issue from weld bead penetration.

I thought 7005 al does not require heat treatment after welding, but my metallurgy knowledge/understanding is quite limited. The following from wiki:
....


its still heat treated and tempered, just via a different process.

I definitely think that you should consider a new frame. However, is there a way to contact the original owner who you bought the bike from? If so, maybe you could contact that person and they could help you get a warranty replacement. I believe that even in the US that Trek will only honor frame warranties for original owners. The other option that you have is a Nashbar frame. They are certainly inexpensive...

http://www.nashbar.com/bikes/SubCategory_10053_10052_202337_-1_202326_202326

To those who are advocating a repair: Stop it! Just about any repair using heat (welding OR brazing) will remove the heat-treatment and weaken the frame. Since the frame already broke, the repair obviously needs to be stronger than the original factory construction, which simply isn't going to happen. Any repair that doesn't use heat (clamps or epoxies or whatever) is not really a repair... perhaps you could rig up some contraption to make the bike rideable for another few miles, but that's about it... it could get you to a shop to buy a frame, but not further.
Also, unless you or a friend has the correct equipment for it, a real repair will almost certainly cost as much as a similar quality replacement frame.

I would feel comfortable TIG welding that crack. It's small, low stress area of the frame, and can be done without heating up the area that much.

Then put in the correct length seatpost and you're goot to go. I don't know what someone would charge to do that, and you need someone familiar with that type of work, but it's not a big deal. Otherwise, go with FBinNY's advice.

The stress on the damaged area is a function of the seatpost's strength and flex properties. If the post is strong enough to support the rider based on the structural top of the frame being at the top tube, then the seat tube extension serves only to support the clamp and resist twisting. Odds are it cracked because the heavy rider flexed the post which was able to take it, whereas the frame near the weld wasn't.

Since it's almost impossible to repair it stronger or more flexible than the original, it's unlikely that any repair will last unless the conditions are changed. One thing the OP can do is buttress the inside of the post in the area from below the top tube to above the clamp so as to reduce flex in the critical area. This can be as simple as finding a wooden dowel rod that's a jam fit inside the post and driving it in to the right depth.

If the post is stiffened, then an external repair of fiberglass and epoxy will robably be adequate prevent the tube from cracking all the way around. and the clamp will be workable. Otherwise the options are bonding the post within the frame, or replacing the frame with a taller one to lower the bending moment at the base of the post. A lighter rider would also help, but that's another issue with it's own complications.

That looks like a classic metal fatigue crack. It's cause by repeated cycles of stress. The weld has lowered the number of cycles that can be tolerated before cracking. A feature of aluminum is that no matter how low you make the stress, it will eventually crack. Steel is different in that it has a threshold below which it has infinite life.

For an aluminum frame, it is possible to make it stronger so that the stress will be low enough that it will have a reasonable life, but it will not be infinite. Using a longer seat post will lower the stress and increase the life. But once it has cracked you have largely lost that opportunity.

Without special hardening techniques, steel has a much better strength to weight ration than aluminum. However, by careful alloying, work hardening, or heat treatment, aluminum can be made to have a better strength to weight ratio. Unfortunately when you weld it, some of these treatments are nullified. Post weld heat treatment cannot put back the benefits of work hardening.

Since it's almost impossible to repair it stronger or more flexible than the original, it's unlikely that any repair will last unless the conditions are changed. One thing the OP can do is buttress the inside of the post in the area from below the top tube to above the clamp so as to reduce flex in the critical area. This can be as simple as finding a wooden dowel rod that's a jam fit inside the post and driving it in to the right depth.


Turn the seatpost upside down and fill with cement !

I would feel comfortable TIG welding that crack. It's small, low stress area of the frame, and can be done without heating up the area that much..

if its low stress, then why did it crack there?

every time the bike hits a bump and a clyde-sized butt slams on the seat, that spot takes a HUGE amount of stress. repeat sufficiently, and it cracks.

BUY A NEW FRAME.

THat thing can be tig over the crack and use it like that until it cracks again somewhere else. Many here talked about reheat the frame and stuff but sometimes is just go and make it simple for the guy. Yes he can tig that thing but at some point sooner or later will develop another crack somewhere else (thats the reason of the heating treatment). If he wants to do it great... is his pocket.

At least is not in a place more complicated stricturally like the BB for example.

Good luck op, I would get a new frame but is your pocket too.

you probably have to re machine the seat tube bore out after the TIG Alumawelding..
both of which may cost more to hire out, US welding and machine shop rates, than a new frame.

I just pulled out my seat post to see how long it is and therefore if it goes well into the tube. I have my saddle fairly high but thankfully the post is very long and has plenty of purchase in the tube (were talking like 8 inches or so).

Doesn't seem to be an unusual amount of use to me :/ but i got it second hand so no warranty.

A new frame from Nash is about $100.

http://www.nashbar.com/bikes/Product_10053_10052_511239_-1___202389

A set of Sora shifters on eBay is more than that.

For the Love of Benji 293372

WOW; plethora of options, but i'm not sure i can find a TIG welder or the right kind of epoxy. I'm also thinking that it might be smarter just to go with a frame that fits me better (now that i have proof that being under the weight limit does not mean that your vast weight won't break your frame) and therefore lowers the stress on the rest of components... now i'm just trying to think what to do with a slightly cracked frame... anyone interested in a cheap, slightly cracked, trek hybrid frame? :innocent:

Boat anchor?

now i'm just trying to think what to do with a slightly cracked frame... anyone interested in a cheap, slightly cracked, trek hybrid frame? :innocent:

If you were anywhere near me, I'd say yes - I need a donor frame for a bamboo bike build I'm planning.

JB Weld the crack, and keep checking it

that stuff will weld anything on this planet :)