Rear swingarm question

[TeamGCS1]

Sorry for all the "stupid new-guy" questions! But what is the difference between the rear swingarm types? Like that of a standard solid rear one like a Pitster or Vinco, or the modified stock Honda style of Thumpstar's, Sikk, and Honda? The reason why I ask is I weigh about 180 lbs and it would seem that a longer swingarm would give me more travel, but it looks like it might bottom out. Please educate me on this subject.

Thanks,

[gotalf]

well i have a vinco and from the research ive done, with a moto style swinger you dont have as much chain slack or flex. ie. you dont wear out chain rollers or guides as often. as far as the weight i weigh 210 with clothes on and if i jump up and down standing still on my vinco i cant bottom it out front or back so id imagine jumping it smoothley wouldnt do any worse.

[moose_guy70]

yea i got one of those long "big bike" swing arms on my rcm and i wish i had a regular swingarm but im a big guy and it bottms out alot when im jumping but the pitster one looks like it would ride a lot different than the big bike style

here is a pic where u can c it to start bottom out

http://i20.photobucket.com/albums/b244/moose_guy/Gas-linebrokenoff025.jpg

[T Bolt USA]

the triangle swingarm design was used by yamaha on the yz series bikes from about 74-81 .this type of swingarm has a tendency to work in only one aspect of the travel .you can set it up for big hits or small stuff ,but not both .the straight or big bike style swingarms are able to handle a wider range of terrain .the bottoming issues can be corrected with proper spring rates .

[Gutty]

generally the big bike style swingers run a higher leverage ratio than the A-frame swingers.

What this means is you get more suspension travel out of a certain size shock compared to the A-frame, but at a softer rate therefore bottoming much easier.

To compensate you need to go up a spring rate or 2, or use a shock specificly built,sprung and valved to suit the big bike style swinger.

IMO unless you have a decent shock, or weigh bugger all, i'd go with the A style if you have a choice.

[Jetster220]

The bigbike style swingarm setup is definetly much superior to the A-arm style, it doesnt typically have more travel, but it makes much more efficient use of the travel. basically, when set up properly with a good shock, it is supple and smooth over small stuff, but will soak up big hits no problem at all, no matter the weight of the rider.

[T Bolt USA]

The bigbike style swingarm setup is definetly much superior to the A-arm style, it doesnt typically have more travel, but it makes much more efficient use of the travel. basically, when set up properly with a good shock, it is supple and smooth over small stuff, but will soak up big hits no problem at all, no matter the weight of the rider.

well said

we agreed on somthing !

[Kurlon]

Ok, the engineer in me is looking at this and trying to figure out what really makes one setup much more 'plusher' vs the other. In the end, both are levers with a dampend spring hooked to them, because they are direct connect, no linkages, the only real difference is the length of the lever, and how far along the lever the shock mounts, changing effective leverage. The big bike style has the pivot and shock closer together, higher ratio, but thats about it. In my mind, you're requiring a higher ratio spring, which means you'll need more damping to match the control of a similar A-arm setup... so an A-arm should be easier to tune in?

What am I missing?

[Jetster220]

The problem that lies with the A-arm style suspension according to what I learned when I was talking with Works on building my new shock lies mainly in the angle at which the shock is. The problem lies that with the a-arm style, as the swingarm and shock move through there motion, at one point the end of the shock connected to the swingarm begins to try and pass the other end of the shock instead of them meeting as they are supposed to. What this does is cause a change in the speed at which the piston and shaft travel of the shock is moving, causing havoc with valveing and shock movement, basically just as TheCrkid said, creating either a setup that either works well with small stuff or big stuff, but gets confused when confronted with either or, essentially soaking up big hits, but being harsh on smaller bumps which is quite the common feel the a-arm style suspension seems to give.

Now when you set the suspension up for the more high leverage setup, you can adjust the shock mounts to be more desirable where as the suspension moves through its travel, shock shaft speed and leverage angles remain the same, and the 2 ends of the shock want to meet each other at the end of there travel essentially the peferct shock angle, allowing the valveing to be more linear and progressively get stiffer as it travels through the stroke, where as on the a-arm style where the shaft speed changes, causing confused valving.

Im not a engineer but that is the understanding I obtained and information that I got from talking with the guys at Works Performance as I was going over all of the pivot angles and such for my bike while having them custom build my new shock.

[Kurlon]

Ok, that makes more sense then.

I still want a linkage base rear. : )

[pitbikeguy237]

Wow, you guys take this swingarm stuff seriously. I dunno if all this info has made me smarter, or dumber. lol.

Well you all had very valid points. But one I would like to add is......The shock matters too. Depending on what shock you are running, it can have all the difference in the world, no matter what swingarm you are running. Now with that said. I like "big bike" style swingarms (though I just can't seem to figure the whole linkage thing yet, so lets say KTM big bike, eh?). So there's my vote.

[trls063]

now to dumb this thread up...what the companys and the links to where you can purchase these "big bike" swingarms...

[Gutty]

The problem that lies with the A-arm style suspension according to what I learned when I was talking with Works on building my new shock lies mainly in the angle at which the shock is. The problem lies that with the a-arm style, as the swingarm and shock move through there motion, at one point the end of the shock connected to the swingarm begins to try and pass the other end of the shock instead of them meeting as they are supposed to. What this does is cause a change in the speed at which the piston and shaft travel of the shock is moving, causing havoc with valveing and shock movement, basically just as TheCrkid said, creating either a setup that either works well with small stuff or big stuff, but gets confused when confronted with either or, essentially soaking up big hits, but being harsh on smaller bumps which is quite the common feel the a-arm style suspension seems to give.

Now when you set the suspension up for the more high leverage setup, you can adjust the shock mounts to be more desirable where as the suspension moves through its travel, shock shaft speed and leverage angles remain the same, and the 2 ends of the shock want to meet each other at the end of there travel essentially the peferct shock angle, allowing the valveing to be more linear and progressively get stiffer as it travels through the stroke, where as on the a-arm style where the shaft speed changes, causing confused valving.

Im not a engineer but that is the understanding I obtained and information that I got from talking with the guys at Works Performance as I was going over all of the pivot angles and such for my bike while having them custom build my new shock.

Good advice, but kinda works on an ideal frame/swinger combo. Not likely on teh bikes TeamGCS1 is looking at.

Basicly comes down to rising and falling rates, and where in the stroke they are applicable(kinda like were you talk about the shock ends passing). I've built many moutainbike rear ends and linkages, and can say from experience that it's very very hard to get those angles etc you talk about just right. Too far one way and you get a spongey rear end that blows through it's travel(worse on big style), too far the other way and you'll get spikes and a harsh feeling rear end(worse on A-style).

The problem i see on alot of big bike style setups, is that the frame and swinger aren't properly matched(unlike your RB frame) therefore creating bad angles. Now a good shock(Avalanche,Elka,Works....basicly anything with proper valve setup and adjustment) can easily over come these problems. But when you're talking about a knock such as TeamGCS1 is, they don't come with good shocks, and chances are you may have to get one custom made if you ever want to replace the stocker. Also the angles/rates etc on knock off bikes with big bike style swingers are quite often CRAP.

So.....If you have a few G's to spend on a new frame/swinger/shock combo, the big bike style setup, done right is almost always going to be far superior.

But....for the sake of this thread, where TeamGCS1 is looking at knock offs, i still tend to say stick with an A style, purely for simplicity of function/strength.

I used to have a program on my PC that you could put all your pivot points and lengths into, and it would graph the rising/falling rates of the setup. It's alot of fun if you're into this kinda thing, especially if you have the ability to make your own rear end, and will also help alot of you guys get a bit of an understanding on the hows and why's of rear suspension. I'll see if i can find it again.....

[Jetster220]

Gutty, I couldnt have said it better myself. Thanks for expanding some on what I was saying.

And yea, I definetly wouldnt trust the knockoff bigbike style swingarms so much, as like you said getting those angles right is incredibly hard and takes alot of R&D. When I was talking to Works about building a custom shock for my RB Frame(because I dont like the ishock on it now) the guy was very impressed with what a great job RB did of getting the angles and all very good. And it was incredibly hard to get a shock short enough to work with my frame and be able to make sure we didnt throw off shock angles I already have.

And Gutty, I would really appreciate it if you could find that program, I would love to tinker with that some as I love this kinda stuff, plus itll help me out when my shock from Works arrives and I have to mod my frame some to get it to fit and I would like to make sure all my angles are the same so I dont mess up anything.

[Gutty]

Searching for it right now......here's a link to teh 4-bar rear end version, kinda useless for our purposes but it gives you an idea of what i'm on abouthttp://www.bikeforest.com/CAD/fsCAD.html

There's another site you can actually download it from, and get to choose the rear end style(single pivot for what we want, something like the Santacruz Bullit).....i'll find it eventually.

[trls063]

so to RE- dumb this this thread again...who makes the big byke swingarm styles...cause i need to upgrade my crf 50. and i don' want to go a arm with my works shock that i already have...thanks.

[Gutty]

Ok, here's the page were you can download a demo version with heaps of different rear end designs. http://www.bikechecker.com/index.php?demo

For the A style swinger probably select something like the Santa Cruz Bullit or Cannondale Gemini. All you do is simply change the pivot locations etc to whatever your frame/shock/swinger is.

For the big bike style, maybe try soemthing like the Tomac 204 Magnum, and just re-arrange the pivots to suit ??

It's been a while since i've used it.....and i'm getting old.... But i'm pretty sure you can also draw your setup from scratch by just putting in a few variables like pivot locations, lengths and wheel size.

have fun !!

[Gutty]

so to RE- dumb this this thread again...who makes the big byke swingarm styles...cause i need to upgrade my crf 50. and i don' want to go a arm with my works shock that i already have...thanks.

Sorry, not real sure on that one.....

[trls063]

so then the experts on this thread that say they have "big bike" swingarms.....where did they get theirs??

[Gutty]

so then the experts on this thread that say they have "big bike" swingarms.....where did they get theirs??

Well i know Jetsters is from Red Barron, but it's a whole frame/swinger/shock kit. He didn't just buy the swinger and throw it on his CRF frame. Thats one of the points i made earlier!! Simply adding a big bike swinger to a frame thats not intended to have one "can" cause you some drama if pivot locations aren't spot on.

Maybe start going throught the parts manufacturers on this page.??... http://www.ministothemax.com/links.htm