vanishing fender mount plug screws seized

macleod113 Posts: 560
edited February 2014 in Workshop
Hi All,

i have recently ditched my crud road racers due to excessive rubbing and have bought some bontrager approved ones.
i have also purchased the hidden fender mount screws (£15 for 4! blimey) but last night i was unable to remove 3 of the 4 original grub screws the bike had installed (Trek 2.1 2013). its a 2.5mm allen screw but the 3 that are stuck wont budge. i have tried spray lube but they wont shift. i have tried different allen keys also with no joy (long l shaped one and my multitool one). with too much force they feel like i am rounding the holes off.
does anyone have any experience with shifting these stubborn boggas?

any help much appreciated
Cube Cross 2016
Willier GTR 2014


  • Tyr soaking them well with PlusGas for a good while and the try removing with either a larger allen key or torx key for better grip. If that fails I would try cutting a slot for a flat head screwdriver before I would contempalte drilling them out.

    Never tried PlusGas myself but several really knowligable people on here say its the best for anything that's siezed. Good luck
  • Thank you for the tips. will try again this evening.

    i've never heard of PlusGas so will be googling that next :-)
    Cube Cross 2016
    Willier GTR 2014
  • balls! tried additional lube and tightening the bolts last night. sadly i must have rounded the screws completely as now it feels like chucking a chipolatta down the mersey tunnel!
    looks like a trip to the LBS to get them drilled out or maybe i can use the o ring mounts from my cruds. will look ugly as sin i reckon but could work out just fine!
    Cube Cross 2016
    Willier GTR 2014
  • keef66
    keef66 Posts: 13,123
    Once they are rounded your options are

    a) try tapping in a slightly larger Torx bit

    b) very careful drilling and use a screw / stud extractor

    c) admit defeat and take to LBS

    If you don't already have the tools, c may well be cheaper than a or b.
  • arlowood
    arlowood Posts: 2,561
    If all else fails take a look at what this guy did to solve the perennial mudguard problem on bikes with no eyelets.


    Might be a better option than the risk of damaging forks/frame when drilling out the grub screws.