Koni Active Shocks

[shogun32]

on the 30 or so ‘sporty’ car projects that have used PU bump stops, all made do with around 15mm of wheel travel to the bump-stop contact point on the front axle, and 20mm at the rear.

from the article assumes "soft" PU stops. My previous comment was in relation to the "hard" type. Squash resistance with the soft PU stops is like having a progressive-rate spring or position-dependent damping. I find it odd that Koni doesn't include the appropriate stops and explicit directions on trimming them to suit spring rate and lowering distance.

Sponsored

 

[TheMegalodon]

Oh my god man you have NO idea how much this helps. This makes complete sense and I wish I would have contacted KONI before hand to know this. There is no instruction whatsoever that comes with the dampers, nothing listed on their website or ever mentioned publicly and nothing on the vendor’s pages (CJPP, AM, etc).

It makes the most sense to me that if these shocks don’t have enough room to travel, they don’t have enough room for the selective damping to work properly.

When I mean stock rear spring rate I mean Performance Pack rear spring rate of 728, with BMR’s performance spring being 740 (this is what I have).

It’s curious to me how Steeda tuned their active damper because they’ve stated they test for them for up to 200f/800r spring rates on the S550 and people have had good results mixed with their progressive spring. I think Steeda tunes their active shocks to work well with their progressive and ultra lite linear spring from what I read.

This is what I trimmed from the stock rear bump stop and I’m wondering if I should trim them back one more notch to the height of the black piece.

Hey Ryan, I reckon definitely contact Koni. No manufacturer can know what every set up will do under specific circumstances so it may take a couple of attempts to get it right, I think you'll go ok if you give them a chance.

Do the Koni instructions say anything about bumpstops?

Please don't throw the plastic rings away, IIRC they should have a slot in them the idea being to prevent a pressure build up between the damper body and the bottom of the bumpstop which in compression can blow the top seal.

This is what Koni said when I asked about lowering springs:

For the 2015+ Mustang the Special Active dampers can be used with mild lowering springs with no issue so long as the springs do not allow for too much bump stop contact. KONI's patented selective damping feature that smooths out the high frequency impacts from the road surface while improving handling control over lower frequency suspension motions adds another wildcard into the mix and thus requires actual testing to see what works appropriately or not when it comes to lowering. However, the Special Active dampers do not care if you have OE or lowering springs at all, but to work properly you do need to do your best not to allow the car to impact the bump rubbers very often during normal use. We know they work well with the Eibach Pro Kit Springs for this particular application.

Although it does no damage to the selective damping system, a harsh, high frequency impact into a bump rubber will be seen by the system just like a high frequency road surface impact and it will be in blow-off mode to allow the energy to be un-damped for a smooth ride,. Since normally a bump rubber impact needs more damping control and not less, the car may likely feel under damped when you spike the bump rubbers hard (this will happen more often with the lowered suspension. Because of this, it is very important for proper function for the car to a keep ride height and spring rate combination from allowing too much bump rubber contact.

I haven't gone back to ask specifics such as how much is 'too much' bumpstop contact. Eibach Pros have a 1.0" rear drop (vs .5) and are progressive although have a higher base spring rate (668 vs 800). It could be that your springs are too soft allowing too much bumpstop contact - see above - and while it's not intuitive that a lower harder spring will give a softer ride it may be the case given the way the damper works. I haven't gone back to ask what bumpstops they recommend for the Eibach spring.

All of this aside, it doesn't explain why @JCFoster experiences it with a stock set up but like I said bumpstop tuning isn't easy; not withstanding what Koni has said these shocks might work best with a tall bumpstop compound that takes compression gradually so the damper doesn't see an impact.

But yeah, talk to Koni...

 

[shogun32]

could you put a ruler against your bump stops so we have a frame of reference? what is the amount of exposed shaft with the car on it's wheels?

 

[TheMegalodon]

could you put a ruler against your bump stops so we have a frame of reference? what is the amount of exposed shaft with the car on it's wheels?

When I was at my dealer having the tech look things over he said there was a “finger width” so 6/8ths of an inch space between the top of the shock body and the bump stop while on its wheels.

• The rear OE bump stop is 3 inches tall
• I cut off 0.625” (as per BMR)
• Total bump stop height 2.375”
• We cut off 0.5” worth I believe (another section in red)
• Total bump stop height: ~ 1.875” (in green)
• Amount of exposed shaft: ~ 1.2” (can’t check this weekend)
• Steeda’s rear short stack bump: 1.5” (for reference)

 

[GT 550]

No worries Ryan, I recall my 'ah hah' moment re bumpstops. Thanks for posting up the data, interesting that the BMR height is greater than the Steeda height but IIRC the Steeda spring might drop a little more?

Also BMR says to trim the cone, one of the cone's functions is to provide progression in the bumpstop compression although it's not hard to see why BMR recommends this in the case of the front bumpstop given its design. Where it's not possible to trim the square end some folks suggest drilling small holes in the top of the bumpstop to try and replicate the rate that's represented by the cone end.

It's easy to disappear down a rabbit hole with this stuff and unless you're a disciplined and addicted modifier with the gear to make spring and damper swaps a snap it can get tedious fast, although there can be satisfaction in being a pioneer.

Good luck with Koni, please let us know what happens.

 

[shogun32]

Why not also cut the black ring off? It's probably just plastic but it's nullifying the ability of that section to compress.

 

[TheMegalodon]

Thank you both your continued responses, suggestions and words of encouragement.
If only it were easier to make adjustments on the fly.

Matt I’m concerned about the impact of cutting off the black ring. However, if I do cut off the section above it I might have to get rid of the black piece otherwise bump stop impact could be harsh.

Even though I’d like to not spend any more money, it’s super tempting to buy the Eibach a Pro kit springs which come with better looking new bump stops and sell the BMR springs. Is that a dumb idea? From the sounds of it the Eibach Pros have progressives rates that match this car well.

For the minimum drop performance BMRs I do not believe the rear springs only drop half an inch when all the pictures of cars I see with 1” drop rear springs sit as low as mine. There’s only 1 finger gap in the rear down from about 2.5-3 finger width gap. Everyone has different width fingers but still. I measured my finger width at the knuckle to be about 6/8 of an inch.

Does this really look like a half inch rear drop? (7/8” up front) - 1” wheel spacers used

 

[shogun32]

Does this really look like a half inch rear drop?

I'm no expert but definitely not. Look at my media page and that's what 0.5-0.75" drop looks like supposedly.

My tires are 275/35. Yours?

 

[TheMegalodon]

I'm no expert but definitely not. Look at my media page and that's what 0.5-0.75" drop looks like supposedly.

My tires are 275/35. Yours?

I always felt like this was a 1” drop because it looks equivalent to other 1” rear drop springs. I was shocked at first with how low it is. I expected the rear to have a gap like the front. The car is sitting level. I’m not surprised I’m having bump stop issues because this rear drop is lower than the 0.5” BMR claims. Not enough of the bump stops is trimmed to work with these shocks. If these shocks need clearance to work properly then I think Steeda’s short stack 1.5 inch PU bump stop may be ideal.

I should reach out to BMR as well to ask what the deal is with these springs.

My summers are 275/40/19 rear and winters are 245/45/19 rear.
heres the winters:

I’ll take a look at your photos and tell ya what I think.

edit: okay wait your car is lowered right Shogun? What springs are you using?

 

[GT 550]

It's not a dumb idea but maybe talk to BMR (and Koni) first to try and ID what the problem actually is. Then get after the solution. The springs should be easy to nail down as they're either at the right height or not.

Understand the temptation to get the Eibach Pros but you don't want to spend the money hoping it's a solution only to find out it isn't. If Koni will tell you what bumpstops they use in that set up it'd be worth a try without spending too much money.

Remember too that manufacturers don't always get it right and there could be incorrect valving in your rear dampers or the springs they sent might be the wrong drop.

 

[TheMegalodon]

Thanks for the guidance. It's pretty rash to think of swapping new parts out and not something I would do unless absolutely necessary. It's so expensive for me as a Canadian to buy parts from the US.

I'll have to reach out to both companies for their insight on this. What's weird with the BMR springs is all of their lowering springs only drop 0.5" in the rear so it's not like they could have sent me the wrong spring. I don't know; it's just weird how low it is and that's impacting shock travel for sure.

I'll speak to Koni as well about what they recommend but there isn't many options for bump stops. There's OE, Steeda, Eibach only available with their springs (those look like good ones too) or trying to find another random vehicle's bumpers like the other guys mentioned. I wonder if Eibach would sell their bump stops separately through special order.

The biggest issue here is this car is my daily so I can't have any real downtime, which can happen if you're trying to make a warranty claim or the manufacturer wants to verify the parts themselves.

I'll try to reach out this week and update everyone on what they say.

It's not a dumb idea but maybe talk to BMR (and Koni) first to try and ID what the problem actually is. Then get after the solution. The springs should be easy to nail down as they're either at the right height or not.

Understand the temptation to get the Eibach Pros but you don't want to spend the money hoping it's a solution only to find out it isn't. If Koni will tell you what bumpstops they use in that set up it'd be worth a try without spending too much money.

Remember too that manufacturers don't always get it right and there could be incorrect valving in your rear dampers or the springs they sent might be the wrong drop.

 

[shogun32]

What springs are you using?

Steeda dual-rates. Supposed to be 0.75" drop.

 

[TheMegalodon]

Steeda dual-rates. Supposed to be 0.75" drop.

Wait your tires are 275/35 right? That’s 1.1” smaller in diameter than my 275/40 summers so that will impact visual difference.

 

[Stone 54]

Hey guys, really appreciate your feedback on the kit.

I am looking to buy the Koni Active struts and shocks and still use the stock spring on my 2017 GT non-pp. I noticed that OP mentioned it will keep the car flat and corner better. But I am wondering if the Koni Active shocks will get rid of the nose dive and squat during hard braking and acceleration?

So is it going to be overall better in terms of performance, vs PP struts and shocks?

My goal is to improve overall handling and maintain ride comfort as much as possible. Let's say 60% performance and 40% comfort. Thanks.

 

[TheMegalodon]

I’d say the kit will improve ride quality on rougher roads as long as they’re not riding on the bump stops; I would trim them even at stock height.

They may help nose dive and squat a bit but normally this is improved by a better set of springs - generally lowering springs because they reduce center of gravity and often have higher spring rates (help manage the car’s weight in direction changes).

At stock height the Koni Actives will work well from my understanding. Steeda and Koni put out a marketing video showing the difference between stock and active dampers in terms of dive and squat under undulating road surfaces. Take a look on YouTube for it.

Hey guys, really appreciate your feedback on the kit.

I am looking to buy the Koni Active struts and shocks and still use the stock spring on my 2017 GT non-pp. I noticed that OP mentioned it will keep the car flat and corner better. But I am wondering if the Koni Active shocks will get rid of the nose dive and squat during hard braking and acceleration?

So is it going to be overall better in terms of performance, vs PP struts and shocks?

My goal is to improve overall handling and maintain ride comfort as much as possible. Let's say 60% performance and 40% comfort. Thanks.

Sponsored