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Thread: Improving Gen III spring rates -> more comfort

  1. #1
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    Improving Gen III spring rates -> more comfort

    Have been toying with the idea of fitting Gen III bags all around but have been put off by the reports of higher spring rates (compared to standard air springs) at both normal and highway heights.

    From what I can determine, the profile of the GenIII piston, made from an aluminium billet, is such that at lower heights, there is considerably less volume and therefore a higher pressure required to provide the required lift. This makes for a higher spring rate.

    As the vehicle rises, due to the piston profile and inverted conical shape of the bellows, there is considerably more volume and therefore less pressure required for the lift, leading to a lower (=more comfortable) spring rate.

    Given that after repeated no-reply emails to Arnotts (= they're not interested) am wondering if it's worth taking the pistons and machining the profile to provide a more comfortable ride at lower height... there must be a competent pneumatics shop who can re-band the bellows to the piston...

    just a wild thought... the harshness of my current ride over broken bitumen is driving me nuts... and long stretches of off-road corrugations shake the tripe out of it albeit with 20 psi in the tyres(Cooper H/T) and much lower speeds

    Thoughts?
    MY99 RR P38 HSE 4.6 (Thor) gone (to Tasmania)
    2020 Subaru Impreza S ('SWMBO's Express' )
    2023 Ineos Grenadier Trialmaster (diesel)

  2. #2
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    Hoges
    Since fitting Gen 111's I have found that the ride is significantly better than the old stock bags. The harshness of ride will also depend on the choice of shocks. For me I also fitted the 2" lift from Hard Range at the same time along with adjustable shocks. When the shocks are set in the comfort setting rather than stiffer the ride is very smooth and comfortable.
    If you are sticking with original heights I believe the bilsteins are the best choice.
    Gary

  3. #3
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    It's not so much that the ride is well dampened but rather the 'hardness'...that it feel like the tyres are solid rubber... I'd swear that even running over a gnat's middle wicket produces a 'bump' .... I'm also wondering if the 50% worn Cooper tyres with their well publicised stiffer side walls aren't half the problem...

    Variable rate long travel springs as per the Classic would float over similar terrain with nary a problem...
    cheers
    MY99 RR P38 HSE 4.6 (Thor) gone (to Tasmania)
    2020 Subaru Impreza S ('SWMBO's Express' )
    2023 Ineos Grenadier Trialmaster (diesel)

  4. #4
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    I also have GenIII with 2" spacers and adjustable shocks and the ride changes considerably dependant on shock settings, you can be as stiff as you like or alternately be quite springy ( best way to describe it??) I find an intermediate setting works well with my 33 bfg km2's
    each to their own I guess. BTW I have Boss Shocks but i'm sure there is something better out there. another project I guess.

  5. #5
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    By the way hoges I'm sure ther are a few "popped" bags out there that could be used bas test mules if you can find someone to do the work!

  6. #6
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    Funny you mention popped bags! I've got a gen III at home that's half way to being separated, the bag is fine but you would need to pull the piston to get the bag re-seated anyway so a perfect candidate for modification.

    If you are keen let me know.

    As for ride quality on gen III's, I wouldn't worry - on my standard shocks its fantastic! Way better at all ride heights than factory bags, and corrugations are pillow like with only minor corru-shake. Better than factory til the cows come home.

    Cheers
    Keithy

  7. #7
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    Thanks Keithy!

    When you changed from the OE bags did you notice the spring rate rose rapidly when you hit a decent bump, i.e, more of a 'dumpy' spring? Also what shockers have you got?

  8. #8
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    I noticed that the car feels more stable - especially in highway mode. In normal it feels much the same and high also. Corrugations in normal and low are better than standard and the car does not wallow over them around bends, it tracks more true and straight. Over bumps (such as potholes) it maintains composure a lot better.

    My shocks are bog standard LR items, painted black with no obvious stickers or markings. But I must admit the shocks are on the way out also...

    I like a smooth ride and would rate the gen III's as better than dunlops and firestones any day.

    Cheers
    Keithy

  9. #9
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    Thanks for that, I was hoping they worked better on the P38's, as they're not that crash hot on the Classics.

    I'm running tired OEM shockers also. Terrafirma now have 2 inch longer shockers for the P38 too which sounds interesting.

  10. #10
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    Quote Originally Posted by benji View Post
    I'm running tired OEM shockers also. Terrafirma now have 2 inch longer shockers for the P38 too which sounds interesting.
    I have a set of the Terrafirma +2"s and don't recommend them. They are ok off-road but I did not like the way my car nose-dived in to corners at decent road speeds.

    My black P38 (the not-for-offroad-yet one) runs Gen 3's and Bilsteins and is quite firm, almost uncomfortable on bumps. Think I need a new steering damper anyway.
    Last week I changed the wheels over with a nice set of Continental Cross Contacts (I think) and the ride was quite different instantly. I am also thinking of just buying a set of Boges to improve it that bit more for SWMBO.

    Hoges - check out the Gen2's instead. I now some people were bagging them (no pun intended) but I don't understand why.

    Cheers, Paul.
    My toys, projects and write-ups at PaulP38a.com

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