The auto racing aftermarket has spring suppliers that generally supply springs in three ID sizes, 1.88", 2.0" and 2.56". Heavier springs have larger wire diameters but they are wound to the same ID so that they fit the same hardware. They can be found in lengths varying from 8" to 14" long. Black ABS pipe or fittings or couplers can be cut to make spacers as needed. Southwestspeed.com is one example; Speedway Motors is another. You can buy 1.88" ID springs for $39 a pair.
Make a tool/compressor to remove the springs from your shocks and measure the springs, spring seats and shock body with a good caliper. Then buy what you want and adapt them to fit. At $39 a pair, buy two sets and try them. I have put aftermarket springs on my stock shocks so I know it can be done. (I have 6 sets of shocks and about ten sets of springs that I have used to build and try various sets for my R3. I am a former suspension engineer and can and do take apart or cut shocks apart to get internal components, springs and valves to adapt to others. Why: I enjoy the challenge.)
120 lb/in rate is too soft for the R3 (I tried them). The stock springs on my R3 Classic with the back breaking stock shocks has a 260 lb/in rate. You will discover the shock compression damping is critical. Too much low speed compression damping and even 120 lb/in shocks feel too hard. The damping plays a bigger role in how the ride feels than the spring rate. If you seek softer springs to improve the ride, you will need to make big changes.
Progressive may make good shocks and springs that work well in some applications but they suffer from "if it fits, sell it!" Which means that a shock body (without the coil over spring) that fits a Thruxton may be sold also to an R3 owner but with a different spring and perhaps different rubbers in the eyelet. But the base shock is identical. No way in Hades that the two applications require the same damping. Hence you see the master list of shocks and then a list of springs from which they mix n match to fit most applications. Works well for them but not soo much for the end user.
The R3 has very heavy un-sprung weight compared to most bikes. And she is front heavy. Therefore getting good ride quality from shocks meant for other bikes is difficult.
The issue of "set in" is often debated. Reality is that what works well for one bike and rider's geometry (bike suspension type, combined bike and rider CG location fore/aft and height) and type of riding is not ideal for another. CG height is less important when the bike is at 35 degrees to the ground but even more important fore and aft then when it is straight up. Hitting the brakes transfers weight forward which extends the rear suspension. Too little travel and the back wheel unloads prematurely and the CG rises even higher. Traversing bumps requires suspension travel in both directions. Too little extension travel and the ride gets harsh because the shocks hit full extension and then try to lift the rear wheel off the ground. Of course what goes up gets slammed back down. I use 4" travel shocks with about 30% travel for rebound. My ride height is about the same as stock but the longer shock travel gives me more travel in both directions.
Cruising smoothly and comfortably on the R3 requires very soft mid to high speed compression damping. But without fairly stiff low speed damping, she will wallow. Rebound damping is directly tied to spring rate and mass. Stiffer springs need more of it than soft springs. Too much rebound damping and the bike will "jack down" and each bump in a series of bumps becomes progressively harsher.
Find what you like. Each of us has a different set of criteria as to what we want for ride and handling. Ask the shock builder or supplier the spring rate they will supply. Ask them about the damping curves of the valves they will supply in the shock. If they refuse to tell you or worse tell you it is too complicated to explain, take your money elsewhere. There is way too much smoke blown up people's backsides in the suspension market because there is so little general knowledge about how these systems work and what each part does systemically.
Make a tool/compressor to remove the springs from your shocks and measure the springs, spring seats and shock body with a good caliper. Then buy what you want and adapt them to fit. At $39 a pair, buy two sets and try them. I have put aftermarket springs on my stock shocks so I know it can be done. (I have 6 sets of shocks and about ten sets of springs that I have used to build and try various sets for my R3. I am a former suspension engineer and can and do take apart or cut shocks apart to get internal components, springs and valves to adapt to others. Why: I enjoy the challenge.)
120 lb/in rate is too soft for the R3 (I tried them). The stock springs on my R3 Classic with the back breaking stock shocks has a 260 lb/in rate. You will discover the shock compression damping is critical. Too much low speed compression damping and even 120 lb/in shocks feel too hard. The damping plays a bigger role in how the ride feels than the spring rate. If you seek softer springs to improve the ride, you will need to make big changes.
Progressive may make good shocks and springs that work well in some applications but they suffer from "if it fits, sell it!" Which means that a shock body (without the coil over spring) that fits a Thruxton may be sold also to an R3 owner but with a different spring and perhaps different rubbers in the eyelet. But the base shock is identical. No way in Hades that the two applications require the same damping. Hence you see the master list of shocks and then a list of springs from which they mix n match to fit most applications. Works well for them but not soo much for the end user.
The R3 has very heavy un-sprung weight compared to most bikes. And she is front heavy. Therefore getting good ride quality from shocks meant for other bikes is difficult.
The issue of "set in" is often debated. Reality is that what works well for one bike and rider's geometry (bike suspension type, combined bike and rider CG location fore/aft and height) and type of riding is not ideal for another. CG height is less important when the bike is at 35 degrees to the ground but even more important fore and aft then when it is straight up. Hitting the brakes transfers weight forward which extends the rear suspension. Too little travel and the back wheel unloads prematurely and the CG rises even higher. Traversing bumps requires suspension travel in both directions. Too little extension travel and the ride gets harsh because the shocks hit full extension and then try to lift the rear wheel off the ground. Of course what goes up gets slammed back down. I use 4" travel shocks with about 30% travel for rebound. My ride height is about the same as stock but the longer shock travel gives me more travel in both directions.
Cruising smoothly and comfortably on the R3 requires very soft mid to high speed compression damping. But without fairly stiff low speed damping, she will wallow. Rebound damping is directly tied to spring rate and mass. Stiffer springs need more of it than soft springs. Too much rebound damping and the bike will "jack down" and each bump in a series of bumps becomes progressively harsher.
Find what you like. Each of us has a different set of criteria as to what we want for ride and handling. Ask the shock builder or supplier the spring rate they will supply. Ask them about the damping curves of the valves they will supply in the shock. If they refuse to tell you or worse tell you it is too complicated to explain, take your money elsewhere. There is way too much smoke blown up people's backsides in the suspension market because there is so little general knowledge about how these systems work and what each part does systemically.
