Problem with gears on my new racer

[raiderskys]

I have a problem with my new racers front set of gears. The chain keeps scraping along the side of the shimano gear mechanism (don't know the exact name for it). I took it back to halfords twice to get it sorted but they said that this was how it was meant to work and couldn't set it any better than what it was at. The scraping does not occur in all the gears but in a lot of them. Is this like what the halfords experts say "a normal operation of the running of the bike"?

 

[Bikelyst]

Don't worry, this is normal on all bikes. What happens is that some gear ratios put the chain in a way that it scrapes with the derailleur. There are two adjustment screws near the derailleur to adjust the positioning, but I wouldn't fiddle around with it. If you really need to adjust it to fit the gears that you use the most, bring it 'round to your LBS.

 

[daveryanwyoming]

... The scraping does not occur in all the gears but in a lot of them. Is this like what the halfords experts say "a normal operation of the running of the bike"?

No, it is not normal for your front derailleur to scrape in a lot of different gears. I don't know if you're running a double or triple set of front chainrings but scraping is more common with a triple and the large spread of front gears. Still the front derailleur should scrape on only the most extreme gear combinations (big front chainring, big rear cogs or small front chainring small rear cogs) which you should avoid using since it puts the chain at extreme angles. If you're not cross chaining as described above (extreme gear combos) you should have little to no scraping.

Some bikes need small front derailleur adjustments as you shift gears to eliminate scrape. It's commonly known as "cleaning your shift" and was standard procedure years ago with friction and early click shifting. I do a lot less of this these days as my front derailleur doesn't scrape in anything but the cross chaining combos which I never use.

Anyway my road bike with 53:39 rings up front and up to 12:27 in the back during training never scrapes. My mountain bike with a triple and wide gears in the back will scrape in a few gears but not very many.

There are a couple of front derailleur adjustments including how it is actually mounted that impact scraping. Take it to your LBS and tell them what's going on. Also pay attention to what gears you ride in and make sure you're staying away from the cross chain combos that are bad from a chainline standpoint and are a lot more likely to result in scraping up front.

Good luck,
Dave