BMR's SP089 Front / SP082 Rear "Minimal Drop" Springs: Now sold as a kit (SP763)

[Roadway 5.0]

I threw a set of these on my PP 15 GT with Koni Active dampers and its a solid street setup. I drive on Chicago/New York bad roads in my city and they manage the bumps, cracks, potholes and uneven pavement well. Perfect height for a year round daily driver.

Anyone here notice the rear bottoms out on the bump stops a lot even after trimming them the correct amount? I’m having this issue and once it got cold the OE bump stops became harder and basically rattle on washboard pavement (to the point of loosening the rear shock top nuts). Already took the rear shocks off again to trim the bump stops a little more and there’s only 2 finger widths of clearance between the top of the shock and the bump stop.

The 0.5 inch rear drop seems to have settled into a lower height than what I’ve seen from other owners.

To answer Kevin: I don’t think these are magnaride compatible. Only springs designated for magnaride are; it’s clearly stated in the product on offering AM.

A rattle is from a loose top nut, for sure. Use some locktight. To add, I am convinced the rear shocks need to be high pressure monotubes on this chassis—no aftermarket mounts needed; if the ride gets bad try a set of Bilsteins.

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[BmacIL]

After a good amount of te


A rattle is from a loose top nut, for sure. Use some locktight. To add, I am convinced the rear shocks need to be high pressure monotubes on this chassis—no aftermarket mounts needed; if the ride gets bad try a set of Bilsteins.

 

[TheMegalodon]

After a good amount of te


A rattle is from a loose top nut, for sure. Use some locktight. To add, I am convinced the rear shocks need to be high pressure monotubes on this chassis—no aftermarket mounts needed; if the ride gets bad try a set of Bilsteins.

Thanks for all the input.

I hear you. There’s no rattle now that the top nuts have been tightened with locktite. Now it’s a rubber bouncing sound and is likely the bump stops.

This is making me wish I had bought the Bilsteins everyone is raving about. Theres so many damper options; it’s hard to know what actually rides well.

The rear of this chassis is so stiff - I mean 700-800 lb rear spring rates? I know why it’s so high but you constantly feel like you’re sitting on this unrefined, overly stiff rear that becomes so tiresome on the highway.

 

[BmacIL]

The rear of this chassis is so stiff - I mean 700-800 lb rear spring rates?

Motion ratio matters. The rear springs compress 0.49" for every inch of travel, unlike the front struts or previous generations where it's basically 1:1 for ride motions. Because of this, the effective rate, known as wheel rate, is (0.492^2)×(spring rate). An 800 lb rear spring provides a wheel rate of 194 lb/in.

Given the lack of this kind issue reported by anyone who has the SP080 or SP763 springs (since the rears are the same), I can only deduct that it's related to the shocks. They probably control low speed movement better (cornering, braking, launching), but high speed (bumps) may not be enough. It's hard to know.

 

[TheMegalodon]

Thank you for your reply. It’s hard to keep track of all of these factors - I remember reading about wheel rate before.

Think it’s best to trim the bump stops more or try the FP bump stops? Or is it grasping at straws and I have to accept that I bought rear shocks that aren’t good enough - even though they claim to work well with cars lowered less than 1”.

Motion ratio matters. The rear springs compress 0.49" for every inch of travel, unlike the front struts or previous generations where it's basically 1:1 for ride motions. Because of this, the effective rate, known as wheel rate, is (0.492^2)×(spring rate). An 800 lb rear spring provides a wheel rate of 194 lb/in.

Given the lack of this kind issue reported by anyone who has the SP080 or SP763 springs (since the rears are the same), I can only deduct that it's related to the shocks. They probably control low speed movement better (cornering, braking, launching), but high speed (bumps) may not be enough. It's hard to know.

 

[Kevin08]

Fronts can. Rears can't.

*sigh* Guess i have some springs to sell.

 

[sinisterblack16]

Is there a drop difference between these and the performance springs? Is the only difference the ride quality?

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