Front Forks Sag and Spring Rate Question Bassa-EV.

[Orange Guzzi]

I put a Bassa/EV front fork stanchions that are adjustable on my 2003 Aluminium.  The Aluminium is not stock and is much lighter than a stock Bassa. 

The front shocks preload/sag with out Me on the bike, 10 mm.  They shocks sag 23 mm with Me on the bike.

There is a lot of data on the WWW regarding suspension rider sag and the three types of springs used.  Straight rate and two types of progressive.

The Bassa uses a straight rate spring.  Does anyone know what the spring rate is?  I prefer a straight rate spring. 

My goal is to have 35mm preload/ridersag.

How much rider sag do you like?

The spring is compressed 31.75 mm on the dampening rod. Then I am getting the 23 mm rider sag.  From my reading about preload, the 31.75 of preload on the the dampening rod should count as part of the 35 mm I am trying to achieve.  To reach this, I need to shorten the spacer on the dampening rod 19.75 mm  (31.75 -19.75 = 12 mm. 12 mm + 23 mm preload/rider sag = 35mm)  or disregard the preloaded on the dampener rod and shorten the spacer 12 mm?  (12 + 23 = 35mm).


Or to make my question more confusing, what effect does a preloaded spring( a spring that is compressed between two points before installed inside the stanchion)   have on rider sag? 

[pauldaytona]

1/3 th of total travel as loaded sag should be near.

[Orange Guzzi]

1/3 th of total travel as loaded sag should be near.

What is 1/3 of total travel?  I ask this because, with the fork cap un screwed, the forks will compress until the fork brace hits the triple clamp, about 6-1/2 inches.  With the C-clip removed from damper assembly and the spring removed, the assembly will compress 8 inches or until the fork brace hits the bottom of the triple clamp.  The springs have enough coils and spacing to compress 8 inches.  What is used as a bump stop and how much travel is there?  Looks to me that the only bump stop is the fork brace hitting the bottom of the triple clamp.

What is the spring rate if you have that also?

I removed 17.5 mm from the black spacer mounted to the spring damper assemble.  I now have 35 mm of rider sag and front suspension that will compress and rebound.  In the mean time, Patricia showed up with rain and I have not been able to take the bike for a ride. 

[twhitaker]

I think the limiting factor is the bottom of the upper tube hitting the spacer that sits at the bottom of the fork lower. YMMV

[Orange Guzzi]

I think the limiting factor is the bottom of the upper tube hitting the spacer that sits at the bottom of the fork lower. YMMV

When I removed the spring, the lower tube will slide up the stanchion tube until the fork brace hits the lower triple clamp  (it is hard to collapse the springs when assembled).  The spring has enough free length to collapse 8 inches or 1-1/2 inches further than the tube will travel before hitting the fork brace on the lower triple clamp.  So, what is the shock travel?  My guess is the fork brace hitting the bottom of the triple clamp and the fender crashing into the generator cover.  The travel distance is determined by how far you have the forks pushed thru the top clamp. 

[oldbike54]

 1/3 of usable travel fellas , and when I have bothered , usually figured closer to 1/4 .

  Dusty

[Orange Guzzi]

1/3 of usable travel fellas , and when I have bothered , usually figured closer to 1/4 .

  Dusty

1/3 of what?  Usable travel?  What is "usable travel" and what is the spring rate?  Bueller? Bueller? 
The two magic numbers must be know by someone?  Not in the owners manual, not on oem spec list and not in Guzziology. 
 

[Orange Guzzi]

Moto Guzzi claims 130 MM of travel .

  Dusty

And where did you get the "claims 130mm"?  I know Moto Guzzi, but from what source as related to the Bassa?  And what about the spring rate.  That would be helpful.


From what I have read, there are only a couple of choices in springs available for the adjustable front end California EV/Bassa.  Those that have changed the springs seem to be happy with a progressive type spring.  Progressive Suspension and Hyperpro.  Wirth does not list anything.  And the Progressive Suspension springs are not listed on their web site. 

Since my bike is nearly 100 pounds lighter than the stock EV/Bassa.  Lighter springs/less preload before sag adjustment was my goal. 

[oldbike54]

 Just checked specs for 2003 Aluminum . Geez , ya want me to do all the work  My guess is the spring rate is very close to 110 inch lb . If you have access to a way of holding the springs , just measure how much weight it takes to compress the springs one inch . Then you can calculate your new lesser spring rate based on weight reduction and desired fork action .

  Dusty
 

[normzone]

I hope this does not constitute too much thread drift, but as the owner of a '99 Bassa, I wonder -

Does the stock adjustment on the fork tops REALLY make a measurable difference ? It seems so insignificant of an adjustment range.

[normzone]

Yeah, that pretty much matches my experience. Granted, I've not followed the instructions re choosing a setting, ride a course, make notes, change the setting, repeat and compare. I just don't feel a discernible difference.

[Zoom Zoom]

I hope this does not constitute too much thread drift, but as the owner of a '99 Bassa, I wonder -

Does the stock adjustment on the fork tops REALLY make a measurable difference ? It seems so insignificant of an adjustment range.

When my first EV was new, I ended up on a road in PA one day that had lots of little hills, or whoopty doos, if you will. During that, I adjusted the compression and rebound to the lowest setting and then the highest setting. I did notice a difference without any doubt. What I finally ended up with was 5 clicks of rebound and 3 clicks of compression. At that setting [for me], the bike became neutral in that it did not porpoise after I settled on those settings if you know what I mean. On the highway, I would leave the settings soft, but I will leave then rebound 2 additional clicks over what ever I set the compression. For the most part, the difference the adjustments made were the most noticeable on the afore mentioned type of road. (Whoopty Doos)

John Henry   

[Orange Guzzi]

I got the 35 mm rider sag I was wanting. 

What I found.  If a spring is preloaded by pressing the stanchion cap down, that is preload which has to be added to the rider sag and if a spring is compressed on a damper rod prior to installing in stanchion, that is preload which has to be added to the rider sag.  This preload has to be taken into consideration when calculating rider sag. 

A shock spring can be installed two ways, one is dropped into the stanchion with or without a spacer tube on non adjustable shocks and two, it can be assembled onto a damper assembly for adjustable shocks with preload.

As far as the compression and rebound setting go, I have them both set in the middle.  I went for a short ride yesterday.  Rider sag makes a big difference.  I went from 23 mm to 35 mm.  23 is less than the recommended 25-45 mm.    With the 23 mm rider sag, the bike ran wide in corners and slid both the front wheel and back wheel.  Now the bike will turn in and hold a line much better and the ride is much smother.   

I found a web site that has a very good set of document that explain the proper set up procedures.  The documents leave out the part about spring preload from the cap being installed and/or preload on damper assemblies. 

http://www.promecha.com.au/springs_basics.htm

The rear shocks, Hagon, were setup with 35 mm of rider sag also.  Up from 20 mm. 

I still have two un answerd questions.

What is the stock straight rate spring rate on the stock 45 mm adjustable marzocchi  front shocks?

What is the stock maximum compression on the stock 45 mm adjustable marzocchi front shocks.
When the damper assembly is removed the slides will raise until the fork brace hits the lower triple clamp.
When I count the amount of spaces between the spring coils and multiply that time the number of spaces, the spring will collapse 9 inches.
When I remove the spring from the damper assembly, the damper assembly will collapse 8-1/2 inches.
There is not an apparent stops built into the fork assembly. 
I applied my front brakes in a couple of test stops to the point the front wheel locked and slid.  The Shock compressed 4-1/2 inches which was the point the fork brace hit the lower triple clamp.  I have the fork stanchions slide 3/4 inch (19.05 mm) up thru the top triple clamp.
Since I dropped the front with the added rider sag, I am going to lower the fork stanchions down 5/8 inch (15.8 m) in the triple clamp.  Giving me 5-1/2 fork travel.  Which should be enough to compress the fork and lock the wheel without smashing the fork brace into the lower triple clamp. 

[Chuck in Indiana]

Rider sag makes a big difference.

Yep, to me the most important of any of the "setting up" of suspension. Sorry, I can't answer some of your other questions, but this will bump it to the top.