Front suspension upgrade Vespa 125 GTR 1974. What to do?
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Member
Vespa 125 g.t.r.
Joined: 08 Jan 2020
Posts: 10
Location: Sweden
Tue Apr 27, 2021 1:23 am quote
I'm looking for at front suspension/spring upgrade for my GTR from 1974. What are the best options? I'm looking for better performance but nothing too expensive. I want to keep it as close to stock looking as possible. Any insights or experiences to share?
Hooked
1972 Vespa GTR, 1963 Lambretta LI 125
Joined: 05 Nov 2018
Posts: 170
Location: Halifax, England
Tue Apr 27, 2021 4:45 am quote
I'm interested in this post. My 72 GTR dives like crazy. I have a stiffer spring that standard and have tried a few different dampers. I'm currently using Forsa which is better than the Escort I was using. I see it as dreadful design and can not understand why it was ever made like it is to start with.
Anyone got any great simple mods to this problem?
bodgemaster
63 GL, 76 Super (x 2), 74 Primavera (x 2), 06 Fly 150
Joined: 26 Sep 2013
Posts: 5830
Location: So Cal
Tue Apr 27, 2021 6:27 am quote
Look here:

Fronk shock
Addicted
GL, PK, PE200 with hack, Sears Rust Badge
Joined: 24 Apr 2012
Posts: 995
Location: Deep in the heart of Texas
Tue Apr 27, 2021 6:37 am quote
These look stockish and reduces the diving a lot. I have the 60psi version and they work great. The price has gone up since my purchase. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSM
Silver is out of stock but the black is available. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FBM
The silver 100psi is available but the higher the psi the quicker the rebound.
https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSL

There are many choices out there that are better then stock but these worked for me and still looks stockish.
Member
Vespa 125 g.t.r.
Joined: 08 Jan 2020
Posts: 10
Location: Sweden
Tue Apr 27, 2021 7:31 am quote
rowdyc wrote:
These look stockish and reduces the diving a lot. I have the 60psi version and they work great. The price has gone up since my purchase. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSM
Silver is out of stock but the black is available. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FBM
The silver 100psi is available but the higher the psi the quicker the rebound.
https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSL

There are many choices out there that are better then stock but these worked for me and still looks stockish.
Thanks for the tip. Did you change the spring as well or just the shock abosorber?
Hooked
1958 Allstate Super Cruisaire 2005 70cc Yamaha Vino
Joined: 23 Aug 2020
Posts: 302
Location: Philadelphia
Tue Apr 27, 2021 7:45 am quote
rowdyc wrote:
These look stockish and reduces the diving a lot. I have the 60psi version and they work great. The price has gone up since my purchase. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSM
Silver is out of stock but the black is available. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FBM
The silver 100psi is available but the higher the psi the quicker the rebound.
https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSL

There are many choices out there that are better then stock but these worked for me and still looks stockish.
holy cow I'm glad I bought the SIP shock back before the price went up!
Hooked
1958 Allstate Super Cruisaire 2005 70cc Yamaha Vino
Joined: 23 Aug 2020
Posts: 302
Location: Philadelphia
Tue Apr 27, 2021 7:46 am quote
LIJ wrote:
rowdyc wrote:
These look stockish and reduces the diving a lot. I have the 60psi version and they work great. The price has gone up since my purchase. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSM
Silver is out of stock but the black is available. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FBM
The silver 100psi is available but the higher the psi the quicker the rebound.
https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSL

There are many choices out there that are better then stock but these worked for me and still looks stockish.
Thanks for the tip. Did you change the spring as well or just the shock abosorber?
I changed the spring and shock at the same time. I have yet to test it out though... so there's that
Addicted
GL, PK, PE200 with hack, Sears Rust Badge
Joined: 24 Apr 2012
Posts: 995
Location: Deep in the heart of Texas
Tue Apr 27, 2021 9:24 am quote
LIJ wrote:
rowdyc wrote:
These look stockish and reduces the diving a lot. I have the 60psi version and they work great. The price has gone up since my purchase. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSM
Silver is out of stock but the black is available. https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FBM
The silver 100psi is available but the higher the psi the quicker the rebound.
https://www.sip-scootershop.com/en/product/shock-absorber-sip-performance-front_78000FSL

There are many choices out there that are better then stock but these worked for me and still looks stockish.
Thanks for the tip. Did you change the spring as well or just the shock abosorber?
Nope. I kept the old 50 year old spring. If you think you want a spring, get the SIP upgrade vs the Stoffi. The Stoffi is just too stiff but great for an Allstate that has no shock.
Banned
2:6
Joined: 11 Jan 2007
Posts: 7732
Location: San Francisco
Tue Apr 27, 2021 12:46 pm quote
just my opinion:

short of changing the fork for a PK/Zip, there is no way to separate the suspension from the braking forces. It's a limitation in the design of a trailing link with the shoes mounted to the link.

The stock spring rate is good for absorbing bumps when not braking, but bottoms out when you apply the brake. So, while riding you can think of it as having suspension OR brakes, but never both at the same time.

An upgraded spring will suck when riding down the road, but can resist the braking force. so, while riding you can think of this as having nothing OR suspension + brakes, "Oh a bump is coming, I should apply the brakes to get the spring into a position where it can do something about it..."
Member
Vespa 125 g.t.r.
Joined: 08 Jan 2020
Posts: 10
Location: Sweden
Wed Apr 28, 2021 8:37 am quote
oopsclunkthud wrote:
So, while riding you can think of it as having suspension OR brakes, but never both at the same time.
A metaphor for life...
Molto Verboso
Joined: 03 Nov 2011
Posts: 1226
Location: Racing Capital of the World
Wed Apr 28, 2021 12:38 pm quote
oopsclunkthud wrote:
just my opinion:

short of changing the fork for a PK/Zip, there is no way to separate the suspension from the braking forces. It's a limitation in the design of a trailing link with the shoes mounted to the link.

The stock spring rate is good for absorbing bumps when not braking, but bottoms out when you apply the brake. So, while riding you can think of it as having suspension OR brakes, but never both at the same time.

An upgraded spring will suck when riding down the road, but can resist the braking force. so, while riding you can think of this as having nothing OR suspension + brakes, "Oh a bump is coming, I should apply the brakes to get the spring into a position where it can do something about it..."
Very well said.

It always gets me back to saying “maybe this model is not for you.” Once you wrap your head around the trailing link system and understand and respect what you are working with, then driving it is that much better.
bodgemaster
63 GL, 76 Super (x 2), 74 Primavera (x 2), 06 Fly 150
Joined: 26 Sep 2013
Posts: 5830
Location: So Cal
Wed Apr 28, 2021 2:23 pm quote
Problem with the pre-P trailing link is there’s virtually no preload to the front shock and thus no rebound dampening from the static position.
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