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      04-16-2014, 01:43 PM   #1
slicer
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Possible Solution for KW Clubsport Inner Wheel Clearance Issues

Problem -
KW Clubsport coil-overs reduce inner wheel/tire clearance by 12mm to 15mm relative to OEM. This inner clearance reduction is due to the stack height of the KW helper springs, main springs, and spring perch. This stack height results in the spring / perch landing at the edge of the tire. BMW's OEM design places the spring perch above the tire (resulting in more available inner clearance).

This inner clearance reduction limits wheel and tire sizing and results in the need for spacers, and/or negative camber. I'm a big fan of running 275mm tires in the front which has resulted in a need for spacers on most of the wheels that I have ran to date. See the picture Below.



I have grown tired of dealing with this issue so I contacted the professionals to discuss my options. My first call was Malek at MRF Engineering. Malek knows the M3 better than anyone I have met, and he specifically has tons of experience with KW Clubsports. Next I contacted KW themselves. Here are my findings.

Solution -
Raise the spring perch. There are a couple of ways to do this.

Option One - eliminate the helper spring. I have never liked this solution because the helper springs are there to keep the main spring in place when the suspension is un-weighted (going over a large bump or curbing on the track). Without the helper spring it is possible that the main spring would become miss-aligned which is not a good thing. There are suspension systems without helper springs, and there are people who have successfully eliminated the helper springs on their KW suspension. I simply didn't think that route was best.

Option Two - Install a shorter main spring while leaving the helper spring in place. This option also creates some potential for problems. The main problem being that the shorter main spring could bottom out (aka block out) prior to the shock/bump stop. This would result in unacceptable suspension feel / performance. Imagine hitting a hard bottom of a metal spring at the end of its travel vs. the more progressive feel of the bump stop. In order to determine the likelihood for success, I contacted KW to discuss this option. KW has not tested and does not warranty this fitment but they were nice enough to provide me with their assessment. KW believes that the installation of a 30mm shorter spring will work at or near my ride height. I will just need to make sure that the suspension will bottom out on the bump stop prior to the spring running out of travel. This change will limit my height adjustment slightly because I will be effectively reducing my maximum spring travel from 92mm to 80mm. This should be a non-issue at or near the ride height that I run. It will however, in theory, reduce my maximum ride height (and travel). In other words I won't be able to raise my ride height as high as would have been possible with the longer spring. This shouldn't be an issue for me because I don't expect to raise my car more than 1/2" from it's current height.


Malek at MRF engineering will be performing the install and we will share the results. If my calculations are correct, this change will allow the fitment of 18x10 et25 wheels with 275/35/18 tires in the front without the use of spacers. Stay tuned!
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      04-16-2014, 11:33 PM   #2
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Interesting. Best of luck on your swap and I'm looking forward to the result!!!
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      04-16-2014, 11:43 PM   #3
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The combination of a shorter coil spring and a "no load" Swift helper spring will reposition the adjustment collar towards the top of the tire and get the clearance you need for the best of both worlds. Added bonus allows to dial in the spring rates you want.

We've done this on a number of track M3s, including our own. Go this route and you'll be fine. If you need the swifts - we're an authorized dealer.
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      04-16-2014, 11:56 PM   #4
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On my AA coils that use Hyperco springs my problem is the perch itself that on an 18" wheel sits right next to the inner barrel. (A taller 19" wheel seems okay as the inner barrel is above the perch) I have about 2mm of clearance on a 18x9 et 22. et 25 would need spacers. Curiuos to hear your results as I have thought about this issue myself.
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      Yesterday, 12:43 AM   #5
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Quote:
Originally Posted by tom @ eas View Post
The combination of a shorter coil spring and a "no load" Swift helper spring will reposition the adjustment collar towards the top of the tire and get the clearance you need for the best of both worlds. Added bonus allows to dial in the spring rates you want.

We've done this on a number of track M3s, including our own. Go this route and you'll be fine. If you need the swifts - we're an authorized dealer.
Thanks for the info. What is the purpose of going to a swift spring versus a KW spring? KW springs are also available in different spring rates. Also what is gained by switching to a different helper spring?
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      Yesterday, 12:54 AM   #6
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Quote:
Originally Posted by slicer View Post
Thanks for the info. What is the purpose of going to a swift spring versus a KW spring? KW springs are also available in different spring rates. Also what is gained by switching to a different helper spring?
Simply more choices on the Swifts and its typically what we work with most- choose whatever you're most comfortable with. Eibach and H&R are also alternative brands, so there's plenty of choices out there.

The no-load helper springs provide only enough tension to keep the springs from dislodging/rattling - without affecting spring rates.
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      Yesterday, 01:16 AM   #7
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Quote:
Originally Posted by tom @ eas View Post
Simply more choices on the Swifts and its typically what we work with most- choose whatever you're most comfortable with. Eibach and H&R are also alternative brands, so there's plenty of choices out there.

The no-load helper springs provide only enough tension to keep the springs from dislodging/rattling - without affecting spring rates.
I think I am running a "no load" helper as it is super flimsy and can be squeezed together w/ 2 fingers and as mentioned is only there to keep everything in check when unloaded, but I still have minimal clearance. I don't see how you can move the perch up w/ springs alone but also maintain the same travel. Am I not thingking clearly Or is it just too late where I am?
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      Yesterday, 01:25 AM   #8
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Quote:
Originally Posted by s85e90 View Post
I think I am running a "no load" helper as it is super flimsy and can be squeezed together w/ 2 fingers and as mentioned is only there to keep everything in check when unloaded, but I still have minimal clearance. I don't see how you can move the perch up w/ springs alone but also maintain the same travel. Am I not thingking clearly Or is it just too late where I am?
Sounds like you have the right helpers.

Would need to know a bit more specs on your setup, including dampeners, spring brand/length, as well as wheel/tire setup. Feel free to email or call if you want to discuss in detail.
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      Yesterday, 07:54 AM   #9
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Quote:
Originally Posted by tom @ eas View Post
Sounds like you have the right helpers.

Would need to know a bit more specs on your setup, including dampeners, spring brand/length, as well as wheel/tire setup. Feel free to email or call if you want to discuss in detail.
do you have any photos that i could look at
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      Yesterday, 11:03 AM   #10
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Quote:
Originally Posted by leigh View Post
do you have any photos that i could look at
Not handy, sorry. I'll get some next time one of the cars comes in for pre-track inspection.
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      Yesterday, 11:51 AM   #11
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Quote:
Originally Posted by s85e90 View Post
I think I am running a "no load" helper as it is super flimsy and can be squeezed together w/ 2 fingers and as mentioned is only there to keep everything in check when unloaded, but I still have minimal clearance. I don't see how you can move the perch up w/ springs alone but also maintain the same travel. Am I not thingking clearly Or is it just too late where I am?
See my original post. A shorter spring will reduce your spring travel but not your shock travel.... Not Directly. When you adjust your car's ride height lower you are decreasing the suspension travel range. The spring that comes with the kit is sized to allow you to raise and lower the car throughout its adjustment range. At lower ride height settings the spring has more range than it needs. At higher ride height settings the spring's full range is needed. Adding a shorter spring limits this adjustment range. It will not however reduce the travel at a ride height within that new range. The key is that you need the suspension to bottom out on the bump stop prior to the spring bottoming out. My understanding is that a shorter spring will limit the upper range of adjustment (not the lower).
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      Yesterday, 12:14 PM   #12
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Quote:
Originally Posted by slicer View Post
Thanks for the info. What is the purpose of going to a swift spring versus a KW spring? KW springs are also available in different spring rates. Also what is gained by switching to a different helper spring?
My thought also. If you go with anything other than KW you will probably need to machine the spring perch/collar. Also, wouldnt you need a new camber plate or and adapter for any spring with a different diameter than the KW?

Let me know how this works. I am heading the same route as you. I have been thinking about this problem for a while.
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      Yesterday, 12:30 PM   #13
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Quote:
Originally Posted by Wendall View Post
My thought also. If you go with anything other than KW you will probably need to machine the spring perch/collar. Also, wouldnt you need a new camber plate or and adapter for any spring with a different diameter than the KW?

Let me know how this works. I am heading the same route as you. I have been thinking about this problem for a while.
Correct, most springs are 60mm.

If going this route - the KW perches need to be milled down a couple of millimeters to accept the new springs, which we perform in-house.
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      Yesterday, 12:42 PM   #14
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Quote:
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Correct, most springs are 60mm.

If going this route - the KW perches need to be milled down a couple of millimeters to accept the new springs, which we perform in-house.
Will the KW camber plates need modification?
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      Yesterday, 01:01 PM   #15
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Quote:
Originally Posted by Wendall View Post
My thought also. If you go with anything other than KW you will probably need to machine the spring perch/collar. Also, wouldnt you need a new camber plate or and adapter for any spring with a different diameter than the KW?

Let me know how this works. I am heading the same route as you. I have been thinking about this problem for a while.
I'm going with a KW spring in the same rate as my original spring (90nm). KW does have different spring rates available but I have observed that different spring rates result in different travel ranges. I presume it is because the higher spring rate requires a thicker wire diameter which thereby reduces the travel range of the spring. For example:
  • The KW Clubsport 3-Ways come with 90nm / 170mm springs which have a travel range of 92mm.
  • 90nm / 140mm spring has 80mm of travel (10.50mm wire diameter)
  • 100 nm / 140mm spring has 74mm of travel (11.00mm wire diameter)
  • 110 nm / 140mm spring has 73mm of travel (11.25mm wire diameter)

My understanding is that the greater the travel range of the spring the better considering I'm reducing that range. Plus I have not been dissatisfied with the stiffness of my current spring. My goal is to make this change while maintaining the same performance characteristics of my suspension.
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      Yesterday, 02:23 PM   #16
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Quote:
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Will the KW camber plates need modification?
If going with a non-KW spring, yes.
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