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Bike pulls to the right when breaking

Discussion in 'Tech Help' started by Matej-O, May 4, 2015.

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  1. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    I'm glad you're taking the fact it wasn't the brakes either maturely :).

    EDIT: Nice ninja edit.

    Let's do this like MH370 - maybe it was pulling to the right cause it's actually in Kazhakstan?
    * Oil level - even on both, so probably not this
    * Differing fork heights - maybe
    * Fork alignment - possible
    * Front brakes - maybe sticking, reset by pushing back on

    Can probably rule out chain alignment if the forks were just pulled in and out.
     
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  2. John.R
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    Im just glad we're equally wrong LOL (even though Im pretty sure I only stated it was a bit odd not to check the brakes while he was at it, but whatever lol)

    I honestly think this is the first time I've ever seen a lack of scientific response from you, so it probably is a little bit immature to be taking the piss this much. Having the mind blown is probably hard enough to deal with as it is :lol
     
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  3. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Again, it's really not mindblowing to me. I had an idea, it was wrong, meh. Though equally wrong might be a bit far, cause without fiddling with the brakes it's still more likely to be related to the forks despite peoples insistence it was the brakes :).

    In any case, this is a scientific response. Had an idea, it was wrong when presented with more evidence, one updates one's thinking and moves on. Not sure why that's mindblowing.
     
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  4. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    So my next guess would be what trezza said, easy to have a small misalignment that gets amplified under fork diving, and the triples are put back into line with each other when the forks are reinstalled. I even allowed for that possibility with my reply to that post :).
     
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  5. rideon
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    rideon New Member

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    That was my guess.
     
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  6. supamodel
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    Differing fork heights is another way to say your one leg further through the triple than the other. The fork alignment I mean is where the top triple is differing rotationally to the bottom triple, as opposed to a fork height offset. Both would pull all of the time but might be either amplified under braking or not corrected automatically by the OP under braking.

    Meh, that's as far as I'm prepared to think about it.
     
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  7. Matej-O
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    Matej-O Member

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    Different fork heights were checked - not the culprit.
     
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  8. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Intriguing. Pretty cool it's solved but :).

    Also, hooooow good do freshly serviced forks feel? Always that little bit nicer I find.
     
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  9. Gosling1
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  10. supamodel
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  11. Gosling1
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  12. supamodel
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    Funnily enough, my Ducati pulls to the right and I know exactly why.

    I'm just too lazy to fix it :).
     
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  13. rideon
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    rideon New Member

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    Yes i know what you meant Between height and alignment , figured more chances of a leg slipping through the triple then a triple rotating Under normall riding conditions, ie without having a bingle. Another common mistake ppl make is not fitting the front tyre properly causing one leg to be slightly bent when clamping onto the axle.
     
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  14. Ron50
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    Ron50 Member

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    How about somebody backing a car into the front wheel on full lock when it was parked, tweaking the fork tubes in the triple clamps?
    Unlikely that the handlebars being offset when the bike was going straight wouldn't have been noticed though.
     
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  15. Gosling1
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  16. Jimmc
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  17. Ron50
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    OK, to sum up in the interest of @Matej-O 's future safety:
    Bike starts to veer right under braking and the veering gets progressively stronger. Everything seems to check out with the forks externally - no leaks, uneven height or low tyre pressure.
    After disassembly the forks are found to have even but low oil levels.
    On reassembly the problem is cured although the cause was not found.
    If I may be so bold, the only scenario that fits - apart from aliens - is a sticking brake piston or pin that was freed up during disassembly/reassembly, probably in wiggling the callipers off over the unworn part of the disc.
    Now pistons and pins don't just stick for no reason: old and contaminated brake fluid will cause corrosion and deteriorated seals and lack of lubrication will make pins stick. This problem will recur!
    So I would strongly suggest the brakes be given a thorough check by someone who really knows their stuff.
     
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  18. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Still doesn't make sense to me, calipers are mounted aft of the axle line on a bike with a single disc and they don't progressively pull to the right when you brake. (Or left, depending on the side the disc is mounted on).
     
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  19. metaltriumph
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    I agree with Ron50 - and also, without knowing @Matej-O or his mechanical ability - perhaps the forks were a bit twisted? need re-aligning?

    My zed wiggled around heaps under hard braking when i had solid (& worn out) disk rotors. I thought perhaps it was the brakes biting harder on one side that caused it.

    So i removed the forks, replaced with newer drilled rotors from a later model, replaced the fork seals and fork oil. Problem solved.

    So was it the fork rebuild or the brakes that solved the problem? hmmmm...... lol
     
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  20. Ron50
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    You're forgetting the gyroscopic forces of the spinning wheel and precession. When everything is free the disc is pinched by the pads; when a pad works on only one side of the disc there is a turning moment because the calliper/pad is behind the axis of the forks.
     
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