I have been searching the forums and the www and found some pictures/info on GS500s with different swingarms.  It looks the the Suzuki RGV250 VJ22 arm and the GSXR 93-95 swingarms have been installed on the GS chassis.  I was just wondering if anyone knows if these swingarms are about the same length as the GS.  As I understand it, if the front is to be maintained at the same rake and the swingarm length changes the angle of it changes as well which may alter the anti-squat behavior of the rear suspension.  Alternatively does anyone know the anti-squat ratio/percent or have measurements of the rear geometry?

Edit:  Or could someone tell me the angle of the stock GS swingarm at rest?

You need to ask yourself why you want to change your swingarm. ie. what do you know that the Suzuki engineers who designed it didn't know?

With that logic, why change the airbox? The front forks? Seats, springs, tires, and exhaust?

Bing-bong.....Ken to the front desk, Ken to the front desk please

My motivation to change the swingarm (suspension) is for both aesthetics and performance. 

I don't know more then a team of engineers.  I can however assume that the engineers probably had to make many compromises in the design.  Low cost was probably a large influence on the design and a reason for the material selection (i.e. steel instead of aluminum) of the swingarm.

Quote from: jacob_ns on March 28, 2011, 07:13:38 PM
With that logic, why change the airbox? The front forks? Seats, springs, tires, and exhaust?

Yes, why?

Because, if you've thought it through, and the economics of an improvement makes sense to you, go for it, I have no problem with that. But once in a while there are posts that suggest IMHO that the poster hasn't thought it through, so I question it.
My motivation is to avoid having people waste their time and money on mods that maybe will not give the improvements they are hoping for.

(OP posted above while I was writing this, but I've posted it anyway as a general comment.)

How about a VFR400 single sided swinger?  That'd be neat just from and engineering standpoint.  I've done swingarms swaps before.  Not really a big deal as long as your willing to play with spacing (axles, bearings, etc..).  Adjustments can always be made with dogbones to correct for things.  What kind of riding will you be doing?

I'm in the process of doing a RGV250 swingarm on my bike. My advise would be, unless you're racing, don't do it. Stocker works well enough.

With that said, I spoke to my suspension guy about this. The main concern regarding squat characteristics is going to be the angle of the swingarm. Anything more than 13 degrees, and the rear wheel is going to tend to want to drive under the bike as you get on the gas.

Swingarm angle can be adjusted by installing different suspension links, or different shocks. The GS500 stock shock is about the shortest direct swap you're going to find, without getting an after-market shock built. The RGV shock will lift up the rear end about 3/4th of an inch, and the GSX-R shock will lift it up a whole bunch (~2".) Katana and R6 shocks are the same length as stock.

I'm not sure how the RGV linkage compares to the GS500 linkage - it may be that the RGV swingarm naturally sits a little lower than the GS swingarm. If so, I'll probably run an GSXR shock, or swap in the GS parts. We'll see.

http://www.tonyfoale.com/

Thanks for the info burning1.  This is along the lines I was wondering.  

Does the RGV arm need to be at a greater angle to maintain the same ride height and front fork rake, if so what is the effective increase on squat?  Alternatively if the swing arm angle is adjusted (with damper or dogbone length) to a proper angle for anti-squat and the forks maintained at the same rake is the ride height reduced significantly?  Which leads to a question if maybe the slingshot or early WC GSXR arm is better suited (length) for the GS chassis?   I was hoping someone would have measured/calculated this.

Foale's book is a great read.  I also highly recommend Cossalter's book. 

I'll be able to answer a lot of your questions better in a few days when I've had a chance to install the new swingarm.

Eye-balling the RGV swing-arm next to my desk, it appears to be somewhat similar in length to the stock GS swingarm... But I'm going by memory, not a side by side comparison. I'll provide full details later when I have real numbers to go by.

BTW... If you're doing this for visual reasons... I think the VFR400 swingarm is cooler looking overall - so give it some thought. As you know, the RGV swing-arm is European only... So get used to ordering stuff from overseas, and spending a lot of time searching the net to find compatible parts.

I'll provide as much detail as I can about it.

One bit of good news for now though... The RGV brake calliper uses the same pads as the old gen (88-07) Ninja 250.

I just checked: The RGV swing-arm is about an inch longer than the GS500 swing-arm, depending on where you put the axle.

Also, while the RGV linkage appears to be similar for the most part, the bike uses a GSX-R style wishbone - your GS500 links won't work with it without building spacers and/or bearings of some sort.

The part of The Ken now will be played by "The buddha"

As surewin is asking his well thought out and very precise questions a hand expression is being made by "The ken" which is like making a fist and holding it to the side of the body and moving it up an down (sorta like a jerking off action).

After the question is complete and ~2 mins have passed ... brrrrrr (blowing raspberries).

Cool.
Buddha.

burning1, Many thanks.  I would have thought just the opposite regarding the length.  Good to know.

Who is "The Ken?"

I'm guessing you were referring to this thread   http://gstwins.com/gsboard/index.php?topic=55220.0


you can change everything and you can change nothing
the GS does not have the best geometry
start looking at different numbers for different bikes
TZ250... the new moto GP bikes
and work your way towards them

if you understand that you are pissin up a rope before you start...GO FOR IT.
if you want bling....GO FOR IT!

the prob with old skool honda SSSA's  no linkage and 800-1200# springs
the GSXR and bandit SA are wider at the swingarm pivot point and use bigger axle  and you have to make ugly brackets to get the foot pegs to clear the SA
the RGV is narrower than the GS and bigger pivot axle  so some spacer/reducers can be fabbed up fairly easily
I need to make a set for my last RGV braced arm


this is the book you need to answer almost all your questions
http://www.amazon.com/Racing-Motorcycle-Technical-Guide-Constructors/dp/0951292927

then you will determine that you make it as good as you can afford
did I mention something about pissin up a rope?   good luck

you probably can skip the chapter on designing new internal gear ratios for individual tracks...but if the budget is there....it would be sweeeeeet

werase643,  I have already read a few books regarding motorcycle suspension and physics.  Thanks for the recommendation though.  After you read the books though you have to apply the material, this means measuring and calculating before doing modification.  I have modeled the anti-squat geometry as well as the wheel rate on other motorcycles I've owned/modified, it isn't that difficult.  See following picture of CAD drawing and Fortran code.

I mainly modify for cosmetic reasons, but I do my best to maintain or improve performance. I wrench on motorcycles for fun just as a hobby, I'm not relying on this GS for daily transportation or worried about the economic analysis of spending a couple hundred bucks on some mods.  Speaking about pissing up a rope, you should see the cafe racer I built.  I spent a ton of time on it and it's performance is still worlds behind a modern sport bike.  

Quote from: werase643 on March 30, 2011, 07:50:35 PM
the GS does not have the best geometry

Can we steer the discussion in this direction?  I would love to talk about ways to improve the suspension geometry.  This was my original intent as I was hoping someone already quantified the anti-squat when they swapped the SA.  

BTW. I am not looking to invest tons of money into my GS500, or build a totally engineered race bike, but I'm sure I can swap the suspension for a nominal amount, perform basic geometry calculations, and still have fun doing it.

Quote from: Surewin on March 30, 2011, 07:24:06 PM
burning1, Many thanks.  I would have thought just the opposite regarding the length.  Good to know.

Who is "The Ken?"

The trend on modern race bikes is to stack the transmission output shafts, attempting to make the engine as compact as possible so that you can install a long swingarm without extending the wheelbase of the bike.

One other thing I discovered about the RGV swingarm... The stock RGV sprocket is 4 teeth larger than the GS500 sprocket. So, there's a good chance you'll need a longer chain, but also a good chance that the gearing will work out nicely for street use, assuming you've stuck to the stock GS500 countershaft sprocket.

make it handle like a fat 1992 TZ250 and you will be happy
the number crunching is almost a waste of time
this is thomas edison light bulb design 101, fab a different SA onto a gs and see what it does
then yo can make the measurement points and plug it into your program to determine if it is ideal

then what determines what is ideal squat for a gs?

Quote from: Surewin on March 30, 2011, 08:43:55 PMCan we steer the discussion in this direction?  I would love to talk about ways to improve the suspension geometry.  This was my original intent as I was hoping someone already quantified the anti-squat when they swapped the SA.

I haven't measured the amount of trail from the GS500 front end, but my impression is that like most entry level bikes, it probably has a centimetre or two more trail than is necessary. On my race bike, I resolved this in part by raising the forks 9mm in the triple clamps. It will be interesting to see what the GSX-R triple I just installed does for the trail numbers, ofset, etc.

At the rear end, the basic suspension design is pretty decent. The stock geometry raises the rear end up noticably when I get on the gas, and provides plenty of additional cornering clearance. I found that a lot of times, getting on the throttle would solve the front end grip and cornering clearance issues I encountered while racing.

Rear end grip seems to be much better than front end grip on this bike. I slid the front end a number of times riding off the throttle. I've only slid the rear end once or twice, even running WOT at pretty extreme lean angles. This may have to do with the tires, suspension, or my riding style as much as anything.

The rear end suspension geometry seems to use a higher lower leverage ratio against the rear shock compared to some newer bikes. E.g. we need fairly stiff springs, despite the fact that our bike is quite lightweight.

Although the linkage on our bike is fairly modern, there is very little clearance around the rear swing-arm cross-member. Physical clearance issues may be what has forced us to run a high leverage ratio suspension design. The RGV swingarm seems to provide significantly more clearance. I'll also be interested in comparing the suspension linkage geometry, to see what can be done with leverage, and ride hight.

I haven't looked a the stock GS linkage or the RGV linkage to comment on how progressive/digressive it is.