Longer Travel fork with more sag VS Shorter travel fork with less sag. What difference does it make?

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Longer Travel fork with more sag VS Shorter travel fork with less sag. What difference does it make?
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Posted: Jan 17, 2022 at 4:01 Quote
Hi there,

I have a simple question as the title suggest's.

I have an ebike with 170mm fork travel (zeb) on an 29er wheel.
I like how the bike ride's when i have a 15% sag on the fork.
But with this sag setting the fork is a bit harsh for me on the small pump compliance and on rocky trails.

So my question is, what if i install a longer airshaft and convert it to lets say into 190mm fork travel but with more sag?
An 170mm fork with 15% sag is about equal (in length when saged - loaded) with an 190mm fork and a 25% sag.

This way i will maintain the geometry of the bike unchanged, and i would be able to set up the fork with 25% sag which will make it smoother.
Obviously, i will use less pressure in the fork and i will adjust the rebound a bit faster (due to less pressure) to compensate this change.

The less pressure will probably make the fork loose mid-stroke support so maybe i will find my self adding a couple of bottomless tokens.

What am i missing here?
Thanks a lot for your time.

Posted: Jan 17, 2022 at 5:44 Quote
What will happen is you will basically have a much softer fork so more fork dive...running 25% sag on the larger fork will be like running more than 25% sag on the shorter fork in terms of softness..it will be super soft in comparison...dive a lot more during braking and over bumps especially on steep declines and generally will be much harder to get the front wheel to lift up. If you fitted the longer fork and has the same percentage sag you would just have a slightly softer fork with a bit more travel. But upping for length and increasing sag a lot will be a massive change to how supportive the front end feels and will feel much much mushier.

Posted: Jan 17, 2022 at 6:01 Quote
Danzzz88 wrote:
What will happen is you will basically have a much softer fork so more fork dive...running 25% sag on the larger fork will be like running more than 25% sag on the shorter fork in terms of softness..it will be super soft in comparison...dive a lot more during braking and over bumps especially on steep declines and generally will be much harder to get the front wheel to lift up. If you fitted the longer fork and has the same percentage sag you would just have a slightly softer fork with a bit more travel. But upping for length and increasing sag a lot will be a massive change to how supportive the front end feels and will feel much much mushier.

Thanks for the advice.
But by installing a couple of tokens maybe i could compensate this midd-support. So overall isn't it possible to just have a benefit (softer fork which is my goal) with similar if not equal mid support?


Why the longer travel fork at 25% sag will be softer than the shorter travel fork at 25%??

Posted: Jan 17, 2022 at 7:26 Quote
Vbar wrote:
Danzzz88 wrote:
What will happen is you will basically have a much softer fork so more fork dive...running 25% sag on the larger fork will be like running more than 25% sag on the shorter fork in terms of softness..it will be super soft in comparison...dive a lot more during braking and over bumps especially on steep declines and generally will be much harder to get the front wheel to lift up. If you fitted the longer fork and has the same percentage sag you would just have a slightly softer fork with a bit more travel. But upping for length and increasing sag a lot will be a massive change to how supportive the front end feels and will feel much much mushier.

Thanks for the advice.
But by installing a couple of tokens maybe i could compensate this midd-support. So overall isn't it possible to just have a benefit (softer fork which is my goal) with similar if not equal mid support?


Why the longer travel fork at 25% sag will be softer than the shorter travel fork at 25%??

It's cause the longer fork has more travel, therefore every mm increases the pressure less in a long fork vs a short one.

Are there tokens in your current fork? Why not take them out?

Posted: Jan 17, 2022 at 8:33 Quote
ssantana wrote:
Vbar wrote:
Danzzz88 wrote:
What will happen is you will basically have a much softer fork so more fork dive...running 25% sag on the larger fork will be like running more than 25% sag on the shorter fork in terms of softness..it will be super soft in comparison...dive a lot more during braking and over bumps especially on steep declines and generally will be much harder to get the front wheel to lift up. If you fitted the longer fork and has the same percentage sag you would just have a slightly softer fork with a bit more travel. But upping for length and increasing sag a lot will be a massive change to how supportive the front end feels and will feel much much mushier.

Thanks for the advice.
But by installing a couple of tokens maybe i could compensate this midd-support. So overall isn't it possible to just have a benefit (softer fork which is my goal) with similar if not equal mid support?


Why the longer travel fork at 25% sag will be softer than the shorter travel fork at 25%??

It's cause the longer fork has more travel, therefore every mm increases the pressure less in a long fork vs a short one.

Are there tokens in your current fork? Why not take them out?

Hey man thanks for the explanation very clear.

I have no bottomless tokens in, i have removed them all.
But the fork is still a bit harsh when at 15% sag.

So what do you think?
Is what i am thinking of a possible solution?
Thanks man

Posted: Jan 17, 2022 at 8:40 Quote
Vbar wrote:
ssantana wrote:
Vbar wrote:


Thanks for the advice.
But by installing a couple of tokens maybe i could compensate this midd-support. So overall isn't it possible to just have a benefit (softer fork which is my goal) with similar if not equal mid support?


Why the longer travel fork at 25% sag will be softer than the shorter travel fork at 25%??

It's cause the longer fork has more travel, therefore every mm increases the pressure less in a long fork vs a short one.

Are there tokens in your current fork? Why not take them out?

Hey man thanks for the explanation very clear.

I have no bottomless tokens in, i have removed them all.
But the fork is still a bit harsh when at 15% sag.

So what do you think?
Is what i am thinking of a possible solution?
Thanks man

It might be possible but I feel like what you want is achievable by your fork. What's your hsc at? Also is there a reason you don't want to run more sag on your current fork?

Posted: Jan 17, 2022 at 10:59 Quote
ssantana wrote:
It might be possible but I feel like what you want is achievable by your fork. What's your hsc at? Also is there a reason you don't want to run more sag on your current fork?

Unfortunately i have the zeb basic version so i dont have damper with settings. Its the closed one the charger R. So no compression settings for me just rebound settings.

I like how the bike feels when my fork is at 15% sag. I get enough support in the mid stroke while at the same time it stands high on its travel. So the bike stands tall in the front and it gives me confidence. But on the other hand its becoming a bit harsh on rocky terrain.
I have it at 65-68 psi.

With lower pressures i have tested it until 50psi with about 35% sag i mange to make it plush but then the fork looses support in the mid-stroke. Adding tokens the fork looses small bump compliance even when at low pressures.
So i am stuck!
What else can i try?

I have ebike and i am with gear 90kgr just for the record.
BTW rockshox recommends 78 psi but this number is out of question. If i have slightly harsh ride with 65 and sag about 15-20% you can imagine how it rides at 78psi.

Keep also in mind i ride on very rocky trails dh tracks.

Thanks!

Posted: Jan 17, 2022 at 12:20 Quote
Vbar wrote:
ssantana wrote:
It might be possible but I feel like what you want is achievable by your fork. What's your hsc at? Also is there a reason you don't want to run more sag on your current fork?

Unfortunately i have the zeb basic version so i dont have damper with settings. Its the closed one the charger R. So no compression settings for me just rebound settings.

I like how the bike feels when my fork is at 15% sag. I get enough support in the mid stroke while at the same time it stands high on its travel. So the bike stands tall in the front and it gives me confidence. But on the other hand its becoming a bit harsh on rocky terrain.
I have it at 65-68 psi.

With lower pressures i have tested it until 50psi with about 35% sag i mange to make it plush but then the fork looses support in the mid-stroke. Adding tokens the fork looses small bump compliance even when at low pressures.
So i am stuck!
What else can i try?

I have ebike and i am with gear 90kgr just for the record.
BTW rockshox recommends 78 psi but this number is out of question. If i have slightly harsh ride with 65 and sag about 15-20% you can imagine how it rides at 78psi.

Keep also in mind i ride on very rocky trails dh tracks.

Thanks!

Oh man that stinks about compression settings. I ride rocky trails as well and my sweet spot was where I was able to run a bit lower pressure with a decent amount of of LSC to keep me high while very little HSC to keep small bump good but it looks like you don't have that option. My concern would be you jump to 190 and you end up getting what you got with high sag on the 170. Your fork has no compression adjustment at all? If it were me I would look into upgrading the damper but I have never run a rockshox fork before

Posted: Jan 17, 2022 at 13:12 Quote
Well i have been waiting this upgrade already for more than 2 months but the damper is still not available to purchase...

This is why i am considering other alternatives for the moment.

The damper i am having now has no adjustments at all. Only rebound nothing else.

Posted: Jan 17, 2022 at 13:57 Quote
Sounds like a vorsprung secus or luftkappe would help quite a bit. It would let you keep a similar pressure and get rid of some of the harshness.

Posted: Jan 18, 2022 at 21:32 Quote
Hi Vbar. I kow you've menteioned that it is not viable to run the fork at RockShox suggested pressure (78psi), becuase you are already runnin it at 65psi and it's already too harsh.

Have you actually tried it at 78psi?

Sometimes air pressure and fork setup doesn't work how we assume. I have a Lyrik that I ran at low pressure for ages and always complained that it was way too harsh. Eventually I put an extra 10psi in it and brough it up to RockSHox recomendation, and it was amazing!
My theory is that at a lower pressure, the fork blows through the midstroke, straight into the end stroke where it gets a bit spikey (due to the fork having much less positive volume when in the end stroke - regardless of spacers). When I increased the air pressure, I got much better midstroke support which stopped it from diving into the spikey end stroke. It would only get to the end stroke when I really needed it (e.g. taking a decent hit, landing a drop etc) and ramp up nicely.

I'm no expert, but I've learned a few things through trial and error. Try having a play with higher pressure and see what it does.

Posted: Jan 19, 2022 at 1:53 Quote
What your feeling is just how air forks work. If you want it to ride high, you need more pressure, at the expense of small bump compliance. If you want soft supple early travel, you'll lose the support and it'll dive into the ramp up. Basically you've got to find a balance.
Also, don't set your pressure by sag, it's impossible to measure accurately and repeatedly. Instead, set it by natural frequency and feel. What feels right, usually IS right.
I also agree with the poster above who suggested setting your pressure to actually what RS recommend - if you haven't done it, how do you know if it's right for you or not? I've spent hours trying to get my Lyrik set how I like, and in that time I've tried everything from 65 to 95psi, and felt that the higher pressure with no tokens works best for me. YMMV.

Posted: Jan 19, 2022 at 2:06 Quote
Cpembo6 wrote:
Hi Vbar. I kow you've menteioned that it is not viable to run the fork at RockShox suggested pressure (78psi), becuase you are already runnin it at 65psi and it's already too harsh.

Have you actually tried it at 78psi?

Sometimes air pressure and fork setup doesn't work how we assume. I have a Lyrik that I ran at low pressure for ages and always complained that it was way too harsh. Eventually I put an extra 10psi in it and brough it up to RockSHox recomendation, and it was amazing!
My theory is that at a lower pressure, the fork blows through the midstroke, straight into the end stroke where it gets a bit spikey (due to the fork having much less positive volume when in the end stroke - regardless of spacers). When I increased the air pressure, I got much better midstroke support which stopped it from diving into the spikey end stroke. It would only get to the end stroke when I really needed it (e.g. taking a decent hit, landing a drop etc) and ramp up nicely.

I'm no expert, but I've learned a few things through trial and error. Try having a play with higher pressure and see what it does.


Hi there.
First of all thank you for your suggestion.
Yesterday evening i eventually tried 75psi and guess what....lolol... the fork worked extremely well! It amazed me.
Indeed you are absolutely correct and the explanation you said makes perfect sense.

Thanks for your comment.

Posted: Jan 19, 2022 at 5:06 Quote
TimMog wrote:
I also agree with the poster above who suggested setting your pressure to actually what RS recommend - if you haven't done it, how do you know if it's right for you or not? I've spent hours trying to get my Lyrik set how I like, and in that time I've tried everything from 65 to 95psi, and felt that the higher pressure with no tokens works best for me. YMMV.

Hi and thanks for your comment.
You are absolutely correct and here is how i ended up here asking this question.

When my bike was delivered to me (about 5 months ago) it was a day before a race and I decided to run the race with my new bike.
So i set the rockshox recommended settings at 78psi with one token in and started the race (after checking all bike bolts etc).

I finished the race (drops jumps etc) and the fork was very very stiff and i didnt manage to use more than 50% of forks travel in a full race !!
With my previous bike and a Yari 170mm also 29er and also on an ebike i was using 87 psi and i was using on every ride all of my travel and on some trails I was also bottoming out smoothly (no tokens in the Yari but i was using the RC2.1 damper which is the best damper that rockshox offers).

So when i realised that the Zeb not only felt very stiff but also that i was using 50% of the travel with 78psi I removed the token and i started lowering the pressure until i manage to use full travel.
Eventually in order to use full travel i ended up with the amazing 36psi (lolol).
Then after a couple of days my rockshox pump went off and i replaced batteries... With new batteries i saw that eventually i was using 55 psi in the fork (and not 35psi....) in order to use full travel.

Then came a DH race in which i was bottoming out an almost all jumps so i started adding pressure in the fork and i ended up to 65-68 psi for the race with very few bottom outs and using 100% of travel. The fork was not harsh as expected.

Now after yesterdays test i managed to use 80% of the travel with 75psi on a local trail that has no gaps jumps drops just rockgardens...
So i strongly believe that if i go to a trail with gaps, drops jumps etc i will most likely use full travel even with 75psi.


Obviously the pump tricked me at some point, but if you consider that initially with 78psi (and a token) i was using in a full race 50% of the travel and now with 75psi (no token) i am using 80% of the travel (without jumps etc) its like the fork somehow softened during the usage.
I really dont know and i cant understand why.

So in sort, to answer your question yes i have tried 78psi with a token and i couldn't ride this fork and make it use full travel.
Now with 75psi (but no token) the difference is night and day. I really dont know maybe the pump was tricking me right from the beginning of the story?
I really don't know.
Additionally after the first race with this bike i gave my bike to very capable DH rider and friend and he also told me that my fork is very very stiff and i should remove pressure. At that point i was having 78psi with one token in...

So please tell me now what is going on here...?

Posted: Jan 19, 2022 at 6:14 Quote
I think like mine the fork needed breaking in...I was barely using half travel also..I had to use the fork for a while until the bushings loosened up. I also did a lowers service...also it cold have been a blocked equalisation port from too much grease etc affecting negative chamber pressure and also possibly trapped air in the lowers.

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