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Is there an art to fitting a rear brake caliper?

Asif TufalAsif Tufal Posts: 109
edited January 2018 in Workshop
Hi all,

My Shimano Tiagra BR4600 caliper returns to its proper position when I squeeze it in my hand. However, once fitted only the right arm springs back and the left is stuck to the brake rim. The front is working perfectly. As it's a used item, Iv'e sprayed the pivot points with WD40 and left it to soak for 8 hours before attempting fitment for a second time but it's just the same. Could it be an issue with the star-shaped lock nut, next to the arm spring on the rear?

Here's the exploded diagram: https://hollandbikeshop.com/images/EV-BR-4600-3142C.pdf

Thanks,
Asif

Posts

  • Sounds like one of the pivots is partially seized. I had the same issue on my rear Tiagra. The caliper needs to be fully dismantled and re-greased.

    These may help:-

    https://youtu.be/_ctDGe9XXf0


    https://youtu.be/TqbCR83psAg

    If you don't have the tools or inclination just buy a direct replacement off eBay for not a lot of cash.
  • crankycrankcrankycrank Posts: 1,830
    +1^^^. Also check that the pivot bolts (assembly #1 & #2) are tightened correctly so that the brake arms move freely but don't have play in them. Since you mentioned they work fine when not mounted you may have a loose nut on one of the bolts.
  • cooldadcooldad Posts: 32,601
    As someone said - clean and lube. WD40 is not a lubricant. It will remove any lube that was there.
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  • bondurantbondurant Posts: 857
    I think it's most likely as described above but it might also be worth checking that the centring screw no. 7 in the diagram isn't making one brake arm pull more than the other. It's there to make sure the pads touch the rim at the same time when squeezing the lever.

    Unlikely though.
  • Thank you all. It appears that bolt #1 was too tight and it's working now. The WD40 helped dislodge the muck that was stuck in the calipers but I'm glad you reminded me about lubrication. Also, I hadn't thought about taking the caliper apart and servicing it but in future will do so at the end of the season.
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