Suspension guide

[XXDEF1ANTXX]

On 2/5/2019 at 9:44 AM, tfaith08 said:

 

Set the main pressure to get your ride height where you want it. I’ve seen 35psi up to 140psi so you’ll have to mess with it. As for Evol pressure, I usually start at 2x the main chamber pressure and work up. I’ve found that I like mine at 48 and 125, but I’ve got a good friend of mine that runs the same arms and 35 and 120. I race at 180 and he races at 135.

For Floats and Evols, you set the pressure with the tires off the ground and then check.

As long as your swingarm isn’t more than +4, you should be okay, but -1” to +2 is the ballpark most like to fall into. Stock length is pretty spot on tbh.

Trails really like 4/1 rims too.


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Thanks for the info! I am currently looking at buying a set of bead locks and tires specifically to tackle hatfield mccoy, any suggestions on sizes and tire type?

[tfaith08]

Thanks for the info! I am currently looking at buying a set of bead locks and tires specifically to tackle hatfield mccoy, any suggestions on sizes and tire type?

Definitely go for 4/1 rims up front. Front beadlocks aren’t THAT necessary and single beadlock rear is usually enough. I don’t like dual beadlocks because of how aggravating it can be to center tires, but go for it if you think the terrain demands it.

I’ve always been a fan of DWT rims and tires and am lucky to be sponsored by them. I am also a huge fan of Goldspeed and OMF, but that’s where my preferences end. I’ve heard good and bad about Alba rims, but I’ve seen them win Baja classes and that’s hard to overlook.

As for tires, that’s going to be dictated by what size you want to run. For 21/20, pretty much any modern, premium tire is going to work well as long as it has a medium compound. I like Duro Hookups but iRzar are just a touch better. Ambush are good tires too.

I’ve never used anything bigger than 21/20 so I’d say to look at what the pros run if you want to go that route.

People will knock the pros because of special parts and payouts, but no pro is going to run shit parts. They’ll run slightly under the best at a minimum. This, I’ve seen personally.


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[XXDEF1ANTXX]

4 hours ago, tfaith08 said:

 

Definitely go for 4/1 rims up front. Front beadlocks aren’t THAT necessary and single beadlock rear is usually enough. I don’t like dual beadlocks because of how aggravating it can be to center tires, but go for it if you think the terrain demands it.

I’ve always been a fan of DWT rims and tires and am lucky to be sponsored by them. I am also a huge fan of Goldspeed and OMF, but that’s where my preferences end. I’ve heard good and bad about Alba rims, but I’ve seen them win Baja classes and that’s hard to overlook.

As for tires, that’s going to be dictated by what size you want to run. For 21/20, pretty much any modern, premium tire is going to work well as long as it has a medium compound. I like Duro Hookups but iRzar are just a touch better. Ambush are good tires too.

I’ve never used anything bigger than 21/20 so I’d say to look at what the pros run if you want to go that route.

People will knock the pros because of special parts and payouts, but no pro is going to run shit parts. They’ll run slightly under the best at a minimum. This, I’ve seen personally.


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Wow man thanks for the detailed response again! I just learned about the iRazrs from a buddy yesterday. They really piqued my interest. I took a step back and decided against getting the beadlocks, instead opting to put more money into getting the best tires I can. I want to do as much as I can to prevent any mishaps before I get out there and spending the money on good parts is not a deterrent for me. Right now I have it narrowed down to the iRazr and Razr 2's, I want to be sure that I have the right tools for the job even though my bike may me better than my banshee for this, which reminds me that I need new tires for that too. Thats another can of worms all together as I have a street plated 650R and that thing eats 50/50 DOT rated tires. 

[tfaith08]

Bump for pin and also spring rate ideas.

A lot of people here will run multiple spring rates but really don’t know much about them. The math behind them is about as complex as finding displacement from bore and stroke which I know almost everyone can do. If you aren’t going to follow the math (again, this is as basic as some of your color scheme ideas), you will not understand it. Just follow along and you’ll understand-ish it.

Say you have one spring and it measures 500lb/in. That means that it takes 500lb to compress the spring 1”. It takes 1000lbs to compress the spring 2”. Inversely, if you see the spring is compressed by 1.5”, you know there is 750lbs on it.

You can take this a step further and calculate it to incorporate the forces seen at preload. Say your spring is 12” long and measures 300lb/in. and you have the ride height set. If you lift the quad up until the tires are off the ground and measure the installed spring, it may come out to 11.5”. That means your spring is under a constant 150lb of force from the start. If you let it back down, it may compress to 10.75”. You now know that it is under 425lb it force.

***Quick side note: if you run a single rear spring and it has to be compressed more than about an inch just to get ride height, you may need a stiffer spring. This doesn’t hold up that well with really high leverage ratios (+14” swingarm for example) and that rule of thumb needs to be altered.

With multiple spring rates, you have this formula:

1/Ke = 1/K1 + 1/K2 + 1/K3

Where:
Ke = equivalent spring rate
K1 = spring rate 1
K2 = spring rate 2
K3 = spring rate 3
Etc.

If you only have 2 springs, you just go up to K2. If you have 4 (PEP and Elka stage 4s ffs), go up to K4.

To get an idea of this, use small numbers and only 2 spring rates. Let’s use 2lb/in and 4lb/in.

Fill those in for K1 and K2 (in any order) an follow the formula. Since all units of measure are in pounds per inch, you can drop lb/in.

1/Ke = 1/2 + 1/4

Simplify:

1/Ke = 2/4 + 4/4

Simplify again:

1/Ke = 3/4

Simplify again:

1/ke = 1/1.333

Finally:

Ke = 1.333

Your total combined spring force of 2lb/in and 4lb/in is 1.33lb/in.

That means that the springs, when stacked in series, will compress 1” when you apply 1.33lb.


Now do it for normal spring rates but without all the simplification. Use 240 and 360.

1/ke = 1/240 + 1/360

1/ke = 3/720 + 2/720

1/ke = 5/720

1/ke = 1/144

Ke = 144lb/in

The combined force required to compress a stacked 240lb/in spring and 360lb/in spring is 144lb.

Now let’s do it with 2x 500lb/in springs to show you the counter-intuition of it. I know most of you don’t like math, but this is simple shit. If you can’t do this then you probably shouldn’t be doing whatever job you’re doing to fund this hobby.

1/Ke = 1/500 + 1/500

1/ke = 2/500

1/ke = 1/250

Ke = 250

2x 500lb/in springs stacked together give an equivalent spring rate of 250lb/in. So again, this is counter-intuitive, but look at what’s actually happening. The spring has to see 500lb to compress one inch. So if you stack 2 together and only compress them a single inch, each spring is only getting compressed 1/2”. The 240 and 360 above have the same effect, but...

The amount that a specific spring out of a set will move in the series is given by this:

Lt (Ke/K1) = L1

OR

Length total x (equivalent rate/individual rate) = individual compressing ratio.

For the 240 and 360 pair, if you want to know how much only the 240 spring compresses if you compress the pair together, you use the formula above.

1” x (144/240) = 0.6”

If you compress them together for 1”, the 240lb spring will take up 0.6” of that.

Your shocks will have crossovers that limit the amount each spring compresses. If you’re running the 240 and 360 springs but the top spring can only compress an inch, you can just work the math to see how the spring rates pan out through the stroke.

72lb of force will compress 0.5”

144lb will compress 1”

216lb will compress 1.5”

Now we know that the 240lb spring can only compress an inch. So if it gets compressed 0.6x the total compressed distance, we can math fuck our way to see where the spring rate changes. I’m not writing the math out, but the formula is here:

(X/L1) = Lt

Where
X = crossover length
L1 = individual compressing distance
Lt = length total

The total length you’d have to compress the 240 and 360 pair before the 240 crossover kicked in and you only have the 360 active is 1.66”, or 239lb of force (144lb/in X 1.66”).

At 1.66”, your spring rate would jump from 144lb/in to 360lb/in.

Notes:

If you increase the main spring, it reduces the total compression length required to pass through the crossover and you may need to change the crossover as well if you want the main spring to be the sole active spring at the same point.

Secondary (or tender) springs can be and sometimes are as strong or stronger than the main spring. I’ve seen this on Works shocks and it works well if done properly.

More consistent leverage ratios are more tolerant of a more dynamic spring rate. If your leverage ratio ranges from 3:1 at full sag to 1.5:1 at full bump for example, you may be able to effectively run a more varied set of springs. If your leverage ratio varies from 5:1 down to 1.5:1 and you ran the same spring stack, your compression and rebound settings would be more difficult to dial in.

Single spring setups are not inherently inferior to multi-spring setups. They are sometimes more effective and sometimes less effective, but they are ALWAYS lighter. However, don’t chase a 2lb weight savings for sloppy suspension characteristics. It won’t make you faster. I ran triple rates up front on my banshee and switched from a dual rate to single rate in the rear. I far prefer a single rate setup to a dual rate setup on my main race quad but the best rear suspension I’ve ever been on (Levi’s hybrid) was a dual rate fox. The best front shocks I’ve ever been on was a quad-rate Stadium and LSR long travel setup. At the same time, people have won championships on single rate fronts. As with any suspension, never chase an arbitrary characteristic; only pursue what you need. A 375lb MX built with a killer suspension setup will always dominate a 300lb MX built with a cobbled together suspension. If you need the weight savings THAT bad, order a titanium spring.

Stiffer springs need less compression and more rebound damping.









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[ClaudeMachining]

F= k * X is the basic formula.

 

F= force

K = spring rate

X = compressed distance

 

For multiple spring, i also suggest to look at it as elctrical resistance putted in series thus the 1/ke = 1/k1 + ....

 

Same thing can be done in parallèl ( if you got 2 shock on the same side) the formula will became the same as resistance putted in parrallel (ke = k1+k2...)

 

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[tfaith08]

F= k * X is the basic formula.
 
F= force
K = spring rate
X = compressed distance
 
For multiple spring, i also suggest to look at it as elctrical resistance putted in series thus the 1/ke = 1/k1 + ....
 
Same thing can be done in parallèl ( if you got 2 shock on the same side) the formula will became the same as resistance putted in parrallel (ke = k1+k2...)
 
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Bingo. I didn’t remember which constants were used off hand so I just kind of used my own, but the math is there.

It always did fascinate me how frequently some things in physics pop up, like this and especially the inverse square law.

Do you know of any free 4 link software that I could use to post some more stuff up without having to rely on putting the maths into layman terms? It doesn’t need to be too complex, just enough that I can show bump steer, what caster actually affects, etc.

It’s way too easy to dive into design with this stuff, but 95% of the people don’t care to know that much or won’t comprehend it without reading it over and over. It’s super simple shit, it’s just that this affects that, that affects the third, the third alters this, and this requires you change the first thing again. So I’m kind of trying to find a balance between explaining it thoroughly enough and only telling people what they need to know in the shop and on the track.




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[ClaudeMachining]

Too drunk, will answer in a couples of days.

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[ClaudeMachining]

Bingo. I didn’t remember which constants were used off hand so I just kind of used my own, but the math is there.

It always did fascinate me how frequently some things in physics pop up, like this and especially the inverse square law.

Do you know of any free 4 link software that I could use to post some more stuff up without having to rely on putting the maths into layman terms? It doesn’t need to be too complex, just enough that I can show bump steer, what caster actually affects, etc.

It’s way too easy to dive into design with this stuff, but 95% of the people don’t care to know that much or won’t comprehend it without reading it over and over. It’s super simple shit, it’s just that this affects that, that affects the third, the third alters this, and this requires you change the first thing again. So I’m kind of trying to find a balance between explaining it thoroughly enough and only telling people what they need to know in the shop and on the track.




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You want a software to write equation??

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[tfaith08]

You want a software to write equation??

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Just something I can use to do basic models for front end setups.


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[375hp banshees]

On 6/9/2019 at 8:57 PM, ClaudeMachining said:

Too drunk, will answer in a couples of days.

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Sober yet?

Bump

[ClaudeMachining]

Sober yet?
Bump

Fook, i forgot about this one!!!

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[tfaith08]

Why does running compression all the way in hurt the shock? I've been running compression on the stiffest setting of my axis shocks for about three years.

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Some shocks won’t hold up like that. If you tighten past the last click, it can cut the fluid flow way too much and can bend the shock. Doesn’t happen much, but it can happen.

If you send a shock to someone like Blommel, he’ll look at your settings and revalve to make that the new center of adjustment if you like how it currently runs. Last click on your current setup will feel like mid-way on your new setup.


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[375hp banshees]

Matt just did mine, great guy!

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[tfaith08]

Bump for the noobs.


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[tfaith08]

Just a lil update for some random information. No particular goal here, just musings and random info.

Caster works together with the KPI. When you turn left, the caster pushes the left tire down and the right tire up. The KPI pushes both of them down.

This means that the KPI and caster together make the right tire stay roughly flat and the left tire push down quite a bit. This loads the front left tire and the back right tire and gives them more traction. This unloads the front right and back left tire and costs traction.

While sliding, this balances traction fairly well. When cornering left, this can make it unbalanced. To simply visualize it, turning toward one direction puts more weight on that tire and the one diagonal to it and they will have more traction.

Greater scrub radius just amplifies the shit out of this. Less offset is always better imo.

To get deeper into it, the quad wants to “seesaw” along those two tires. Depending on how hard you slide to the direction you’re turned, it can rock to one side or the other. Hanging off the inside will bias the weight and keep it flatter and more stable in a slide. The problem with a banshee is quite extensive here.

1. Ackerman wants the tire you’re turning to to be turned in sharper. When you seesaw to that direction, the tires want to pull it in 2 directions at once. This is okay for XC since you don’t slide as much and are usually at lower speed (greater Ackerman is better for lower speeds). For higher speed corners, lots of guys to go LT450R knuckles to keep he Ackerman more parallel and make that seesaw motion less noticeable. But for a banshee, that seesaw motion can load the other front tire (which is pulling less to the direction you’re traveling) and throw you back over the seesaw pivot.

2. The banshee is top heavy and front heavy. Amplifies the effect.

3. Short swingarm lifts under acceleration. Great for those who weight transfer well but terrible for those who don’t, especially in a sliding corner exit. This further lifts the quad.

TL;DR: too much caster can kill corner stability and make it more difficult to physically turn. Too little can make it highly unstable under braking.


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