Progressive Spring lengths - GS1000 v GS1100

[salty_monk]

Anybody confirm the free lengths of the 1000 or 1100 progressive springs? Hoping not to have to tear my forks down to measure...

From Summit racing I got:

11-1106 for the 1000 (1978)
11-1107 for the 1100 (1983)

Both 35/50 lbs in. rating.

Outside dia is effectively the same (the 1100 ones are allegedly 1mm larger dia but the internal dia of the fork tube is the same so this shouldn't matter).

1106 - 19.12"
1107 - 18"

Also if anyone can remember how much spacer they needed on top of the progressive (for the 1000 only is fine, don't really need this info for the 1100) to bring it level with the top of the fork leg that would be great (as per progressive "starting point" preload instructions).

I am putting an 83 1100 front end on my 78 1000 to give me both preload & rebound adjustment plus their are other mods they did such as anti friction rings etc which were also seen as an improvement. Mostly though I'm doing it as I got a set with brand new forking by frank fork legs in it for a killer price...

Dan

[bwringer]

I'm a bit confused by what info you need, but I do know the Prog. springs for the 1100 going into 1100 forks do not require a spacer.

So, if what you're up to is placing 1000 springs into 1100 forks, you'll only need a spacer equal to the difference in length, then adjust preload to taste.

[salty_monk]

Ok thanks. So if Summit racings info is correct I need a new set of springs then. The 1000 spring seems to be longer according to them so I doubt they'll give the correct preload as I have to put 3/4" of emulator in the spring stack as well.

One piece of info I'd really like is for someone to confirm the GS1000 progressive springs 11-1106 are 19" free length.

[TheCafeKid]

1106 are actually longer than 1107 iirc 1108 are longer still. Posplayr accidentally ordered 1108 when he did his, and they were good and stiff, even with Chef on them when he still had em and me on em after i bought em off him.
They're currently on Brett griffins 1100e and they're too stiff and he's still a tad heavier than you I'd guess so don't go with those

I put 1107 in my 1100ES, and I did add a spacer but that's what it required for sag to be correct with my weight on it and at the second click of preload on the adjuster. Prolly could have not put a spacer in there if I went up a click or two but I didn't want to max out on my adjuster and have no headroom left.
Iirc I used 1/2" of spacer. I didn't have emulators in mine, but i thought that bike handled very very nicely without em. They'd probably have put that bike over the top and I'd have never sold it

[salty_monk]

Well I spent some time in the garage last night.

Summit's info is 100% correct on the 11-1106 & stock for the 1100 measures the same dia & 18" as listed so that is likely correct as well.

I don't want to stiffen my progressives by cutting them down so I will either get a set of Sonic straight weight or I will mess with the stock springs to see what I can come up with there....

Sonic list a 0.9 kg/mm for my weight on the 1100.

Useful link http://www.pontiacracing.net/js_coil_spring_rate.htm

1 pound = 0.45359237 kilogram
1 inch = 25.4 millimeter
0.45359237/25.4 = 0.0178579673228346

The conversion factor is 0.0178579673228346

So, to convert lb/in to kg/mm you multiply by 0.0179 and to convert kg/mm to lb/in you divide by 0.0179

0.9kg/mm is 50lb/in which is what the Progressives supposedly are on their heavier weight end...