[wolverine_peltz]

What loaded/rider rear sag are you guys targeting for your bike? I believe rear wheel travel for the Bobber / Speedmaster is 73mm. Following some of the shock supplier recommendations, we should be targeting about 25% of that for standard riding -- or 18.25mm.

Is that roughly what you have set rider sag to target on the rear?



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[Mike]

Short answer: I use 25% for compression.

Long answer:
I use the compression of the actual shock instead. For me, it's easier. Most instructions I've seen for this method recommend 30% compression but I cheat slightly to 25% because of the short travel. Frankly, the difference between 25% and 30% is not really much on such a short travel, but that's my sweet spot.
However you do it, any adjustable aftermarket shock is a massive upgrade over stock but there's no perfect setting with the Bobber. The travel is very limited and even the best aftermarket units cannot change that. I wouldn't get overly bogged down by any one specific recommendation or number. It's more a question of what bothers you the least, the type of roads you ride on, and your riding style.
Too much preload gives the unit more travel to absorb bumps, which allows you to use a softer dampening, but it also has less travel to drop for a divot and will be rougher in that direction. Too little preload and the opposite is true. Same for the dampening. Your choice in the end comes down to stiffer/never bottoms out, soft/bottoms out often, or somewhere balanced in between that can handle most but occasionally bottoms out on larger bumps.

I would recommend you set the preload somewhere in that 25-30% range (18-21mm using your method, an insignificant difference), then test ride and adjust the dampening to your taste. That's where you'll find the bigger variability and customization.

 

[wolverine_peltz]

Short answer: I use 25% for compression.

Long answer:
I use the compression of the actual shock instead. For me, it's easier. Most instructions I've seen for this method recommend 30% compression but I cheat slightly to 25% because of the short travel. Frankly, the difference between 25% and 30% is not really much on such a short travel, but that's my sweet spot.
However you do it, any adjustable aftermarket shock is a massive upgrade over stock but there's no perfect setting with the Bobber. The travel is very limited and even the best aftermarket units cannot change that. I wouldn't get overly bogged down by any one specific recommendation or number. It's more a question of what bothers you the least, the type of roads you ride on, and your riding style.
Too much preload gives the unit more travel to absorb bumps, which allows you to use a softer dampening, but it also has less travel to drop for a divot and will be rougher in that direction. Too little preload and the opposite is true. Same for the dampening. Your choice in the end comes down to stiffer/never bottoms out, soft/bottoms out often, or somewhere balanced in between that can handle most but occasionally bottoms out on larger bumps.

I would recommend you set the preload somewhere in that 25-30% range (18-21mm using your method, an insignificant difference), then test ride and adjust the dampening to your taste. That's where you'll find the bigger variability and customization.

Thanks Mike. So what is your exact MM rider sag? In talking to Nitron, they recommended 30mm for this bike. That would seem to be on the high end, but they also said wheel travel was 100mm, not 73mm, for the Bobber / Speedmaster.

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[Mike]

I've never measured the sag that way so unfortunately I cannot give you an answer. I've only measured on the shock. The suspension will only travel what the shock travel allows, so if you are doing a percentage of that you're good. There's no guesswork on what the travel is elsewhere.e.g. 73mm or 100mm?

Best to measure the unloaded distance between the piston walls of the shock on your bike and do a percentage from there. (I added a photo of an old shock with notes to show where I'm talking about.) That is its maximum travel potential. Measure wall to wall, ignore the rubber stopper. If the unit is already installed, jack the bike up at the rear until the wheel hangs freely to get the weight off before measuring.

Preload is definitely important, but I really wouldn't worry about being super precise to the ½mm. It's not that critical. Get it close as reasonably possibly and don't lose any sleep beyond that. Once it's set, you can forget about it. The dampening adjustment is where the real wow factor is. With preload now adjusted, you should be able to cover the entire range from too soft to too hard. And the best part with these bikes is that the dial is very accessible, at the rear under the seat. You can reach back at a light and make an adjustment during your ride. Start with whatever factory set, and then go one click at a time softer or firmer depending on how it rides. (The firmer your seat is, the more you'll notice the differences.)

 

[stjan]

Hm.. 50 mm probably is not ok?

 

[Mike]

Hm.. 50 mm probably is not ok? View attachment 57878

The 73mm/100mm mentioned earlier is not for here. It is for a different measurement. Do not worry that this is only 50mm, but you very possibly might still need to adjust the preload. I don't know how much you weigh, but I have the same shock as you and it has a lot more preload. I was surprised when I saw in the photo how little you have.

For your measurements:

• lift the bike so that the wheel hangs free.
• measure the distance on your shock. It will now be a bit longer than 50mm. It will be X mm.
• Bring the bike down and sit on it with all your weight and gear.
• Measure the shock now with your weight on the bike. It will be Y mm.
• Y mm should be 25% smaller than X mm. 0.75 * X mm = Y mm
• If it does not match, adjust the preload.

You might need a friend to help measure when you sit on the bike.