[Tej]

I am in talks with KW to replace my front two dampers for my V3's on my 2010 335i xDrive sedan. They quoted me for the dampers and I asked them for replacement springs and they said "You can go up to 150 lbs per inch only."

It seemed surprisingly low and close to stock so I was very confused. I asked why and they said "Any more can cause damage to damper."

Can someone explain what they mean and why I'm seeing people with springs that are 200-300+ lbs/in compared to what they're offering me. Wish I knew what my current spring rates were but I didn't buy the KWs car came with them.

[Tej]

Any input would be helpful just need to know if I should buy replacement springs and replace my current ones or not.

[Tambohamilton]

150lb/in is a joke really. I think BMW perf springs are just shy of 200, and almost everything aftermarket is over 200. I seem to remember seeing kw springs that were 400lb/in though?

Are you sure it was 150lb/in though? 150kN/m would be 850lb/in, which sounds more plausible as a damage threshold for the damper.

[whyzee125]

I think they're mistaken, here are the KW spring rates according to Mr. 5's excellent thread from back in the day.

KW v1-v3 (non M3)
Front: 190-256 lb/in (progressive average)
Rear: 545-570 lb/in (progressive average)

KW Street Comfort
Front: 286 lb/in
Rear: 572 lb/in

KW Clubsport (non M3)
Front: 400 lb/in
Rear: 570 lb/in

M3 KW v3
Front: 285 lb/in
Rear: 630 lb/in

M3 KW Clubsport
Front: 508 lb/in
Rear: 800 lb/in

KW is not going to sell you a different spring than came with the V3's but if you're wanting to move up or down a bit, I'd look into a swift spring conversion from HPA. It's like $300 and you get linear swift springs and custom upper mounts to run them on your KW's. Or I'll sell you my street comfort springs and I'll get the swift conversion LOL. There was a guy a while back who was wanting KW camber plates but they only sell them with a few of their coilover kits and not separately. A vendor on here replied and said they'd be happy to sell them to them directly so you could probably reach out to one of the many Forum sponsors with the part numbers of the KW springs you want (for example if you wanted clubsport springs for your V3's) and they'd likely sell them to you. Hope this helps!

[Tej]

Originally Posted by Tambohamilton

150lb/in is a joke really. I think BMW perf springs are just shy of 200, and almost everything aftermarket is over 200. I seem to remember seeing kw springs that were 400lb/in though?

Are you sure it was 150lb/in though? 150kN/m would be 850lb/in, which sounds more plausible as a damage threshold for the damper.

100% certain they said pounds per inch. I have the email. It seemed really strange to me so I might give them a call at this point and see what they say.

Originally Posted by whyzee125

I think they're mistaken, here are the KW spring rates according to Mr. 5's excellent thread from back in the day.

KW v1-v3 (non M3)
Front: 190-256 lb/in (progressive average)
Rear: 545-570 lb/in (progressive average)

KW Street Comfort
Front: 286 lb/in
Rear: 572 lb/in

KW Clubsport (non M3)
Front: 400 lb/in
Rear: 570 lb/in

M3 KW v3
Front: 285 lb/in
Rear: 630 lb/in

M3 KW Clubsport
Front: 508 lb/in
Rear: 800 lb/in

KW is not going to sell you a different spring than came with the V3's but if you're wanting to move up or down a bit, I'd look into a swift spring conversion from HPA. It's like $300 and you get linear swift springs and custom upper mounts to run them on your KW's. Or I'll sell you my street comfort springs and I'll get the swift conversion LOL. There was a guy a while back who was wanting KW camber plates but they only sell them with a few of their coilover kits and not separately. A vendor on here replied and said they'd be happy to sell them to them directly so you could probably reach out to one of the many Forum sponsors with the part numbers of the KW springs you want (for example if you wanted clubsport springs for your V3's) and they'd likely sell them to you. Hope this helps!

Depending on how much you're gonna charge me I'd take the clubsport springs off your hands. I have heard people talk of swift springs before, but wasn't certain they'd make a big difference.



Tbh I feel like they're trying to sell me BMW oem parts compared to KWs. The strut replacements seem relatively cheap compared to buying all new V3s all around lol. Also $80 for KW V3 springs seems pretty cheap too.

[Tej]

Originally Posted by whyzee125

I think they're mistaken, here are the KW spring rates according to Mr. 5's excellent thread from back in the day.

KW v1-v3 (non M3)
Front: 190-256 lb/in (progressive average)
Rear: 545-570 lb/in (progressive average)

KW Street Comfort
Front: 286 lb/in
Rear: 572 lb/in

KW Clubsport (non M3)
Front: 400 lb/in
Rear: 570 lb/in

M3 KW v3
Front: 285 lb/in
Rear: 630 lb/in

M3 KW Clubsport
Front: 508 lb/in
Rear: 800 lb/in

KW is not going to sell you a different spring than came with the V3's but if you're wanting to move up or down a bit, I'd look into a swift spring conversion from HPA. It's like $300 and you get linear swift springs and custom upper mounts to run them on your KW's. Or I'll sell you my street comfort springs and I'll get the swift conversion LOL. There was a guy a while back who was wanting KW camber plates but they only sell them with a few of their coilover kits and not separately. A vendor on here replied and said they'd be happy to sell them to them directly so you could probably reach out to one of the many Forum sponsors with the part numbers of the KW springs you want (for example if you wanted clubsport springs for your V3's) and they'd likely sell them to you. Hope this helps!

So I just got off the phone with them, and they did correct themselves and say that I currently have 197 lb and that I can go up to 262 lb. They also mentioned that any more than 262 lb can damage the strut heavily.

So my question to you is how am I able to get swift springs with a much higher spring rate, but not risk damaging the strut?

[Tambohamilton]

262 is the safe limit for the strut, it doesn't matter which brand of spring.

....but maybe they're wrong again, and the safe limit is actually higher?

[whyzee125]

Originally Posted by Tej

So I just got off the phone with them, and they did correct themselves and say that I currently have 197 lb and that I can go up to 262 lb. They also mentioned that any more than 262 lb can damage the strut heavily.

So my question to you is how am I able to get swift springs with a much higher spring rate, but not risk damaging the strut?

Anytime you modify anything, you run the risk of accelerated wear/damage.

It would be the same as telling BMW "My tuner said my tune is safe but you're saying I might break something."

KW warranties struts for life so they're going to give you spring rates that will allow the struts a long life. There's a range, too, so even if going to swift springs I wouldn't go way outside of that but gives you a little room. LMK if you want my street comfort springs haha as I've been curious to see how the swift ones of the same rate compare. Shoot me a PM if interested, no pressure!