The car shock on my Cozy Rocket has very limited travel, and sprung so hard that my 76 kg weight barely moves the suspension when bouncing up and down on the bare chassis. Part of the problem was the swingarm pivot, but I have re-designed using a proper pin and bearings. The spring however is still very stiff, and if it did move the travel would be only 34mm to the shock shaft bump stop. I understand that sidecars are typically sprung a lot stiffer than a bike, but this seems to be a bit too stiff, and very limited travel?
YSS shocks are made here in Thailand so I am leaning toward a new YSS unit, but they have zero technical support and I have no idea what would be an appropriate shock or spring rate. Importing a shock will increase the cost by about 70%, so in spite of any customer support, I would prefer to buy YSS.
A YSS RZ series (preload and rebound adjustment only) is available with the same 12mm eye mounts, and available with a wide choice of spring rates. For example. the Sportster version of this shock has a 25-35 N/mm progressive rate, and a large range of both linear and progressive spring rates are available.
The RG series shock is a piggyback reservoir design with both compression and rebound adjustment.
Bike is a Royal Enfield 650 Interceptor, with standard forks fitted with .9kg/mm linear springs, and cartridge emulators. Rear shocks are YSS fully adjustable piggyback units with 17-25 N/mm springs - same spring as when the bike was solo, and will likely increase this spring rate for the sidecar application
Sidecar will normally be run empty, and the wife is 50Kg.
Questions:
1 I know there is no universal spring rate answer for the sidecar, but given the swingarm geometry and weight of the Cozy, does anyone have a starting point for spring rate? Springs are not expensive and can easily be changed, but it would be nice to have a reasonable guesstimate as a starting point.
2. Remote reservoir with both compression and rebound damping, or integral reservoir with rebound only on the sidecar shock? Price difference is about 250.00 USD for the pair I am leaning toward rebound + compression adjustment in the hope that I will be able to refine the WAG
3. I do not have the luxury of buying a shock valved for the application. Should I try and find a shock for a very light bike, tug weight, tug + hack, or something in-between?
4. Increase the bike rear spring rate? Next spring up is a 20-30 N/mm progressive rate.
YSS will only sell in pairs, so if anyone needs one.........
Robert, Of course we know nothing about the situation in Thailand but here in the US suspension specialist shops often have spring rate and shock testers. Possibly you could find such a vendor and take your current shock and spring to them and ask for testing if you agree to buy a replacement from them.
Quote from Al Olme on August 28, 2021, 10:16 amRobert, Of course we know nothing about the situation in Thailand but here in the US suspension specialist shops often have spring rate and shock testers. Possibly you could find such a vendor and take your current shock and spring to them and ask for testing if you agree to buy a replacement from them.
I bought the sidecar used, but it looks very much like a car spring - Endurance brand from India, dated 2018, and probably the original Cozy part.
I could test the spring, however the existing shock has only 35mm of travel, and a very high spring rate, due in part at least to that limited travel. I am not sure what would be gained, other than telling me that the spring rate is very high
Anyone with a cozy swing arm arrangement that has fitted an alternate shock/spring?
There must be a way to calculate the optimal spring, given the known swingarm geometry?
Contact Klaus at High Performance Motorcycle Suspension from EPM Performance Imports. He is a EPM, YSS and Wilbers dealer in the USA his email and phone # is on his web page. He is an avid motorcyclist & sidecar driver himself, very knowledgeable and helpful. He is also a member and advertiser USCA .
Ed,
You're right, Klaus is the guy I was thinking about when I wrote, but.... The original poster is in Thailand. Klaus might have an opinion, which would be valuable, but it's a long way to ship a shock for testing. ;^)
I don’t know if this will help but. I took shock & axel assy throw them in trash. Got adjust 450 lb. torsion axel assy , extended the torsion arm 2” (arm is 1” by 2” solid metal) and off set wield together with arm remove from the rubber section. Made a frame under cozy fram to mount the assy adjust it level and in line with motorcycle wheel. Put trailer wheel 15” & tire. Then add a wider fender( you know with a torsion assy don’t need any damping). Been running 20,000 mile on 2012 Triumph se bonneville. Tops out about 92 mph runners true. Rudy
Quote from rudyr on August 29, 2021, 7:46 pmI don’t know if this will help but. I took shock & axel assy throw them in trash. Got adjust 450 lb. torsion axel assy , extended the torsion arm 2” (arm is 1” by 2” solid metal) and off set wield together with arm remove from the rubber section. Made a frame under cozy fram to mount the assy adjust it level and in line with motorcycle wheel. Put trailer wheel 15” & tire. Then add a wider fender( you know with a torsion assy don’t need any damping). Been running 20,000 mile on 2012 Triumph se bonneville. Tops out about 92 mph runners true. Rudy
I already trashed the stock axle, wheel, and swing arm assembly and fitted an 18" alloy rim with stainless spokes and disc brake. Swingarm geometry is the same as OEM. A trailer stub axle will not be easy to find, so thinking to stay with a conventional shock design.
Your idea is interesting, and something to consider if I ever get back to Canada - have any pics?
