Steel vs. aluminum frame stretch ?

Joko
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Joko
Edited Date/Time 8/28/2013 7:08am
Curious to see if there is any documentation of late model steel frames stretching over time with use? I recall in 1988 there was a Dirt Bike article that documented a maintenenace schedule of a CR250 over the course of a season. If memory serves me, there was an increase in the steering head to swingarm pivot dimension of .100". I also recall info describing RC going through frames every 2 weeks or so during his 2000=era KX250's. Does the current crop of aluminum frames break before stretching? Anyone change frames as regular maintenance?
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Skerby
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Skerby 8/27/2013 9:00pm
8/27/2013 9:00pm
Have a 2009 YZ250 with 300+ hours of intermediate level motocross, I check the frame for cracks every few rides, solid so far, couldn't tell ya if it has stretched or not.
Beast666
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Beast666 8/28/2013 7:08am
8/28/2013 7:08am
Over time all frames are going to stretch as they all have to flex as they are going over bumps and jumps and cornering. The factories replace the frames after so many races just to play it safe to prevent a DNF from a broken frame.

As for the AL frames vs Steel I have seen less AL frames breaking over Steel But that being said I also broke more frames in the late 70's and early 80's than I did in the late 80's. my current 94 KX250 has more hours on it than any of my race bikes and i have only had a few minor cracks show up. As for stretch?? I have not measured it but I am sure it is a small bit longer today than the day it came off the line.

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