Koni Active Shocks

[TheMegalodon]

Anyone here having issues with rear bump stops? I feel like the Special Actives are underdamped in the rear and regularly hitting the bump stops. I’ve trimmed the top two sections off leaving only one section before the black ring. I’m getting rubber bouncing noise from the rear over multiple sharp bumps. There’s barely any clearance for shock travel - maybe two finger widths. Not too happy at all. Everything is tight but something is up. Fronts are fine thankfully.

Mine are paired with BMR SP763 minimum drop springs which claim a 0.5” drop in the rear but sometimes feels lower than that.

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[slaslo]

Got them on but car is now stored for the winter. Drove about 10 miles on them and could feel a difference, especially on rough road, but will not be able to really evaluate until next spring. I only have 150 miles on the car, but it is my 3rd S550 so I am very familiar with ride characteristics.

 

[JCFoster]

@JCFoster and @RNMAAS how's it going with the new dampers, still happy? Grateful for your feedback and anyone else's who's been running these.

Cheers

I’m still running them and they are definitely better than oe shocks that came on my car in ‘16. I test drove a lightly used ‘19 a little bit ago that was the same configuration as mine. Both non-pp GT with 18” wheels and the ‘19 rode a tad better. I got to wondering why and found out Ford has a different version of the struts and shocks for the ‘18 and up.

I didnt get a chance to see if the ‘19 had the bad bounce or hop in the front that the 15-17’s had, but it general it road well enough I probably wouldn’t spend the money to upgrade unless it was doing something annoying.

The only annoyance I get is the rear make some noises while going slow over some rough asphalt. Other than they’re quit and work well.

 

[TheMegalodon]

‘The only annoyance I get is the rear make some noises while going slow over some rough asphalt. Other than they’re quit and work well.

Okay so I’m not the only one! What noise are you hearing from the rear end with the Konis? Are you lowered as well? Did you trim your rear bump stops and how much?

thanks

 

[JCFoster]

It’s a light bumping noise at slow speeds over a rough section of my road. I changed the shocks out to see if it was the oe mount, but it’s just the shocks. I’m on stock springs and upper mounts. I thinks it’s just the internals of the shocks. I only hear it just as I’m leaving home.

 

[TheMegalodon]

It’s a light bumping noise at slow speeds over a rough section of my road. I changed the shocks out to see if it was the oe mount, but it’s just the shocks. I’m on stock springs and upper mounts. I thinks it’s just the internals of the shocks. I only hear it just as I’m leaving home.

Okay so you’re not hearing this while driving on your regular routes? So you hear this at stock height with factory strut mounts? Wow that’s interesting. What surprises me is all of the owner reviews of this shock and strut setup, nobody mentioned rear shock noise. I thought it was a safe bet to try these since it’s claimed they do better on rougher roads. Even Koni’s/Steeda’s marketing video shows the improvement on an S550 Mustang.

I’ve had nothing but headache with mine paired with minimum drop springs. It feels like the rear shocks don’t offer enough compression strength and bottom out on the bump stops over multiple back to back jarring bumps, which is what I thought they would manage better than OEM.

Wish I would have known about the Bilsteins because it sounds like their monotube rear shocks offer much better support.

 

[shogun32]

It feels like the rear shocks don’t offer enough compression strength and bottom out on the bump stops over multiple back to back jarring bumps,

you need to measure stroke length unladen and laden. Granted that's a tad tough with the plastic grime shield in place. I believe there is supposed to be 3 inches at full slack about 2 at static loading. But I may be wildly mis-remembering. @SteedaTech should be able to illuminate.

 

[JCFoster]

Your correct, I don’t hear anything other than just leaving my house at a slow speed. I noticed that when I put the bump stops and dust covers on they compressed easily compared to the oe’s. I wonder if the bump stops Steeda sells would help with that or a different shock mount that would raise the shock to give it more travel?

 

[GT 550]

Seems you're both getting noise but under different circumstances.

Ryan did you use trimmed oe bumpstops or trim the Koni ones? Bumpstop tuning can be a black art. They tend to act either as a simple physical barrier to stop the damper bottoming out (usually the short version) or do this while also playing a part in the overall damping function (usually a much taller version that's always in play). OEMs increasingly seem to do the latter in later models. I once received a set of Konis for a car with minimal suspension travel and the bumpstops were like sponge rubber, very disappointing, and it took quite some time to find the right ones which is unnaceptable IMHO.

I'd suggest contacting Koni. I reached out to them a while back with some general questions about these dampers and they were nothing but helpful, and suspect they'd happily work with you to resolve the issue. Given these are quite new they'd probably welcome the feedback as it could be a manufacturing issue.

I'm assuming you both clocked bushings etc when installing...

 

[TheMegalodon]

Thanks for the reply man. I trimmed the OE bump stops according to BMRs instructions for their Sp763 minimum drop performance springs. After install I had the bushings indexed and proper alignment. The issue didn’t present itself during the first 1000 miles that included an 800 mile road trip.

After it got a bit colder and I put my winter wheels on, the noise started to present itself slowly and then got louder. My winter tires have the same tire height in the rear as the OE PP tires.

Took the car to my dealer to have them check everything out to make sure nothing dangerous was loose. Everything was tight except the strut top mount nuts which had loosened from the bump stop impact. Tech claimed there was only a finger width of travel from shock body to bump stop when laden. We cut off another section of the OE stop to provide more clearance but the noise is still there.

Koni doesn’t supply bump stops with their dampers. Just bump stop spacers (plastic rings) for whatever the hell they do. I feel like removing them.

I should contact Koni about this. Was curious if others have seen similar issues.

I thought I was going conservative with minimum drop springs that have 170f/740r spring rates (within 5% of OE PP springs) and Koni Special Actives are supposed to be a good pair for rougher roads. Steeda makes their version of the active shocks and claim they work well with sub 200f/800r spring rates but obviously they could valve them differently than Koni.

Seems you're both getting noise but under different circumstances.

Ryan did you use trimmed oe bumpstops or trim the Koni ones? Bumpstop tuning can be a black art. They tend to act either as a simple physical barrier to stop the damper bottoming out (usually the short version) or do this while also playing a part in the overall damping function (usually a much taller version that's always in play). OEMs increasingly seem to do the latter in later models. I once received a set of Konis for a car with minimal suspension travel and the bumpstops were like sponge rubber, very disappointing, and it took quite some time to find the right ones which is unnaceptable IMHO.

I'd suggest contacting Koni. I reached out to them a while back with some general questions about these dampers and they were nothing but helpful, and suspect they'd happily work with you to resolve the issue. Given these are quite new they'd probably welcome the feedback as it could be a manufacturing issue.

I'm assuming you both clocked bushings etc when installing...

 

[TheMegalodon]

I’m actually in touch with Steeda to order a set of their adjustable bump stops so I can use the rear short stack, but sadly the shipping prices to Canada are ludicrous (2/3 the cost of the bump stops). I don’t know if I want to waste so much money on shipping for some pieces of rubber. They need to get back to me with a quote and I was hoping they could sell me just the rear set.

My front struts are fine, no noises or issues with OE bump stops trimmed according to BMR

Your correct, I don’t hear anything other than just leaving my house at a slow speed. I noticed that when I put the bump stops and dust covers on they compressed easily compared to the oe’s. I wonder if the bump stops Steeda sells would help with that or a different shock mount that would raise the shock to give it more travel?

 

[shogun32]

look for an Ohlins dealer near you. I think the shock shaft is 12mm? The motorcycle 'twin-shock' parts use that size I believe. Otherwise you should be able to find a Kayaba distributor. If 12mm isn't handy 14mm will suffice. You can use an o-ring to hold it in place if you really care.

Now that I remember, Elka Suspension is on your side of the border. GIve them a holler. The other option is to see Koni-NA has as their authorized rebuild companies in Canada and have them supply bumpers.

 

[GT 550]

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]

(ed. Hard) bump stops should never be used as part of a damping curve. They are a last ditch catastrophic damage avoidance mechanism. If you're on the stops, the only thing left to act like a suspension is the tire sidewall.

If you're contacting the bump stops with any kind of regularity (on the street in particular) the stops are way too long or your springs aren't supporting the weight of the car adequately as it shifts around. If you're contacting the stops on (not too severe) square edged bumps, the compression damping and spring combo aren't able to decelerate/dissipate the bump energy before running out of travel. One or both need to be increased.

 

[GT 550]

Hey Matt I may have failed to explain my point no doubt this does it much better...

https://www.vehicledynamicsinternational.com/features/insights-into-bump-stop-tuning.html

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