09-25-2023, 11:01 AM | #1 |
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Has anyone put any other lowering spring on a KW HAS kit?
Reason I ask: The front springs that came with my kit don’t sit quite as low as I’d like whereas the rear sits much lower with room to go even lower. The fronts are bottomed out. Any ideas to make the KW HAS work and achieve a lower front end fitment?
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10 E90 M3 /// Dinan Intake, X Pipe, Exhaust, Underdrive, 3.62 Diff, Coilovers, Alpine e85 Tune - sold
16 F80 M3 /// MaxPSI 4 Pin, DP, CP, SL Mid-Pipe, TMIC, KW HAS, EU5's, AB Performance Flex Tuned |
01-18-2024, 01:34 AM | #2 |
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I am curious also as well if it’s possible to use Swift or other coilover springs wjtb KW HAS kit. Just don’t want a progressive speing and want to use linear springs.
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01-18-2024, 06:37 AM | #3 |
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The lower spring diameter is much smaller diameter than a stock or lowering spring. Also, if you switched to a linear rate spring, it would need to have a higher spring rate than a typical lowering spring linear rate to prevent the car from continuously riding the bump stops. Front suspension travel is limited in the front to begin with and is reduced by a lot with a HAS kit.
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02-01-2024, 06:05 AM | #4 | ||
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Just curious, how did this help make your task easier and more convenient? Passing on it or…? |
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02-24-2024, 01:44 AM | #5 | |
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02-24-2024, 06:52 AM | #6 |
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Is this for a setup using zcp dampers and a KW HAS or ??? A linear race spring has a constant 2.25”, 2.50”, 60 mm, or 65 mm IDs which means they won’t work with a HAS kit of any kind…unless the lower spring seat matches one of the three linear race spring?
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02-24-2024, 09:29 PM | #7 | |
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Are you saying the IDs of these linear race springs don’t match the KW HAS lower spring seat? Would that be the front or rear? Let’s say I can find one that works, how would I go about figuring out the spring rates and the length? Any info is appreciated as I’m pretty new and learning. Thank you! |
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02-25-2024, 12:07 AM | #8 | |
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Below are pictures of the KW HAS springs (yellow) and Eibach linear constant diameter race springs (red, the middle black spring is a tender spring, and the black spring on the right is a helper spring). The two springs in the middle of the top picture are the KW HAS front beehive/barrel springs. The bottom of these springs is the end that sits on the KW HAS height-adjustable lower spring seat which are on the left side of the picture. If you look closely at the bottom diameter and compare it to the diameter of the two springs on the right side of the picture you’ll see it is a larger diameter. The rear springs on the right are most likely a 60 mm (2.36”) ID spring. The HAS front spring upper diameter is even larger in diameter and it interfaces with the OEM front strut top mount (or an aftermarket camber plate that has an upper spring seat that matches the diameter of the upper diameter of the stock spring). It is a much larger diameter than the three linear race spring diameters. So a constant diameter linear race spring has a diameter that is too small for the HAS lower spring seat. An aftermarket upper camber plate could be assembled to have the correct linear race spring ID and the correct stock strut threaded piston rod diameter. However, the linear race spring ID is too small for the HAS lower spring seat and it’s probably too small to even fit over the stock strut diameter. So there’s nothing that will work with the the stock front strut lower spring seat and a linear race spring ID The rear is simpler and likely just a direct swap. The KW HAS rear spring ID is most likely a 60 mm ID which can be confirmed by simply measuring the HAS rear spring ID. I believe the HAS rear spring is a linear rate spring so selecting a new spring rate is as simple as picking a new spring rate from Hyperco, Swift or Eibach. The length also is easy to select because you already have the length of the HAS rear spring. For small changes in spring rate, you’d use the same length spring as the HAS spring. For larger rate changes, you’d estimate the new length from Lnew = Lold * (Kold / Knew) For example, Lold = 10”, Kold = 400 lbf/in, Knew = 800 lbf/in, Lnew is Lnew = 10 * (400 / 800) = 10*0.5 = 5” A 5” long spring would likely be too short to remain seated at full droop so you’d either increase the spring length and count on the adjustable rear spring seat to set the correct ride height OR you’d use a helper spring or a tender spring to keep the spring seated at full droop. A helper spring “helps” hold up the main spring and doesn’t alter the rate of the main spring because its stiffness is negligible whereas a tender spring “tenderizes” the main spring rate became its stiffness is not negligible and for two springs in series the equivalent spring rate is: Keq = (Kmain * Ktender) / (Kmain + Ktender) For example, coupling together two springs with the same spring rate of 1000 lbf/in, you get: Keq = (1000*1000)/(1000+1000) = 1000000/2000 = 500 lbf/in You’d also have to buy a spring coupler to be able to combine a main spring and a helper/tender spring. So a front linear race spring will not work but it is possible to select a new rear linear race spring. Last edited by M3SQRD; 02-25-2024 at 12:13 AM.. |
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02-25-2024, 01:19 AM | #9 | |
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It seems that the rear springs would be relatively straightforward. But for the front springs, if I can get a linear spring ID that matches the lower spring seat AND also have a camber plate spring seat that matches the lower spring seat, then would all I need to do is use the math you provided to get the spring length? Please let me know if my understanding is correct. I do see that Swift produces 60mm, 62mm, 65mm and 70mm ID springs. |
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02-25-2024, 09:47 AM | #10 | |
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Choosing the front spring rate can be more challenging if the HAS front spring has a progressive spring rate (gets stiffer as the spring is compressed) so you need to know the primary secondary spring rate, if the spring has one. Also, you have to be careful on the length of the front spring because the stock struts do not have a lot of compression stroke. BMW tunes their suspensions to use the bump stops to limit suspension travel. So you can only lower the front, and shorten a bump stop, by a relatively small amount before bottoming out a strut becomes a real concern. Furthermore, the stock dampers can only handle a small increase in spring rate before the dampers cannot control the spring. What don’t you like about the spring rates and ride heights offered with the HAS kits? |
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03-09-2024, 05:06 PM | #11 | |
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I was evaluating my options for an aircup setup because they require linear springs. Was also curious to see if it was possible to swap the spring rates but it seems that the dampers are also a problem if I wanted stiffer springs. Seems the solution is to just stay with the HAS kit until I switch over to coils. Thank you for all that info. I definitely learned a lot! |
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03-09-2024, 05:17 PM | #12 | |
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Here’s a link to what someone did to convert KW HAS to linear springs on the g8x. jetbill is a professional race car driver. https://g80.bimmerpost.com/forums/sh...54&postcount=5 |
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