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InvisiBill · April 28th, 2014, 06:28 PM

The softness in the rear is a direct result of the spring rate. If you don't know what spring rate your bike needs to match your weight, or what the spring rate of a specific shock's spring is, you can't make an informed decision on what will work best. One of the EX500 suspension gurus stated that the spring rate is probably 80% of how well the shock will work for you.

In the most simplified terms, the spring lets the suspension bounce X amount, and the shock controls that movement. If the spring is too heavy, the suspension won't absorb any of the jolts and the whole bike will skip over bumps. If the spring is too soft, the suspension will feel mushy and the shock will be working overtime trying to contain the wild swings. If you have the right spring, the suspension will move just the right amount to absorb bumps and still have the movement controlled properly by the shock.

It seems at least a few people have used the ZX600 shock on the PreGen (http://faq.ninja250.org/wiki/Installing_a_ZX600_shock), so I assume it gives at least adequate results (I did see it mentioned that it was better for smaller riders). However, I haven't seen its spring rate actually posted anywhere, and I'm a bit wary of people's anecdotal evidence after seeing posts saying that the 47%-stiffer spring on the PreGen feels softer than an EX500 shock/spring. The ZX600 shock is also shorter, which will actually slow the handling of the bike (it'll feel less flickable).

The NewGen/300 shock should be pretty similar to the PreGen shock (since it's just a newer revision of the same bike). It should behave similarly to the way it was engineered, but has a stiffer spring to handle a heavier rider. Again, I don't know what the ideal spring rate is for your weight on a PreGen, but the NewGen spring is 18% stiffer than the PreGen, so it will definitely stiffen it up. It also has a preload adjuster, so you can actually set the sag on it and have the shock operating in the proper range of the spring. It's also a bit longer, so it'll lift the rear and make it handle a little quicker (others have mentioned this makes the bike feel much better, which matches up perfectly with EX500 advice/experience).

I'd personally feel safer going with a shock that's very similar to what the bike comes with, just with a stiffer spring (those are the reasons I'm currently using a NewGen shock on my 500). It should give you similar results, just with a bigger spring to handle a heavier rider. The ZX600 shock may have more features, but it's also a lot older and there doesn't seem to be much info on it to figure out if it actually is better than either of the other options. Additionally, the NewGen shock should improve the feel of the steering, while the ZX600 would take it in the opposite direction unless you got shorter dogbones too.

April 28th, 2014, 06:28 PM	#7
InvisiBill EX500 full of EX250 parts Name: Bill Location: Grand Rapids-ish, MI Join Date: Jul 2012 Motorcycle(s): '18 Ninja 400 • '09 Ninja 500R (selling) • '98 VFR800 (project) • '85 Vulcan VN700 (sold) Posts: A lot. Blog Entries: 1 MOTM - Aug '15	The softness in the rear is a direct result of the spring rate. If you don't know what spring rate your bike needs to match your weight, or what the spring rate of a specific shock's spring is, you can't make an informed decision on what will work best. One of the EX500 suspension gurus stated that the spring rate is probably 80% of how well the shock will work for you. In the most simplified terms, the spring lets the suspension bounce X amount, and the shock controls that movement. If the spring is too heavy, the suspension won't absorb any of the jolts and the whole bike will skip over bumps. If the spring is too soft, the suspension will feel mushy and the shock will be working overtime trying to contain the wild swings. If you have the right spring, the suspension will move just the right amount to absorb bumps and still have the movement controlled properly by the shock. It seems at least a few people have used the ZX600 shock on the PreGen (http://faq.ninja250.org/wiki/Installing_a_ZX600_shock), so I assume it gives at least adequate results (I did see it mentioned that it was better for smaller riders). However, I haven't seen its spring rate actually posted anywhere, and I'm a bit wary of people's anecdotal evidence after seeing posts saying that the 47%-stiffer spring on the PreGen feels softer than an EX500 shock/spring. The ZX600 shock is also shorter, which will actually slow the handling of the bike (it'll feel less flickable). The NewGen/300 shock should be pretty similar to the PreGen shock (since it's just a newer revision of the same bike). It should behave similarly to the way it was engineered, but has a stiffer spring to handle a heavier rider. Again, I don't know what the ideal spring rate is for your weight on a PreGen, but the NewGen spring is 18% stiffer than the PreGen, so it will definitely stiffen it up. It also has a preload adjuster, so you can actually set the sag on it and have the shock operating in the proper range of the spring. It's also a bit longer, so it'll lift the rear and make it handle a little quicker (others have mentioned this makes the bike feel much better, which matches up perfectly with EX500 advice/experience). I'd personally feel safer going with a shock that's very similar to what the bike comes with, just with a stiffer spring (those are the reasons I'm currently using a NewGen shock on my 500). It should give you similar results, just with a bigger spring to handle a heavier rider. The ZX600 shock may have more features, but it's also a lot older and there doesn't seem to be much info on it to figure out if it actually is better than either of the other options. Additionally, the NewGen shock should improve the feel of the steering, while the ZX600 would take it in the opposite direction unless you got shorter dogbones too.