prj71

Just picked up a new Trek Domane. Noticed that the front derailleur (shimano 105) was rubbing on the chain a little. Did some investigation and noticed that the support plate was missing from the seat post and the support bolt wasn't engaged. My investigation reveals that the support bolt swings the back end of the derailleur around so that it's parallel with the chain ring. I assume that is necessary for everything to work properly?

Page 9 on the attached document.

Iride01 

If it's missing from the seat tube then you might need one unless Trek did something different.

New bike.... let your Trek dealer handle it. They need to know or else they'll explain why it's not needed so you'll know.

The rub might be the the DR not correctly held by it's mount or a few other reasons..

prj71

Yeah. I already told the dealer.

Trek doesn't do anything different. It's a carbon bike so you can't exactly plunge the bolt into the carbon frame.

Iride01 

So what did they tell you about the noise? Or is that not an issue now? Is there even a question or was this just a PSA?

prj71

Just a PSA and looking for some feedback. Maybe people find that the support bolt isn't always necessary?

They LBS didn't say anything about the noise. Just said to bring it in.

When I went for the initial ride on the bike last night, in some of the gears the chain was rubbing on the front derailleur while in the big chain ring and even the trim shifting wouldn't make it go away. Having dealt with this before on previous bikes my first thought was just to adjust the cable tension so the derailleur would swing out farther. So after researching online and finding the support plate in my bag of parts that came with the bike, I discovered that the support bolt kicks out the back of the derailleur to ensure that it's parallel with the chain ring.

The LBS has been crazy busy. They had to assemble 30 bikes before mine and since I picked it up they've added another 20 to their list. I'm sure it just got missed in all the craziness..

cxwrench

Yes you can. Trek carbon frames haven't needed the support plate for at least 2-3 years. On some frames there isn't room for it. The front derailleur mount area is reinforced and you won't hurt it w/ the support screw.

prj71

Do you have a link or something I can reference that supports this statement?

cxwrench

No, but I did have an '@trekbikes.com' email address for a few years. Contact Trek if you'd like, they'll confirm.

prj71

Interesting thanks. Glad I posted this.

bikeme

A bike industry friend told me about the need for the support bolt and its plate to properly support the front derailleur because of the torque the FD puts out under a shift. My new Emonda did not come with it installed and shifting was not bad but I was told it'd be awesome after installing the plate and setting the bolt properly. When I contacted the LBS I bought the bike from, they played all sheepish, like they sort of knew about it but dismissed the need to cover their laziness/oversight. I talked with Trek and they told me that you need to used the bolt for best shifting. Now, they did not go as far to say that you could damage the bike without using the bolt and its plate. However, my friend had personally witnessed braze-ons that cracked or broke off as well as screws that were ground into carbon seat posts because the plate was not in place! There are two plate styles shipped with new bikes: one flat and one round--one or the other should fit on a seat tube. I had to use a flat one and install it flipped compared to the position in Shimano's instructions. Shifting is now faster and crisper and I have peace of mind about the braze-on. Now for some laughs about the LBS...they told me they'd install it for me so I had them do it on my post-sale tune up. Those kooks just arbitrarily stuck it on (a curved one on a flat surface no less) behind the FD nowhere near the bolt and it was even falling off when I got home (the tape just positions the plate, the bolt holds it). I called them on it and they said sorry, we'll do it properly, blah, blah. Screw that, I decided to do it myself as I could not trust them to do it right--and I'm glad I did. Lastly, my friend said that 80% of the bikes he sees don't have the plate installed--lots of lazy mechanics. Here's a great article about installing it and why: https://www.roadbikerider.com/are-yo...t-derailleurs/

bikeme

That's not what the Trek rep told me--he said "follow the instructions and install the plate"

cxwrench

Which instructions? Shimano's? You can trust me on this one, I had an @Trekbikes.com email address for years, was a service manager at a Trek owned store and have been through the Trek Expert Tech class in Waterloo. When I say I probably know more than 'the Trek rep' when it comes to the technical stuff you can believe me. Our old rep had no clue about any of the that stuff.

prj71

I guess I never followed up on this post from a year ago. LBS wasn't sure when I asked them about it so they contacted Trek Directly. Turns out cxwrench is correct. You don't need it.

The Shimano instructions are just generic in nature in case the shifter does get installed on a bike that needs it.

After some adjustments, I got the chain rub to go away and haven't had any issues with the front derailleur since.