Sunday, January 29, 2012

Suzuki GS500E/F Suspension Upgrades-Stock Fork Improvements

I am often asked about the suspension upgrades I have done to my Suzuki GS500E.I have done so many,it's hard to go through them all in one post.So I'll break it down into three posts,stock fork improvements,rear shock options,and upgrading to an 88-97 Suzuki GSX600/750F Katana complete front suspension.

The GS500 forks are just ok for cruising around on, if you're under 140 pounds.The later GS500F models (02+) seem to have a better spring rate than 89-01 models.I haven't been able to confirmed this.I am going based on word of mouth from internet forums.Anyway it goes,the forks are still lacking performance.Most people complain about the front forks bottoming out and being squishy.Squishy is a technical term used when discussing the soft GS500 suspension.The best upgrade is new fork springs,better heavier oil,and a fork brace fender mount.The GS500 forks are only 37mm in diameter,which is tiny and flexible.

FORK SPRINGS-What's best for me?
There is no perfect answer for this,So I will break it down based on my opinion, on what I have learned from my experiences,as well as others that I have talked to.First, there are two types of fork springs, progressive rate and straight rate.Please don't confuse Progressive "name" brand springs with progressive "rate" springs.Progressive rate springs get stiffer the more the suspension is compressed.Straight rate springs are completely compressed after the weight rating is exceeded.Straight rate springs are sized to the application and rider.Example,a rider that only rides solo and commutes can get away with a softer spring.Where as a heavier rider, that rides two up through curvy roads, will need a stiffer spring.

I break it down like this.
For the general rider that commutes and does light traveling, with a little sport riding thrown in,progressive rate springs will work great.The springs are progressive so the manufactures don't usually give out rating numbers.They are also the cheapest cost wise,usually $20 to $50 cheaper than straight rate springs.

Progressive Suspension Fork Spring 11-1128

80kg/mm-under 140lbs total riders weight
85kg/mm-under 160lbs total riders weight
90kg/mm-under 180lbs total riders weight Race Tech Fork Springs - 0.90kg/mm FRSP S2938090 Most popular option.
95kg/mm-under 200lbs total riders weight
These weights can actually go 30lbs either up or down.It's just a guideline.Going up on kg/mm gives a stiffer spring rate.There is no 100% correct spring rate.It's all based on personal preference.

Stock springs are rated at .594 kilograms per millimeter AKA kg/mm.

I recently had a discussion,with Tmod on KatRiders forum, on this very subject.I used factory 15w Suzuki fork oil, after rebuilding my forks.I decided to do some cold weather riding,at least cold for my area.The temperature ranged from mid 50'sF to low 40'sF.My front end was rigid.Even after 120 miles, my forks never softened up.When I would hit a bump at speed, the front wheel would lift off the road surface.Sounds fun eh?Nope,not when it's out of your control.During my discussion,I was put on the right track to solve my rigid cold fork problem.I was referred to a product that is perfect for most applications.A quick issue needs to be addressed here.As temperatures drop,oils thicken.To solve this problem,we need an oil that maintains it's viscosity over a broader range of temperatures.Bring on the synthetic blend fork oils.Tmod introduced me to Torco RFF fork oils.They hold their viscosity better in all temperatures.The best for most applications is Torco RFF 15.If you're under 150lbs,try out the Torco RFF 7.Each fork holds approximately 382ml or roughly half a quart.

Torco tech sheet PDF

Torco RFF 7 Fork Oil

Torco RFF 7 Fork Oil

These are 100% custom made.I have never ran one on a GS500 front forks.I know they help.Anything that stiffens the front end, and keeps the tire running true,helps feel,feed back,and performance.The fork sliders can move ever so slightly out of line, when moving up and down the chrome fork stanchions.Along with this,the sliders can rotate ever so slightly, causing the front wheel to track off in relation to handle bar position.Most riders will never push their GS500 hard enough to notice this.For those of us that do,we need a fork brace fender mount.There are three ways to get them,hope that one comes up for sale on ebay,check GStwins forum to see if anyone is making/selling them,last but not least,take your stock fork brace fender mount to a machine shop, and have them make one out of 3/8 inch aluminum plate.They're simple and people report having them made between $40 and $60.

Emulators,these are a whole different monster.Unless you are racing in a class that requires you to use stock forks,forget them.They are expensive and require extensive knowledge on how to set them up and tune them.The forks have to be partially dismantled to make adjustments to them.Money would be better spent on upgrading to an 88-97 Suzuki GSXF600/750F Katana front end.I will be doing a write up on that soon.

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