Aluminum bike chassis.

Zim · #1 07-16-2009, 07:53 PM

I bought a wrecked bike and it has a bent subframe. The subframe on these bikes are welded in instead of bolted. I plan on replacing the subframe, but there are two cast aluminum bars that the subframe is welded to that are bent. Can these be heated slightly and pulled back into place?

entropy · #2 07-16-2009, 09:20 PM

As a general rule of thumb...
You can not heat aluminum and have it do anything but lose strength...

FrogDog · #3 07-16-2009, 09:44 PM

I agree with 'E'

I'm not an aluminum connoisseur, but even with steel I will try to bend or straighten cold first depending on the structual needs of peice in question...

cheers bro..

Dog....

fabcam · #4 07-16-2009, 10:05 PM

x3 I wouldn't even bend it back and trust it, never mind the heating issue.

Zim · #5 07-16-2009, 10:07 PM

Do I have a chance of cold straightening it without it cracking? It's only about an inch out, but that seems like alot for aluminum.

Zim · #6 07-16-2009, 10:07 PM

Your to fast for me cris.

smackdaddy · #7 07-16-2009, 11:33 PM

can we have a pic??

shaggy10000 · #8 07-17-2009, 12:23 AM

A pic would help, but if its a relatively tight bend then the aluminum is toast. It doesnt like to bend, again as a general rule.

Zim · #9 07-17-2009, 07:32 AM

I'll get a pic up by the end of the day.

SUPERD · #10 07-17-2009, 12:09 PM

Quote:

Originally Posted by Zim

I bought a wrecked bike and it has a bent subframe. The subframe on these bikes are welded in instead of bolted. I plan on replacing the subframe, but there are two cast aluminum bars that the subframe is welded to that are bent. Can these be heated slightly and pulled back into place?

the newer aluminum frames have welded subframes because they are not designed to be repaired.
I would never trust my life on a straightened aluminum part.
that is why insurance companies are so quick to total street & dirt bike with aluminum frames "Liability"
all the newer BMW's & AUDI's (cars) have aluminum subframes & suspension components & they firmly state to never straighten anything, no matter how minor. If it is bent or has been hit even slightly it must be replaced.
Yes, this sucks & is freaking expensive but someones life could be cut short because of fatigue cracking at a later time, you don't want a wheel flying off @ 70mph.

I would cut off everything damaged & weld on a new piece on if it is even available.

Zim · #11 07-17-2009, 10:27 PM

Not sure If I'm doing this right.
<a href="http://s828.photobucket.com/albums/zz203/Zim6/?action=view&current=BIKESUBFRAME4.jpg" target="_blank"><img src="http://i828.photobucket.com/albums/zz203/Zim6/BIKESUBFRAME4.jpg" border="0" alt="Photobucket"></a>

This is the bar that is bent on each side. Everything welded on behind this will be replaced.

<a href="http://s828.photobucket.com/albums/zz203/Zim6/?action=view&current=BIKESUBFRAME2.jpg" target="_blank"><img src="http://i828.photobucket.com/albums/zz203/Zim6/BIKESUBFRAME2.jpg" border="0" alt="Photobucket"></a>

<a href="http://s828.photobucket.com/albums/zz203/Zim6/?action=view&current=BIKESUBFRAME3.jpg" target="_blank"><img src="http://i828.photobucket.com/albums/zz203/Zim6/BIKESUBFRAME3.jpg" border="0" alt="Photobucket"></a>

Bonehead · #12 07-17-2009, 11:24 PM

Bonehead · #13 07-17-2009, 11:25 PM

Bonehead · #14 07-17-2009, 11:26 PM

entropy · #15 07-17-2009, 11:42 PM

I could be 100% wrong.

Be safe find a frame...

Zim · #16 07-18-2009, 09:58 AM

You dont think it would be wise to cut it off at the weld in front of the shock in the first picture?

SUPERD · #17 07-20-2009, 12:38 PM

It's your life & checkbook.
do you trust your abilities or is someone else gonna do the welding?
I would check the steering neck & the rest of the frame before I put much time in it. there may be more damage than you are noticing since you are concentrating on the rear. secondary damage can go unnoticed easily.
aluminum is not a very forgiving material, I would look for a frame.

Zim · #18 07-20-2009, 04:14 PM

I'm going to Tig it. Found a subframe online so I won't have to bed anything. Plan on adding a few gussets and boxing in the sub for some extra support for the 12 o'clock bar. Thanks for all the replys guys.

SUPERD · #19 07-23-2009, 11:24 AM

Hey Zim, you butch that frame up yet?

TrxR · #20 07-23-2009, 02:06 PM

That look like a bad bend. I would definitely look close at that frame.

On a another note a local stunter here cracked his frame by the steering neck on his GSXR 750 about 3 years ago in an accident as well as mangling the subframe. He had a local machinist weld the frame and it has been fine and it gets abused as it is a full time stunt bike. But a stunt bike is different then something that is going to see alot of street duty or a road course .