A question about springs

[Thomas Dylan]

This winter I'm working on the suspension for a post 750. I'm ~200lbs and was thinking of getting a ~18kg/mm shock spring for the rear (currently no free sag because of the preload needed to get the correct rider sag) and straight rate .95kg/mm for the front (I think the fronts are shot I currently have 30mm of free sag).
I was just wondering if anyone has changed springs and how they felt the ride changed. I'm looking for some real world impressions vs. the spring rate calculator provided online to help in making choices.

[mcssls]

talk to tmod

[mammut89]

This winter I'm working on the suspension for a post 750. I'm ~200lbs and was thinking of getting a ~18kg/mm shock spring for the rear (currently no free sag because of the preload needed to get the correct rider sag) and straight rate .95kg/mm for the front (I think the fronts are shot I currently have 30mm of free sag).
I was just wondering if anyone has changed springs and how they felt the ride changed. I'm looking for some real world impressions vs. the spring rate calculator provided online to help in making choices.

got a resprung , revalved and overhauled rear 750 shock, plus the racetech 1.0kg/mm springs and spacer pre cut from Tmod.

Just drop in the parts and got a new bike. badabing badabom. best omney ive spent so far. Im thinking of doing the racetech cartridge emulator next winter when I have a full fork service.

[Tmod]

I'm looking for some real world impressions vs. the spring rate calculator provided online to help in making choices.

I know you didn't find the 18 kg/mm on any online spring rate calculator as Racetech's calculator for the rear spring is wrong.

mcssls, He is looking for feedback from those that have had new springs installed vs the stock springs. I could tell him my opinion but that may sound biased.

Tmod

[Kreylyn]

I know you didn't find the 18 kg/mm on any online spring rate calculator as Racetech's calculator for the rear spring is wrong.

mcssls, He is looking for feedback from those that have had new springs installed vs the stock springs. I could tell him my opinion but that may sound biased.

Tmod

I'm biased your opinion would be the right one, so I vote for you to share anyways...

Krey

[Thomas Dylan]

A question about springs

I checked through the forum's and I think I'm close on selecting the front springs .95 kg/mm. mammut89 I'm guessing your close to 200lbs?
But I've haven't seen much info in the forum about rear springs. I did check out Racetech but it suggested 11 kg/mm for the rear on line but I have not contacted them yet (seems light to me based on my search the web). The VFR forum's would suggest 18-22kg/mm would be in the range for my weight but that's for a VFR.
Is it better to err on the heavy side or light side?

[mammut89]

tomas yes im roughly 200lbs yes

[Tmod]

11 kg/mm is the rate of the stock spring, Racetech came up with those numbers from my bike and they made a mistake when they selected a spring for my weight but have since never changed the database to reflect the proper spring for the weight of the rider. That only applies to the rear and the front rate suggestions are accurate.

I don't understand searching the VFR forums for a spring for a kat but maybe there is something I am missing. If you are going to get a spring it would be best to not error on either side and just get the one that is correct for you and your riding style and take into account any two up riding as well.

Tmod

[Thomas Dylan]

A question about springs

mammut89
Thanks, I think .95 to 1.0 kg/mm up front are my choices.


TMod
"I don't understand searching the VFR forums for a spring for a kat but maybe there is something I am missing."

When I searched in the Katriders forum there was info on front springs not that much on rear springs. So I picked a bike, Honda VFR 3rd-4th generation similar weight and suspension set up, that I felt was closest to a 750 Kat and had a good forum on suspension.
Most riders on the VFR page with similar weight riders were using 1000-1200 lb/in rear springs. But the shock leverage looks much less on the Honda than on the Kat so I wasn't sure what effect that has.

"and your riding style and take into account any two up riding as well."

90% commuting on 2 lane back roads almost no two up riding, I don't want the suspension to race track firm.

[Tmod]

When I searched in the Katriders forum there was info on front springs not that much on rear springs. So I picked a bike, Honda VFR 3rd-4th generation similar weight and suspension set up, that I felt was closest to a 750 Kat and had a good forum on suspension.
Most riders on the VFR page with similar weight riders were using 1000-1200 lb/in rear springs. But the shock leverage looks much less on the Honda than on the Kat so I wasn't sure what effect that has.

"and your riding style and take into account any two up riding as well."

90% commuting on 2 lane back roads almost no two up riding, I don't want the suspension to race track firm.

I would suggest a 900 lb/in / 16.1 kg/mm spring on the rear with 10mm preload. In the front go with a .95 and put 25mm preload on it.

When comparing or selecting springs bike weight has little to do with it, The kat 1100 is not a light bike (546 lbs dry) yet it has a 8.4 kg/mm spring stock on the other hand a CBR600 F4i is a somewhat light bike (370 lbs dry) and has a 14.1 kg/mm spring on it. The leverage ratio will control what spring you need as well as the rider weight.

Tmod

[Thomas Dylan]

A question about springs

Tmod
Thank you for the info. When I first started this I thought changing the shock and fork's valving and oil would be first but after looking into it, it seems as if springs come first then shock damping.

Regards

[Tmod]

Tmod
Thank you for the info. When I first started this I thought changing the shock and fork's valving and oil would be first but after looking into it, it seems as if springs come first then shock damping.

Regards

Yep it is a little hard to set the valving when you have no idea what spring you are going to use. The rebound valving is there to control the spring and going from a 600 lb/in spring to a 900 lb/in spring is a wee bit different.

Tmod

[Thomas Dylan]

A question about springs

Tmod,
Just out of interest, would you know, or guess at, if the Racetech spring rate calculators uses shock leverage in their recommendations?

[Tmod]

Tmod,
Just out of interest, would you know, or guess at, if the Racetech spring rate calculators uses shock leverage in their recommendations?

Let me answer it this way, When a bike goes into Racetech they will take a leverage ratio reading and use that info to match the proper spring and valving for the rider. Also taken into consideration is what the free sag vs rider sag is, For instance in my case after my testing I took a 1000 lb/in spring and with preload at 8mm I was getting 32mm rider sag and about 4mm free sag. The leverage ratio is not built into a calculation on the Racetech website for spring selection as that info was used to arrive at what spring works for what weight rider. Adding or changing weight of the bike as in Race vs Street will give you different results as well.

Did I answer your question?

Tmod

[Thomas Dylan]

Tmod,
Yes, from your answer it seems as if Racetech sticks to their recommended free and rider sag numbers and spring rate recommendations are based on getting these numbers.
Thanks again.
Regards