[Vermont]

Hi guys.....i noticed a crack in my 5 year old hard tail...i had a friend throw a weld on it...i got a new frame and was thinking of using this one for slicks...kind of a Vermont road bike...any of you techies have any reservations about riding this frame...see pics of the weld.
thanks

 

[Vermont]

pic#2

 

[Vermont]

pic#3

 

[Matt D]

It's generally thought of to be a bad idea to weld Al for general riding. I surely wouldn't ride a welded DH bike (could snap on big impact) or trailbike (getting stranded 20 miles out isn't fun).

I would however probably use it for commuting.

How bad was the crack before it was welded?

 

[Zaskar Rider]

The only thing that worries me is I think they heat treat all Al frames after they are welded. but who knows it might be Ok

 

[Vermont]

the crack was on the driveside chainstay along the weld of the chainstay bracket furthest from the bottom bracket on the inside ..it wasn't all the way around the chainstay ...my LBS guru said it would be fixable but he mentioned the heat treated thing too....as i said my plan is to build it up with cheap parts, put slicks on it and use it as a dirt road bike...it will never be used off-road for sure. The guy who welded it is a professional Al welder who used the smallest possible wire size to reduce the amount of heating to the tubes.

 

[Westy]

The heat from welding reduces the strenght of AL. Most AL frames are heavily butted so there is more material in the heat affected/weakened zone, if you put a weld on a thinner part of the frame that was not designed to take a weld it will ultimately fail again. It might be OK for road riding but I would not trust it for real MTB riding.

 

[TWISTED]

If you want an informed professional answer the most important factor is whether the frame is 7000 series, as in 7005 which should be baked after welding for 12 hours at 200 and then 400 degrees but naturally hardens to T6 after welding in about 1 1/2 years.
6000 series aluminum, 6061, 6066, etc., after welding must go through a solution heat treating process prior to baking. This process heats the frame almost to the melting point, which lets the molecules of the metal flow evenly. Then it is quenched in a glycal tank which freezes the molecules into position. at this stage the frame is soft and easy to align. Baking is next, 8 hours at 300 degrees, if I remember correctly (if not at least you get the idea).
So 7005 weld and ride? Not a good idea but possible.
6061 weld and ride? Weak area around the weld, sure to fail.
Hope this helps.

 

[Vermont]

it is a GT Avalanche frame..no idea what type of Al it is.
Thanks for you info p

 

[Vermont]

i do believe it's 7005 Al so i may be okay for using it for road riding...its really a bitch that Pacific didn't honor the lifetime warranties that GT promised when selling the bikes but this frame was a replacement for a frame i broke 5 years ago...so i can't complain to loudly..lol. anyone know why the pic i uploaded to RM isn't showing under my nick on left?