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Thread: FJ40 is riding Jumpy - Solution?

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    Default FJ40 is riding Jumpy - Solution?

    Dear Toyota FJ40 enthusiasts – I need your expert opinion as you might have dealt with it at some point. Since I have put in bigger tires (265 with 16 inch Rims) and have lifted the vehicle 2/3 inch. FJ is riding jumpy as if there is no suspension and to the point that something must be done. Some have suggested to go with at least 90’s LandCruiser leafsprings. I am wondering what kind of modification/invasion is required and if such setup is viable option. Also, as a bonus question, if the 90’s LandCruisers Leafsprings are same length/width as compare to stock FJ 40?
    I know nothing except the fact of my ignorance.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comFJ40 is riding Jumpy - Solution? - P
    Regards,


    God grant me the serenity to accept the things I cannot change, courage to change the things I can, and the wisdom to know the difference.

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    ^^^ No personal experience of LC-40s, but few obvious things.

    Firstly increasing tyre size should not make the ride jumpier, infact if anything it should ride better. Check your tyre pressure, it should be no more that 30psi, 28 would be reasonable compromise for economy vs ride.

    2nd point, how did you raise the vehicle? Mostly simple longer shakles with no alteration to leafspring length, or body foundation lift should not adversely affect the ride, just the handling. However additional leaf-springs and/or curvier leaf-springs (turrh barhana) would definitely make it harsher ride. Angle of shackle also makes a difference.

    Finally the shocks would have a significant role as well, i.e which shocks? lenght of shocks etc all make difference.

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    Suhaib Kiani @ IJC has been playing around with his ride's suspension recently to improve things overall, I am sure he can provide some useful input.

    Would be good idea to post pix of your front n rear suspension set-up showing all leaf springs and also all shackle angles etc!

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    Hi, I have also replace tires and have bigger then your tire size 285/60/18 I have no such prob. at all. It's just fine in ride
    FJ40 is riding Jumpy - Solution? - 209054

    FJ40 is riding Jumpy - Solution? - 209055

    FJ40 is riding Jumpy - Solution? - 209056

    FJ40 is riding Jumpy - Solution? - 209057
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    As I have learnt, out here calibrating leaf spring suspension is more of an art than a science......

    I have put in RKR/70 series TLC springs on my FJ40 at the back which have resulted in a somewhat softer ride, although if I were to do it again I would work with stock springs and save the money. I don't see why the stock springs should not be made to work fine with the tire size you mention....

    Yes, please post pics of your springs (showing number of leafs in the pack) and shackle angles..... the most likely reason for a rough ride is a mismatch between the spring rate of the leafs and the weight of the FJ, second would be a bad shackle angle.....
    "If YOU don't believe in what you're doing it'll never work."

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    @SK - Boss can you depict a right shackle angle through any picture?
    <<<The Obstacle Is The Path>>>
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    Okay please understand this vehicle will never ride like a prado.. but lets see the problem, if there is any

    1. What tire pressure are you running? the larger the tire width, the lesser pressure you should be running.. i think even 28psi would be a bit high for 265 on an FJ40.. try 24psi.

    2. Post the pictures of front and rear spring shackle angles?

    3. If there has been a recent work on kamani.. you need to give it some time.. take it out to a 200KM dirt ride

    4. What shocks are you running? How old? Check them, they might be hard!

    if aal iz well.. ignore the bumps.. rather enjoy them.. its a short wheel base leaf spung cruiser of the 80's.. that how it rides
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    Quote Originally Posted by akifjanjua View Post
    Okay please understand this vehicle will never ride like a prado.. but lets see the problem, if there is any

    1. What tire pressure are you running? the larger the tire width, the lesser pressure you should be running.. i think even 28psi would be a bit high for 265 on an FJ40.. try 24psi.

    2. Post the pictures of front and rear spring shackle angles?

    3. If there has been a recent work on kamani.. you need to give it some time.. take it out to a 200KM dirt ride

    4. What shocks are you running? How old? Check them, they might be hard!

    if aal iz well.. ignore the bumps.. rather enjoy them.. its a short wheel base leaf spung cruiser of the 80's.. that how it rides
    As far as the suggestion of taking it out for a fatigued journey - i agree with this as the very first day i had the leaf spring service job done to my bj61 i had the same problem but i got along with it - last week i had a very rash offroading in a desert and while coming back from that trip - monster was far more softer and comfortable.
    <<<The Obstacle Is The Path>>>
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    A very effective way of making the ride better is to have small size rim and have large size tyre. Like the bad of the tire should be more from top to bottom. The ideal on 40's is 15" rim with either 31" or 32" size tyre which will make the bed of around 8.5". The more the tyre bed is, the more area it has to bend from the bottom.
    In the first pic, the rim size is 16" but the total tyre size is 29" which will make the ride very hard.
    The second pic has 15" rim having 31" tyre size which will be far better than the first case.
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    first pic

    FJ40 is riding Jumpy - Solution? -209217

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    2nd pic

    FJ40 is riding Jumpy - Solution? -209218

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    @Noman bhai - is this 33" Nexen or 31"? any idea about 33"x15 tyre size availablility and price? especially used ones.
    <<<The Obstacle Is The Path>>>
    1984 BJ41, 1967 FJ40, 1984 BJ61 , 1983 Mutt M825, 1982 CJ5, 1942 Willys

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    <FONT color=black><FONT face=Verdana><FONT color=black><FONT face=Verdana>Thank you guys for your suggestions.
    From the tire pressure to shocks, I have noted down all possible fixes. There are 5 leafsprings front and back. Tire pressure is around 30psi. All 4 shocks are Procomp and fairly new. For Akif bhai I will post the pictures for spring shackles and angles (once I figure out what the heck are those). I do understand that it would never ride like a Prado, but I think it is riding way too hard and it can (and must) do better. It is almost absurd not to demand the best of everything J<FONT face=Calibri><?xml:namespace prefix = o ns = "urn:schemas-microsoft-comFJ40 is riding Jumpy - Solution? - P
    FJ40 is riding Jumpy - Solution? -209232
    God grant me the serenity to accept the things I cannot change, courage to change the things I can, and the wisdom to know the difference.

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    @isiddique brother, hope you are fine.

    In shadow of all gurus & expert brothers, I would say the least and dare to contribute.
    The standard leaf springs on J40s are a good set that goes well with the weight of the vehicle. As the vehicle was originally designed for slow speeds off-road with load & troops' hauling, and now we need faster, comfortable ride with lesser weight in it, certain adjustments are inevitable.

    Without replacing/changing any major/expensive item of your vehicle, what I think is easily doable is to

    a. remove the smallest/lower leaf from all sets. Thats the load carrier. You will be amazed how much flex u'll get after removing that.

    b. As a general rule of thumb, they say it should be 45 degrees. My understanding of it is that:
    If leaves are flatter....the shackle angle should be more than 45 deg. with reference to ground. And
    If leaves are arched properly,....the shackle angle should be between 15-45 degrees with reference to ground and not the top leaf itself.

    c. With the existing set of tires & tarmac use, considering the weight of the vehicle, I suggest trying between 20 - 25 psi. There might be almost unnoticeable effect on acceleration in drag-like situation and fuel economy but the comfort will be worth that cost.

    d. Checklist of leafspring service
    Ensure all the bushes are replaced on every service or when damaged.
    Ensure all the pins are straight (not bent in the middle) without deep groves or cuts that would cut the bushes.
    There should be no gap between springs when placed in position while servicing/tuning upside down untightened. (hope I'm able to convey what I mean LOL)
    Liberally use grease (not oil) between the leaves. That keeps dirt & water out for the maximum period and flex is maximized.
    The pin collars should be in good shape so as not to squeeze the bushes tight.

    That all for now that I can suggest.

    Wassalam

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    Quote Originally Posted by machine View Post
    @Noman bhai - is this 33" Nexen or 31"? any idea about 33"x15 tyre size availablility and price? especially used ones.

    These r 31". No idea about 33"

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    Tareen, Suhaib Kiani and Akif Janjua and others - Thanks for your help. You guys are always helpful. I do now have few positive leads based on your input and will try one by one. I know the solutions lies in one of your suggestions.
    All the good things in life are either illegal, fattening, expensive or complex .
    God grant me the serenity to accept the things I cannot change, courage to change the things I can, and the wisdom to know the difference.

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    Quote Originally Posted by isiddique View Post
    All the good things in life are either illegal, fattening, expensive or complex .
    ....or married to someone else!

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    for shackle angles.. see the following link
    Leaf Spring Tech: Shackle Length & Shackle Angle

    post pics of your ride's front and rear shackle angles... more mashwaray will pour in
    75% of earth is covered by water... the rest by Jeep
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    Quote Originally Posted by tareen View Post
    ....or married to someone else!
    Very true

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    Quote Originally Posted by akifjanjua View Post


    for shackle angles.. see the following link
    Leaf Spring Tech: Shackle Length & Shackle Angle

    post pics of your ride's front and rear shackle angles... more mashwaray will pour in
    nice info

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