racetech suspension question...

i'm upgrading my 2005 VFR 800A's stock suspension to something more suitable for me (240lbs). I'm going with 1.0 kg/mm in the front and 17kg rear spring. i like to ride in twisties for some spirited type stuff but i don't do track on this bike nor am i dragging knee on public roads. does this setup look right or should i go with a heavier rear spring?

 

i would consider heavier fork springs. I weigh 160+ pounds and I thought the 1.0 springs were good for my weight. A lot of it has to do with how aggressive you ride, do you ride the front wheel hard or do you consider yourself a rear wheel kind of rider? for aggressive street riding 1.0 is probably going to be a little light for your weight. Try to use the heaviest spring you can get away with and use lighter oil. it's much easier to change fork oil weight and heights than it is to buy new springs. Remember, with these forks you have no compression adjustment, you have oil weight and height, and rebound only....it's better to have the preload backed all the way out. it just gives you more options with fine tuning.



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My suggestion would be to speak with the technician at the place you're planning on buying from. Two reasons, one, they will most likely have a better understanding of what your looking for and two, if it's not to your liking, it's easier to have it changed out as it would have been their suggestion and not yours.

I just had a stock ABS rear shock revalved and resprung by Daugherty Motorsports as well as purchased the components for the front end too. Jamie Daugherty is a member on VFRWorld and has helped many a member improve their bikes suspension. I'm not saying that other members can't provide you useful advise, just saying that if you're going to invest your money on something like suspension, talk to an expert. YMMV

Cheers

 

Do you happen to know the stock spring rates and front and rear travel lengths?

Those fronts you are looking at are about 56 lbs/inch, so the combined front rate would be 112 lbs/inch. If you were braking hard doing a 1g stop then you would bury that thing over 2 inches just from your body weight. Do you bottom out the forks when you brake currently? How much of the total fork travel do you use? You will have to measure the "sag" when you are sitting on the bike and compare that to the total available travel, plus know or measure the current spring rate in order to calculate how the new springs will affect the settings. i agree about on the street use the lowest preload and maximize travel--forks and shocks don't damp unless they are moving and the more they can travel the better they work.

The 17 kb rear springs are about 960 lbs/inch. The leverage ratio of the swingarm is about 3:1, so the rate at the rear wheel is 1/3 of that, or 320 lbs/inch. The same applies here, measure your "sag" and compare to total available or "desired" travel, then calculate and adjust to set it like you want it.

i don't like the rear to pivot past the over-center point of the swingarm travel, that is to say where the required chain length is the longest (tightest chain spot), so that is what i use for the "desired" travel length. The reason is that the length of the wheel base gets shorter when the wheel travels past this point-- and that is not something that you want to feel in a corner under full compression. On the street it is doubtful you would push that hard in a corner, but if the spring is too soft for your weight it might be possible to get into that nonlinear region during spirited riding in the twisters.

There are numerous websites and books with the details of how to measure and make these calculations. Some general guidelines for street riding suggest to set it up such that when you are sitting on the bike the "sag" is no more than 25% of your total travel. It's easy to measure using cable ties on the fork tubes.

 

my understanding of the dynamics of the motorcycle was that the wheel-base changes when the front end compresses, thus you should get your inputs done (not to be confused with a 3-input woman) and turn the bike at that time also un-loading the front tyre is a good practice, crack that throttle a CH... this way, you have a quick steerer, (short wheel-base = fast turner.)

Rake and trail are pretty advanced things, remember reading an awsome article aboot someone that was campaigning a KTM race-bike and finally, after reading the entire article, I understood rake/& trail.

Anyway, Cheers and gud luck!!! Having quality suspension is sweet!

 

thanks for the info guys

 

I weigh in around 180. I put 1.1's on the front and have not been happier. I do 2-4 track days per year and those springs are exactly what I need. I would suggest, imho, that you get stronger springs than 1.0