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Thread: Dinan Caster Plates

  1. #1

    Post Dinan Caster Plates

    Dinan has developed a set of caster plates which fit the Z8 and are supposed to improve the car's handling. Dinan fits them on full S2 modified Z8s which means they are used in conjunction with Dinan's slightly lower/stiffer spring package. They also offer them as a separate item.

    Most people are familiar with the concept of increasing the negative camber (as opposed to caster) settings on a performance car to improve its cornering ability. Doing so tilts the top of the tire towards the middle of the car which is supposed to counteract the tire's tendency to lean out during cornering, thereby keeping more of the tire's contact patch in touch with the pavement during cornering. This is a static change which means the negative camber setting is a constant factor and as a result, there are some trade-offs. Under straight ahead driving, inside tire wear will be accelerated due to the extra pressure applied to the insides of the tires and the tire will have less grip due to the uneven pressure across the tire's contact patch.

    An alternative approach to counteracting the tire's tendency to lean out during cornering is to change the caster setting more towards positive. This may or may not result in a small static negative camber increase (depends on the plates used) but more importantly, it also results in a more pronounced negative camber setting during cornering, which is just where we want it to come in. The beauty of this approach is that you don't have to pay the penalty for increased static negative camber settings yet you get increased negative camber during cornering. One big benefit of this approach is that your front tires have more even pressure across their contact patch in straight running and this means they will react more quickly to steering input. Excessive static negative camber up front means less steering response. Another effect of increasing positive caster is that the steering becomes more stable, especially at high speeds. Someone running a very tight autocross might want to go the other direction with caster changes to make the car more maneuverable, but I doubt that is what most Z8 owners want to do with their cars. Increased positive caster also makes it harder to turn the steering wheel so there is a limit to what is beneficial, although today's power steering makes this mostly an academic point for street applications. Finally, increased positive caster gives the car better on center steering feel, sort of like the difference between an overly power assisted steering system which tends to be vague and the ones BMW usually builds into their cars which provide much better feel for what the car is doing.

    Dinan's caster plates mount on top of the spring/struts and add app. 1/2 degree of positive caster to a stock Z8 and closer to 1 degree of positive caster to an ACS lowered Z8. Because they are mounted on top of the existing strut parts, they do raise the front of the car app. 1/4".

    It has already begun snowing where I live, so my driving experience with the caster plates installed has been somewhat limited. It should be mentioned that my Z8 has the ACS suspension kit, Dinan adjustable anti-roll bars and I am running SO-3s in stock sizes on stock wheels. The changes to the car's handling are positive, though I don't believe I have their full measure yet. Steering accuracy and stability at high speeds (straight line and cornering) is noticeably better, especially when the road surface is uneven (less hunting). Steering response is an interesting mix: the steering feels a tiny bit slower during small inputs (this is to be expected) but much better during quick transitions since the increased negative camber begins to come into play. Overall, understeer has been reduced slightly and cornering ability has improved. The other thing you'll notice is the steering wheel wants to return to center more than before (this is also to be expected with positive caster changes). Overall, I like the changes and plan to put many more miles on the set-up before I give my final recommendation.

    An interesting part of this process was the changes made to the car's overall alignment settings. Up front, I ended up with 7.5 degrees of positive caster, 1.0 degree of static negative camber and I set toe-in to essentially zero. Toe would normally be set "in" a bit to keep the car from wandering on uneven surfaces but the increased caster allowed me to go straight ahead which improves the tire's response to steering input (autocrossers often run toe out for this very reason). In the rear, I ended up running a small amount of toe-in (never use toe out in the rear) and 1.7 degrees of static negative camber. The combination works extremely well. While researching this set-up, I discovered that the E46 M3 uses virtually the same alignment settings right from the factory. Maybe we're on to something here!

    For those of you who are not familiar with the term caster, let me go into a little more detail. Caster is defined as the angle between a line drawn vertically through a wheel's centerline and the axis around which the wheel is steered. It is also sometime's referred to as the kingpin angle. An easier way to visualize this is to picture one of those motorcycle's with its front wheel waaaaay out front, aka a chopper. This front suspension set-up has a ton of positive caster. These bikes are very stable in a straight line (they make great cruisers) but are very reluctant to go around sharp corners. You may also have noticed that when their front wheel is turned, it tends to lay over on its side quite a bit. That is the increased negative camber during cornering I referred to.

    In any case, I will report back if and when I get some more miles on the set-up.

    Originally posted by 'Grease Monkey' on Roadfly
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  2. #2
    This upgrade makes the car drive more cleanly, and also puts a large aluminum under the shock tower crown, adding quite a bit of meat to the area. I have mine attached as the lower part of my PP where it give the advantage of being better steering feel as explained above, and being an all aluminum metal to metal match beneath the shock tower dome.
    Andrew Macpherson

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  3. #3
    Z8Mania
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    Are these still available?

  4. #4
    I think that Dinan has a few sets of these still available, but I know the swaybars are all gone, but the stiff H&R bars are available. I have them, but haven't got round to trying them yet.
    Andrew Macpherson

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  5. #5
    Z8Mania
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    How much of a must have are these? As you know I have the sway bars.

  6. #6
    That is something I can't answer with ease, because I put them on this car years ago, and honestly can't remember the difference. It is a subtle change, much less notable that the sways, but one on the reasons I like it that is it is a big slab of aluminum under the shock tower crows, and is actually rather more substantial than the lower PP ring.
    Andrew Macpherson

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  7. #7
    Z8Mania
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    I will research this when its time for me to do the suspension. Right now I have another project in the works and then I will get to this. There is a slight chance I wait until the fall or even next year.

  8. #8
    Administrator thegunguy's Avatar
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    To me, these are a must from a protection standpoint. They are simply better constructed than even the replacement hats from the PP.
    thegunguy

  9. #9
    Z8Mania
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    I will add these in when I do my work.

  10. #10
    Carter Carter Rise's Avatar
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    These seemed like a good idea until I read that they raise the front of the car. I have the PP and thought that I had read that they replaced a part of the PP under the shock tower. Did the PP raise the front end too or am i just confused?

  11. #11
    Yes, the PP did raise the front of the car fractionally, maybe 1/8" and the Dinan plates maybe 1/4". I kept the Dinan plate on mine as they are aluminum, and didn't use the lower steel ring of the PP, only the top one.
    Andrew Macpherson

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  12. #12
    Z8Mania
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    I got the car back from having the caster plates installed today. We used GM's suggested alignment settings. Im very pleased with the difference. Especially the handling on highway sweepers- I feel like the understeer has been cut down significantly. Yet the car is not twitchy. The car is also more stable going straight ahead and also under hard braking, where as she would like to sometimes follow the road now she goes straight. The only downside is at low speeds pulling out of streets, the car really wants to get back to center - its an adjustment I have to make. Overall I knew we weren't going to turn it into a GT3 but I wanted to reduce the understeer while driving on highway sweepers and this does it. I am really pleased!

    Please note Im running the full Alpina EU suspension and Dinan sway bars set to stiffest.

  13. #13
    We have duplicate suspension set-ups now, and I really do love mine as it is. For the speeds I want to progress at on the public highway the car is simply perfect now. Sure it isn't a GT3, but I also never took the GT3 anywhere but the track because it wasn't such a pleasurable road car.

    Are you also on 20" rims & Pirellis or MSS?
    Andrew Macpherson

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  14. #14
    Z8 Ate My Homework! Norcal's Avatar
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    Same set-up here (with 20s), not sure if we have the same alignment. I can say at the track it works great too. Much less understeer, and as you noted, more stable under braking too. Soft, but really hooks up well once it settles onto the springs. Much better than stock.

  15. #15
    Team Z8 ZMates's Avatar
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    Quote Originally Posted by macfly View Post
    Yes, the PP did raise the front of the car fractionally, maybe 1/8" and the Dinan plates maybe 1/4". I kept the Dinan plate on mine as they are aluminum, and didn't use the lower steel ring of the PP, only the top one.
    Is there a lower steel plate? I only got the upper in my PP.
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  16. #16
    Z8Mania
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    I believe there is supposed to be a lower steel plate. When we took out the suspension to do the Dinan Caster Plates, we discovered there was no lower plate in place. I'm not complaining, just sharing an experience with you.

    Norcal, I agree about that- its still soft but thats OK. Something's got to give- its actually like the non HGTE 599 in that regard- you get it settled down on its suspension and then you can really make her dance. I feel like these changes doesn't change the underlying personality of the car but it does give it quite a bit more capability. I really like that. Before with the stock suspension, stock wheels, but with MPS2 tires, going 85+ on the highway sweepers (and my roads are not perfectly flat) the car would be giving me a signal that I was fast running out of suspension capability. Now the car feels comfortable doing those same sweepers at 20+ MPH more. Not that I go that fast- 85 is probably the fastest but its nice to know you have more "headroom" in the suspension. And the Alpina springs give better straight ahead comfort and a more progressive feel to the act of "carving" which is how the Europeans would describe it.

    Andrew, yes, I am on the Alpina 20" wheels with MPS2. I did those last year and theres really no need to change the tires right now. One day I will though.

    Whats interesting to me is how much roll the stock Alpina suspension (using the standard Z8 anti roll bars) allows. It really needs the stiffest Dinan setting.

  17. #17
    Administrator thegunguy's Avatar
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    There is no "lower plate", only the plate that sits on top of the tower where the strut mounts to the body/frame. There is, however, a new steel mount/spring-hat with rubber bushing (if I recall the original parts were aluminum and nylon) that attaches to the top of the strut, which is then bolted to the frame.

    If you're using the Dinan plates thye attach to the new mount at the top of the strut and relocate the angle of the strut back a degree or two.

    The order from the top would be:
    1. New plate
    2. Body
    3. Dinan plate (optional)
    4. New mount/hat
    5. Spring/strut

    See photo.
    1. Rings in plastic bags are the new top plates. (mid right of photo)
    2. Heavier discs with bushings are the new mounts. (bottom of photo)
    3. Gaskets in mid left of photo.
    4. Hardware in baggie in center.
    5. Cross brace.

    I hope this helps clarify some of the confusion. I think it's all a difference in terminology. I don't know if my terms are "correct", but calling the new mount a "lower plate" is a bit misleading as it might make someone believe there should be two additional rings like the top plate. Anyway, the photo should help most of all.
       
    thegunguy

  18. #18
    Z8 Ate My Homework! Norcal's Avatar
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    How new are the lower mounts? When were they released? I wonder if I have those?

  19. #19
    Administrator thegunguy's Avatar
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    Anyone with the PP should have these same steel/rubber mount, unless BMW has changed the PP along the way, which I can't believe is likely. So, if you've got the PP, you should have the same parts in my photo.

    From my own backyard engineering assessment, which is pretty worthless, the steel/rubber change from aluminum/nylon is really what makes the PP worthwhile, not the cross-brace, which in my opinion doesn't provide much stiffening due to the curve. The heftier mount and change in materials serves to strengthen the connection while softening the impact with the rubber bushing. I also believe the top plates only serve to assist in keeping the bolts from spaying and doming the the strut tower. As such, a lower plate wouldn't accomplish anything. The Dinan plate seems to provide some additional impact protection, but this is just my guess.

    The photo was from my PP when it was released.
    thegunguy

  20. #20
    Administrator thegunguy's Avatar
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    Here's a screen capture of the parts list of the PP from BMW's install instructions. As you will note, they're the same parts as in my photo. I believe Andrew was just mistaken in his previous post about a "lower plate". There has never been one.
     
    thegunguy

  21. #21
    Sport Button On - DSC Off Juergen Wunderlich's Avatar
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    I bought a PP last week and all the parts are still the same as seen on Rifles picture. I also bought the first PP available from BMW years ago and there is no difference so far. I can also confirm that there was never a "lower plate" and there is no difference in the hight of the car.
    Best Regards,

    Jürgen

  22. #22
    Z8 Ate My Homework! Norcal's Avatar
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    Thanks, Part "D" was the one I asked about. Sounds like it has always been part of the PP.

  23. #23
    That's interesting, now I wonder what I've got under the domes? When I had mine fitted I was sure the team at Peter Pan asked if I wanted the lower plate to be put in as it would have lifted the car higher with the Dinan plate. I said just go with the Dinan plate, so I wonder if I still have the original shock mount?
    Andrew Macpherson

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  24. #24
    Administrator thegunguy's Avatar
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    You can probably tell from just jacking the car up slightly. I believe you should be able to see the mount fairly easily. The original one was a brown/white nylon color.

    Or...if you have your original parts accessible, you could see what's in your storage box.

    If you didn't have the Dinan plates on, I'd say that the old mounts wouldn't work with the top plates as the bolts are slightly longer, but the Dinan plates negate this as they relocate the mounts with new bolts in the offset plates. So, you're going to need to peek underneath.
    thegunguy

  25. #25
    Administrator thegunguy's Avatar
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    Quote Originally Posted by Norcal View Post
    Thanks, Part "D" was the one I asked about. Sounds like it has always been part of the PP.
    That's my belief as I also believe it's the critical part of the whole kit to begin with.
    thegunguy

  26. #26
    Z8Mania
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    Thanks for the clarification and information. Where does "D" (Spring Strut Support Bearing) attach to? If the OEM shock/strut was removed in favor of the Alpina ones would that be removed as well?

  27. #27
    Z8 Ate My Homework! Norcal's Avatar
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    "D" would mount on top of the strut.

  28. #28
    Z8Mania
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    Right so here is a picture of my OEM suspension, which was in the car when we did the PP, just removed to do the EU Alpina suspension- is D attached to those shocks or no? Looks to me that its not, which means its still in my car Btw- Rifle, in thinking about it, what you say makes a lot of sense about whats so important. I can tell you that when I got my car back from the PP, the whole car felt so much stiffer.
     

  29. #29
    Z8 Ate My Homework! Norcal's Avatar
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    Hmmmm... don't see the old part "D"... now I need to check mine! I'll call Dana today. When did you have the Euro Alpina suspension done?

    EDIT: Ah, so you did the PP (got the new hats then), then upgraded to Aplina, so, the old hats would have come out when you did the PP not the Alpina. I think it makes sense now. Did they give you any old parts when you did the PP?

  30. #30
    Z8Mania
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    Wouldn't the "D" part stay inside the wheel well?

  31. #31
    Administrator thegunguy's Avatar
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    Let's see if I can help answer these:

    Quote Originally Posted by Z8Mania View Post
    Thanks for the clarification and information. Where does "D" (Spring Strut Support Bearing) attach to? If the OEM shock/strut was removed in favor of the Alpina ones would that be removed as well?
    No.

    Quote Originally Posted by Z8Mania View Post
    Wouldn't the "D" part stay inside the wheel well?
    No.

    1. Part D is the same on the Z8 and Alpina. It would not be included if you were changing to the EU Alpina setup.
    2. Part D must be removed to change the suspension or install the PP (obviously with the PP as it's exchanged for a new part). It's attached to the strut via the nut at the top (can be seen by removing the dust caps on the towers under the hood). This holds the spring under slight tension, and then Part D attaches the strut/spring assembly to the car. To change the spring or strut, you have to use a spring compressor to generate enough slack to loosen the top nut and separate Part D which holds it all together.

    See these photos from when my Dinan suspension was installed. In the first you see the OE spring in the compressor. You can clearly see the nut at the top holding the assembly in tension. The silver ring is the original Part D with the bushing facing down (see my second photo from the post on 6/15 at 10:24). The second shows the new assembly with the Dinan spring (uses OE struts - Alpina uses a different SACHS strut) and caster plate at the top. Both photos are form 11/05 - pre-PP.

    You can also note from these photos that Part D appears to be aluminum in appearance, but it's purely a visual guess. The new Part D from the PP (in my previous photos) appears to be basic black steel. It could be a difference in finish/polish, but the bushings are definitely different - rubber vs. nylon.

    Did this make sense now?
       
    thegunguy

  32. #32
    Z8Mania
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    Yes it does- thanks Rifle.

  33. #33
    Administrator thegunguy's Avatar
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    Here's another view from RealOEM.com. The strut fits up through the center of all parts shown with part 12 resting on a purchase in the middle of the strut. #1 in this view is Part D in the PP install parts list.
     
    thegunguy

  34. #34
    Z8Mania
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    That makes sense- so if you had the PP installed and then part D/ #1 was in there when you changed your struts, whomever did the change over would just reuse Part D/ #1 without any second thought.

  35. #35
    Z8Mania
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    So in adding the Dinan Caster plate, we've added another piece of metal into the mix which I am guessing couldn't hurt in the event of an impact.

  36. #36
    Administrator thegunguy's Avatar
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    Quote Originally Posted by Z8Mania View Post
    So in adding the Dinan Caster plate, we've added another piece of metal into the mix which I am guessing couldn't hurt in the event of an impact.
    That's my non-qualified engineering assessment as well.
    thegunguy

  37. #37
    Z8 Ate My Homework! Norcal's Avatar
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    Andrew, I have been gathering some pretty serious wear on the outside of my front tires. I'm thinking I need to find more neg. camber. Any ideas? Do you have your readouts from your last alignment? I'm wondering if there is still room for more adjustment. Dinan says you will gain -.7 camber and 1 caster. I wonder if that is at full-lock or what? I think I need more ALL THE TIME! Any idea if they can be rotated by one screw to add neg. camber? This will decrease the caster but increase the neg camber all the time? I'll need to ask Dinan or Matt, I think.

  38. #38
    Yes, those are questions beyond my realm of knowledge, for sure Matt would know, and the Dinan guys have always been very helpful.
    Andrew Macpherson

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  39. #39
    DSC Off JohnAnthony's Avatar
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    Hey guys,
    anyone have a lead on some of the Performance Package parts?

    specifically parts D & E

  40. #40
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