JHall250

So I got my Bilstein shocks in the other day and after some Sherlock style observation I realized that Bilstein's are much MUCH larger in diameter than Koni's. Koni bodies are 42ish millimeters in diameter and Bilstein's are 50mm
So after realizing there is a huge size different I grabbed my calipers, went out to my car, measured the shock tower hole and realized something...it's also 50mm.

So I call up Ground Control and ask them if their extended top hats fit Bilstein's and the guy was like yah, of course we're Ground Control after all. I ask him if he's sure they will work and he again reassures me they do. So I guess Ground Control top hats either cheat physics or they don't actually work with Bilstein's which leads me to my next question. Does anyone here run Bilstein's with extended top hats and if so what are the dimensions of the extension piece?

Thanks for the input.

beanbag

Let me tell you a little story about a conversation I had with some other motorsports guy:

Me: "Does Ground Control know what they are talking..."
OMG: "No."

The 50mm OD Bilsteins will not work with the GC top hats unless you like jamming metal into metal.

With that said, the Steins may have a shorter body length than the Konis allowing for more suspension travel anyway.

I do have custom extended top hats in the rear with Bilsteins, but that is only because my shocks have excess stroke and I wanted the tophats to pull the shaft higher so the springs don't come loose on full droop. There are spacers and bumpstops inside so I don't jam metal into metal.

U need to measure your shock lengths and strokes and etc to set up these new shocks.

JHall250

To send the record straight I installed my Bilstein Sport front shocks with 400lbs/in Ground Control springs and extended top hats. The GC extended top hats do work and, when compared to the OE unit, place the bump stop up about 24mm. HOWEVER the flange on the lower part of the top hat also extends down to cup the bump stop which heavily influences the bottom out characteristics in a different way than stock top hats. This combination is very effective when combined with the damper fork and utilizes every last bit of negative travel before bad things start happening (like upper arms colliding with the shock towers).

In summary GC top hats:
-do provide more negative travel (roughly 24mm)
-also modify bottom out characteristics (makes the bump stop compression process shorter and more abrupt)
-shocks don't contact top hat (even with 50mm body Bilstein's)
-when combined with the damper fork trick the car completely bottoms out just a few mm before the upper arms contact the shock tower.

Side Note: in case anyone was wondering OTS Bilstein Sport shocks aren't tuned to handle 400lbs/in front and 600lbs/in rear linear spring rates...at all. I have new pistons and valving on order from Bilstein.

STN_Pat

shock tower hit is much more appreciable than shock body bottoming out

but that's just me

JHall250

Far more because you KNOW you're getting every bit of travel you can out of the suspension. It's quite genius really, Honda designed the EK so that if the damper fork breaks the upper arm hits the shock tower before the frame/oil pan/crossmember hit the ground.

beanbag

So the shock doesn't actually go thru the top hat and you are only using the extended-ness to waste droop travel. There are better ways to waste droop travel, including having a rebound spacer put in when you get your steins revalved. This is actually better for the shock because it reduces the side load on the shaft bushing.

JHall250

I have Sport's in the front with the damper fork moved all the way up to the beginning of the body. I have a decent amount of preload on the springs and the ride height is still even with the fender, I could benefit from more front droop actually. I will try that on the rear to minimize the droop. Also my OE front lip drags on the ground once the car gets up on 3 wheels, good stuff.

As for the revalve I'm taking out those digressive pistons and putting in linear ones with shim stacks recommended for my spring rates.

Ecugrad

Hmmmm, how did you come up with your valving? Currently have Koni's but have been thinking of switching to the Bilsteins and have no idea how to valve them.

JHall250

Bilstein used to sell parts directly but not enough people actually order from there so they now sell parts through a distributor who is more than willing to help you with valving, partially because he is selling the parts and the other part is he's a great guy.

Bilstein's are cool because they have 3 different pistons (progressive, digressive, and linear) so depending on your application there are many different way to tune your shocks. I'm using Ground Control straight rate springs so I am sticking with a linear pistons and valving to match my rates. I'll post a link to his website when I get access to my work computer tomorrow.

liam821

I know this is old, but I was searching for something and came across this thread and wanted to add my 2 cents. I also run GC tophats (front and rear) with Bilstein shocks...

I run 600/800# springs and like JHall250 said the standard Bilstein valving isn't sufficient. My shocks were sent into Bilstein to be revalved and since I've been extremely happy with the setup. The ride, though stiff, is outstanding with very good compression/rebound control - very progressive and linear. I've been very happy with this setup.

JHall250

FYI in this picture your bump stop is installed upside down. Also thanks for the post, I'm hoping to get more people trying Bilstein's as they are a very good shock for the money.

After having Koni's and Bilstein's I'm never going back to Koni's, I liked my improperly tuned Bilstein's over tuned Koni's. I will say this though, machining down the damper body for more negative travel (the damper fork trick) anymore than about 5mm is a bad idea.

I originally had GC tops hats AND an additional 15mm machined off the damper body. Lets just say my bump stop was "helping" my lower arm bottom out on the body. Took 10mm back out so it was only GC top hats and 5mm on the shock body and now everyone is happy.

liam821

Yeah, I had the bumpstock upside down in that picture and have since fixed it but thats the only picture I have of them. And I agree with you about the Koni, the Bilsteins are so much better. Although i've never tried the Koni 3012 race shocks...but for that much money i'd be looking at ohlins/penske/motons...

Good to know on the damper body height, mine are unmodified and work well with the GC hats.

JOE BD-0

Subscribed...Wanting to try Bilstein's. Civic/crx track only (550/800). Top hat or no top hat? More info please...Thanks guys.

beanbag

Try measuring your suspension first.

Edit: I can't believe I have to dispense this kind of advice.

snotrocket

I've been thinking about purchasing Bilsteins because of the monotube design. Right now my spss3s are to low and I'm not happy about running excessive preload on the street. Are the Bilsteins adjustable? I'm in for the link Jhall250 has. I'll be running 500lb front and 750 rear.

JHall250

Bilstein's are user serviceable but not externally adjustable in terms of damping.

To Joe: Top hats are always a good idea unless you have shorter body shocks.

solo-x

Your understanding of droop travel and preload is wrong. Increasing droop travel by shortening the droop limited won't have any affect on your ride height, all else being equal. The exception is if your shock is fully extended at static ride height (referred to as zero droop). Just wanted to clarify that.

Also, there is nothing wrong with preload. I run 350lbs of preload myself. Finally, the bump stop works just fine either way.

JOE BD-0

Yes I knew that thanks. My koni yellow double adjustables are shortened / re valved which is why I'm looking for some more real world info on the Bilstien set up from the "experts" or at least the guys that have the setup...thanks guys...

JHall250

What are you talking about my understanding of droop travel for, I never said droop travel limit had anything to do with ride height. The top hats do not have any effect on ride height and I never said they did. Changing the position of the damper fork relative to shock body does affect ride height. Also I never said there was anything wrong with preload so I don't know where you're pulling that from either.

Turns out the reason things didn't seem happy up front was because the amount of additional negative travel gained by both the 15mm of shock body shortening and 25mm of additional travel provided by the top hats was a bad idea. I added 10mm of length to the effective shock body length which made things better but it seems that there is still the occasional upper arm contact with the shock tower. I'm planning on adding the additional 5mm back into the effective shock body length and testing it for contact but from what it seems the top hats extract about as much negative travel as you can safely get from the front end of an EK.

I have Sport's in the front with the damper fork moved all the way up to the beginning of the body. I have a decent amount of preload on the springs and the ride height is still even with the fender, I could benefit from more front droop actually. I will try that on the rear to minimize the droop. Also my OE front lip drags on the ground once the car gets up on 3 wheels, good stuff.

beanbag

There is nothing you can do to fix this besides run more bump stop or raise the suspension.

Kozy.

Why so much? What effect does actually have on the car? You are the only person I have seen that runs a significant amount (outside of single seaters) and would actually know what it was doing...

JHall250

Or add 5mm to the effective shock body length which is what I plan to do next. Also I was thinking about getting harder bump stops as the GC top hat bump stops seem too soft, that would also slightly limit the negative travel during extreme compression situations and, hopefully, yield better bottom out characteristics.

beanbag

Why don't you just clamp the shocks in the forks at the normal location, like most normal people?

JHall250

I wanted to make sure I was getting the most amount of travel possible. After I add an additional 5mm shim to the existing 10mm the damper fork will be back in the stock location and I will be normal people again.

solo-x

You said that with "quite a bit of preload" your ride height was still lower then you'd like. You then said you could use more droop travel. It seemed to me that you thought that more droop travel would raise the car which would be incorrect. Increasing the extended length of your shock/fork combination would not increase your droop travel, but would increase your static ride height.

The preload comment wasn't directed specifically at you, though I can see how you might have thought that. It was directed at the general concession that preload is bad and/or unnecessary.

To answer Komodo, the reason I run so much preload on my car is quite simple. With big Hoosiers on grippy concrete the inside front has very little load on it while cornering near peak lateral acceleration. Since it is unrealistic to assume I'll never encounter a bump while cornering, I run a bit of preload to insure that the suspension can still follow the contour of the surface if a bump is encountered. Basically, I don't want to reach max extension of the main spring prematurely as that is effectively the same as droop limiting the suspension. Droop limiting the front of a fwd car isn't good for grip, and especially bad when you use a torsen diff as I do.