Rear Shock Springs

[Tmod]

Anyone know where to get stiffer rear shock springs for a stock 06 750 kat rear shock?

Tmod

[GregS]

RaceTech, Eibach, Works Performance, WP Suspension, Wilburs, Hagon
None will list your application but all can figure out your needs.

[Tmod]

RaceTech, Eibach, Works Performance, WP Suspension, Wilburs, Hagon
None will list your application but all can figure out your needs.

Yeah they are not much help as they don't get excited about changing a Kat spring but I got one that will work from Racetech. If anyone cares it looks like a spring from a 06~07 GSXR 750 will work.

Kat spring dimensions: ID= 56mm, Free Length=181mm
06~07 GSXR 750 spring dimensions from Racetech: ID= 58.2mm, Free Length=178mm

Racetech has several different rate springs in that size for anyone that wants to get a stiffer spring.

Tmod

[tone]

Just one point to remember guys ......

just because a spring has a higher (stiffer) rating does not always mean it will make your bike stiffer at the rear If it is intended for another bike

The reason for this is because as most bikes are rising rate monoshock, a lot of the feel is down to the swingarm length & the leverage applied by the linkages

Eg a stiff spring will feel soft if a lot of leverage is applied & a soft spring will feel stiff with a small amount of leverage, Try compressing a shock off the bike & you will see what i mean

Trial & error is probably the only way a home mechanic can sort out this problem imo & even then i wouldnt expect to get the shock working perfectly within its design parameters, the same applies to swapping a complete shock

cheers tone

[Tmod]

Just one point to remember guys ......

just because a spring has a higher (stiffer) rating does not always mean it will make your bike stiffer at the rear If it is intended for another bike

The reason for this is because as most bikes are rising rate monoshock, a lot of the feel is down to the swingarm length & the leverage applied by the linkages

Eg a stiff spring will feel soft if a lot of leverage is applied & a soft spring will feel stiff with a small amount of leverage, Try compressing a shock off the bike & you will see what i mean

Trial & error is probably the only way a home mechanic can sort out this problem imo & even then i wouldnt expect to get the shock working perfectly within its design parameters, the same applies to swapping a complete shock

cheers tone

If the free length and the coil id is the same and the only thing you change is increase wire diameter the spring will be stiffer no matter what the ratio is on the bike, Especially if the newer spring has fewer coils. I do agree that changing the ratio on the bike will make one spring feel softer then another, The spring manufacturers don't design a spring based on a unkown ratio but rather free length, compressed length, coil diameter, number free coils and coil wire diameter.

I am comparing spring rates to spring rates and measurements to measurements on the springs not ratio's.

Tmod

[tone]

If the free length and the coil id is the same and the only thing you change is increase wire diameter the spring will be stiffer no matter what the ratio is on the bike, Especially if the newer spring has fewer coils. I do agree that changing the ratio on the bike will make one spring feel softer then another, The spring manufacturers don't design a spring based on a unkown ratio but rather free length, compressed length, coil diameter, number free coils and coil wire diameter.

I am comparing spring rates to spring rates and measurements to measurements on the springs not ratio's.

Tmod

Absolutely the correct way to try to figure it out, i was just checking that you were not just thinking oooh a spring from a different bike will work as most people do

[Tmod]

I found a series of springs that are a direct replacement for the stock kat spring on the post 750 shocks. Other years and models of kats may be the same as well but I cannot verify this as I don't have any pre 600/750 springs or post 600 springs. The replacement spring comes from Racetech and it is the spring for the Yamaha R6 shock. Racetech has up to a 11.7 kg/mm spring and from there Eibach would have the be the source as they continue up to 23.3 kg/mm.

Here are a couple images of the Stock Post 750 Spring and the Racetech R6 Spring.





Tmod

[Black_peter]

Be careful.. I noticed the OD is critical on the Pre 98. The coil can foul the swing arm.
I thought it was the dog bones (and this the 98+ might be OK) but I'm not sure the 98+ has anymore room in the "throat"...

[Tmod]

Be careful.. I noticed the OD is critical on the Pre 98. The coil can foul the swing arm.
I thought it was the dog bones (and this the 98+ might be OK) but I'm not sure the 98+ has anymore room in the "throat"...

I have about .250 + all around the shock and the R6 spring is .1 bigger in OD so .050 a side I should be safe.



Tmod

[FASHER]

Interesting........can you really notice the difference?

[Black_peter]

How did you get that photo Tmod??

Turn the bike upside down??

[Tmod]

How did you get that photo Tmod??

Turn the bike upside down??

Yeah I decided it was time to get back into lifting.

Actually just held the camera against the tire and got lucky.

Tmod