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Liked a comment about slideshow How To Get The Most Out Of Your RockShox Suspension 6/19/2015 10:22 PM
C138_rockshox_spota

I'm impressed by your enthusiasm.

Re-read my comment with the graph. I don't disagree with you about how a volume change at the same starting pressure will alter the spring rate.

However, the slope (aka spring rate) does indeed change when you up the air pressure. Let's do some very basic math, using the nice orange and red dots at the 2-inch travel mark on the 4-inch chamber lines as an easy reference point.

Rise / Run = Slope

The 4-inch chamber with 200psi rises from 200lbs at 0-inches to 400lbs at 2-inches.
The 4-inch chamber with 100psi rises from 100lbs at 0-inches to 200lbs at 2-inches.

400lbs - 200lbs = 200lbs
200lbs - 100lbs = 100lbs

200lbs (rise) / 2in (run) = 100lbs/in
100lbs (rise) / 2in (run) = 50lbs/in

While they may look "more or less parallel," they're far from it.

This slideshow has 35 comments.

Liked a comment about slideshow How To Get The Most Out Of Your RockShox Suspension 6/19/2015 9:41 PM
C138_rockshox_spota

kc358, you've got some wires crossed. Changing air pressure does indeed change the spring rate. Here's a graph from RockShox to illustrate this fact:



Spring rate describes the stiffness of a spring and is defined as the (change in force) / (change in displacement). It's usually measured in lbs/in - the pounds of force necessary to compress the spring by one inch. In the graph, note the red and orange lines that represent different pressures in the same volume. In the case of the 100psi red line, we see a change in force of 100lb over 2-inches. The 200psi orange line sees a change of 200lb in those same 2-inches. If the spring rate did not increase as you increase pressure, the change in force over those 2-inches would be the same.

As you noted, almost all air springs have a progressive spring rate, which means that they get stiffer the more they are compressed. As you also noted, yes, changing the volume also increases the spring rate (note the red and blue lines and their respective 100lb increase vs ~200lb increase over 2-inches) - this is why many riders will reduce air pressure by a few psi as they add more Tokens in order to keep a similar sag level and initial stroke feel.

Yes, the force necessary to initially compress the air spring due to the static pressure (breakaway force) also increases as you up the pressure, but RockShox offsets this with their auto-adjusting SoloAir negative spring, The effect of the negative spring isn't shown in this graph, but the breakaway force is reduced by the amount of force created by the negative spring pressure.

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Liked a comment about news blog RESULTS - Leogang World Cup Downhill Final 6/14/2015 8:52 AM
C50_twitter3_1382472127



Courtesy of Uncle Cliffy.

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Liked a comment about news blog RIP Dirt Magazine (Print) 3/31/2015 11:19 AM
C50_screen_shot_2015_03_09_at_2.10.12_pm_1425936051

i think my comment about "paying a couple bucks" got focused on too much. subscription revenue never pays for a magazine's existence, the ads do, just like with vital. we run MTB company ads so we can provide you all with free content that's magazine-quality. with that said, i'd imagine it's just really hard for advertisers to find value in print as they focus on online ad campaigns or instagram/social media campaigns. was my post above dramatic? yes, but it is really sad to me that there isn't room for a print magazine like dirt, regardless of timeliness of content or cost. looking at dirt on an ipad isn't the same as holding the paper version, but i'm sure dragging a buggy across the plains with a horse had a satisfaction that driving a car doesn't give, too. times change and i think it's ok to lament that.

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Liked a comment about product review Tested: GT Sanction Pro Frame 11/19/2014 2:52 PM
Liked a comment about product review Tested: GT Sanction Pro Frame 11/19/2014 2:51 PM
C50

Two questions for ya Jeff:
1) How do you think this compares with the new SC Nomad or YT Capra? They all seem like bikes with similar purposes in mind.
2) Is a shock swap something you think would help the mid-stroke support? Maybe a Vivid Air or CCDBair?

This product_review has 23 comments.

Liked a comment about video Vital RAW - World Champs Hafjell DH Practice 9/4/2014 4:41 PM
C138x104

I think for world champs raws need to be extra long. Like this is one of the last glimpses of raw we'll see for awhile, we deserve extra long and extra awesome raw vids

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Liked a comment about feature Value DH Project: Building The Best Downhill Bike For Your $$$ 6/20/2014 1:18 PM
C50_fastesttoilet_1403751711

I know it goes against every fiber of your being looking at something that's not brand spanking new, current model, even if it's cheaper. But the much bigger reality of buying more affordable bike parts is buying parts that have been sitting in a warehouse for over a year and aren't getting marketed as hard as the first 5 minutes of its life. Do some of that. Because that's what really constitutes a cheaper build for most people while still not buying used.

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