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I have a specialized turbo electric bike and just had the shop put in a rock shox paragon front suspension. They didn't have the rotor size adapter for the disc brakes so they swapped my 180mm rotor with a 160mm rotor. They put my old fender on my new shock as well.

Riding it home I noticed that when I brake, there is a noticeable hard shift of the wheel left (to the disc brake side). It's all the more noticeable because I can see it move in relation to the fender above it. It looks like it's shifting 5-10mm.

Is this normal? Is it an optical illusion and it's the fender that's moving and not the wheel? Is the disc brake pulling the wheel over? Did installing the fender cause it? Is it caused by the replacement of the rotors?

I'm a bit at a loss to figure out if it's a problem and how to diagnose. I suppose I can undo the fender and then do some other things one step at a time but I wonder if there's an easier way to diagnose other than taking the parts off one at a time.

  • Is the bike also pulling to one side if you brake? – Carel Aug 11 '18 at 16:53
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First thing to do is check if the wheel is actually moving in the fork, or that the fork has slop or play in it.

Stand next to the bike, hold the bars, apply front brake and try to move the bars side-side and front-back. If you feel slop or play, don't ride it and take the bike straight back to the store that did the installation and have them fix it.

It may be that braking is causing the fork to bend slightly and move the wheel left. You could also take the bike to the store, show them the problem and ask them to check their work.

  • Looks like a very serious shop that didn't have the correct brake adapter. (Irony off.) See if the front axle, quick release, through axle or nuts are correctly tightened! – Carel Aug 11 '18 at 16:52
  • I checked for side to side and front to back slop or play - and it seems tight and the quick release seems tight. It looks like when the disc brake engages hard, it tilts and slants the wheel to the left a good 10 mm. – MonkeyBonkey Aug 13 '18 at 15:29
  • @MonkeyBonkey Well that sound like fork flex. – Argenti Apparatus Aug 13 '18 at 15:40
  • So took it to the shop and found out that the quick release was not tight enough. Even though it didn't shift while stationary, braking hard at speed was causing enough force to push the wheel around. Really cranking on the quick release did it, but it probably means that a quick release lever won't be tight enough for the front fork. – MonkeyBonkey Aug 14 '18 at 18:59

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