Bilstein and OEM damper specifications

[greenberet]

I recently had a set of Bilstein shock absorbers revalved to OEM 1991 specifications. Since neither Honda Europe nor Acura USA could (or perhaps would) tell me what those specifications were, I bought some new OEM dampers and had them measured. Both Honda and Acura said the correct part numbers for a 1991 5-speed are 06511-SL0-950 (front) and 06521-SL0-950 (rear).

Attached are the measurements Bilstein made of the OEM 1991 shock absorbers and of their own NSX shock absorbers (before revalving). Some information on OEM 1997 shock absorbers is given in the attached article from Automotive Engineering.

While I was at it, I also weighed the shocks:

Honda
- 06511-SL0-950 (front): 2.71 kg
- 06521-SL0-950 (rear): 2.50 kg

Bilstein (including the lower spring base so that it’s comparable to the OEM shock, which has the lower spring base welded on)
- F4-B46-1663-H0 (front): 2.35 kg
- F4-B46-1665-H0 (rear): 2.21 kg

In case someone else wants to revalve shock absorbers, we now have a little bit more information to work with. Happy tinkering!

 

[goldNSX]

Very interesting! I had planned the same as I revalved mine but didn't have new OEM shocks at hand. OEM front is quite linear, Bilsteins are softer at low velocities as I suspected, saves you some comfort but decreases turn-in response.
Where did you revalve them and did you go to 91 specs?

A great advantage of Bilstein having them revalved to whatever you like. Unlike other shocks who are fixed and you don't even know their characteristic. Every shock should come with a diagram of specs IMO.

 

[greenberet]

Yeah, I had the Bilsteins revalved to '91 specs and the work was carried out by Bilstein Austria. I wanted to have Bilstein revalve them at their German headquarters, but they said the quality would be the same and turnaround would be quicker if they were revalved in Austria.

In retrospect, it was good to have the work carried out close to home in order to pesonally meet the guy who did the revalving (Werner Jahrbacher). Bilstein was not thrilled about revalving their shocks to emulate OEM shocks. They said their engineers had developed the shock absorber characteristics on the Nürburgring to improve both the handling and the ride of an NSX. After hearing that Honda's ex-Formula 1 engineers supposedly did 30,000 kilometers of testing on the Nürburgring with input from Ayrton Senna in order to develop the OEM dampers, Bilstein took the OEM specs more seriously.

As you have already mentioned, Bilstein reiterated that their NSX shocks, which are soft at low damper velocities, will give a plusher ride than OEM over small bumps at the expense of turn-in sharpness. They also said that since their front dampers are stiffer than OEM at high velocities, oversteer will be decreased (understeeer increased) compared to OEM.

And I agree that shocks should come with specs!

 

[goldNSX]

Interesting infos! I just gave mine with a data sheet to Rikli who knows the guy at Bilstein Germany. So I had no direct contact with them. Interesting also that their setup gives even more understeering.