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Thread: Advice for Sierra based roadster

  1. #11
    frequent forum contributor Club Member
    Join Date
    Nov 2011
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    924

    Re: Advice for Sierra based roadster

    We have a member located in Walsall (Midlands) with a Julietta. Somewhere on this site he shared his experience with a problem ref mounting of rear shockabsorbers on his car. YKC supplied AVO for their Sierra based models, because they can be rebuilt. In my experience the mini strut used on the front end tends to be on the stiff side. It is very short. I can think of several members with very hands on knowledge of Sierra based YKC models and I am sure one of them will come along with good advice for you.

  2. #12
    Club Member
    Join Date
    Nov 2011
    Posts
    341

    Re: Advice for Sierra based roadster

    I am not familiar with the YKC Roadster set up so canít make any specific recommendations. The Sportster has upper wishbones that are fully adjustable. The Cabrio has fixed welded arms although slight adjustment can be made by shimming out the pivot brackets. I guess the Roadster suspension is similar the Cabrio. If all three are based on the Sierra so the set up should be similar. Judging from Dannyís post by Sierra based you might be referring to the engine and gearbox but not the suspension. In which case, this post is even less useful.

    Danny could be referring to this thread:
    http://www.marlinownersclub.com/foru...light=Julietta

    To check the set up on both my cars I use axle stands adjusted to be close to hub height. These are used to support two parallel strings approximately 1.7m apart. These are placed on either side of the car and adjusted to be as close as practice to equally distant from all four wheels. Of greatest importance is that they are parallel. Measure the parallelism first and last. If practical check the rims for run out. If necessary put a low or high point at the bottom or top.

    A fuller description can be found here:
    https://ralphhosier.wordpress.com/20...-using-string/

    A more sophisticated set up is shown here:
    http://suspensionsecrets.co.uk/how-t...-your-car/?i=1

    I measure from the front and rear of the rim to the string on all four wheels to see if the wheels have toe in or out. The rears should be parallel the fronts should be (from the Haynes manual):
    Production toe-setting:
    Saloon, Hatchback and Estate models: 2.0 mm Ī 1.0 mm toe-in

    It is my understanding that the front wheels are angled in slightly so that in normal running the forces on them cause them to be parallel. The Sierra suspension has a number of rubber bushes that will flex under driving conditions.

    I made up a small plum line jig to measure camber. On both my cars camber varies as the suspension rises. When lifted off the ground the wheels are out at the top (positive camber). When fully compressed the wheels are in at the top (negative camber). This improves handling when cornering by increasing negative camber on the outside wheel as the body rolls into the corner, helping to keep the tyreís tread in contact with the road. When the suspension is at rest the wheels should be about vertical. You mention excessive camber and I wonder if this might be because the ride height is out.

    People seem to run quite happily with wildly differing ride heights. As a rule of thumb Sierra based cars should have tie rods that are parallel to the ground. This presumes the steering rack is in about the right position.

    At the rear ride height seems to affect toe in. The trailing arms are not perpendicular to the cars axis. For a long time I lived with rear wheel that were toed out. Raising the suspension by about 25 mm made them more parallel. Ride height must also change rear camber but I have not measured it. This small change made a big difference to rear tyre wear.

    Caster angle is really difficult to measure on the Sierra as the top and bottom ďkingpinsĒ are on different centrelines (in four planes). This causes the geometry to change as the car is steered. They are actually ball joints which canít be accessed. The best I can do is to measure from a fixed point on the car to the countersunk hole in the top and bottom ball joint mountings. I have measured from a pin set in the centre hole in the rear wheel hubs to swivel joint. It is easier to measure from a fixed point nearer the front of the car such as the anti-roll bar mounting. The absolute measurement is not important but the comparison top to bottom, side to side is. The lower swivel should be in front of the top. I drove for about 12 years with one side 20mm further forward at the bottom on the nearside due to a bent anti-roll bar. It didnít really make much difference to my conservative handling requirements. There are machines with computer guidance that can measure caster and every other angle but Iím not likely to buy one.

    The caster angle at each steering lock should also be similar. Again the geometry is such that the outside wheel will have a greater caster. Again the important thing is that both sides are about the same.

    Iíve heard it said that Lewis Hamilton is such a good driver because he can feel how the car is set up for different tracks and make minor adjustments to his steering geometry, suspension, brakes and aerodynamics. If you are thinking of driving on the edge in that way you need way more sophisticated help than I can give.

    In my opinion the best indicator of suspension set up is tyre wear. Uneven tyre wear certainly indicates bad tracking.

    Hope this helps. If you can a photo of the Sierra based Roadster suspension would be a big help to me.
    Paul

    PS: I have been told in no uncertain terms by a couple of members that you need lasers to set up suspension accurately. I am unconvinced. Shine a laser down a piece of string in still air and it will cast an even shadow on the floor. Measurements to within 0.5mm should be satisfactory.

    PPS: I am sure others have more to contribute.

  3. #13
    frequent forum contributor Club Member
    Join Date
    Nov 2011
    Posts
    924

    Re: Advice for Sierra based roadster

    The top suspension on the Sierra based YKC Has a mini macpherson strut located in the Sierra upright the bottom has the Ford track control arm which is located with a tie rod made up from the outer ends of the anti roll bar and reversed from one side to the other and tied forward. (Marlin used the mini strut on several Cabrio models) However the back end is a 5link dedion tube set up which is a delight. Paul give me a call or email please I would like to pass on some important information about Cabrio front set up.

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