suspension for SR500 with sidecar

Stuff that I'll just make the bike faster/more powerful. I've worked long and hard on this gut/stomach(6 pack more like 2 doz pack) and no under powered piece of machinery is going to make me go to jenny craig.
Curly

Hi,

My best friend and ex competition sidecar passenger owns Premier Sidecars (and is currently trying to sell the business to me), he uses Ikon shocks on all the sidecars he builds. Aside from the cost (Ikon shocks are made in Aust therfore cheaper than most other shocks here), the big advantage of the Ikons shock is the adjustable damping, which makes it easier to set up the sidecar suspension. Determining the correct spring rate for the sidecar suspension is mostly trial and error combined with previous experience, and depends on the actual geometry of the sidecar suspension, i.e. swingarm length, angle shock is mounted at etc, so it is not really possible to advise what weight spring to use. I am sure that there would be some internet forums for sidecars in the US, and these may be your best bet for advice about the sidecar.

On the matter of sidecar chassis being made heavier here in Aust, you are farly correct, most makers use 2" heavey gauge box section steel tubinf for the chassis on general road/touring sidecars. Better a bit heavy than breaking 100-km from no where. The chassis's of the cometition sidecars that I used to build were made from 3/4" and 1" thin wall round tubing, but weight was (is) a big issue in observed trials and braking a tube at trials speed had no unfortunate consequences.

As to the bit about rider weight, I now weigh 125kg in riding gear (I am 193cm (6' 3" tall), and truely believe that there is no point trying to shave a couple of Kg of the weigh of the Sr when it would be both cheaper and healthier to loose 20kg of my onw body!

CJ

For the rear shocks, any good quality shock would do, but adjustable damping is a feature that is well worth the extra cost.

As to a spring rate for the rear shocks, the "rule of thumbs" was always to increase the spring rate by 10% as a starting point (i.e. if the std spring is 100 lb/in then fit 110 lb/in springs). This give you a starting point for furhter experimenting. Note jacking up the spring preload with alter the static ride hight but will not actually stiffen the suspension.

You then move on to looking at the static and loaded sag of the suspension. A lot of people say static sag should be about 1" (25mm), but this is dependant on the overall suspension travel, as a percentage, static sag should generally not be more that 25% of the overall suspension travel. To measure the static sag you need to accuratly measure between a fixed point on the rear of the bike (for rear suspension a top shock mounting bolt is good) and the ground, with the outfit on a level concrete floor and unladened (no excess stuff on the bike or in the sidecar). You the take a second measurement, with the suspension fully extended, ie lift the back up until all the weight is off the rear suspension and the rear wheel is starting to lift off of the ground. The difference between these to meaurements is your static sag. Knowing the this figure and the total suspension travel you can the work out the percentage of static sag.

Loaded sag is measurement the same was except instead of the outfit being unladened, you have the normal load of ride, passenger and luggage on the bike/in the sidecar for the first measurement (he extended measurement should be the same). There is a lot of variation on how much this should be, with opinions ranging from 25% thru to 50% of the avaialble travel, my personal preference is around the 30 - 35% mark.

Taking all of the above into consideration, there are big trade offs between comfort and handling. If your suspension is hard, the outfit will handle more precisely with very little "body roll" when cornering but be uncofotable when riding over rough or corrurgated roads. If too soft, it will wallow around when cornnering (sometime to dangerous levels) be be a comfortable as a lounge chair over a rough road.

On the outfit that I am currently building on my XS1100, I am fitting an old air assisted shock from a Kawasaki GT750, as it gives me the ability to adjust the overall spring rate not just the spring preload. I also intend to fit simmilar shocks to the rear suspension, when I find a set and will probably use the same shocks on the leading link front forks that I will eventually make for it.

Here is a picture of the progress so far on the XS1100


CJ

Ebay US has a Tarozzi fork brace for the SR500, $99 USD

Search for this item no.: 170167071000

fork brace should fit no worries

DO you have photos of the install? How's it feel in the turns
and on braking? Maybe only my SR500 will get presents
this christmas.