Hot Shock!!! Should I Worry?

Discussion in 'Mechanics Garage' started by RllwJoe, May 19, 2018.

  1. RllwJoe

    RllwJoe Insider

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    Attempted to upgrade the rear shock on my '98, inexpensively.

    Bought a used 929 rear shock off of ebay. Had a local shop do a rebuid/ recharge (no I didn't send it to DMR), built a DMR-type extention, and finally installed it today.

    After taking it for a 1/2 hour ride, I reached in and wrapped my hand around the spring. I was supprised at how hot the spring was. I expected the "remote reservoir" to be fairly warm, but it was almost too hot to touch!

    Have any of you noticed how hot the rear shock normally gets?
     
  2. TOE CUTTER

    TOE CUTTER Mullet Man

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    Sounds like exhaust heat from here.
     
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  3. OZ VFR

    OZ VFR Member

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    A shock reservoir will easily get to 75°C after a spirited ride.
    It is why they must be vaccum pumped to get any moisture out before oil is added.
    And why the oil used on shocks is much more fade resistant than fork oil.
    Exhaust on our bikes doesn't help, but won't affect it much.
    Which way is your reservoir facing?
     
    Last edited: May 19, 2018
  4. RllwJoe

    RllwJoe Insider

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    It is pressed up against the plastics that protect the wire harness and fuses.

    I also wonder if the compression and rebound dampening, when close to full hard, would cause more heat because of the higher restriction.
    compression is set at one turn out, and rebound at 3/4 of a turn. Remember, this is a stock 929 shock, with the stock internal valving.

    Also note that the air temps were around 50-54 F, so it was a cool ride. I was working the suspension by weaving back and forth in an attempt to eliminate the chicken strips on the tires. The rear, a T30 EVO has only 3/8 of an inch unscrubed, without a track day. So I'm getting there. Us "flatlanders" don't have canyons to carve, so we pretend to "carve the canyon" while riding on a flat and straight two lane road.
     
    Last edited: May 19, 2018
  5. OZ VFR

    OZ VFR Member

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    The stock 929 is a much lighter bike, and being a true sports bike, loads the front a lot more than the VFR.
    So both the rear spring and the valving is too light for the 5G.
    I can't comment on setting, as I have no idea where it is as is (stock 929).
    The more compression damping you give it, the more it will heat up.
    As stated, exhaust heat is nothing compared to how much heat a monoshock will generate, even when set up properly.
    I always recommend that if you're doing the swap, do it properly, why go half arsed?
    You would have been better of just rebuilding the stock one with a stronger spring.
     
  6. OZ VFR

    OZ VFR Member

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    Also remember that the compression damping screw only adjusts slow speed (it is just an adjustable bleed passage bypassing the valving), it will also affect high speed but most of the high speed is controlled by the valve shims/piston ports.
    So no amount of screwing in or out will have much effect on high speed compression damping.
    Same goes for rebound damping.
     
  7. OZ VFR

    OZ VFR Member

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    The rear shock spring on the 929 is 15.3kg/mm, the same as the 5G.
    This is fine if youre a midget or a 12 year old girl.
    So going to the 929 shock hasn't really given you any advantage.
    The difference is that the VFR is over damped to make up for the light spring, the 929 isn't.
    I'm not having a go at you, just explaining how it works.
    If your old shock was totally had it, you're at least a bit better off now, but don't expect any great improvements.
     
  8. RllwJoe

    RllwJoe Insider

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    Thanks for your insights Oz. I've spent about 100 bucks so far, and I figured that if the spring is too light I could buy one, change it myself, and still have around $200 into the upgrade.

    The stock shock is not rebuildable, and has very limited adjustment compaired to the 929 shock.
     
  9. JamieDaugherty

    JamieDaugherty New Member

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    The OEM shock on the VFR is rebuildable and upgradeable - in fact that's a great option for the street (and even trackday) rider.

    A common misconception is the 929 shock, in stock form, is an upgrade for the VFR. It is not! In fact, the 929 shock has some downsides so at best it is a zero gain. In order to make the rear suspension function properly you must have the correct spring rate and most importantly the correct damping characteristics.

    I hope this helps!
     
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  10. RllwJoe

    RllwJoe Insider

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    Thanks Jamie, do you still work on that type of upgrade involving the 929 shock? I purchased this shock and did the retofit because, for a time your site didn't appear to offer any options. Now I see that you have your own. How does that compare to your reworked 929 version?
     
  11. RllwJoe

    RllwJoe Insider

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    Update. Took it out for a 1/2 hr easy cruze. After which I felt the shock again. It is hot to the touch, but so is the swing arm section beneath and in front of the shock. In fact, all of the parts in that area are hot. So I'm thinking that as TOE CUTTER stated;
     
  12. JamieDaugherty

    JamieDaugherty New Member

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    Shoot me an email to jamie@daughertymotorsports.com for more information on our upcoming rear shock.


    So, this is not really accurate at all. The swingarm gets hot because it is connected to the engine so that's a completely different situation.

    The rear shock's job is to convert mechanical energy (bumps) into heat - plain and simple. That means it will get hot. The standard test temperature I use on my dyno is 110°F. A shock gets to that temperature in about a minute or so. Once there is noticeably hot to the touch. So, in short, a shock should be hot because that indicates it is doing its job.

    An OEM shock from a CBR929 is very far from having the correct spring rate and damping characteristics needed for the VFR. I think you are already finding this out! Once you have the correct spring rate and damping characteristics I think you will find the difference to be pretty remarkable.
     
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