GS/SS Front Shock Oil
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Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1153
Location: Siam
Mon Nov 18, 2019 6:54 pm quote
I am going attempt to change the oil in my original front shock (for SS180). I have figured out the process, but I'm confused on the type of oil to re-fill it with. I have read all kinds of numbers: Mobil 62 (10W30 SAE), Shell Tella 13 (10W SAE), Shell Morlina 10 (10WSAE), or "motorcycle fork oil" 5W SAE.

Apparently the oil must have "seal swell" characteristics to cause the O-ring seal to swell for a tight seal around the shaft. The problem is that all the oils that I see currently available have additives to prevent seal swell.

Does anyone know of a simple, non-high tech oil I can use? I'm not racing and I'm not picky. I just do not want the rubber O-ring to disintegrate after I've done the work.
Hooked
1955 Allstate 1958 lambretta 1965 Allstate 1968 sprint
Joined: 20 Jul 2017
Posts: 397
Location: Central california
Mon Nov 18, 2019 7:03 pm quote
Shock oil
The additives in Lucas pwr steering stop leak is the additive your looking for. Not sure if this helps, but it might be something to look at.
Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1153
Location: Siam
Mon Nov 18, 2019 8:27 pm quote
Re: Shock oil
Sjanuary wrote:
The additives in Lucas pwr steering stop leak is the additive your looking for. Not sure if this helps, but it might be something to look at.
That makes sense. It probably swells the O-ring to stop leaks which is what is necessary for the GS shock. Thanks very much.
Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1153
Location: Siam
Tue Nov 19, 2019 7:33 am quote
Through a little more digging, I may have found the best oil. Shell Morlina 10 is now called Shell S2 BL 10. It's a light mineral based oil. I've ordered some, so when it comes, I'll overhaul the shock, ride it, see how it holds up, and then post a result.
Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni
Joined: 13 Oct 2012
Posts: 7507
Location: Ashburn, Va. Home to the Internet
Tue Nov 19, 2019 12:52 pm quote
Why not use Fork Oil, kind of what it is made for. You can get it in different weights.
Hooked
58 VB1T, 81 100 Sport
Joined: 06 May 2019
Posts: 173
Location: Long Beach, CA
Tue Nov 19, 2019 1:23 pm quote
WEB-Tech wrote:
Why not use Fork Oil, kind of what it is made for. You can get it in different weights.
Seconded. Most cycle shop suppliers will have a variety.
Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1153
Location: Siam
Tue Nov 19, 2019 3:35 pm quote
The fork oils I have seen have additives to prevent seal swell. Evidently, from a blog I've read, the seal or o-ring in the GS shock must swell. Which is, well, just swell.
Enthusiast
Vespa GS160mk1 / Vespa GTS300 super / Vespa LX50 4V
Joined: 26 Nov 2016
Posts: 64
Location: The Netherlands
Thu Nov 21, 2019 12:02 am quote
I used fork oil 15w because i get tired of the fork diving.
In combination with the Newfren Antiaqua itís a great setup, no more diving and i can use the front brake very well without a jamming front wheel.
The fork oil is without seal swell but in combination with the new modern seal rubbers it is not needed.
I made a topic in Dutch but hopefully the pictures are clear enough:
https://www.vespaforum.be/index.php?/topic/30716-revisie-van-de-originele-gs160-schokbrekers/
Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1153
Location: Siam
Thu Nov 21, 2019 4:30 am quote
Pilaf wrote:
I used fork oil 15w because i get tired of the fork diving.
In combination with the Newfren Antiaqua itís a great setup, no more diving and i can use the front brake very well without a jamming front wheel.
The fork oil is without seal swell but in combination with the new modern seal rubbers it is not needed.
I made a topic in Dutch but hopefully the pictures are clear enough:
https://www.vespaforum.be/index.php?/topic/30716-revisie-van-de-originele-gs160-schokbrekers/
The link is very, very useful. Thank you very much.
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