Best motion ratio

[350skabarat]

Hi guys, i thought i'd start a discusion about this as ive heard different ideas on the subject. Im designing a frame for a shee with a-arms and swing arm. Now im trying to decide where to mount the front shocks on the a-arms. Closer to the wheels or halfway or where?

 

Now what ive heard is a motion ratio of 1:1 or close to 1:1 is best. why? 1.Because this transmits less stress into the frame of the bike and 2.Helps improve body role. Ok now if you have a motion ratio of say 2:1(wheel travels 5" and shock travels 2.5") then you obviously need a shock that is valved with stiffer shims in it. The shock is also going to travel SLOWER. Half the speed of the 1:1 ratio. This is better in the way that your shocks wont fade from getting too hot (due to low shock velocities) and you get more travel outof your shock.

 

Ok so in my understanding is that both setups would work and they do work cause hundreds of quads are setup close to 1:1 and evan some more than 2:1.

 

Ok here's my big question. Lets say the travel of the shock is not an issue, you can mount it anywhere and have lots of travel. Where would you mount it. My question boils down to what is the best velocity a shock operates at?

[350skabarat]

Thanx for your input, When you say you can control the motion, do you mean in terms of tuning? Like to tune a shock that works at high velocities produces better results than that of low velocites. . . .

[So Cal Suspension]

This term "motion ratio" strikes again.

 

When you're building a frame with as little travel as an atv has, travel differential is less of an issue as shock angle. Even long travel Banshees only get about 12" of active wheel travel.

 

Keep your shock angle at 50-60 degrees.

 

You're over thinking "motion ratio". If you were dealing with 20"+ of wheel travel, it's something to take into consideration. On ATV's, however, it's an often ignored aspect with superb results.

 

1:1 isn't possible unless you were planning on running a leaf spring and straight axle in the front with your shocks vertical overtop of the axle.

 

1:2 is probably closer to where you need to be. 12" of wheel travel with a 6" travel shock is attaintable. Keep your shock angle around 50-60 degrees.

 

 

Point blank, ATV shocks don't displace enough oil, or create enough friction to generate a significant amount of heat, so don't worry about any of that.

 

Get your shock angles right, and have at it.

[dirtydownunder]

where can i get this leaf sprung suspension kit ?

[So Cal Suspension]

It's an easy swap. 1923 Ford T-Bucket monoleaf. Gangster.

[Coupelx]

It's an easy swap. 1923 Ford T-Bucket monoleaf. Gangster.

 

buggy spring ftw. make sure you get some of those friction shocks too!

[350skabarat]

This term "motion ratio" strikes again.

 

When you're building a frame with as little travel as an atv has, travel differential is less of an issue as shock angle. Even long travel Banshees only get about 12" of active wheel travel.

 

Keep your shock angle at 50-60 degrees.

 

You're over thinking "motion ratio". If you were dealing with 20"+ of wheel travel, it's something to take into consideration. On ATV's, however, it's an often ignored aspect with superb results.

 

1:1 isn't possible unless you were planning on running a leaf spring and straight axle in the front with your shocks vertical overtop of the axle.

 

1:2 is probably closer to where you need to be. 12" of wheel travel with a 6" travel shock is attaintable. Keep your shock angle around 50-60 degrees.

 

 

Point blank, ATV shocks don't displace enough oil, or create enough friction to generate a significant amount of heat, so don't worry about any of that.

 

Get your shock angles right, and have at it.

 

Thanx for that. You kinda missing my question though. If a vehicle has 1000" of wheel travel or an atv has 12" of travel. When these 2 vehicles hit an identicle bump both shocks will displace the same amount. So travel wasnt of concern in my question.

 

My question in other words: would you want a shock that moves 200ml/second of oil through the piston(high shock velocity) or would you want a shock that rather moves 20ml/second (low shock velocity)? These two extremes must definately have an effect on damping smoothness and performance. I mean if you had a liquid other than oil in a shoch that has a very low vescosity, low motion velocities would be useless as this "thin" liquid wouldnt create enough resistance traveling through the ports of the shock. With oil the vescosity is higher "Thicker" so motion velocities can be slowed down to get a good damping effect.

So high and low shock velocity must obviously have advantages and disadvantages regarding tuning and performance. I would like to know where this optimum balance is? I know its alot to just ask like that but thats why i started this thread so we can all share our knowledge on the subject. You cant just say "Dont worry about motion ratio or shock velocity on a quad" Do you think elka and fox and pep and all these shock manufacturers just ignore the shock velocity their shocks will work at? i dont think so. They design these shocks to work most effectively at a certain shock velocity. Obviously this can be a range of velocities. Sure you can take any shock and change the valving to run higher velocities but what are the extents that oil will allow this.

 

Thanx though for that info. Im not attacking anyone. Just a debate.

[So Cal Suspension]

Thanx for that. You kinda missing my question though. If a vehicle has 1000" of wheel travel or an atv has 12" of travel. When these 2 vehicles hit an identicle bump both shocks will displace the same amount. So travel wasnt of concern in my question.

 

My question in other words: would you want a shock that moves 200ml/second of oil through the piston(high shock velocity) or would you want a shock that rather moves 20ml/second (low shock velocity)? These two extremes must definately have an effect on damping smoothness and performance. I mean if you had a liquid other than oil in a shoch that has a very low vescosity, low motion velocities would be useless as this "thin" liquid wouldnt create enough resistance traveling through the ports of the shock. With oil the vescosity is higher "Thicker" so motion velocities can be slowed down to get a good damping effect.

So high and low shock velocity must obviously have advantages and disadvantages regarding tuning and performance. I would like to know where this optimum balance is? I know its alot to just ask like that but thats why i started this thread so we can all share our knowledge on the subject. You cant just say "Dont worry about motion ratio or shock velocity on a quad" Do you think elka and fox and pep and all these shock manufacturers just ignore the shock velocity their shocks will work at? i dont think so. They design these shocks to work most effectively at a certain shock velocity. Obviously this can be a range of velocities. Sure you can take any shock and change the valving to run higher velocities but what are the extents that oil will allow this.

 

Thanx though for that info. Im not attacking anyone. Just a debate.

 

There's a reason most of us GOOD shock companies have multiple blends and types of oils. I use 14 different synthetic oils ranging from 1wt, up to 19wt. I also use different oil blends and additives, depending on the application, setup, and rider preferences.

 

I'm unsure what you are trying to do. I answered your question and told you that 1:2 is where you need to be. It's a comfortable medium that I think is the easiest to attain with the short a-arms that ATV's run. Are you planning on manufacturing your own shock start to finish? If you aren't, you should find which shocks you are going to use, and build your front end around that.

 

You keep using the term "velocity" as though there is a set industry standard? A shocks velocity varies depending upon the shock angle, and travel ratio. Being that I have worked at the worlds largest shock manufacturer, I can tell you, hands down, ATV shocks from the factory are pretty much cookie cutter shocks with nothing more than valving changes. When Elka, Fox, or PEP sends you shocks for a 180lb rider on +2 std travel arms, on a dune bike. You're getting the exact same shock as a 160lb rider on +3 std travel arms who rides an MX track. They're not considering what your specific "target velocity" is. They build the shocks for the right length, and that's it. You don't honestly believe that Elka comes out with a "Banshee" shock, and it has different internal parts, aside from valving, than a YFZ450 shock, do you? They consider eye-to-eye length, the angle the shock will operate at, and a target amount of wheel travel.

 

Building a shock around a target "velocity" is like building a motor around a target coolant temperature. Sure, it matters, but there are 100 other variables that will affect the coolant temp. In this scenario, shock angle and wheel travel are the two BIGGEST factors that will affect a shocks "velocity". Using numbers like 200ml/second doesn't make any sense. Is that at 20, 30, 40, 50, 60mph? Or do you want the shock to displace 200ml/sec regardless of speed? There is no industry standard, or perfect "velocity" that shocks are built for. The adjustments are made with valving and oil viscosity. The piston that's used in a long travel Elka TRX450R shock, is the same piston that's used in a standard travel Banshee shock.

 

A dual rate Elka shock is not valved the same as a triple or quad rate Elka shock when it leaves my shop. EVERYTHING is taken into consideration that could have an affect on ride quality, but I most certainly don't ever ponder the variances in "velocity". I have enough experience to know how certain bikes behave, and what my customers want. I can change shaft lengths, extended lengths, and collapsed lengths based on what travel ratio we are looking to get.

 

To me, it sounds like you're fishing for an industry standard that EVERY shock operates at. The answer is simple. There isn't one. EVERY shock is different, and EVERY shock operates differently.

[350skabarat]

There's a reason most of us GOOD shock companies have multiple blends and types of oils. I use 14 different synthetic oils ranging from 1wt, up to 19wt. I also use different oil blends and additives, depending on the application, setup, and rider preferences.

 

I'm unsure what you are trying to do. I answered your question and told you that 1:2 is where you need to be. It's a comfortable medium that I think is the easiest to attain with the short a-arms that ATV's run. Are you planning on manufacturing your own shock start to finish? If you aren't, you should find which shocks you are going to use, and build your front end around that.

 

You keep using the term "velocity" as though there is a set industry standard? A shocks velocity varies depending upon the shock angle, and travel ratio. Being that I have worked at the worlds largest shock manufacturer, I can tell you, hands down, ATV shocks from the factory are pretty much cookie cutter shocks with nothing more than valving changes. When Elka, Fox, or PEP sends you shocks for a 180lb rider on +2 std travel arms, on a dune bike. You're getting the exact same shock as a 160lb rider on +3 std travel arms who rides an MX track. They're not considering what your specific "target velocity" is. They build the shocks for the right length, and that's it. You don't honestly believe that Elka comes out with a "Banshee" shock, and it has different internal parts, aside from valving, than a YFZ450 shock, do you? They consider eye-to-eye length, the angle the shock will operate at, and a target amount of wheel travel.

 

Building a shock around a target "velocity" is like building a motor around a target coolant temperature. Sure, it matters, but there are 100 other variables that will affect the coolant temp. In this scenario, shock angle and wheel travel are the two BIGGEST factors that will affect a shocks "velocity". Using numbers like 200ml/second doesn't make any sense. Is that at 20, 30, 40, 50, 60mph? Or do you want the shock to displace 200ml/sec regardless of speed? There is no industry standard, or perfect "velocity" that shocks are built for. The adjustments are made with valving and oil viscosity. The piston that's used in a long travel Elka TRX450R shock, is the same piston that's used in a standard travel Banshee shock.

 

A dual rate Elka shock is not valved the same as a triple or quad rate Elka shock when it leaves my shop. EVERYTHING is taken into consideration that could have an affect on ride quality, but I most certainly don't ever ponder the variances in "velocity". I have enough experience to know how certain bikes behave, and what my customers want. I can change shaft lengths, extended lengths, and collapsed lengths based on what travel ratio we are looking to get.

 

To me, it sounds like you're fishing for an industry standard that EVERY shock operates at. The answer is simple. There isn't one. EVERY shock is different, and EVERY shock operates differently.

 

Great stuff, that makes total sence thanx dude. i guess i was looking at this way wrong. Just one question. when you speak shock angle? what does this effect? ive heard people say that when your shocks are bottoming out the angle between the shock and a-arm must be closest to 90 to have a rising rate of motion and therefor it will resist bottoming out more cause it travels faster for that last bit. Is that why the angle is considered or what?

[350skabarat]

One more question, Ive included a picture of a 250r frontend. see how the shocks are mounted almost verticall? does thiss have a benifit? im thinking it kindof must cause these bikes handling is the shiz niz!!!!

[So Cal Suspension]

Great stuff, that makes total sence thanx dude. i guess i was looking at this way wrong. Just one question. when you speak shock angle? what does this effect? ive heard people say that when your shocks are bottoming out the angle between the shock and a-arm must be closest to 90 to have a rising rate of motion and therefor it will resist bottoming out more cause it travels faster for that last bit. Is that why the angle is considered or what?

A 90* angle on a double a-arm setup is possible, but not logical. The reason I say to keep your shock angle around 60 degrees is that an equilateral triangle has all sides at 60 degrees. A triangle is the strongest/most stable shape known to man. The closer you can get your upper shock mounts, the better. If you can keep the shocks at 60 degrees, and your upper shock mounts close together, you will have the greatest amount of wheel travel possible. I understand this isn't always feasible, but see the image that I made up that shows what I'm trying to describe. Basically, keep everything triangulated.

 

 

 

One more question, Ive included a picture of a 250r frontend. see how the shocks are mounted almost verticall? does thiss have a benifit? im thinking it kindof must cause these bikes handling is the shiz niz!!!!

You have the greatest control over shock valving when the shocks move at a consistent speed. For example, a volkswagon beam style front end, runs the shocks at 90 degrees. completely vertical. It is VERY easy to valve those shocks, and get the PERFECT. They move at a constant speed through their entire travel, therefore a standard valve stack can be used. In cases where the shocks are at angles, and operate at different speeds throughout their cycle, we use two, sometimes three valve stacks on either side of the piston. Often called "low, mid, and high speed valving". As the speed increases, it engages the second, and third valve stacks.

[350skabarat]

Kewl man thanx for the effort in trying to explain that. appreciate it. So if i understand what your saying correctly then if your shock angles are say at 45 degree's, then you have a lower triangle which will be more stable but at the cost of travel? ive seen a few banshee's where the shocks are mounted at the outside limit of the a-arms, would that be bad?

 

And as you say it would be best to mount the top of the shocks as close to eachother as possible which makes sense, i just wonder why quad manufacturers havnt done it then? i dont see why it cannot be done?

[So Cal Suspension]

Kewl man thanx for the effort in trying to explain that. appreciate it. So if i understand what your saying correctly then if your shock angles are say at 45 degree's, then you have a lower triangle which will be more stable but at the cost of travel? ive seen a few banshee's where the shocks are mounted at the outside limit of the a-arms, would that be bad?

 

And as you say it would be best to mount the top of the shocks as close to eachother as possible which makes sense, i just wonder why quad manufacturers havnt done it then? i dont see why it cannot be done?

 

If you were to put the shock at 45 degrees, you wouldn't really sacrifice stability, but you will sacrifice some travel. Also, the speed of the compression will slow down at +/- 20* of the apex. This is where hi/mid/lo speed valving play a role. Keep in mind when choosing shocks, what your compressed vs collapsed length needs to be. Putting them further out you will need a super long shock, but also a super short shock when it's fully compressed. That's not always easy to find in a shock.

 

The further out you mount your shocks, the best control you have over valving. The closer to the frame, the more travel you can get out of a certain length shock, which is why 60 degrees is the best of both worlds.

 

Honestly I have no idea why manufacturers don't build proper suspension setups from the factory. My best guess would be, that it has to fit a WIDE range of customers. A 60* setup would have to be fine tuned for a specific rider.

[350skabarat]

MattSCSS thank you so much for your help. Its awsum that people like you are willing to share their knowledge with others. Well i think im gana make the upper shock mounting brackets on the frame 1" higher and 2" closer compared to a stock banshee frame.

 

OR

 

Ive read a few of your posts (MattSCSS) around the forum and you've said that the 250r frames where good untill 2004 when the yfz came out, so i was wondering, as you said i must get shocks first and build around that, if i must get a set of sweet shocks for a yfz 450 and build my front setup around that instead of a 250r setup? or whats your recomendation as for shocks to build around? like shock length and stuff? sorry i hope im not draging this on and on, but input from someone that knows suspension (MattSCSS ) would be great.

[zach45]

Yfz450r LT setup

 

 

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