Out of interest; how difficult would it be to crack a zaskar

This is just something random ive been wondering really. Just because of the zaskars apparent reputation for being 'bombproof' and i dont think ive seen it being discussed before

I am probably reffering just to the 91-95 models where the frames were 6061 and shared the same beefy gussets


Some factors...

1: sure the frame is heavilly gussetted which makes it tough but the frames were probably overbuilt because the early-mid 90s were still early days in aluminium frame building and the frames were more likely to fail without that added strength

2: 6061 is a softer grade of aluminium than the 7005 which newer frames are made from. However werent the more expensive frames made out of 6061? :?

3: alu frames are reccomended to be replaced something like every 5-10 years? And the zaskar is over 20 now

So my questions are; how does the zaskar fair in strength compared to a modern aluminium frame? Do all the gussets make it stronger and less likely to fail than a modern frame? Or do they just give it a stiffer ride? Also how difficult would it be to crack one of these frames? Arent all alumium frames bound to fail eventually? And dispite its reputation of being bombproof, cracking one surely isnt impossible... Is it?

My zaskar for example is 22 years old. I weigh about 150ibs and i use my bike for everything from road riding to trails, and hitting the occasional jump and drop off on it. Im not the heaviest rider but im also not the most forgiving with my bikes, and id hate for this frame to fail on me because i love it but even with how strong people say it is, its still an old bike so i have that worry in my mind, given its use

...so anyway: that started off as a little queery but turned into a bit of a novel. Im just interested in hearing peoples input who may be more clued up on frame construction than me

Sean

Zaskars, US made were all 6061 (until maybe post 2000).
From dredging up my memory when I did metalurgy stuff (badly), 7005 is stiffer or stronger (or somesuch) and so lends itself more to butting (not that 6061 can't be) so you can retain the stiffness wile being abe to tune the tube for better feel. But 6061 is easier to weld and therefor make frames out of. 7005 had issues when welded, change in grain structure at the weld, the stiffer/thiner tubes were more brittle...hence why all the manitous, yetis, alpinestars etc crack to bits. This is why Easton went from program/varilite 7005 to 7000SC scandium as the prime roll of the scandium is to fix the weld issues (not weight or strength that people think).
So yeah Zaskars are good because they are overbuilt (being aluminium they are light but not uber light, I think the butted Easton 6061 from 97 on are pretty light though) they are also well built, and not so brittle.

But they do break, Ive seen one broken and the guy wasnt then most hardcore rider out there.

The harder the material, the more it is prone to crack. See Easton tubed frames like manitou. 7005 Aluminium is very hard, so you can make it quite thin and light, but still stiff. But being that hard, the harder Aluminium is more likely to crack. And there is the heat and setting-issue. Some types of Aluminium need quite sophisticated heat treating to reach their maximum strength. That knowledge had to be develoded in the beginnings...
I dont think you can just say all Aluminium frame have to be replaced after xx years. If made well, not too thin, and the right material, they would last "forever".

From memory, the 6061 tubing was heat treated (T6) which meant that the hardening process is still taking place albeit very slowly.

If wikipedia is to be believed, it has a lot of mechanical advantages over 7000 series. If you look at how 7000 frames crack, it doesnt follow reason. Its an almost random pattern until you look more closely and you see how the metal has failed:

my own Fisher - some builders used extrusion with no reinforcement rings



As for lifespan, it depends on use. My own frame is into year 23 and has covered around 50,000 miles in its lifetime and still feels exactly the same. Some far older steel road frames feel dead on a ride then theres a twang and everything starts moving again - theres a physics explanation and I'll harang my local aluminium frame builder as to what is what later.

With the zaskar, the most common issue was fitting too long travel forks that would try and rip the headtube off. The other is stress from the welding process as the heat has to remain within a certain window before damaging the structure altogether.

Thats my memory finished.

More later when I've spoken to an actual welder of alumniumnmnmuinm

<wanders off muttering something about 'grain' and structure>

i'm an absolute zaskar fan and i love to ride mine. in my opinion the only way to ruin such a frame is using a seat post that's too short.
i've only seen cracks on zaskars on the top end of the seat tube or at the weld between top and seat tube.

Very difficult...............

A lot of the aluminium cracking is due to work hardening and then fatigue as the frame flexes under load.
The Zaskar has minimal flex in it (compared to many of it's aluminium contemporaries) so it *should* be significantly more durable.

It's why i didn't buy one when i had the chance, as a 9 stone XC rider it was way too rigid and crashy to be comfy for more than about a 20 minute ride. Ended up on a far more comfy Ti. (Not Xizang)

Yes, the zaskar frame was as hard as nails and not for non burly riders.

7000 series tends to be failures of the tubing itself

6000 series is welding failures as mentioned earlier

The filler rods for 6000 (4043) is a strong alloy but prone to cooling cracks as it contracts a lot. 5356 which is used on 7005/ 7020 is less prone to cracking.

6000 is not inherently stronger but doesnt mind being manipulated and is more ductile. 7000 just isnt as malleable.

Look at the differences in cast iron and stainless steel for how 7000 and 6000 differs in structure.

Extrusion is a mess of weak points, large crystals being stronger than the surrounding areas creating fracture points. Making these crystals small and uniform across the object be it a frame tube or crankset makes it stronger and more durable and it aligns the grain structure with the form of the tube. As extruded tubes tend to be used in the headtube - you guessed it, cracked heatubes.

Or a big lump of sugar (7000) and Brighton rock (6000)...

Then theres the mixing of the alloys within the welding pool, penetration etc etc!

hope this helps!

^nice description.

Re:

some really interesting info here

ive heard of people ripping the headtubes off through misuse such as jumping large sets of steps and DH but ive hardly seen any broken zaskars (early ones at least) i suppose the most likely place of the frame to crack then is the top of the seat tube...?

this below must of been genesis for the zaskar in the mid to late 80s, i read that all the ones made cracked and failed and the bike in the picture is the only one left in existence. im guessing that GT threw a bunch of burly gussets on it for strength, neatened up the welds and it evolved into the 1991 zaskar.

legrandefromage":1g44rgz0 said:

Yes, the zaskar frame was as hard as nails and not for non burly riders.

Click to expand...

I'd never heard that before. In my 20s when my Zaskar frame was being dragged home in it's box from the LBS I was 10 stone.. all this time later I'm about 10.5. I never had a problem with mine but maybe I need to eat more cake and beef up a bit... hmmm...