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Discussion Starter · #1 ·
Has anyone here run longer stroke 62.5 or 65mm on SB150?

Due to some travel spacer issue on my shock I've been riding it on 65mm stroke recently, yes fully aware of the warranty part, lets not get into that.

I know the main issue is the seat tube clearance, as I'm a lightweight at 68-70kg I have don't have tire rubbing seat tube issue. It also depend on what I had on my rear wheel, currently running 2.4 dissector. I believe if I'm on a assegai, most likely it will have rub on the rear.

What I also notice, is the bike doesn't pedal as well as before regardless how much I change the compression.
Normally I do run very close to bottom out since the bike is quite linear even with 4 positive spacer, I do get bottom out occasionally on huck to flat but that's expected for such kind of landing.

Another good point now, due to having longer stroke I don't bottom out so much now. The progressiveness seems to be spot on, having a few mm left the end of stroke even for some big landing.

btw, I'm on the 2021 SB150 frame, the rear triangle is noticeably stiffer than 2019 which added the rear flex less probably save abit to prevent rear tire rub.

Anybody running longer stroke here?
 

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The only impact changing shock stroke has in and of itself is how soon the bike bottoms out. Think of it this way, the bike has no idea what the shock stroke is unless you are on the bottom out bumper. Everything else is due to how much sag you are running at the wheel. If you are running 30% sag out of 65mm of shock stroke the wheel will be sitting deeper in its travel at a point with less anti-squat. If you were to decrease sag to 27%, ((0.3*60)/65), it would make the sag at the wheel identical to running 30% sag on a 60mm stroke shock. This results in the bike feeling exactly the same as before except for bottoming out a little deeper in travel.
 

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Discussion Starter · #3 · (Edited)
Ah I see, so my bike is actually in lowered compare to before with less anti-squat which explains why it pedal different.
So your saying if I put my 65mm stroke to 27%sag it will feel like 30% of 60mm stroke, this sound too good to be true, does it really feel exactly the same, I mean in terms of rebound, damping, compression all that? if this is the case, I wouldn't ever need to go back to 60mm stroke anymore and just play with the sag to reach what I want to be to simulating 60mm stroke's sag with a 65mm stroke.

According to your formula, ((0.30*65)/60)=0.325 which means if I put my original 60mm stroke to 32.5% sag, it would be identical as 30%sag in 65mm stroke, am I getting it right?

Also would changing stroke change the progressive curve too?
 

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Ah I see, so my bike is actually in lowered compare to before with less anti-squat which explains why it pedal different.
So your saying if I put my 65mm stroke to 27%sag it will feel like 30% of 60mm stroke, this sound too good to be true, does it really feel exactly the same, I mean in terms of rebound, damping, compression all that? if this is the case, I wouldn't ever need to go back to 60mm stroke anymore and just play with the sag to reach what I want to be to simulating 60mm stroke's sag with a 65mm stroke.

According to your formula, ((0.30*65)/60)=0.325 which means if I put my original 60mm stroke to 32.5% sag, it would be identical as 30%sag in 65mm stroke, am I getting it right?

Also would changing stroke change the progressive curve too?
You are correct. The ride height with 30% sag and a 65mm stroke shock is equivalent to 32.5% sag with the shorter shock stroke.

The only change to the leverage curve when a longer stroke shock is installed is the end of the curve extends out past the original stopping point. So for the first 60mm of shock stroke you have the exact same leverage ratio at any given time meaning all damping and spring characteristics would be the same. Technically it's a little more progressive because of that extension to the end of the leverage curve, but looking at that progression percentage is a very small portion of how it feels on a whole. Bottom out resistance is roughly proportional to shock stroke squared, so if you keep spring rate the same, increasing shock stroke to 65 from 60 adds 17% more bottom out resistance for a single large impact. The progression percentage is only really useful when looking at two bikes with the same shock stroke and same amount of travel.

But anyway, yeah if you run 27% sag and use the same shock settings as you did with the 60mm stroke, it will feel identical over that 60mm stroke range. This is why it's silly when companies offer different travel amounts for a frame by changing shock stroke. Sag is everything unless the eye-to-eye for the shock changes or the length of any other frame member.
 

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Discussion Starter · #5 ·
This is getting interesting. So a change of eye to eye or length of frame is where the Cascade Link come into to play I assume?

According to what you mentioned, would longer stroke actually be better choice as long as it doesn't reach a limitation of the frame like rubbing seat tube or stressing linkage, longer stroke increase bottom out resistance, extend progression all based on how much you play to maintain the original sag point?
 

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This is getting interesting. So a change of eye to eye or length of frame is where the Cascade Link come into to play I assume?

According to what you mentioned, would longer stroke actually be better choice as long as it doesn't reach a limitation of the frame like rubbing seat tube or stressing linkage, longer stroke increase bottom out resistance, extend progression all based on how much you play to maintain the original sag point?
Eye-to-eye stays the same with the links, but linkage dimensions change which alters leverage curve.

Changing the eye-to-eye length is common for mullet yokes. If you look at the combined length of the shock and yoke, by increasing that length It's pretty much extending the leverage curve on the top out side of things and then cutting the leverage curve short on the bottom out side of things if that makes sense.

I have never seen a downside to running the longest shock stroke possible with a frame as long as it doesn't cause issues. Confirming that there are no issues is something that needs a lot of attention though. It's not like I'm ever trying to pedal at bottom out so having that little bit extra travel at the end really doesn't have a downside. If you keep sag at the wheel the same it pedals the same, but then it gives the option for a little more sag for shuttling or park laps for example.
 

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The only impact changing shock stroke has in and of itself is how soon the bike bottoms out. Think of it this way, the bike has no idea what the shock stroke is unless you are on the bottom out bumper. Everything else is due to how much sag you are running at the wheel. If you are running 30% sag out of 65mm of shock stroke the wheel will be sitting deeper in its travel at a point with less anti-squat. If you were to decrease sag to 27%, ((0.3*60)/65), it would make the sag at the wheel identical to running 30% sag on a 60mm stroke shock. This results in the bike feeling exactly the same as before except for bottoming out a little deeper in travel.
You are assuming ther eye-2-eye has increased instead of removing the bottom out spacer which does not effect the percentage. There is just additional travel beyond what was specified.

Sent from my SM-G781V using Tapatalk
 

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You are assuming ther eye-2-eye has increased instead of removing the bottom out spacer which does not effect the percentage. There is just additional travel beyond what was specified.

Sent from my SM-G781V using Tapatalk
Definitely wasn't assuming eye-to-eye was changing. That causes a whole array of changes. If you are talking about percent sag, removing the stroke reducer and doing nothing else definitely affects that number. The amount of sag in mm won't change, but the percentage will. 30% sag of 60mm is 18mm. If you keep the same air pressure/spring rate and remove that stroke reducer your sag is still 18mm, but that has become 27.7% of the total shock stroke. The assumption was that pedaling issues were likely due to running 30% sag on a 65mm stroke shock which equates to 19.5mm of sag. That would be 32.5% sag if the same air pressure/spring rate was used with a 60mm stroke shock. Running more sag in terms of actual amount the shock sags and not percentage puts the BB lower while pedaling and results in there being less anti-squat in the pedaling position.
 

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Discussion Starter · #9 ·
You are correct. The ride height with 30% sag and a 65mm stroke shock is equivalent to 32.5% sag with the shorter shock stroke.

The only change to the leverage curve when a longer stroke shock is installed is the end of the curve extends out past the original stopping point. So for the first 60mm of shock stroke you have the exact same leverage ratio at any given time meaning all damping and spring characteristics would be the same. Technically it's a little more progressive because of that extension to the end of the leverage curve, but looking at that progression percentage is a very small portion of how it feels on a whole. Bottom out resistance is roughly proportional to shock stroke squared, so if you keep spring rate the same, increasing shock stroke to 65 from 60 adds 17% more bottom out resistance for a single large impact. The progression percentage is only really useful when looking at two bikes with the same shock stroke and same amount of travel.

But anyway, yeah if you run 27% sag and use the same shock settings as you did with the 60mm stroke, it will feel identical over that 60mm stroke range. This is why it's silly when companies offer different travel amounts for a frame by changing shock stroke. Sag is everything unless the eye-to-eye for the shock changes or the length of any other frame member.
With following what you've explain so far,
How or what formula you use to get 17% more bottom out resistance from?

As I'm planning to get an coil shock at the moment too, but changing sag point is very difficult as spring comes in fix increment, plus progressive spring is a different curve too.

Would Sprindex coil would be a better choice due to the changeable spring rate?
 

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With following what you've explain so far,
How or what formula you use to get 17% more bottom out resistance from?

As I'm planning to get an coil shock at the moment too, but changing sag point is very difficult as spring comes in fix increment, plus progressive spring is a different curve too.

Would Sprindex coil would be a better choice due to the changeable spring rate?
The amount of energy stored in a linear spring is (1/2)k(x^2) where k is the spring rate and x is the amount the spring is compressed. If you use the same spring rate then the ratio boils down to (65^2)/(60^2). The assumptions this makes are that damping is set such that it dissipates the same amount of energy on the same impact as before and that the spring is linear. Non-linear springs will obviously be different, but it still works as a good approximation for them. Air suspension will actually see a larger increase in bottom out resistance especially with the use of volume spacers because the longer the shock stroke is the more pronounced the end of stroke ramp is.

Sprindex is nice because you can set the sag however you want, but the range isn't super large. Usually I get a couple of inexpensive steel springs to find the correct spring rate and then get a lighter spring once I have it figured out. That's just because I like keeping part count on a bike down as much as possible. So I guess that comes down to priorities.
 
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