Could 10mm of extra travel contributed to cracking my chainstay?

[DMan]

I thought it was a rock hitting my chainstay, as I took a big rock hit on my last night ride, but it has been floated that it could be the extra travel on my rear shock. My bike came factory with a 130mm travel fork. The dude before me, original owner, fitted a shock with the same eye to eye but 140mm of travel. I've been riding it for last 18 months happily but the guy who fixed it thinks it could be the stress from the extra leverage caused by the extra travel? The shock doesn't foul or hit anywhere and I've never bottomed it out, hence I've never really though too much about it. So I could look at having the shock reduced in travel I guess as I don't want to go back to a DPS from my DPX2. Thoughts please?

 

[SummitFever]

Longer travel shock (with same eye-to-eye) will not cause any extra leverage (unlike a longer travel fork) as the rear wheel position is fixed by the axle.

 

[fatboyonabike]

10mm of extra Send is what damaged your frame!

 

[DMan]

Longer travel shock (with same eye-to-eye) will not cause any extra leverage (unlike a longer travel fork) as the rear wheel position is fixed by the axle.

It may be my lack of understanding Le engineering in his defence, not his explanation. Would there be a lot of extra stress put on the chainstay by that extra travel??

 

[DMan]

10mm of extra Send is what damaged your frame!

I can't read sarcasm. Are you confirming what he said?

 

[SummitFever]

It may be my lack of understanding Le engineering in his defence, not his explanation. Would there be a lot of extra stress put on the chainstay by that extra travel??

Hard to imagine but we'd need to see the suspension design of the frame. Max. force on the chainstay typically occurs on bottom out. The extra travel should actually reduce the peak forces involved by spreading them over a larger amount of movement (eg. travel).

 

[Zaf]

Removed by user

 

[fatboyonabike]

I would like to think that bike engineers are not designing frames that close to the breaking point and they have some level of over engineering to accommodate this

 

[Jpez]

I can't read sarcasm. Are you confirming what he said?

You can’t read sarcasm and you hang out here?

 

[DMan]

Hard to imagine but we'd need to see the suspension design of the frame. Max. force on the chainstay typically occurs on bottom out. The extra travel should actually reduce the peak forces involved by spreading them over a larger amount of movement (eg. travel).

It broke about an inch back from where the tape starts

 

[DMan]

You can’t read sarcasm and you hang out here?

Are you being sarcastic?

 

[Zaf]

Removed by user

 

[DMan]

Got any photos of underneath the tape?

I haven't. What did you want to see though? It's all welded up now

 

[Ackland]

It broke about an inch back from where the tape starts

Not the fault of the shock or travel! There's a lotta beef in that stay

 

[Zaf]

Removed by user

 

[leitch]

Like this?? Seems like it's more likely related to the elevated chainstay design.

https://forums.mtbr.com/trek/trek-full-stache-chainstay-breaking-1150175.html

 

[SummitFever]

If it's like that MTBR pic then that crack is the typical crack at the edge of the weld heat affected zone. Nothing to do with a bit of extra shock travel. May be a design flaw.

 

[fatboyonabike]

has Trek issued a recall, easily checked...might get a new frame out of it

 

[DMan]

Like this?? Seems like it's more likely related to the elevated chainstay design.

https://forums.mtbr.com/trek/trek-full-stache-chainstay-breaking-1150175.html

Yep, that's it!

 

[DMan]

If it's like that MTBR pic then that crack is the typical crack at the edge of the weld heat affected zone. Nothing to do with a bit of extra shock travel. May be a design flaw.

The photo that @leitch posted is pretty spot on where and what it looks like.