USD fork conversion spring rates

[pumacorp]

So anyone who has done the USD conversion what spring rate are u using and how is the ride?
I have used the gsxr750 front end with a 0.90 rate which I think sucks and now im trying a hayabusa one,,Ill be putting it on in 2 weeks or so...

So please post your conversion and the spring rate that your using ..Im sure everyone would be interested..

 

[satariel666]

Depends.

How much do Your bike weight?

Mine v-max is serioulsy lightweigted and I've found 1,2kg spring way to hard.
Curently Im running with 1kg spring and I can say its ok.

More pain in the ass is finding the good fork oil weight and good suspension settings.
V-max dont work good with typical suspension SAG setting.
I mean its no good to set the SAG as much in the front and rear.
V-max likes harder rear.
Well, thats my case.

 

[pumacorp]

My bike is as light as u can make a max...Sportbike rims front and back,,,all tins were replaced with plastics,,,gsxr front end,,,no air box,,,Any weight u can take off a bike has been done...I havent weighed it yet,,but im guessing 500 or so,,,but im a 200 pound rider ...

 

[satariel666]

My bike is as light as u can make a max...Sportbike rims front and back,,,all tins were replaced with plastics,,,gsxr front end,,,no air box,,,Any weight u can take off a bike has been done...I havent weighed it yet,,but im guessing 500 or so,,,but im a 200 pound rider ...

Same here. I weighted mine ans it was around 230kg, full tank and fluids included.

Id say go with 1kg springs and 10W oil.

 

[davidon]

I'm using busa forks and hyperpro springs 10w oil. I think the valving is also crucial in getting the forks in the range of action you're looking for.

 

[DanQuin]

So anyone who has done the USD conversion what spring rate are u using and how is the ride?
I have used the gsxr750 front end with a 0.90 rate which I think sucks and now im trying a hayabusa one,,Ill be putting it on in 2 weeks or so...

So please post your conversion and the spring rate that your using ..Im sure everyone would be interested..

Can you explain what sucks? Is it chattering? Harsh? Does it not track well?

Rather than changing out complete front ends repeatedly, you may try troubleshooting what the replacement front end is doing. If you've gone from a pretty non-adjustable Vmax front end to a fully adjustable one, it should be capable of being tuned pretty close.

• sag should be approximately 30-40% of the total travel
• rebound should be set after sag to point where the suspension tops off from a firm push without bouncing a second time
• compression should be set to a point where the front and rear of the bike respond similarly when pushed at the same time/same pressure

Also... most sportbike suspensions are set for 5wt or even less oil. Using too heavy an oil can potentially put the hydraulic damping curve well outside of the spring progression curve and give an overly harsh ride.

 

[pumacorp]

instead of redoing the inerts its easier and cheaper to go with a busa front end which is geared towards the weight of my max anyway..Valving is way off cause the gsxr 750 is a much lighter bike..I made a mistake by using a 750,,but the only reason I did it was because I wanted to see if it would work and they are black which also saved me the time of painting the forks to match my all black bike..
Everything is black and a little chrome so those ugly copper or red forks are just so out of place ..

 

[DanQuin]

instead of redoing the inerts its easier and cheaper to go with a busa front end which is geared towards the weight of my max anyway..Valving is way off cause the gsxr 750 is a much lighter bike..I made a mistake by using a 750,,but the only reason I did it was because I wanted to see if it would work and they are black which also saved me the time of painting the forks to match my all black bike..
Everything is black and a little chrome so those ugly copper or red forks are just so out of place ..

The GSXRs are typically valved a bit stiffer than the Busa, even though the Busa has much more weight. The Busa appeared to have a 25 mm valve, where the later models had 20 mm valves for both compression and rebound.

Should be a fun build. More options and spring than the Vmax had.

 

[satariel666]

The GSXRs are typically valved a bit stiffer than the Busa, even though the Busa has much more weight. The Busa appeared to have a 25 mm valve, where the later models had 20 mm valves for both compression and rebound.

Should be a fun build. More options and spring than the Vmax had.

All of late 43mm USD forks from Kayaba has 20mm valves. No matter its Yami, Suzi or Kawi they all looks similar inside.
Im using 2007 zx10r fork.
Im considering buying aftermarket valving system.

 

[DanQuin]

All of late 43mm USD forks from Kayaba has 20mm valves. No matter its Yami, Suzi or Kawi they all looks similar inside.
Im using 2007 zx10r fork.
Im considering buying aftermarket valving system.

The part number for the Race Tech valve for the 99-07 Busa is FMGV S2530, which indicates it's a 25 mm valve. Also the 07-08 Yamaha R1 had 24 mm pistons (FMGV S2420G).

Have you decided on a kit yet? There are a couple of competitive parts out there. I build one or two sets of forks each month. Hardest part is gathering the tools.

 

[pumacorp]

I went with the 05 gsxr front forks cause I got a steal on them with the calipers..So I took my gsxr750 gafner rotors 320mm shim them to fit the 1000 set up and also spaced up the calipers 5mm to make up for the larger rotors I had..Used a hayabusa axle cause the spread on the forks is wider than the 1000...the ride is decent,,but I have to get better springs cause they are .95 and im getting too much dive...Im guessing 1kg springs might work..I was going to go with 1.1 but im thinking it will be too rough and I ride in ny with alot of big bumps..Anyone have input I would appreciate it..Oh I can not find progressive springs which would be nice instead of the rough linear spring ride anyone know who makes progressives for sport bikes?

 

[Thevmaxrider]

My bike is as light as u can make a max...Sportbike rims front and back,,,all tins were replaced with plastics,,,gsxr front end,,,no air box,,,Any weight u can take off a bike has been done...I havent weighed it yet,,but im guessing 500 or so,,,but im a 200 pound rider ...

Actually you are wrong. You can loose another 75+ lbs doing a chain drive conversion. My Max has EVERYTHING done to remove weight and still comes in at 520 lbs. give or take a bit cause a truck scale is not exactly calibrated very well that low. Pick up a set of Racetech springs after you weigh the bike and tell them the combined weight of bike/rider and they should be able to hook you up with the right springs.

 

[pumacorp]

Yeah I was trying to avoid race techs cause I have used them on the sport bikes and man are they stiff as hell...

 

[Thevmaxrider]

I had to dial out some pre-load for sure and get the rebound and damping set properly before my forks became something other than pogo sticks for sure. Once set up properly though they are awesome.

 

[pumacorp]

are u talking about you chain drive conversion max??I have been pondering the chain conversion for awhile now..What size springs did u use?

 

[Thevmaxrider]

Yep, I am talking about my chain drive Max. Run an 03 R1 front end with Racetech springs and 5wt. oil. Love the chain drive for sure!!!! Actually did a 4th gear power wheelie even with the 6in stretchunk:

 

[pumacorp]

wow thats awesome...What size springs u running? 1.0kg?1.1

 

[satariel666]

Actually you are wrong. You can loose another 75+ lbs doing a chain drive conversion. My Max has EVERYTHING done to remove weight and still comes in at 520 lbs. give or take a bit cause a truck scale is not exactly calibrated very well that low. Pick up a set of Racetech springs after you weigh the bike and tell them the combined weight of bike/rider and they should be able to hook you up with the right springs.

I think Your scale is wrong Jimo.
I used a salvage yard scale some time ago and got 230kg around.
You should be close to 210kg right now.

wow thats awesome...What size springs u running? 1.0kg?1.1

Dont run with 1,2 springs unless You have stock bike with side bags and fat girl on Your back seat LOL

I say stick with 1,05-1,1 and You should be fine.
Changing the valving may be necessery.

 

[satariel666]

The part number for the Race Tech valve for the 99-07 Busa is FMGV S2530, which indicates it's a 25 mm valve. Also the 07-08 Yamaha R1 had 24 mm pistons (FMGV S2420G).

Have you decided on a kit yet? There are a couple of competitive parts out there. I build one or two sets of forks each month. Hardest part is gathering the tools.

Sorry mate, I miss that.

All forks that ended in my dirty hands were equipped with 20mm valves.
As all Kayabas looks pretty the same I agree, they could use diffrent valving.
Still much to lern.

07-08 R1 are a diffrent story forks, 6 piston calipers etc.


I had found that theres no big diffrence which oil will ya put, donnor forks still use the same valves which limitates You possible changes.

Most defo I need diffrent valving. I think I will stick with Racetech gold kit.
On winter.

Whenever You will hear that someone claims that his USD conversion on his v-max went absofuckinlutly marvelous without big changes, that would be LIE like hell.


About the tools...I never bought any OEM tool for any bike I've had in my life. Im a machinist so I have a little comfort.
Im always making tools myself and bealive me this way somethimes sucks on the whole line.

 

[one2dmax]

I am curious what you did end up getting Jim since I have an R1 setup I can trying to get ready for a customer. We want to have him order his Racetech parts but need what works right to let him know.

Sean