Identifying Boge vs Sachs struts
 

I’m ordering new Bilstein front strut inserts for my ‘85 Carrera, but I’m not sure whether I have Boge or Sachs in it right now- does it matter? My understanding is that Sachs inserts are sometimes found in Boge struts, but there is no actual Sachs strut…?

The Inserts are black, and look to be original to the car.

The Boge ones have Boge stamped on the outside, usually facing the wheel.

Take the wheel off, give the strut a good wipe down with a rag, and you should see the familiar B O G E logo — each letter in a rectangle of its own. You can then also confirm the part number to make sure nothing has been changed + ensure you get matching inserts.

Thanks. I was looking in the wrong place for the BOGE markings...

From my photo reel — sanity checking my struts before I got Koni inserts.

http://forums.pelicanparts.com/uploa...1761595316.jpg

There were either only Boge or Bilstein struts for the front axle. For the Boge strut you find many shocks from different vendors incl. a Boge version of Bilstein shocks. Exceptions are the Bilstein struts - they only take Bilstein dampers. Boge struts could be equipped with shocks from Sachs, Boge, Bilstein, Kayaba, Koni, and as said they could also be equipped with Bilstein shocks. But be aware: From the Boge struts are two versions available: earlier ones with inner thread on the top, and later ones with outer thread/nut. Check out which you have. You need the right ones for yours struts. Afaik most shocks available for Boge struts are for the earlier struts with inner thread. Afaik the change from inner to outer thread was either 1985 or 86.
At the rear you can mount any shocks, no changes between the model years. US cars often were equipped originally with blue woodhead shocks. They were the softest ride setups available.
Today Boge shocks aren't available any more from factory, Boge has been acquired by Sachs and later they became part of ThyssenKrupp. But the Sachs brand still exists. So Boge shocks are completely replaced by Sachs shocks. Todays new Sachs shocks are stiffer than earlier times. I suppose that the Kayaba as an oem replacement for the shocks are one of the softest ride setups on the market, no personal experience yet.
Thomas

Definitely BOGE… I’m guessing that these are the externally threaded version? My car was manufactured Dec 1984. Our host’s strut cartridge listings are: up to 3/85. And 4/85 and later, so mine are the earlier 1985 style.

http://forums.pelicanparts.com/uploa...1761616233.jpg
http://forums.pelicanparts.com/uploa...1761616233.jpg

Dave, IIRC, the Pelican catalog lists the same Koni strut inserts for Boge struts from 1969 to 1989. If your car takes the Koni Sport struts, I highly recommend them. I use them and find the external adjustment knob extremely easy and convenient. I crank them up a click or two for autocross, then drop them back to full soft for daily use.

They come with steel ring spacers to adapt to fit different years of struts.

Pete- are you adjusting both rebound & compression with that one knob (I assume so)?

Some adjustability is better than no adjustability, provided you are somewhere in the ballpark to begin with.

The one thing I don't like about the Bilsteins is that they are gas charged, but not serviceable.

Good question. 30 years ago, when I used Koni's on my 914, I recall specifically reading that the adjustment on the Konis adjusted both compression and rebound. That would make sense. I can't find that info in the current literature, but Chat GPT says it adjusts rebound only, and specifically references the rear 8210-1159Sport. So which is it? I'm not sure.

The Bilstiens are serviceable, but you need special tools to do that and recharge the shocks with nitrogen. Elephant Racing and several other vendors can do that, and revalve the Bilsteins too.

The problem w/ adjustability is that there are far more ways to get it wrong than to get it right, The adjustee has to have some skill and knowledge.

Bilstein's are fully serviceable, I've changed length, valve stack, gas pressure, bearings, spindle height and covers on mine.

when changing valve stack you just have to know what you want the resulting curve to look like and t-bar sizes.
You want a digressive curve, for either street or track

Bill- I have a moderate amount of experience tuning my track bike suspension- spring rates, geometry, different damping fluids, adjusting valve stacks, etc… I understand suspensions, as they relate to motorcycles. Cars have many similarities, but from I have gathered, there are definitely some differences… having never sought to have a car shock/strut serviced or re-valved before, I assumed (wrongly) that the only way this would be possible would be to install something like Ohlins, or another $$$$$ damper. This is good news! I don’t feel like I will be stuck now, if the off the shelf damper ends up being unsatisfactory.

Generally-
If I was going to drive car really hard, or track it, the torsion bars would be the first thing I would replace, and I would be working with someone like Elephant to put a package together that would get me close to where I wanted to be, and then start tuning from there. With this car, torsion bars and anti-roll bars will stay stock, at least for now. This will, hopefully, lower my expectations and allow me to be satisfied with something off the shelf, and not going broke!

The fact that our host lists Bilstein specs using some other unit of measurement for compression and rebound than the actual shock manufacturer uses, as well as using different terms to describe the dampers, and they change the part number to something unidentifiable- this has created plenty of frustration for me, when I try to research dampers for this car…!

Or does our host supply dampers that have been custom valved, so the Bilstein part numbers will not correspond? I’m a little confused, obviously.

Pete- if the Komi is only a rebound adjustment, I see that as a positive thing.

I must confess that the Bilsteins I installed years ago on my ‘74 S transformed that car, and that most every other off the shelf damper I have installed on any car has been a disappointment… but I have never tried Konis. KYB’s were a massive disappointment.

Koni, Vons, Bilstein, Ohlins- they are just names. I understand that you can take any damper, so long as you can open it up and you have the time and resources, to make it into whatever you want it to be.

Here, with this Porsche, while I risk being called a Luddite or worse, “confused”, I simply want the car to be a little better than it rolled out of the factory, and not have to redo my work later. I have my old Ducati to tinker with and obsess about seconds at the track. I bought this car and haven’t been able to enjoy it except for the 20 minute drive home, where it went up on blocks. It had nearly 30 years of deferred maintenance, and I decided to put a stop to that on day one, as I felt it deserved better.

I am starving for my 911 experience right now- I bought it to drive, not to tinker, so I’ll be putting another 200,000 miles on this car, as soon as it is running again. I don’t collect things- I want to directly experience operating them. Daily. I lost my first 911 15:years ago, due to unfortunate circumstances, and vowed to replace it. I’m almost there.

You guys are a fantastic bunch, and I very much appreciate you taking the time to help someone who is obviously trying to take a shortcut here, and end up with something less than optimal. But I’ll be fine with something less than perfection, as long as I feel that it’s just a little better than “factory”.

Dave

The factory did a decent job when they decided how to equip these cars, but they were aiming to please a very wide variety of expectations and uses.
They all have the same basic t-bars which did get larger over time, and just a few different sway bar sets

They used twin tube shocks for the less demanding driver because they are cheaper and comfier, they used Bilstein's for the more demanding performance-oriented driver.

what has changed over the last 60 or so years is the understanding of how to make shocks better suit both camps

the old style shocks used linear valve stacks , whose specs were usually in nm at a single, usually too high, speed. This is what you see in the catalogs, The Pelican listing is not very informative.

For a 911 front there are 2 lines Bilstein, b6 & b8
the b6 has several variants as does the b8
stock would be a b6
Bilstein b6 frt strut, 16.01lbs part#35-001270 1665/1605 nm @ .52m/s

these are linear and the speed is on the high side of where you are interested in. The sad part is that it doesn't really describe much other than in comparison to other shocks sped the same way.

ideally the shock would have at least 3 regimes, each adjustable for rebound and compression,
low - maneuvering
medium - braking
high - larger road irregularities

For the street you don't need that and for us amateurs it's overkill even for track use.

so a reasonable compromise short of MCS or JRZ or Penske or Tractive is a digressive valve stack, These raise the damping at lower speeds and middle speeds while capping high speed, for a better ride

Even w/ a digressive stack you need to match the rates at least w/ the t-bar rates.

Elephant is a great resource for those that want a bit more from their 911

The stock hd Bilstein i mentioned above is ok, there are stiffer versions of the b6 and also of the b8, and some versions have different lengths, but w/ stock t-bars you really aren't interested in most of these options.

What is interesting is the Vonn insert option for Bilstein struts, These retain the desirable upside down/gas pressure features of stock Bilsteins but are digressive and come w/ a choice of different damping levels.

When modifying the handling of these cars I'd start w/ wheels and tires, this is the biggest bang for the buck and also the most visible.

Once you get better grip from the wheels/tires roll becomes the next and most objectionable target to address, Stiffening the suspension is a 2 edged sword, as the stiffer it is the less mechanical grip is available, so you don't want to go stiffer than you really need for your use.

once the t-bars are set then you address ride height and shocks which are inextricably entwined. The ride heigh and t-bars determine what's needed from the shock specs, things like spindle height, steering knuckle height and shock length should all be spec'd to suit ride height, wheels & tires

lastly sways are used to tweek the above if necessary

My car was built in 07/85 so it was the later build with different CV joints and axles, and the different front shocks.

If your car was built in Dec of 84, for sure that is the earlier style of shocks.

Doh, Just realized that you are looking Bilstein inserts for Boge

34-001141

1505/1160 nm @.52m/s

non rebuildable as far as i know

Thanks for all the great info, Bill.

Bill, which rear shocks would you recommend? I have read here that quite a few owners have gone with the Bilstein sport in the rear?

Before I went to custom valving used hd front and sport rear, I didn't notice a huge difference from the o.e. hd/hd combo, but it was way better than the sport/sport that I tried for a short period of time

hands down custom digressive all around is the best by far, short of MCS or such.

I'm trying to decide between taking my HD/Sport Bilsteins out and having them revalved or just getting a new set of Vons... I'm not sure I'd notice a difference if they are both valved for the same car setup... only real difference at that point is the lower bushing on the rears with Vons is not rubber... and I think the Vons are shorter....

Thank you.

Dave, as Bill and others have pointed out here many times, suspension setups require juggling trade-offs. Thus, if there's any way you can drive other people's 911's with different setups, you should do so.

Are you a member of PCA? If not, join, and if so, check around your local region for members with modified suspensions. Explain to them what you have written here, and ask if you can test drive their cars. Most PCA members will be happy to discuss and demo their cars and let you drive them. Another source: Go to a local PCA-sponsored autocross and chat with the drivers about their cars. Many AX 911's have suspension mods, some mild and some extreme.

That said, I think you're gonna find out that increasing the T-bar size is one of the first mods people do (along with changing the shocks) for a couple reasons: It's relatively inexpensive; it decreases the roll of the car; and it allows the ride hight to be lowered a little more without bottoming. For a street car, keep it conservative: 20mm front/26mm rear, or a little more sporty but still good for the street, 21mm/27mm.

Don't agonize over what's "best". Pick something a bit more than stock, and spend time driving your car. That's what you bought it for. After you drive it for a few thousand miles, you will have a better idea of how you use it, and whether you want to make other tradeoffs for your uses. And, you'll have fun doing it.