GS 1100 fork question

[Wolfdogg40]

Hey Guys,

I have a set of 80-83 GS 1100 forks on my GS1000. I am looking to upgrade to Racetech or Sonic 1.0 spring rate.

when I research Race-tech, I seem to be getting conflicting information the the fork diameter. I have read online that they are 37mm, racetech site says 39mm and part number FRSP S3234100 says 41 mm. Can someone please help me clear this up. I will also be doing the twinpot brake conversion as well

I also hear that sonic and racetech are pretty much the same?

Thanks,

 

[posplayr]

They are 37mm; just measure them. You have a digital caliper don't you?

 

[tas850g]

I just installed sonics 1.1 with 10 wt oil. Spring rate may be a bit too much but I love them. Went for about a 125 mile ride yesterday and it felt so much better. Very planted with no harshness at all. After spending the last 5 years on the track I now tend to break harder and there is little dive and no wallowing at higher speeds.

And YES, these GS’ need better brakes.

 

[Steve]

Thanks for the report, Todd. I seem to remember suggesting the 10w oil to go with whichever springs you chose (1.0 or 1.1).

I have the 1.1 springs on my bike, but I have the added weight of a fairing, and it feels GREAT. :encouragement:

.

 

[Rob S.]

Are Sonic progressive?

I was told by my mechanic that the chart said to choose between .9 and 1.0 Race Tech (straight weight) because I was 160lbs and not at all aggressive on the front end. I quickly wished I had gone for 1.0 instead of .9, but I don't feel that anymore, even though I've gained weight.

I think the five years offsets the ten pounds. I'd still like to replace the air assist that I destroyed in an accident since I spent the money on the parts (including the special pump and gauge), and I like original functionality, even (especially) in practically invisible parts like these. The owner's manual recommends never changing the stock 7.1 lbs, though 1982's Cycle World suggests 12 lbs as a compromise between ground clearance and performance at the track. (I never go to the track.)

 

[Steve]

Sonic springs are not progressively-wound.

Air used as a suspension medium can be a wonderful thing, but you have to have EVERYTHING working properly. One of the problems using air to supplement the coil springs in the forks is that any additional air pressure forces the seals against the fork tubes, causing them to stick harder, preventing movement. There is also a tendency to wear out quicker because of the additional friction.

You should be aware that even if you don't add any air, there WILL be air trapped inside your forks when you screw on the caps. As the forks are compressed when you hit a bump that air adds to the spring rate, and it does it progressively. Rather than add air to increase the effective spring rate, it would be better to add some preload to the coil springs, because the additional air is going to eventually leak out, anyway.

.

 

[Keith Lane]

Can you tell me where you bought the pump/gauge? I've looked a bit and asked my local Suzuki shop and they looked at me like I had grown a third eye.

 

[Grimly]

Can you tell me where you bought the pump/gauge? I've looked a bit and asked my local Suzuki shop and they looked at me like I had grown a third eye.

After much dicking around trying to find one, this came up trumps.
I've been using it a lot, because the damned forks leak air every day, unlike the rear Showa air shocks which remain stubbornly airtight.
If not for the leakage I'd be quite happy with the ride quality, but it's the leakage that is driving me back towards a simple straight-rate spring again (the originals were progressive mushy things, but they did ok).
https://www.amazon.com/gp/product/B006ID37ZS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

[Steve]

The gauge in Grimly's link is a good gauge. You are looking for something that will handle LOW pressures, mostly less than 25 psi. Some bicycle hand pumps will work, but their gauges might be for higher pressures. Low air loss when connecting/disconnecting is a plus, too.

.

 

[Rob S.]

Can you tell me where you bought the pump/gauge? I've looked a bit and asked my local Suzuki shop and they looked at me like I had grown a third eye.

The pump and gauge (one package) are Drag Specialties. I may have ordered them from the local Suzuki dealer, who ordered them from I don't know where.

 

[Keith Lane]

After much dicking around trying to find one, this came up trumps.
I've been using it a lot, because the damned forks leak air every day, unlike the rear Showa air shocks which remain stubbornly airtight.
If not for the leakage I'd be quite happy with the ride quality, but it's the leakage that is driving me back towards a simple straight-rate spring again (the originals were progressive mushy things, but they did ok).
https://www.amazon.com/gp/product/B006ID37ZS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Thanks!
Do you get much leakage when you disconnect?
I've looked off and on for a while, just didn't ask in the right place till now!

 

[Grimly]

Thanks!
Do you get much leakage when you disconnect?
I've looked off and on for a while, just didn't ask in the right place till now!

I think it barely loses half a psi on disconnection.

 

[Rob S.]

I seem to remember suggesting the 10w oil to go with whichever springs you chose (1.0 or 1.1).

What weight oil is usually used, higher or lower than 10?

After much dicking around trying to find one, this came up trumps.
I've been using it a lot, because the damned forks leak air every day, unlike the rear Showa air shocks which remain stubbornly airtight.
If not for the leakage I'd be quite happy with the ride quality, but it's the leakage that is driving me back towards a simple straight-rate spring again (the originals were progressive mushy things, but they did ok).
https://www.amazon.com/gp/product/B006ID37ZS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

This one looks to be a good deal less expensive that the one I bought and pictured, which is a separate pump and gauge. Don't think I've used either one.