Stripped mounting bolt on 105 derailleur. Is this common?
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Like I've said in my other posts, I'm still new to this all, so be patient.
I have had my bike about a month now, and within about 1-2 weeks I noticed the chain was rubing quite a bit on the front derailleur. Today I was on my trainer, and the front derailleur stopped working all together. I took a good look, and found the mounting bolt was stripped, causing the derailleur to flop all around and drop in the bracket, causing the cage to rub the gear teeth. So, my question is this: is this a common problem with 105 compnents, or was it just on overzealous mechanic? I am sure it will be covered under warranty, but if it will be an on going problem, I may just step up a grade or two to save the hassle, even though I hadn't planned on upgrading components quite yet.
Like I've said in my other posts, I'm still new to this all, so be patient.
I have had my bike about a month now, and within about 1-2 weeks I noticed the chain was rubing quite a bit on the front derailleur. Today I was on my trainer, and the front derailleur stopped working all together. I took a good look, and found the mounting bolt was stripped, causing the derailleur to flop all around and drop in the bracket, causing the cage to rub the gear teeth. So, my question is this: is this a common problem with 105 compnents, or was it just on overzealous mechanic? I am sure it will be covered under warranty, but if it will be an on going problem, I may just step up a grade or two to save the hassle, even though I hadn't planned on upgrading components quite yet.
By ''flop all around the drop'' mean you have a brazed-on front derailleur. The mounting bolt is stainless eel while the derailleur bracket to which it bolts to is aluminum (which is softer than steel) - are you sure its the bolt that's stripped?
There is a bracket coming off the downtube that the derailleur is bolted to. I can tell from slight wear marks that the derailleur was initially mounted relatively high in the slot, so when I say it dropped, I mean it dropped to the bottom of the slot in the bracket.
Also, I took the bolt out and lookd at it, and the threads are definitely stripped, as are the threads in the derailleur, to some extent.
As far as I know, the 105 front derailleur uses a helicoil because the aluminum is too soft and will strip its threads at the torque required to mount the derailleur. The good news is that you can have the helicoil replaced. The bad news is that it'll probably cost as much as a new derailleur. This is another one of those excellent reasons to use a torque wrench and follow the manual.
John Swanson
www.bikephysics.com (http://www.bikephysics.com)
There is a bracket coming off the downtube that the derailleur is bolted to. I can tell from slight wear marks that the derailleur was initially mounted relatively high in the slot, so when I say it dropped, I mean it dropped to the bottom of the slot in the bracket.
Also, I took the bolt out and lookd at it, and the threads are definitely stripped, as are the threads in the derailleur, to some extent.
As far as I know, the 105 front derailleur uses a helicoil because the aluminum is too soft and will strip its threads at the torque required to mount the derailleur.
Helicoil for mounting?
The brazed on mounting for the 105 is as per the pic - Aluminum body of the front der, a mounting bolt with a washer. The bolt is stainless steel.
Scott, If the bolt is stripped as are the threads in the derailleur, you can perhaps use a slightly larger diameter steel bolt hoping to make new threads on the aluminum deralleur body.
Helicoil for mounting?
The brazed on mounting for the 105 is as per the pic - Aluminum body of the front der, a mounting bolt with a washer. The bolt is stainless steel.
Scott, If the bolt is stripped as are the threads in the derailleur, you can perhaps use a slightly larger diameter steel bolt hoping to make new threads on the aluminum deralleur body.
Thanks for the replies. I took it back to the shop I bought it from, and they will replace the derailleur under warranty. I may go ahead and upgrade to an Ultegra, as they are not too much money :dunno:
Yes, but I was unclear. The helicoil is placed inside the aluminum derailleur body - not the brazed on mounting bracket. The helicoil can be pulled out or wrecked quite easily as I found out one lazy Sunday afternoon while working on my bike...
John Swanson
www.bikephysics.com
Helicoil for mounting?
The brazed on mounting for the 105 is as per the pic - Aluminum body of the front der, a mounting bolt with a washer. The bolt is stainless steel.
Scott, If the bolt is stripped as are the threads in the derailleur, you can perhaps use a slightly larger diameter steel bolt hoping to make new threads on the aluminum deralleur body.
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