Bilstein strut cap, need help.

[psiconauta911]

Hi,

I´ve bought some B4 to replace my S2 Avant tired front dampers and noticed they came with 50mm strut cap and my struts are 55mm, can I reuse the original strut caps? If not where can I get Bilstein 55mm strut caps?

Thanks in advance for the help.

[Bowie69]

When you buy the dampers they have a spec on them, either 50 or 55mm, and as you have found, the caps are supplied.

[B5NUT]

If they have the 50mm cap then they won't be the correct damper for your S2.

[psiconauta911]

Well I guess I bought the wrong part, I did refer to the Bilstein Catalog here: https://web1.carparts-cat.com/defaul...04&14=4&12=130 for options but since my struts are 55mm I can only choose 55mm dampers right?
The 50mm in their catalog is for S2 without sport suspensio if they exist I suppose.

[B5NUT]

Been there and got the Bilstein tee-shirt. See my old thread https://www.s2forum.com/forum/genera...18#post2111072

Looking at the last post on that thread you need part number 34-030868. For the UK they were out of stock and they were waiting on delivery from the factory which according to Bilstein UK was going to be Feb/Mar time. I gave up in the end with Bilstein and went Koni. They fitted first time with no problems.

[Lago Blue]

Bilstein's use of 'sport suspension' does not mean 'Audi' sport suspension here. What Bilstein intends with that term is that, for springs shorter than those from the factory, B8s (being shorter than stock by approx. 1" at full extension) will still keep those under sufficient tension (to not fall out of position within the strut perches); when the struts are at full droop. If you have any sort of factory springs, the B6s will be fine with them.

The 55mm version gets you a slightly larger dia. damper (36mm piston OD) that will be less stressed than the 50mm (@30mm OD). This gives the 55 a fair performance margin over the 50 due to the overall increase in volume and surface area. The 55 should therefore last longer given the same work.

Here's a handy guide for selection, install and removal:

https://www.s2forum.com/forum/techni...-strut-install

[psiconauta911]

So from what I understand the ones I´ve got are useless even if I had the 55mm strut caps right?

[B5NUT]

I would not use them. Best find the correct shocks.

[Lago Blue]

Re: "So from what I understand the ones I´ve got are useless even if I had the 55mm strut caps right?"

Yes, I'm afraid so (unless you want to convert to 50mm struts, but that would be somewhat retrograde), even if you had 55mm caps, those are for the larger OD dampers, not the 50s. Both sizes of cap-nuts are made to carry specific rubber seals (see photos in guide) which must also mate with the correctly corresponding chrome tube (either 30 or 36mm OD), and are not interchangeable between the two cap-nut sizes. I know it is sometimes frustrating, we must endeavour to know more than the folks who simply want to sell us something. Bilsteins, correctly installed are really worth the trouble it takes to get the correct ones and tackle all the install details and preventative tips in that guide. Did you get a proper Bilstein wrench too?

[psiconauta911]

Ok, I´ll leave it to the 90 20v, must see if the struts are 50mm. Must go and find another.