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Thread: Necessary cut bump stops?

  1. #1

    Default Necessary cut bump stops?

    Hi All,

    I tried searching in OzMPS and out but couldnt find clarity in regards to why bump stops need to be cut.

    I found some threads giving yes and no answers as to needing them shortened but not really why.

    Car: Gen II
    Setup: Koni Yellows/H&R Sport Springs

    Question:
    1. Do I need to shorten the bump stops with my setup?
    2. If so, how much to cut off?
    3. Why is there a need to shorten?

    Cheers.

  2. #2

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    The rear bump stops are excessively long and hits too early even though the damper still has travel. I've got Bilsteins/Eibachs and cut about an inch off the bottom. Basically cut away the excess just below where the dust boots sit. The Bilsteins have internal bump stops on the fronts, this may be different for Koni

    I am not sure if the Gen 1 and 2 rear struts are the same, but I think they are. Also I can't confirm the amount travel on the Koni's, so hopefully someone with Koni's can chime in

  3. #3

    Default

    Quote Originally Posted by lup15 View Post
    The rear bump stops are excessively long and hits too early even though the damper still has travel. I've got Bilsteins/Eibachs and cut about an inch off the bottom. Basically cut away the excess just below where the dust boots sit. The Bilsteins have internal bump stops on the fronts, this may be different for Koni

    I am not sure if the Gen 1 and 2 rear struts are the same, but I think they are. Also I can't confirm the amount travel on the Koni's, so hopefully someone with Koni's can chime in
    Did this make for a less bumpy ride by trimmin the bump stops?

    Will this make the shock travel more since the bump stops are now shorter?

    Sorry, still trying to understand the need to trim bump stops..
    09 Aluminium Silver MPS
    || Accessport - Stage 1 Tuned || COBB SRI + Airbox || Koni Yellows Sports || Eibach Pro-Kit || Corksport RMM || Graphite Wheels || DBA T3 Slotted Rotors ||
    || Vinyl Wrap Rear Valance || LED kit - Plates and Parkers || Windows Visors || Custom Plates ||

  4. #4

    Default

    It won't affect the ride unless you're sitting on full travel while driving normally. I suspect you have other issues if this is the case :P

    By cutting the bump stop it allows the strut to utilise its' full travel as it isnt limited by the bump stop.

    Basically the purpose of the bump stop is to provide a cushion for when the strut reaches close to its full compression. Its basically a buffer zone. When the strut hits the bump stop, there is no more dampening. This is why we want the strut to be doing the dampening and not the bump stop.

  5. #5

    Default

    Quote Originally Posted by lup15 View Post
    It won't affect the ride unless you're sitting on full travel while driving normally. I suspect you have other issues if this is the case :P

    By cutting the bump stop it allows the strut to utilise its' full travel as it isnt limited by the bump stop.

    Basically the purpose of the bump stop is to provide a cushion for when the strut reaches close to its full compression. Its basically a buffer zone. When the strut hits the bump stop, there is no more dampening. This is why we want the strut to be doing the dampening and not the bump stop.

    Very good info. Cheers!

    Given my current setup - is there a recommendation to trim the bump stops?
    09 Aluminium Silver MPS
    || Accessport - Stage 1 Tuned || COBB SRI + Airbox || Koni Yellows Sports || Eibach Pro-Kit || Corksport RMM || Graphite Wheels || DBA T3 Slotted Rotors ||
    || Vinyl Wrap Rear Valance || LED kit - Plates and Parkers || Windows Visors || Custom Plates ||

  6. #6

    Default

    Would need to seek advice from people who have installed Koni's. You might want to check on the mazdaspeedforums as well. I think there is a massive thread on there which was from the experience of Koni's. But I think they were FSDs

  7. #7

    Default

    Quote Originally Posted by lup15 View Post
    Would need to seek advice from people who have installed Koni's. You might want to check on the mazdaspeedforums as well. I think there is a massive thread on there which was from the experience of Koni's. But I think they were FSDs
    Found that thread and yes that was for FSD's...
    09 Aluminium Silver MPS
    || Accessport - Stage 1 Tuned || COBB SRI + Airbox || Koni Yellows Sports || Eibach Pro-Kit || Corksport RMM || Graphite Wheels || DBA T3 Slotted Rotors ||
    || Vinyl Wrap Rear Valance || LED kit - Plates and Parkers || Windows Visors || Custom Plates ||

  8. #8
    Join Date
    Jun 2013
    Location
    Brisbane Northside
    Posts
    33

    Default

    Put coilovers in. Dropped 2 inches. No need to cut the bump stops.

    Just realised its for a Gen 2. Mine is a 6 MPS

  9. #9
    Join Date
    Aug 2009
    Location
    hunter valley
    Posts
    6,403

    Default

    If running konis leave the bumps stops! IF running bilstiens B8's remove the bump stop

  10. #10
    Join Date
    Aug 2009
    Location
    hunter valley
    Posts
    6,403

    Default

    I had Konis and mazdaspeed lowing springs 15mm drop in my gen1, I left the bump stops in they hit hard often. I have Bilstien and kings in my gen2 no rubber stops and they are a whole full 100yrs ahead!

  11. #11

    Default

    Dunno what you did with yours but I used the rear bump stops to put the dust boots on. It's annoying the fronts didn't come with any... reused the stockers with ghetto zip ties

  12. #12
    Join Date
    Oct 2009
    Location
    Moorooka, Brisbane
    Age
    48
    Posts
    7,059

    Default

    Quote Originally Posted by RedDjinn View Post
    I had Konis and mazdaspeed lowing springs 15mm drop in my gen1, I left the bump stops in they hit hard often. I have Bilstien and kings in my gen2 no rubber stops and they are a whole full 100yrs ahead!
    You took your rear stops out altogether?

    Sent from Samsung Note 2 LTE
    Redbull is DEAD!!

    Long live the Redbull ... V2



  13. #13
    Join Date
    Aug 2009
    Location
    hunter valley
    Posts
    6,403

    Default

    Quote Originally Posted by Yeldarb View Post
    You took your rear stops out altogether?

    Sent from Samsung Note 2 LTE
    SORRY the bottom bump stops are untouched in the rear on swing arms (forgot about them). The ones on the rear shocks are cut right down.
    Many want Power not many hold it long.........

  14. Default

    Generally you would trim off the last bit of the bump stop for added shock travel but it all depends on the spring. Sometimes the manufacture designs the coils to be used with the standard length bumpstops, it all depends and you would have to clarify with them.
    I have a set if Bilstein B8's and H&R coils on my Gen 2 and the rear bumpstops are trimmed.

  15. #15
    Join Date
    Apr 2012
    Location
    South Perth, Western Australia
    Posts
    400

    Default

    I'm running BC BR-RA Coilovers, fairly low at the moment too - with stock bump stops.
    The coilovers are pretty firm, which is why i haven't needed to cut.

    Will be going lower soon, so i imagine i'll have to give them a trim. They're really quite huge!

  16. #16
    Join Date
    May 2010
    Location
    Sydney
    Posts
    2,600

    Default

    Modifying bump stops sounds like a terrible idea!

  17. #17

    Default

    Quote Originally Posted by Reedy View Post
    Modifying bump stops sounds like a terrible idea!
    Even if lowering the vehicle?

  18. #18

    Default

    its more so if you are using aftermarket shocks as the stock bump stop limits the amount of useable travel

  19. #19

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    Quote Originally Posted by lup15 View Post
    its more so if you are using aftermarket shocks as the stock bump stop limits the amount of useable travel
    I'm using koni sport shocks with h&r sport springs

  20. #20
    Join Date
    May 2009
    Location
    Sunshine Coast Qld
    Posts
    749

    Default

    The rear bumpstops are long in the MPS so as to work with the oem spring rates.Oem front and rear springs are progresive.
    Changing the springs and shocks to koni sports (advise you do some research before chopping bumpstops as you cant buy them as separate items if you stuff them )
    Im personally running Koni FSD,s ,used std lenght rear bumpstops and fat cat motorsports front bumpstops,.
    Heaps of good info at MSF.

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