From a distance it appeared as though the 340mm length RFY shock was much the same as the 320mm unit. This is true when concerned with the piston, body, and reservoir. However, upon a recent inspection it became clear there are significant and important differences.
The most consequential of which is that the shock body length is increased. As a result, the shock rod itself has also been lengthened. This serves to provide the shock with significant increase in total travel. After top out spring replacement, the maximum shock travel was 3.2 inches, not accounting for the bump stop. For comparison, the 320mm bodied shock has 2.8 inches of travel after top spring replacement. This should help to solve the bottoming issues that many have with their 320mm units, though if the additional 20mm of ride height is undesirable, the 320mm body still might be the better choice.
This lengthier package also came with a taller spring than the more common 320mm unit. The spring measured 8.75 inches in free height versus the standard spring that comes in under 8 inches. Assembly of the unit proved that reducing preload was difficult. The 8.75 inch spring grew more than 20mm. This meant that after significant effort to reduce preload an approximate .5 inches of spring compression remained while at maximum damper rod extension.
This specific shock was equipped with an 8mm wire spring which is the heavier of the available RFY springs. At this moment it unclear if this 8mm spring is the same as what comes on a 320mm unit. I would tend to believe that the 320mm unit would come with a shorter 8mm wire spring, but I cannot confirm this at this time. Additionally, it appears that RFY has moved away from the conical style spring towards a straight-wound version. I have not seen a single conical wound spring since last fall, though my sample size is relatively small in regards to the total market of these dampers. This 8mm spring produced an average rate of 140lbs./inch over a 6 run test. That’s a significant increase in rate over both the conical 7mm spring at 87lbs./inch as well as the straight 7mm spring at 102 lbs/inch. Nevertheless, heavier riders will probably find this spring more appropriate than the 7mm spring especially if their bikes are over 350lbs. Riding style/preference, road condition, and several other factors of course should be considered before purchasing.
Had alot of time on the set you rebuilt for me, on my sportster they are still a little stiff, but we did use the heavy weight oil, thinking I should of gone with the lower weight oil as I’m no very heavy my self either lol. All and all they perform great, I have never bottomed out and I ride it like a dirt bike, over curbs, jump speed bumps ect, just wanted to finally get you a review on them, thanks again for the rebuild!
My 340mm dampers have 2.8 inches of travel like the 320mm ones you pictured. I think you just get what you get being china stuff.
Yes, the internals are the same across lengths. This is partly why in my FAQ section I don’t recommend these shocks for offroad uses.
Thanks! It’s a street ct70