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10-31-2008, 06:54 PM | #1 |
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More Findings & Discussions About Lowering the M3
Suspension Travel Before Loading Bumpstop
So amid the discussion of how much suspension travel is in the front before the progressive bumpstop is contacted, I went to my car and measured. I basically pushed the bumpstop downwards as much as I can and measured the gap using a piece of paper. The result - 3/4 inches. See picture. (Dinan claims 1/2") H&R Responses to Dinan's Design The H&R springs would drop the front by 1 inch, so basically the car would be riding on the bumpstop before any loads. So I called a technical manager at H&R and asked him about the effect of riding on the bumpstop prematurely, and here is his answer (paraphrase): The bumpstops in modern day vehicles aren't really a bumpstop in the traditional sense, because in the past bumpstops are basically firm rubbers that prevented the car from bottoming out. On modern vehicles, the "bumpstops" are engineered foamy elastomers, and are part of the suspension system, making the compression progressive. So I mentioned that a competitor is offering a design with a shortened bumpstop and guide support to avoid premature bump stop contact, and he said: Shortened bumpstops are made to be stiffer than stock to work properly, which means that there will be a drastic change in the stiffness of the suspension system when compression reaches a certain level. This means rougher stops when the spring is near full compression. That's why H&R kept the factory bumpstop. Here's an H&R article: http://www.hrsprings.com/technical/m..._jounce_bumper Stock Bumpstop Facts: Front: 2.25" (my measurement); 2.375" (Dinan's claim) H&R M3 Springs Facts: Front lowering: 1" Rear lowering: 1/2" Front will compress bumpstop by 1/4" when stationary Dinan Springs/Bumpstop/Guide Support Facts: Front lowering: 1/2" Rear lowering: 1/2" Front bumpstop 1/4" shorter than stock (claimed) 1/8" according to my measurement; guide support 0.3" shorter than stock Front will have 0.55" travel (0.5" factory travel + 0.3" guide + 0.25" bumpstop - 0.5" lowering) before loading bumpstop Front full compression travel will increase by 0.3" into fenders (assuming Dinan bumpstop has same full compression height as stock) So, hope this helps. Just trying to offer the story from both sides. Both Dinan's and H&R's stories make sense, and I guess the best way to compare the two is to have a side-by-side track test. Any one planning on getting a Dinan system soon? (If there are any mistakes in my calculations please let me know) Last edited by rzm3; 11-04-2008 at 12:26 AM.. |
10-31-2008, 07:08 PM | #2 | |
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One other thing. That 3/4" you meaured would be decreased significantly with a passenger and when the car is in motion just because of the load exerted on the suspension by the engine. So it is possible that you'd be very close to the buumpstop before you even hit a bump causing suspension compression. |
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10-31-2008, 07:10 PM | #3 | |
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11-03-2008, 10:32 PM | #5 |
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Good work. Looks like H&R designed their springs to be used with the stock dampers, while Dinan want's you to buy their system since you'll need new dampers in order to compensate for the stiffer springs since the bump stops are stiffer.
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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."
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11-04-2008, 12:24 AM | #8 |
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Well, both are designed to be used with stock dampers. The only difference is that Dinan provides more travel before contacting the bumpstop.
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11-04-2008, 02:17 AM | #9 |
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Some H&R's are designed to be used with the stock dampers, but obviously can be used with aftermarket dampers.
I wonder what happens with the suspension travel if you install coil overs?
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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."
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11-09-2008, 08:01 PM | #12 |
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11-09-2008, 11:23 PM | #13 |
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What about the Eibach Pro springs... Almost seems like best of both worlds... the price like the H&R but a drop that is similar to Dinan?? (IE not as agressive drop as H&R)
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11-10-2008, 12:08 AM | #15 |
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What did they set you back, the Eibachs cost around $265?
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MY22 X5 M-Sport 45e White, 22"rims, Red Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, otherwise all option boxes are ticked. |
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11-10-2008, 03:03 AM | #16 |
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I believe that the RDsports springs have the most aggressive drop of them all (greater than Dinan, Eibach or H&R)
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11-10-2008, 10:34 PM | #17 |
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nice writeup. Thanks. I have been having the same dilema about which setup to go with. I am interested to see how this develops.
Im really surprised that we havent seen anyone with the dinan setup yet. Also surprised that I have not heard of any EDC issues with any of these springs. Encouraging for sure. |
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11-10-2008, 10:44 PM | #18 | |
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I dont know anyone crazy enough to spend $900 on springs(&bump stops) that dont even drop your car so I cant say how they stack up to Dinans Great post rldzhao! |
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