Ohlin rear Spring Rates

Ghezzi, ignore my last post, the O.D. is too big at 84mm

Built this today........
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And at ghezzi's request did some measuring.....
Original Sachs Shock :
Stroke = 41 mm - Compressing the bump stop hard to about 5mm thick
Free length of spring = 188 mm. (Yes 188mm) Coil Dia-11.3 mm. ID-56mm OD-79 colour RED

Ohlins AP9340 Shock :
Stroke = 52mm - compressing bump stop to about 11mm thick, quite hard with this much force.

1091-31 spring 95 kg /mm rating Free length = 160mm. Coil dia= 11.3mm OD=80mm ID= 57mm

1091-36 spring 105kg/mm rating Free length= 160mm. Coil dia=11.5mm OD=80.2mm ID=57mm

I'm not sure why yet , but Ghezzi wants me to measure the stroke of each shock - on the bike to calculate ratios ? Thats tomorrows job, as Black beer has called me , and it WINS

Due to the difference in shock lengths, plus the Ohlins is adjustable, at starting point (topped out) the rocker ratio should be different.

On top of that, all my measuring has been on a Bellagio. While it shares swingarm, rocker and link arm, the frames are different, and hence top shock mount could be in a different position.

Yessssss, and then ?

You've completed lesson #1.
Now go and do your home work like a good boy.

Yes Master

I'm confused as to why the 1091 spring has been used as a replacement when it's 20+mm shorter than the Sachs spring.  Isn't the 1095 closest to the correct length?

Sorry John, it does look a bit weird. I have an Ohlins AP9340 shock off an Aprillia Tuono . The valving is more tunable / compliant and it has a longer stroke which should add up to a better ride ? Hence the measuring today to see what the old vs new rocker ratios are.  here she is with the new heavier spring and lower fork fitted
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Oh, sorry, I thought you were putting the Ohlins spring on the Sachs shock. (Is this the same Sachs that made motorcycles in the 60s?)

Well, it seems our good mate Todd at guzzi tech is offering Ohlins shocks for GRiSO, they are made to order. Prices from USD$1150 to $1760.

So Ohlins are available.











Bastard!
While looking around his suspension offerings I see a link to my Bellagio mod thread. The man's a marketing guru.

Beetle, Or Pete , how much did you under state your weight for a matris shock .
Nev

10kg. IIRC.

10 kg gee that seems quite a bit , I told Izzy my actual leathered up weight ,
too late now , ill see how it goes .
thanks Mark.

Hey Nev, my Matris R was ordered directly from the factory and supplied to another rider only slightly heavier than myself. Hence my impression that they favour superbike race settings.

As you have ordered from Izzy at Suspensions R Us in Melbourne, you might get a more realistic spring for road use.

10kg about covers leathers boots etc.

What weight did you tell him?

I'm pretty sure the springs have 10kg rating ranges. I would expect if you were 90kg or 100kg, you'd get the same spring.

I found this chart on a Yamaha R1 forum, so remember the spring not only holds your fat ass in the air, it also has to contend with the weight of your bike.

GRiSO and R1 don't weigh the same ....................... nor do they have the same suspension linkage system.

P.N. ____ Spring # ______ Rider Weight
YA 638 21040-31/95 ..... 150 - 175 (equal to Stock GRiSO spring rate)
YA 638 21040-34/100 ... 175 - 200
YA 638 21040-36/105 ... 200 - 225
YA 638 21040-39/110 ... 225 - 250

YA 788 21040-31/95 ..... 150 - 175
YA 788 21040-34/100 ... 175 - 200
YA 788 21040-36/105 ... 200 - 225
YA 788 21040-39/110 ... 225 - 250

So if you do some clever calculations, you should be able to arrive at a suitable spring rate.
Best option though, is have your local suspension tech measure your static and rider sag and make a judgement from there.

Told Izzy 85kg with jacket and helmet, no pillion and I'm no a racer on country roads ,
Izzy replied yees yees spring and valves for Australian conditions .
I only ordered less than two weeks ago, he said I caught his order just leaving Italy
Think he posted it on yesterday to the west .
Maybe I sould have waited for a suspension guru in the city, but these enough info here I reckon.
Nev

Well , I did the measurements and the results are very un-astounding.
Ratio Average is 1mm of Shock travel to mm's of rear wheel travel
Original GRiSO Sachs Shock Average = 2.46:1 over 39mm of shock travel = 96mm rear wheel travel.
Ohlins AP9340 Shock Average = 2.47:1 over 52 mm of shock travel = 130mm rear wheel travel.
the initial ratio from full top out is a bit higher , but only for the first couple of mm's travel of the shock.
So this weekend, the new spring goes on and sag gets set , then ride and flog the piss out of it again

So the biggest problems with original Sachs shock is a spring which is too soft for most riders and rear wheel travel limited to less than 100mm.

So why does the factory claim 120mm rear wheel travel?

Ron, what was the initial ratio with the Ohlins (topped out). This will indicate how much extra rear ride height you got with the longer shock.
From there I can tell you reduction in rake angle.

None of this will help me ride any better, A loss of pilot Kilos and an injection of skill is what I could use