[madpharma]

After some bouncing around on the dh bike around the house, I noticed that I can push the bottom out bumper till the end of the stroke just pushing down hard. Sag its 30-31% so nothing crazy, and its a progressive leverage bike.

I dont bottom out often, or at least not a hard bottom that I get to notice, but reaching the bottom out bumper so easily made me ask myself if Im using the right spring rate besides what sag % its telling me.

Are you people able to push it to the end as easy as this?

Cheers.

 

[djjohnr]

That doesn't sound right. Have you used a spring calculator to figure out a starting point? http://www.bearandwife.com/bear/cycling/springcalc.html

 

[madpharma]

Yes the spring its inline with what the calculator gives me, the sag at the shock its ok, and the shock works as it should.

Im just curious as i never noticed that that I could push to the end so easily bouncing around and pushing down. Have you tried?
cheers

 

[SkaredShtles]

Def sounds wrong.

 

[Sandwich]

I've found that sag can lie a little bit depending on the smoothness of your rear suspension as well as the accuracy of your measurements. Are you SURE your sag is 31% and not 35%? Are your pivots moving smoothly without binding? Or if you're from the future, your marin/polygon SLIDEYTUBERINO?

Sounds like you need to go up 50-100lb in spring rate to me. I'd try a 100, if you have access, and see what your sag then measures. I have had bikes that measure sag very similarly with large changes in spring rate. It can be a bit of trial and error, regardless of what calculators tell you. I think TFtuned's calc spitballs like 150lb under where I am now.

edit: just checked and it's 100lb lower than the rate I settled on.

 

[Sandwich]

I've found that sag can lie a little bit depending on the smoothness of your rear suspension as well as the accuracy of your measurements. Are you SURE your sag is 31% and not 35%? Are your pivots moving smoothly without binding? Or if you're from the future, your marin/polygon SLIDEYTUBERINO?

Sounds like you need to go up 50-100lb in spring rate to me. I'd try a 100, if you have access, and see what your sag then measures. I have had bikes that measure sag very similarly with large changes in spring rate. It can be a bit of trial and error, regardless of what calculators tell you. I think TFtuned's calc spitballs like 150lb under where I am now.

edit: just checked and it's 100lb lower than the rate I settled on.

double edit: I also have a shock with a bottom out assist (RC4). TFTuned recommends a 410-450, and I believe I'm on a 550 with bottom out cranked.

 

[madpharma]

I've found that sag can lie a little bit depending on the smoothness of your rear suspension as well as the accuracy of your measurements. Are you SURE your sag is 31% and not 35%? Are your pivots moving smoothly without binding? Or if you're from the future, your marin/polygon SLIDEYTUBERINO?

Sounds like you need to go up 50-100lb in spring rate to me. I'd try a 100, if you have access, and see what your sag then measures. I have had bikes that measure sag very similarly with large changes in spring rate. It can be a bit of trial and error, regardless of what calculators tell you. I think TFtuned's calc spitballs like 150lb under where I am now.

edit: just checked and it's 100lb lower than the rate I settled on.

Thanks for the answers!
Pivots are running smooth (changed them last week) and sag its 27mm on a 89mm stroke which gives 30%.
I almost never had a harsh bottom out with the coil shock. Im just surprised that I can get that deep bouncing hard and dont bottom out harsh in a jump for example.

The bumper must be working lol haha

If anyone tries with the dh bike to do the same can feel free to post if it happens the same.
I will put a harder spring just to try, as Im happy with the performance of the shock.

 

[6thElement]

double edit: I also have a shock with a bottom out assist (RC4). TFTuned recommends a 410-450, and I believe I'm on a 550 with bottom out cranked.

Is that on your Fury?

 

[Sandwich]

Is that on your Fury?

Yeah, it's a very linear bike so I think it rewards running less sag than a more progressive one, but I've been in love with the performance of my current setup- good through the bumps and awesome over high speed lips. The bike has been pretty flexible with setup, even running a lighter weight spring was still pretty good, though jumps suffered. Now I have consistent performance throughout.

@madpharma , one thing to consider is the leverage that you're putting on the bike when you're way over the back like that. It's hard to get a handle on just how much force you're throwing. It's possible you're reaching bottom out levels of compression...but again my bet is that you need a firmer spring and something is just slightly off with your measurements.

 

[canadmos]

Not that I know much... but in your parking lot test, could you simply not be activating the high speed compression? While out on the trail in real world conditions, you're getting moar damping?

 

[madpharma]

Not that I know much... but in your parking lot test, could you simply not be activating the high speed compression? While out on the trail in real world conditions, you're getting moar damping?

Could be a good explanation, because landing a jump most definitely exceed the force and speed that I can make just pushing hard with my legs and I dont feel any bottom out.

 

[madpharma]

Yeah, it's a very linear bike so I think it rewards running less sag than a more progressive one, but I've been in love with the performance of my current setup- good through the bumps and awesome over high speed lips. The bike has been pretty flexible with setup, even running a lighter weight spring was still pretty good, though jumps suffered. Now I have consistent performance throughout.

@madpharma , one thing to consider is the leverage that you're putting on the bike when you're way over the back like that. It's hard to get a handle on just how much force you're throwing. It's possible you're reaching bottom out levels of compression...but again my bet is that you need a firmer spring and something is just slightly off with your measurements.

Yes, I could be subestimating the force im aplying. Anyway Im going to follow you advice and try a harder spring to compare setup/feeling/measurements

 

[Loki87]

I've found that sag can lie a little bit depending on the smoothness of your rear suspension as well as the accuracy of your measurements. Are you SURE your sag is 31% and not 35%? Are your pivots moving smoothly without binding? Or if you're from the future, your marin/polygon SLIDEYTUBERINO?

Sounds like you need to go up 50-100lb in spring rate to me. I'd try a 100, if you have access, and see what your sag then measures. I have had bikes that measure sag very similarly with large changes in spring rate. It can be a bit of trial and error, regardless of what calculators tell you. I think TFtuned's calc spitballs like 150lb under where I am now.

edit: just checked and it's 100lb lower than the rate I settled on.

I too have noticed on some bikes that the spring rate could vary rather drastically with little change in sag.
Definitely try a stiffer spring and see how that feels.

 

[buckoW]

30% is usually too much sag, imo. Try around 25%

 

[Westy]

Probably needz moar shimz

 

[Happymtb.fr]

I have yet too see an online calculator that give accurate results for anything else than a perfectly linear linkage...