Bilstein B6 and B8 explained

[Racecomp Engineering]

We've received lots of questions lately on the Bilstein B6 and B8 dampers, so I thought I'd do a rundown on these two fixed perch shocks. I just got a set in for my own car (because I really like them!) so I thought it was good timing.



Short version
The Bilstein B6 (formerly called Bilstein HD) dampers are an OEM fitment replacement, fixed perch, monotube damper with inverted front strut. The Bilstein B8 (formerly called Bilstein Sport) have a few differences and are specifically intended to be used with lowering springs, but have the same valving as the B6 dampers. I recommend the B6 even with lowering springs. We'll talk about that more later.

These are excellent as a replacement for your high mileage OEM suspension or as a performance upgrade with lowering springs. Both work with lowering springs. They ride well and they're durable.

Is a monotube like the Bilsteins better than a twintube?
Sometimes. Monotubes and twintubes each have their advantages and disadvantages, and either one can be good or bad. Monotubes are generally more responsive and sometimes better on bigger bumps, sometimes at the expense of a "busy" ride over smaller bumps. Bottom line, Bilsteins are good and the valving is really nice.

What is an inverted strut?
An inverted strut is upside down. This means that inside the Bilstein front, the base of the damper is actually up at the top inside what looks like the massive shaft. The actual shaft is down at the bottom inside the yellow body. This reduces unsprung weight slightly and improves resistance to side loads. So, it's a little more durable. Nice for high grip track cars and rally cars. The rear is a conventional shock, not a strut, so they don't see the same side loads and you don't usually see them inverted. You also don't usually see twintubes inverted.

Where are the bumpstops in the front?
Since it's inverted, the bumpstop is inside the lower part of the strut body. Yes you can open these up and have a look, but I don't really recommend replacing the internal bumpstop. The non-inverted rear uses a regular bumpstop you can see (you reuse stock).

Are these better than coilovers?
It depends! The Bilstein damper itself is very high quality and certainly better than what's in most low end coilovers. You're limited in that you can't easily run coilover springs, so your choice in spring rates and overall drop isn't the same. If you don't need stiff springs or a bigger drop, these make a lot of sense. If you want more than 300 lbs/in spring rates or like to make adjustments, I'd consider coilovers. But these ride great, are still good on track, and are a lot more simple than an adjustable coilover.

Are these rebuildable/revalveable?
Yes! You can send these to Bilstein (and a few other places) and have them rebuilt to factory fresh or revalved to custom specs.

What kind of springs can I use with these?
Stock works. Our RCE Yellows are great too and the combo with Bilsteins is fast, fun, and simple. Other lowering springs work (Swift, STI, Eibach Prokit), but I'll always recommend a relatively mild drop.

Should I get B6 or B8?
Bilstein B8 are supposed to be paired with lowering springs...but we still recommend B6 instead. The difference between B6 and B8 is NOT in the valving. That's identical. The B8s have slightly less droop, or extension travel. The idea is that shorter lowering springs don't need the droop travel or wouldn't be fully secure with longer travel. In reality, all lowering springs for this car are designed around the OEM dampers dimensions so this simply isn't needed and actually droop travel is good. So, get the B6s. The B8s are still very good if you have them.



- Andrew

[Racecomp Engineering]

I'll post side by side pictures with stock dampers here.
Covid is delaying me installing this set for now.

A lot of places carry these, but they occasionally have supply issues. We do have a couple sets of these in stock and know a good bit about Bilstein from experience and can help you put together a good package.

- Andrew

[Dadhawk]

Originally Posted by Racecomp Engineering

Hey, make sure he's careful with that, it could be dangerous!



Joking aside, look forward to reading your comparison.

[TommyW]

The stock vs B6 comparison photo will be great to see

[marco_mc22]

Seems your dog likes them a lot as well

[JIM THEO]

Do Bilstein B6s work better than the OEM tS Sachs (MY18) with the tS pink springs?
I have read for some reason front springs on B6 sit higher so car has height difference, is it right?

[jhalagian]

Originally Posted by JIM THEO

Do Bilstein B6s work better than the OEM tS Sachs (MY18) with the tS pink springs?
I have read for some reason front springs on B6 sit higher so car has height difference, is it right?

I believe the thought process is usually Bilsteins over the Sachs when purchasing new, but not enough of a performance difference to justify upgrading.


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[Racecomp Engineering]

Originally Posted by JIM THEO

Do Bilstein B6s work better than the OEM tS Sachs (MY18) with the tS pink springs?

Unsure, I have never tried Bilstein B6 with tS pinks. I think it would be very good but I don't know how it would compare to the tS shocks.

Originally Posted by JIM THEO

I have read for some reason front springs on B6 sit higher so car has height difference, is it right?

Yes that's another good point I should add. Since Bilsteins generally have a lot more gas pressure than OEM shocks, the car will sit a little higher due to the lifting force of the gas. It's only a few mm though.

- Andrew

[JIM THEO]

Originally Posted by jhalagian

I believe the thought process is usually Bilsteins over the Sachs when purchasing new, but not enough of a performance difference to justify upgrading.


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I mean for someone with tS and a lot of miles that wants Sachs replacements

[Racecomp Engineering]

Originally Posted by JIM THEO

I mean for someone with tS and a lot of miles that wants Sachs replacements

Ah, in that case, I think they would be very happy with Bilstein B6 and that's what I would probably do myself.

- Andrew

[JIM THEO]

Originally Posted by Racecomp Engineering

Ah, in that case, I think they would be very happy with Bilstein B6 and that's what I would probably do myself.

- Andrew

Thanks, I thought you have a BRZ non tS and an Impreza STI.
By the way tS pinks are almost linear compared with other springs, aftermarket STI (Bilstein) pinks included

[Racecomp Engineering]

Originally Posted by JIM THEO

Thanks, I thought you have a BRZ non tS and an Impreza STI.
By the way tS pinks are almost linear compared with other springs, aftermarket STI (Bilstein) pinks included

I meant if I had a tS.

- Andrew

[Drifter X]

Great information! When should I be replacing my SACHs struts? Will I notice a difference upgrading to the B6s? I’m on RSR down sus springs.


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[JIM THEO]

Originally Posted by Drifter X

Great information! When should I be replacing my SACHs struts? Will I notice a difference upgrading to the B6s? I’m on RSR down sus springs.


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When you have the money and a reasonable amount of miles...

I am sure that B6 are an upgrade over OEM Sachs, the question is do they work better with OEM pinks?