Coil over suspension setup for 505??
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  1. #1
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    Default Coil over suspension setup for 505??

    Has any body done this with their 505?

    A rally racer that I know had the stock strut housing of a VW Golf modified with threaded collars and 2.5" springs for his rally car. Great selection of spring rates, easier to dial in caster and camber with adjustable top plates, and damping can be increased with heavier shock fluid.

    I thought this would be a great way to set up my 505 Turbo... I would like to lower it a bit with an increased spring rate and heavier racing shock fluid to increase the damping rate.

    The rear looks like it could be replaced by a coil over shock as well if properly set up.

    Has this been done already by anybody - or are there after market parts that do this? Has anybody done suspension mods with favorable results and are willing to share?

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    Thanks!

    Rabin
    Last edited by bean; 29th October 2004 at 03:44 PM.

  2. #2
    Gone Fishin' Ray Bell's Avatar
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    Would be nice... and it's not impossible...

    Adjustable top mount for your strut isn't all that hard, and with a smaller diameter spring you can really crank on camber or caster.

    At the rear I'd suggest that any coilover you might use be mounted much nearer the back end of the trailing arm... at the moment there is about a 2:1 ratio of movement to spring/damper movement. Take out the swing arms and weld nice brackets on the end to mount something like you describe, and fabricate a housing in the inner guard strong enough to take the loads.

    This is for a competition car, of course, I wouldn't do this on the back of a road car. For the front, yeah, not so bad.

  3. #3
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    Default Interesting...

    I'm curious about the idea to mount the coil-over on the rear most part of the trailing arm...

    Is this for dynamic reasons - say more room for suspension travel? Is the shock location limited in some way or does the spring rate end up being so high that the car is a bugger to tune the handling?

    I think it's a great idea when I think of how much lower the spring rate would be, but I was thinking it would be so much easier to use the stock locations with some minor re-enforcement. It's also nice to be able to mod the existing subframe since if the car were to take a tumble I could hopefully salvage the suspension and put it into one of my other 505's.

    At first I was thinking just different springs and shocks could be used at the rear - but having adjustable coil overs gives me ride height control as well - probably lighter and easier to work with also.

    Has anyone in Australia done anything like this? (Road or race)

  4. #4
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    I have coil over shocks on the rear of my 504. They are inside of the main coils in the normal shockabsorber position.They came out of a car I wrecked so I don't know their history. I do remember that there were 2 spacing tubes at the lower mounting point rather than 1 longer tube for the mounting bolt to slide through.

  5. #5
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    Quote Originally Posted by Bob D
    I have coil over shocks on the rear of my 504. They are inside of the main coils in the normal shockabsorber position.They came out of a car I wrecked so I don't know their history. I do remember that there were 2 spacing tubes at the lower mounting point rather than 1 longer tube for the mounting bolt to slide through.
    They are probably Koni shocks, designed for carrying heavy loads.
    Coil overs have been made for 504s, I could give you the contact details for a company (1 man) that has made them.
    Graham

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    Gone Fishin' Ray Bell's Avatar
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    Yes, probably Koni Loadajusters, which have a two-piece spring base that you remove by hand compressing the spring and dismantling.

    You can adjust the damping rate on those by taking the spring off and carefully closing down the damper... you feel the dogs on the bottom the piston engage in the footvalve and then you screw it in a turn or so... there's about 2.5 turns of adjustment and you strip the thread if you try too hard.

    The springs are progressively wound so that they don't give much assistance until you've got a fair load on...

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    Default Contact details please...

    Contact details would be great!

    Course I'm not sure it's feasible for me to actually have some made and then sent all the way to Canada - I'd be happy to make some sort of arrangement to pay for info though if necessary.

    My initial plan was to increase the spring rate by 30% of stock and calculate a 1.5" drop - then just use some heavier weight shock oil in the front struts. The rear is the problem because I have no idea on what to spec for damping characteristics.

    I do not want "load levelers" - a proper coil over is what I'm after in the rear. Something with adjustable height and hopefully with some damping and rebound adjustment - but I'm happy with just damping. I'm also wanting to use readily available 2.5" springs so that I can do some tuning to make sure I don't loose that wonderful balance of the stock suspension.

    That's what I love about these cars - they're big sedans that you can really throw around and they behave so beautifully that they end up beating a lot of faster cars in competition because you can drive them so well at 9/10ths and 10/10ths.

    Rabin

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    Gone Fishin' Ray Bell's Avatar
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    Any keen and competent engineer could make you up threaded sleeves and some spring collars that can be welded to the struts.

    There is a wide range of coil-over shocks made that could be adapted to the rear, with Spax (from England) probably the most economical. There is EVO as well, from England, these being the kind of thing home made racing cars use. If you want to spend money there are Koni double adjustables... adjusting separately for bump and rebound as well as spring height. Cost more than the car, though.

    For real control at the front, you might be able to adapt (as you are mucking around with the struts anyway...) some externally adjustable Koni inserts to fit.

    Check and see if they have websites... and local distributors...

    The reason, as Graham mentioned on another thread in the last day or two, that it's preferable to move the rear spring/shock mount further back is to: 1. reduce the mechanical advantage and give the things a chance to do their stuff; and 2. because they are loading up every bush and bearing as the loads force the heavier spring to work.

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    Oh, forgot to mention...

    Don't even think of heavier oil in your struts... it's at very best a temporary solution (I mean it works, maybe, for a mile or two...) and it is not the fluid they are designed to use.

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    Default Excellent feedback!!

    This is so cool!

    I'm thoroughly enjoying these discussion.

    Front strut oil is pretty much unavalaible and I've heard some suggestions that ATF (Dexron III) or something usually works fine. I was hoping to use AMSOIL racing shock fluid. It comes is various weights depending on what damping characteristics you need.

    When I was crew chief on a Subaru rally car - the rear STi Bilstein struts blew out during a spectator stage the night before the rally. In a desperate attempt to get them working we disassembled and refilled with hydraulic jack oil. (!) Surprisingly enough the damping actually improved from the original and the car was fantastic - completed the next day without incident and we got another top 10 finish in a national rally.

    I dissassembled again and filled with AMSOIL racing shock fluid and we competed in additional 5 rallies on those same rear struts and they worked flawlessly. The only thing we could do was put a slightly tighter spring on the seal to add some more tension - struts were not rebuildable apparently and you can not get new seals for them... (Team was privateer = no money)

    My hope with the Peugeot is that proper racing shock fluid and a new strut seal will work - granted I'm not going to be crazy and put in 30W oil in or anything - just slightly higher viscosity to see where it gets me.

    There's a really good suspensin tuning book out: Race Car Engineering and Mechanics [R-308] by Paul Van Valkenburgh that says not to over spring cars - the secret is to have a softly sprung car with stiff damping. He's also not a big proponent of sway bars - but he said far too many people tune behaviour with spring rate. I'm therefore going to shy away from very high spring rates (30% higher maybe than stock) and hopefully a matched increase in damping.

    My car is firstly a road car - so I'm not wanting to go crazy - I just want to firm things up a bit and lower the center of gravity.

    Softly sprung and stiffly damped - That describes the Peugeot ride in a nutshell - I just want to increase everything by about 30% and lower ride height by about 1 - 1.5".

    Rabin

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    From memory, when we dismantled original Peugeot struts the fluid was almost like water, very low viscosity...

    The same applies to Konis. These are properly made, maybe I should say precision made, dampers and they rely on small appertures to created their damping forces.

    The difference with dampers that have larger holes and stronger springs behind the valves is that they don't have the same level of progression... creating a high level of flow through small appertures brings with it a lot of drag and hydraulic pressure.

    There is some progression with all of them (it's essential... big movements need to be brought quickly into control), but that progression is greater when you rely on small apertures.

    I do like, by the way, the new system devised by someone and used by the Citroen (or was it Peugeot?) team in the Paris-Dakar... above the piston it has a heavy piece that slides up on the shaft above the piston when the movement downwards are extremely fast.

    This means that when a wheel drops into a hole, when a car gets airborne over a jump and that sort of thing, it rises relative to the piston due to its inertia. This opens valves and allows the fluid to quickly be displaced until the wheel catches up with the terrain... then normal damping resumes.

    From what I was told, this accounted for the Parix-Dakar crew getting through the event on one set of dampers. Heat normally created by the damping was lessened and the things lasted much better.

    Here in Australia there is a small company (in Canberra) that is adapting this technology to Edelbrock... or is it that Edelbrock use it and they are adding something from somewhere else to the Edelbrock? Not sure... but they have tried these on our 5-litre touring cars and found them to be tremendous.

    But mainly I have described that to underline the fact that forcing oil through small apertures takes a lot of energy, that energy being dissipated in heat.

    As for sway bars... racing car fine tuning will always see the bar tightened at the rear if the driver wants more understeer, or the front if he has too much. Or the opposite bar backed off, as the case may be.

    In other words, sway bars are used to degrade the traction... I know that's not the whole story, but it's a part of it...

  12. #12
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    Quote Originally Posted by bean
    This is so cool!

    I'm thoroughly enjoying these discussion.

    Front strut oil is pretty much unavalaible and I've heard some suggestions that ATF (Dexron III) or something usually works fine. I was hoping to use AMSOIL racing shock fluid. It comes is various weights depending on what damping characteristics you need.

    When I was crew chief on a Subaru rally car - the rear STi Bilstein struts blew out during a spectator stage the night before the rally. In a desperate attempt to get them working we disassembled and refilled with hydraulic jack oil. (!) Surprisingly enough the damping actually improved from the original and the car was fantastic - completed the next day without incident and we got another top 10 finish in a national rally.

    I dissassembled again and filled with AMSOIL racing shock fluid and we competed in additional 5 rallies on those same rear struts and they worked flawlessly. The only thing we could do was put a slightly tighter spring on the seal to add some more tension - struts were not rebuildable apparently and you can not get new seals for them... (Team was privateer = no money)

    My hope with the Peugeot is that proper racing shock fluid and a new strut seal will work - granted I'm not going to be crazy and put in 30W oil in or anything - just slightly higher viscosity to see where it gets me.

    There's a really good suspensin tuning book out: Race Car Engineering and Mechanics [R-308] by Paul Van Valkenburgh that says not to over spring cars - the secret is to have a softly sprung car with stiff damping. He's also not a big proponent of sway bars - but he said far too many people tune behaviour with spring rate. I'm therefore going to shy away from very high spring rates (30% higher maybe than stock) and hopefully a matched increase in damping.

    My car is firstly a road car - so I'm not wanting to go crazy - I just want to firm things up a bit and lower the center of gravity.

    Softly sprung and stiffly damped - That describes the Peugeot ride in a nutshell - I just want to increase everything by about 30% and lower ride height by about 1 - 1.5".

    Rabin

    Use motor bike fork oil, many grades available at bike shops.
    Graham

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    the 4WD mob "old man emu" used to or maybe still do supply a coil over for the rears for 504's

    my sister had some in her car once and they were pretty good seeing as the springs were starting to get the normal sag anyway
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  14. #14
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    I think you are again talking about an auxilliary spring, aren't you 'rambo...

    In other words one that give additional spring rate to augment the spring that's already fitted.

    bean has already said he's not interested in those.

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    There's a place in the UK that specialises in rebuilding and modifying all kinds of shock absorbers - even many supposedly non-rebuildables. Unfortunatly I can't remember the name but I'll try to look it up.

    Ray, are load-a-justers basically a normal Koni red with that external spring added? (I've got a set in the shed).

    Stuey

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    They're the ones...

    You can run them, of course, without the spring. But don't lose the retainer bits!

    They're a slightly smaller diameter in the body to the regular Konis, by the way. You'll find the Koni brand name and part number stamped into them near the base, along with the month and date of production.

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    Originally posted by Stuey
    There's a place in the UK that specialises in rebuilding and modifying all kinds of shock absorbers - even many supposedly non-rebuildables. Unfortunatly I can't remember the name but I'll try to look it up...
    There are places in Australia too, I'm sure...

    WW Shock Absorbers in Brisbane, are they still in business? Pedders grew out of that business, but I don't think they'd do it any more.

    The biggest issue is getting the seals.

  18. #18
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    Default Rear coil overs...

    I think I'm going to see if I can spec some coil overs from a catalogue to see if I can match a set already in production that would be suitable for the car.

    That's the only way I can keep it affordable and repeatable for my other cars.

    Hopefully I can improve the ride characteristics - But mostly I want to be able to get this car into shape so that it can put the power to the ground. Once I can get the car to hook up and put it's power to the ground - I can then work at making the power excessive again..

    My first start will be to do the conversion of the front struts this winter - if successful I can then look at doing rear coil overs to match the set up at the front... It may just end up being easier to get springs to replace the stock units for ride height and spring rate and then look at a damper that has the characteristics I'm looking for.

    I should be able to fab up an adjustable perch that would give me the ride height adjustment should I need it - or maybe just shims would do it...

    Just bouncing ideas around - feel free to shoot them down!!

  19. #19
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    Can you tell me what advantage you see in coilovers on the rear?

    Otherwise, you're on the right track, I think...

  20. #20
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    Default Advantages of rear coil overs...

    I want height adjustibility, stiffer spring rate, and stiffer damping.

    I'm choosing coil overs because height adjustment is a piece of cake, and with 2.5" dia springs - tuning the suspension with different spring rates and lengths is very easy to do and very inexpensive as well.

    A decent coil over usually has adjustible damping as well - so that will also aid in the tuning of the car for ultimate handling - since I'm somewhat limited in how I do the front - I want to make sure the rear system is very tunable so that I can match the characteristics of the front - thus keeping the car nicely balanced.

    This is just my plan though - nothing concrete to say if I'll be successful - but I think it should work nicely.

  21. #21
    Gone Fishin' Ray Bell's Avatar
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    I'm sure that you'd do better if you do what I suggested initially...

    But what you have planned should work if you're restricting the modifications you're prepared to make to the body.

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