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I have a direct drive trainer and the directions say when taking the bike on and off the bike to take shift the bike into the hardest gearing (cross chaining even). This is the smallest cog in the back and largest cog up front.

I know I am not supposed to bike in this gear and it causes chain rub up front. I have taken my bike into a couple of mechanics and the gist of what they told me is don't ride in that configuration. So what I have been doing is I switch to it just to take the bike on and off the trainer, but I am wondering is this really correct. For sure the chain rubs the deraiuller but since I am not riding it hard or long it is hopefully doing minimal damage.

So my question is what is the correct thing to do in this situation? Do I continue to just have it rub a bit, find a new mechanic, or maybe try to re-index the gears myself? I am most troubled by the third option because if the other experienced mechanics gave this setup an ok I am not sure I can do much better.

Thanks!

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  • A) Why do you need to be in a specific gear to setup/remove the bike from the trainer? B) Even if you had to cross-gear for a pedal revolution or two to get into that situation (which you don't for large-chain ring/small cog), the amount of wear you'd get from those couple of revolutions would be statistically insignificant.
    – FreeMan
    Mar 31, 2022 at 18:34
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    The answer to A is I am not sure why I have to, it's what the directions from wahoo said to do and I follow it because sometimes directions exist for a reason and I don't want to damage anything. Honestly, I think it is because it's easier to line up the rear smallest cog and the chain as a point of reference than trying to do it in the middle. I agree with B and that is what I have been doing for months, but it has always bothered me and I wanted to learn more. Turns out I learned I am not even cross training something else must be wrong with my drivetrain which is valuable info already.
    – Ebay89
    Mar 31, 2022 at 19:24
  • @FreeMan: Usually it’s easier to remove a wheel when you are on the smallest rear sprocket.
    – Michael
    Apr 1, 2022 at 7:04

2 Answers 2

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The biggest gear on a bike (large chainring, small rear cog) should always be a useable gear. The gears you should stay out of are the cross gears, because the chain is at an extreme angle in those positions. In the highest gear it's the opposite; the angle is near-optimal.

Problems with the chain rubbing the FD cage in the highest gear are usually either a simple lack of cable tension (addressed with the barrel adjuster or re-clamping the cable) or if not that then a derailleur setup issue. Two of the more common scenarios on recent road bikes is a long-armed Shimano road 11 front derailleur with not enough cable tension (they need a lot) or a knuckle type Shimano road 11 front derailleur that hasn't been set up correctly.

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  • Interesting. Ok I guess I will try taking it to a new mechanic since I moved away from the last one. I wonder too if my stuff is damaged, I recently changed the chain because I noticed it was bad with a chain checker and had to replace the front deraiuller because it snapped under load. Also, had this problem with the old FD so maybe the bike shops mechanics don't know what is wrong or are covering up that my stuff has some wear or tear. Either way it is frustrating, I used velofix and a bike shop mechanic and nobody thought to tell me my chain was well need of replacing.
    – Ebay89
    Mar 31, 2022 at 2:50
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To add to Nathan’s excellent answer:

With real cross-chaining (big chainring and biggest rear sprocket or small chainring and smallest rear sprocket) it’s normal for the chain to rub on the front derailleur. With the small/small combination it can sometimes even rub on the big chainring.

This is usually not a problem since the sideways-force against the derailleur is minimal and it’s made out of hard steel which has to survive thousands of front gear changes. In any case you are not really supposed to use those gear combinations, so you shouldn’t spend much time in them anyway. But a few seconds while climbing up a short ramp or sprinting for a green traffic light (both situations where you want to avoid shifting in the front since it’s hard to do under load and can cost precious seconds) won’t hurt at all.

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