Suspension guide

[tfaith08]

Suspension discussion

 

I’m not really sure that there is a comprehensive guide to ATV suspension anywhere, much less a banshee, so I’ll do my best to throw as much info into this as possible.

 

Terminology (in no particular order):

 

Camber- defines how the tires lean in at the top. The more elevation changes from your left to right (uneven surface or steep berms), the more camber you may want. 1-6* is common.

 

Toe- the inward facing angle of the front tires when viewed from above. More is good for stability in corner exit, straight lines, and rough terrain. Less is good for smooth and slow speed terrain. 2-6* is common.

 

Caster- defines how the top of the steering angle leans back when viewed from the side. Use more caster for rough terrain. Flat track is commonly 1-3*. Desert racing is commonly around 7. Everything else is usually in the middle. Helps keep the tires straight under impacts. More caster will give more camber on the outside tire when turning and can help dig more. Some people add caster to prevent the tire from rolling over the sidewalls on the outside tire, but the real solution isn’t more caster; its to add more tire pressure.

 

Steering Angle Inclination (SAI) or King Pin Inclination (KPI)- the line drawn between the pivot point of the upper and lower ball joints, and how that line is related to the centerline of your tire when viewed from the front. Basically the same as caster except viewed from the front. You can’t change this unless you use different knuckles. When you turn the handlebars, this is the angle your tires turn around when viewed from the front. Google has sufficient info on this.

 

Included angle- the combined angle between KPI and camber. Since you can’t change this with practically any independent front suspension ATV, it is irrelevant here, but it is easy to mix up with KPI.

 

Scrub radius- the distance between the KPI and the center of your contact patch where they meet the ground. This is your #1 contributor to feedback. This is usually 1” or so. You want it at around 1/8”. Different offsets, different tire heights, different tire pressures, camber settings, and different tire profiles affect this. A positive scrub radius means that when you hit something with a front tire, that tire will push back and turn the bars (feedback). A negative scrub radius will make the tire turn the other way. Zero scrub radius can be unpredictable in rough terrain. Flat track setups can vary the most (flat tire profile). 4/1 rims are very good for tires under 21”. 21-23” front tires can be made to work with 3/2 offset, but will come down to rider preference. 95% of all setups will benefit from a 4/1 rim setup. Wheel spacers are neither mechanically not geometrically wise.

 

Scrub- how the tires move in and out through the suspension stroke when viewed from the front.

 

Rake- the angle that the suspension leans back in front. Helps with rough terrain, sudden impacts.

 

Compressed length- the length of the shock when fully compressed. Some give this number when the shock body contacts the bumper, some give it when the bumper is pushed through. Some give both. Too long will cut available up-travel. Too short will cause you to lay the frame on the ground.

 

Extended length- the non-compressed length of the shock. Too long can bind ball joints. Too short cuts ground clearance.

 

Leverage ratio- the ratio of vertical wheel movement to shock shaft movement. Also called a motion ratio. 1.7-2.8 is common. 2-2.4 is most common. 11” of wheel travel and 5.5” of shaft travel equal a 2:1 leverage ratio. Lower ratios are usually better.

 

Long travel- doesn’t necessarily mean more travel. It can be more wheel travel, it can be more shaft travel, it can be both or neither. What it means for the ATV crowd is that the setup in question will have leverage ratios have been altered, usually in favor of a lower ratio. Long travel also means a longer than standard shock is used. Longer shocks are a better choice the majority of the time.

 

Standard travel- uses OEM compressed and extended length shock specs.

 

Preload: how much a spring is compressed beyond its resting length. This is also used when adjusting ride height in that adjusting the retainer down will compress the spring(s) more and increase ride height.

 

Compression- the resistance the valving has to being compressed.

 

Low speed compression- the resistance the valving has to being compressed when compressed slowly. Affects body roll, brake dive, bottom out resistance on the face of a jump or very smooth landing of a jump.

 

High speed compression- the resistance the valving has to being compressed when compressed quickly. Affects impact resistance, choppy terrain, slamming the suspension.

 

NOTE: low or high speed compression has to do with SHOCK movement speed, not ground speed.

 

Rebound- the valving’s resistance to the shock extending too fast. Faster riders and choppy terrain need less rebound.

 

Bump steer- how toe changes through the suspension motion.

 

Feedback- force felt from the terrain that is felt in the handlebars that wants to turn the bars.

 

Feedback and bump steer are NOT the same.

 

 

 

PLANNIING A SUSPENSION SETUP

 

This is where most of you fuck up. This assumes you have the money required to build a functional and safe setup.

 

Pick your riding terrain. XC, MX, desert, drag, hillclimb, etc. This will determine tire size, a-arm width, and swingarm length.

 

Choose a-arms based on width required, find companies that offer that length, then take the time to research the company’s background. This is critical for one reason: ball joint limitations. This is a simple concept that isn’t very easy to explain without pictures, so I’ll include this short list:

 

LSR: mostly desert, some MX, some XC. Drag guys, you already know what you’d need from them anyway.

 

Roll Design: mix of desert and MX

 

Fireball: MX, general purpose

 

Alba: desert, General purpose

 

Laeger’s: MX, some desert

 

JB: MX, some XC

 

Fireball: general purpose, dunes

 

Next is swingarm selection. Very simply, shorter is more agile and rider input is easier to see, but they are inherently less stable. It is also much easier to transfer weight front/rear and side to side. Due to a shorter swingarm’s steep angle when at ride height, they can cause the rear of the quad to lift under acceleration. This raises the COG and can cause you to wheelie much more easily. A shorter swingarm will have less travel as well, but will have a lower leverage ratio.

 

Longer is more stable but will reduce turning ability. The major downside beyond handling is weight distribution, but most uses of an excessively long swingarm have no interest in quick cornering. Since they sit at a flatter angle, lifting is far less of an issue.

 

80% of trail and MX banshees will find the best handling at -1.5 to +2.” This is largely because a banshee is very front heavy and the fenders don’t allow sufficient movement to get enough weight over the back. A -1” swingarm, race position pegs, forward a-arms, lowered subframe, rigid 19” tires, and a wider axle will cut seconds off a lap time. Not tenths. Seconds.

 

XC is very similar out back to MX.

 

Dune guys usually want +2 to +6.

 

No-link setups are best served by relocating the upper shock mount. Otherwise, the leverage ratio will be sky high but it is still doable for some scenarios. Don’t think that the 3-4lbs you save from going no-link will benefit you if you don’t have a good shock built. Solid struts don’t apply here.

 

Choose tire size next. MX setups with front tires ranging from 18-21” can be useful. Rear tires are usually 18-20”. 20/18 is a common setup. I prefer the smallest front tire I can get away with and 18” rears. Bigger tires add comfort and absorb impacts better. Small tires are more nimble and deform less under heavy stress.

 

XC is doable on 20-23” fronts and 19-22” rear. Know your terrain for this. My preference for XC is 21/20.

 

Once you have the frame, arms, link (if used) together and tires INFLATED TO RUNNING PRESSURE, lay the quad down onto 2 2x4s lying flat on the ground. Place one under the frame rails at the pegs and another under the frame rails before they rake up. For MX or TT, use a treated 2x4. For drag, use a treated 2x4 in front and a full size in rear (big tires compress more). For others, use a full size 2x4.

 

Ballpark the alignment. Accuracy isn’t important at THIS step. Just make sure the tires are roughly straight ahead and that the camber isn’t more than 10 degrees.

 

Measure eye to eye where your shocks mount for compressed length front and rear. Accuracy is important here. Check both front lengths to make sure something isn’t bent, broken, etc.

 

Lift the quad up until the instant the tires come off the ground and keep the lower frame rails level. Depending on your components, this may be your front or rear tires. Measure from the 2x4 to the lower frame rails. This is your travel number. Continue lifting until the other tires lose contact and take your second travel measurement.

 

Completely lift the quad off the ground so that the tires hang. Measure eye to eye for both front and rear. This is extended length.

 

Subtract your compressed length from extended length, then divide your travel by this number. Travel/(extended length - compressed length) = leverage ratio.

 

You may end up with something like this:

 

FRONT

14” compressed length

19.5” extended length

11.5” travel

11.5/(19.5-14) = 2.09:1 leverage ratio

 

REAR

9.5” compressed length rear

13.5” extended length rear

10.3” travel rear

10.3/(13.5-9.5) = 2.58:1 leverage ratio

 

Just copy this to yours and fill it in here:

-Compressed length

-Extended length

-Travel

-Travel/(extended L-compressed L) = LR

 

NOW you can call a shock builder with this info, your weight, experience, etc. Some will ask different questions, some will ask these, some will ask a mix. These are the fundamentals, but some builders will know some of this info already. Ask them about what brand and model shocks fit your basic dimensions. If they don’t have them on hand, buy them used and send them in.

 

If you don’t do things this way, you will almost certainly run into a chassis that bottoms out easily, that rides far too high, that doesn’t soak any terrain up, etc. It is VERY possible to Frankenstein a setup together and it perform at the national level, but that rarely happens.

 

 

 

SUSPENSION KITS

 

This is the way most of you will go. For the average rider, this is good enough and requires less effort, but the above method is better and will guarantee better performance.

 

There are 2 main issues with kits: the shock manufacturer will likely not set the shocks up with the best setup, and you may not be running the tire height that the setup was designed for. Yes, they may be “setup for your weight and riding style” but that doesn’t mean jack about whether they did a good job or not. If you have problems with suspension or are talking up your setup and the words “setup for my weight and riding style” then you’ve lost all credibility. You’re just regurgitating words off of a product description.

 

-Elka has a solid reputation for sending great shocks out the door with shit setups. Always set money aside to send them to a shock builder after you test them and see what they need.

 

-Works are usually fairly accurate but don’t perform at the higher levels. Low-cost.

 

-Fox are hit and miss but are extremely capable. Cheaper to rebuild.

 

-PEP have a reputation for having a very accurate setup out of the box. 250R guys are PEP fan boys, but for good reason. Also, $$$

 

-Motowoz are good, inexpensive shocks and people swear by them, but none of the pro guys I hang out with talk about them.

 

-Axis are usually fairly accurate but occasionally miss the mark. Arguably the best quality shock you can buy. More 250R fan boys.

 

-Exit are gaining a lot of attention and perform really well.

 

-Stadium reputably have the single most accurate setups out of the box. Hands down most comfortable shocks I’ve ever been on.

 

-TCS were great at one point but not many parts available to the builders I’ve used. I’m not up to date on TCS so take it with a grain of salt.

 

-Öhlins are very good shocks, but very few quad guys run them.

 

If it’s any consolation, I am sponsored by Fox and have no plans to change that. They’ve been good to me and are precisely what I need.

 

The best piece of advice that I’ve ever heard regarding picking a shock manufacturer was “just pick a top brand and go with them. They all have an equal chance of getting the setup right the first time. If not, send them to a builder. Don’t think too far into it.” Furthermore, the top shocks today (in no particular order) are Elka stage 5, Fox Evol, Pep PB1, Custom Axis, and Stadium.

 

Whatever you do, pay for something with more adjustments.

 

As for tire size, your shocks are going to be setup (as they usually are) for a wide demographic, so that would fall with a 21/20 front/rear. I got my second set of Fox installed on my main quad and it was very bottom out happy. I called Fox and my rear shock had a compressed length that was meant for a 20” rear tire, not 18”. This matters for 2 reasons: 1” less ground clearance at full bump, and the valving wasn’t optimized for the leverage ratio given with my measurements on an 18” tire. The leverage ratio of the linkage and swingarm setup drop severely (along an exponential curve) as you approach full bump, so I should have had a lot more bottom out resistance a good inch earlier in the travel. Fox sorted this out very quickly.

 

 

 

SETUP

 

Take the time to take the springs off your shocks and double check the compressed lengths so that the frame rails aren’t too close to the ground and make sure that the shocks bottom out before the ball joints bind. You can usually disassemble aftermarket shocks in a few minutes.

 

Reassemble the shocks, bolt them up, and make sure your tire pressure is set how you want it.

 

Set caster first. This should be 1-5 for TT, 3-6 for MX and XC, and 5-8 for desert. The rule of thumb is that the greater the chance your tires are going to lose contact with the ground in rough terrain, the more caster you want. If you do general riding, 5 is a great start.

 

**********

Everything after this point will require you to get on the quad and have someone take measurements.

**********

 

PROCEED IN ORDER

 

Set ride height. You measure this under the frame rails just before they rake up in the front and under the pegs. This measurement is given F”/R”. You usually want 4.5-6”/4.25-6” for TT, 6.5-7.5”/6.5/7.5 for MX, 7-8”/7-7.75” for XC, and 7.75-10”/7.5-9.5” for desert. I run 7.25/7 for most MX tracks. Some people fall outside of these ranges. Most fall within them. If you don’t know that you need something different, go with this.

 

Lower will corner better and be more stable but requires more compression so it will be stuffer. Higher will be more comfortable but will tip and dive more.

 

Rear can be equal to the front or lower, but almost never higher. This does not apply to drag or hillshooter setups.

 

 

Set camber next. Turn one tire straight ahead. Put a square beside the tire with one side on the ground and one against the tire. You want roughly 1/4” from the sidewalk to the square. Add more for hard berms and uneven terrain. Subtract for smoother surfaces. More camber digs into corners better. Less camber brakes harder and tracks a touch straighter in some cases. Do this with both tires.

 

Set toe next. Measure from the center tread on both tires in the front and rear of the front tires. You usually want between 1/8” and 3/8” total. Less can be darty and works for low speed stuff. More can be better for high speed stability but too much can be dangerous. Make sure your bars are straight.

 

Once you’re riding, setting the valving can be done in any order but I follow these steps:

 

*NOTE* do not EVER run the compression all the way in. This is a good way to destroy shocks. 2 clicks from max is safe. 1 is still pretty safe.

 

Drop high speed compression all the way.

 

Run low speed compression almost at max.

 

Run rebound at max.

 

Go for a ride at a slow pace. Every time the shocks bottom out, add 2-3 clicks high speed compression.

 

If you get into a series of rough terrain and the shocks soak up the first few bumps very well and then get stiffer and stiffer or bottom out, or if the back kicks up hard off a jump face or off a bump, back the rebound out 2-3 clicks.

 

I prefer all the low speed compression I can get, but if you want more comfort, run it all the way down. Every time it rolls excessively or wants to bottom out going up the face of a jump or landing softly rom a landing, add a little low speed compression.

 

Generally, valving is a mix between performance and comfort. You want the softest compression and highest rebound settings you can get away with.

 

Write these settings down for each place you ride. It only takes a minute to adjust them. As you get closer and closer to max adjustment, you may want to consider a revalve.

 

If you find that you’re getting close to maxing your compression or at minimum rebound, you can do a few things: raise ride height (effective), run a higher tire pressure (short term patch), or send the shocks in for a revalve (best). When you do, keep the settings where you currently have them and let the shock builder know this. Tell them every complaint you have. Tell them when the shocks underperform. It may take some of you 3-4 revalves to get a truly good suspension setup.

 

When I last called my builder for a revalve, I told them this: “I need more high speed compression, a little more low speed compression, and the rebound is fine.” You can ballpark your thoughts, but let your adjustments lead your decisions. If you do it right, the adjustments won’t lie. Don’t call and say, “I’m getting faster and the shocks aren’t good enough.” They don’t know how they aren’t good enough unless you tell them. They’ll have to reference their charts and you may hate what they’ve come to find works well for the majority.

 

 

 

Side notes:

 

If you want to run YFZ shocks on standard travel banshee arms, read this entire thing again. If you still want YFZ shocks on standard travel arms, just go ahead. You won’t listen anyway.

 

As stated earlier: set up for your style and weight isn’t the magical phrase that means your suspension is golden. It could be complete shit.

 

Any shock manufacturer is going to only be “somewhat likely” to nail your needs at best. I’ve seen Works and Elka perform out of the box extremely well. I’ve seen Custom Axis and modified Evols perform like shit. More often than not, Fox, Axis, PEP, Stadium, and Motowoz perform very well out of the box. No one manufacturer is always going to nail it. The rule of thumb is that the more you pay, the better quality shock you’ll get and the better chance you’ll have at getting a solid setup the first time.

 

Suspension is just like the rest of your quad, you should build it around the way you ride, not ride it around the way it is built.

 

 

 

There is definitely more to it than this and this is NOT a comprehensive guide, but this should be enough to get you going.

 

 

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[ClaudeMachining]

Nice work dude. I'll re-read everything when ill be sober.

 

Thx.

 

Envoyé de mon SM-G965W en utilisant Tapatalk

 

 

 

 

[Canadianshee]

Great job, will help in upcoming set up.

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[dano3]

Appreciate you taking the time to write all that up, especially on your iPhone!! Thank you. 

[ek hatchhh]

Going to setting up my front end soon, when it warms up anyway. Thanks a lot! Nice write up.

[gusto]

One of the best write ups ever posted on this site!

 

this guy has helped me a ton on my set up! 

[tfaith08]

There is so much that I just flat-out forgot to include. I wrote it over a few weeks to make sure I included as much as I could, but you can’t think of everything.

Probably the biggest ones concern width, stabilizers, and bump steer.

A lot of guys will flip rims and run spacers to gain width but that’s a good way to break a wrist. I’d take a 45” wide build over an identical build except with wheel spacers added any day of the week. If you don’t address the scrub radius, you WILL fight the quad more. If you have a scrub radius of 3/8” (which I believe is what you get with stock tires on stock banshee knuckles) and you flip the rims, you just multiplied your feedback at the handlebars by 3.67x. Once you factor other frictional losses both before and after, that figure bumps to around 4x. Of course, that doesn’t add up to much with small bumps of 1-2”. But if you misjudged a corner and you’re about to nail a tree with your right tire, the best solution is to yank the tires to the left at the last split-second and ram the face of the rim into it instead (pro-tip). This will save a wrist in most cases unless you did some dumb shit like ride a setup with a scrub radius of 1-3/8”.

Stabilizers are pretty straight forward. Puck is better than stick. Precision is the very best. A stabilizer can save your wrist or keep you rubber side down. They heat up with use, which is one reason stick types don’t work as well. In dead cold winter, you can make do with stick types, but just like everything else, you have to pay for the best. Precision pieces go for $550 MSRP (last I checked) and they’re worth every penny. I’ve sold several of them for precision just by letting people ride my bike.

Not much you can do to address bump steer on a stock frame except for going wider or altering the stem flag height, but it is relevant. You can modify the frame if you want, but you’ll need more info than I’m going to include here if you plan on doing that.

If you’re just hungry for more info, the design side of things is a good place to dive in. A few of the buggy and trophy truck forums have a good knowledge base.




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[ZillaFreak]

TL/DR

[tfaith08]

Another thing that idk if I included: shock manufacturers don’t make a banshee, YFZ, or TRX specific shock. They make different length shocks with different inserts, reservoir bodies, valving, and springs. A 19.5” shock from a YFZ will fit a banshee setup that requires a 19.5” shock. The compressed length may have to be altered and the valving and inserts swapped, but the shock body is the same.

When looking for shocks, don’t narrow your search specifically to your application. Get the correct length and send them in to a builder.


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[m671054]

Any thought on front vs rear width?

[SandSlingerOR]

Amazing write up. I shared with my buddy, well done!

[tfaith08]

Any thought on front vs rear width?

I always approach it as shooting for the maximum width I can get away with. The wider you go, the less it likes to tip and the more traction the inside tires get. The traction is also more consistent. I would never sacrifice correct geometry for the sake of width, however. That rules out any widening kits, wheel spacers, flipped rims, etc.

Any time you add width to the front arms, you reduce bump steer, so there’s another plus as well.

Adding a +3,+1 front end on a banshee will make it 6” wider and switching from stock offset to 4/1 will bring the total width down around 2” to a total of 4” wider than stock. That loss of 2” may not sound nice but you’ve reduced bump steer from the wider arms, still increased overall width, and corrected the scrub radius so your feedback will be significantly lower. That makes for a much more agile build.

IIRC, +3, +1 and 4/1 rims will give 46.5-47” at ride height. Width at ride height is what matters here. You may be at 43” wide while fully extended so don’t match your rear width to that.

As for a balance on F/R width, some prefer a slightly wider front, some prefer a slightly wider rear, and some prefer them to be equal. I personally prefer them to be equal within 1/4”.

When I brake into a corner, I have all 4 wheels locked up. When I first brake, I slide back and kick the quad in the direction I want it to go before I fall down onto the inside of the quad so that I can slide into a corner. You also have to factor your brake pedal being on the right side so you may have to wait to kick it to the right until just a little later because your legs are only so long (yet another place that a lowered subframe helps). To time it right is a matter of about 1/2-3/4 second. In this case, the wider the rear is in relation to the front, the more the leading front shock will compress when braking into a corner. You can fix this with a little more compression on the front. A slightly less effective solution is to add a tad more rebound in the rear (be leery about adding rear rebound if the terrain is rough).

The reality is that most riders prefer less than 1” total width difference. This effect is small and 99% of riders will never see it unless you take the same corner in the same way over and over and over. You can calculate it, however.

You won’t get it 100% accurate the following way, but you can get a ballpark idea.

Draw a pyramid with the peak at your COG and the corners at your mean center of your contact patch. If your COG is 24” high and your horizontal width to a corner is 24” wide, you can corner at 1g before tipping. If your COG is 12.5” high and your horizontal width to the corner is 25”, you can corner at 2g. Keep in mind that if you’re cornering at 1g, you also have 1g pulling down. 1g down and 1g lateral give you a 45* tipping point. If the angle from the contact patch to the COG crosses the line made by the forces from gravity and cornering, you will tip. Hanging your body off the inside can move your COG toward the inside and down and lay that 45* angle down to a smaller angle, making tipping harder.

Keep in mind that dozens of factors determine this, such as tire pressure, tread design, terrain makeup (dirt, sand, etc.), terrain shape (smooth, bumpy, flat, berm...), body position (including X, Y, and Z placement), suspension operation, chassis flex, etc. You can be cornering below your tipping force and catch a rut just right and increase the lateral force enough to break your tipping point.

This is also why riders that keep their ass in the same spot and put their weight to the outside peg can never corner as fast as someone who moves their ass down to the inside and sits on their heel. The quad doesn’t care where you are; it cares about the forces involved. You can lean inside all day but the quad only sees where you put that weight. If it’s all on the outside peg, that’s where your quad sees the force and it will tip easier.

As with any suspension topic, there is almost always a matter of compromise. Regarding height and compression, higher will offer more suspension travel but tip more and have less equal traction. Less compression will be more comfortable and offer better traction but will bottom and roll more. On a track, you may be able to gain 2 seconds in the corners by changing setup but you may lose 3 seconds because you can’t hold it straight. You have to be thoroughly analytical.

At the end of the day, you’re left with one thing with width: buy an adjustable axle, buy a front end setup that fits your width requirements, and buy a front wheel offset that gives you a good scrub radius (usually 4/1). Once you get your front components, you can’t exactly alter width, so the balance has to be made up in the rear.

You’ll likely never get on a quad and say, “wow I don’t like the way this F/R width balance acts.” You’ll notice 20 other things first but even though you probably can’t notice it, it is still there.

Small things add up. Pennies make dollars and ounces make pounds.




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[XXDEF1ANTXX]

I have a set of older Roll Desgin A-arms that I had Powder Coated and installed new pivots and ball joints with a Fox Float 3s. This is a new set up that I havnt ridden yet. Also to add, I had my oem rear shock re sprung and valved for my weight. Will this setup be adequate for east coast trails? do you have an idea for a starting point for the PSI of the Floats? I have it set at 90psi now but I dont know if thats right. I am 275lbs.

thanks

[Keno]

Awesome post. This needs stickied.

[tfaith08]

I have a set of older Roll Desgin A-arms that I had Powder Coated and installed new pivots and ball joints with a Fox Float 3s. This is a new set up that I havnt ridden yet. Also to add, I had my oem rear shock re sprung and valved for my weight. Will this setup be adequate for east coast trails? do you have an idea for a starting point for the PSI of the Floats? I have it set at 90psi now but I dont know if thats right. I am 275lbs.
thanks

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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