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De Dion camber and toe in


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#1 mantisman2020

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Posted 26 September 2020 - 16:44

Would appreciate suggestions on an initial toe in and camber for a Jaguar special(Lister replica) that I have just recently completed.

First drive impression was not very encouraging, Car is not stable over undulating road surface in a straight line.

Front end bump steer,i..e. toe change is very minimal through full suspension travel, a small room for improvement is till available.

Have the rear toe set at 1/16 inch in on each side and 1 deg. neg. camber .Any suggestions from experience with the Lister style De Dion most welcome.



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#2 Joe Bosworth

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Posted 26 September 2020 - 20:37

Your rear, de dion, settings are not bad as a static starting point.  They definitely would not result in the undulating straight line lack of stability.that you desribe.

 

There is far too little info to give you much help in solving your described problem but if it were mine I would take spring/shock units off and string line front and rear toe, camber and direction at wheel plates being pointed as they move up and down.  I would also take springs springs off the shocks and make sure that your 4 shocks all have similar and sensible resistances up and down.

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Good luck and regards.



#3 mantisman2020

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Posted 27 September 2020 - 00:05

Thank you, you may have just pointed me onto something I had forgotten about. I corrected the corner weight difference after the initial set up done by measurement by screwing the coil over adjustment to correct a 40lb difference left to right.

Car loaded  and ride height set at the time I now notice that the front springs have settled by about half an inch. Have not rechecked the corner weights. again..



#4 GreenMachine

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Posted 27 September 2020 - 00:46

I doubt that corner weights are the root of the problem.

 

I'd follow the above suggestion of Joe's, to go back to fundamentals and ensure that all movement is free and working as intended, and settings are correct.  Settling at the front won't be an issue if bump steer is minimal.  What front alignment settings are you using?



#5 Greg Locock

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Posted 27 September 2020 - 04:32

Does the steering wheel pull, or is it that the car weaves? Very hard to tell the difference, admittedly.



#6 mariner

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Posted 27 September 2020 - 05:45

What sort of longitudinal and lateral location links  on your De Dion , and how long are they?

 

Also any steep link angles or divergence between any fore and aft linkages?



#7 mantisman2020

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Posted 27 September 2020 - 05:58

acceleration and braking ,left and right turns all appear ok.no pull either side under these conditions,  Built the car for street use ,on radial ply tires so set the caster at 3.5 deg  Listers used 6 deg (Dunlop Racing tires back then )

zero camber and 1/16 toe in each side. My concern was with the rear set up ,having no prior experience with this set up,  was concerned that I had it all wrong.

Some other facts about the car which may be contributing to the "skittishness" is the 70 profile tires ,and an almost within a few pounds,50/50  front to rear weight balance. Was hoping to have a bit more weight on the front. 



#8 GreenMachine

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Posted 27 September 2020 - 07:53

How hard is your braking/accelerating?  These will induce suspension movements similar to 'undulating road surface', the difference being the first act in opposite directions (the car rotates around its CoG), the second together - both compression or extension (the whole car rises and falls on the suspension).  It sounds like you have some suspension steering happening, which might be related to geometry (Mariner's questions), or could be mechanical (bushings, springs, shocks etc).   A thorough alignment, without springs and shocks, with a test of the spring and shock functioning seems like a good idea to resolve the questions identified above.

 

What is your front toe and camber - is that what you describe above?  In the short term, I'd dial in some more camber if so (1-1.5* at least), and maybe double the toe-in, and see whether that improves things; that's easily done, and easily reversed if necessary.  Even if it improves matters, there may still be other factors involved though - the thorough examination of the suspension is still a good idea.

 

We all (well I did) drove cars with 70 tyres and I don't remember them being skittish (other terms do spring to mind), and 50/50 weight distribution is supposed to be ideal isn't it?



#9 mantisman2020

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Posted 28 September 2020 - 00:32

Thank you to all for your input, Will take into account all the recommendations. Through the winter,(fast approaching) will do a full assessment and reset both front and back.

Have ordered a stiffer set of front coil springs to try, will re- visit this site next year again and advise the results ,thanks again.