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trying to get good info on spring rates


rhb

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I'm a researcher. If I don't know something about an upgrade, I read everything I can about it before deciding to buy something, call it methodical or whatever.
when searching about info on front fork upgrades, the various solutions, cost etc. I found a lot of conflicting info on the stock front fork springs on the FZ/MT07. I present the following for everyone's benefit and also solicit any informed opinions  as well.
 
various unsubstantiated forum posts (not necessarily this forum):
 
"The stock front springs are for a 165 lb rider. If you weigh more than that....you need stiffer springs to stop the front end dive".
 
"I agree the stock forks are not too bad, especially if you are 150 lbs or under".
 
"Traxxion changed the front springs from .9kgs to 8.5kgs for my weight... 165 pounds with gear"
 
:
Now the facts from three trusted sources, but with 2 different opinions. They are three very well known manufacturers and or shops, I won't put them on the spot by mentioning names:
 
vendor A
At 175-180 lbs in gear, If your're in the market for front springs, I'd ditch the factory springs and go for the next lower rate of 0.85 kg/mm.
the stock rate is 0.875 kg/mm, which is only incrementally firmer. (so splitting hairs) The proper approach to fixing brake dive will be to address the damping.
 
Vendor B
we’d recommend trying it with the OEM springs. We rated the OEM springs in the FZ07 at .87 kg/mm.
VendorC
.875 is good for your weight.
 
Here is the kicker and it goes against the common opinion it seems, I am 175-180 pounds with gear, not a 150 pound Japanese rider. Is it possible the bikes are or have been supplied with different springs in different markets, or are people just mis-informed.
 
 

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According to http://www.racetech.com/ProductSearch/2/Yamaha/FZ-07/2015-16
"Stock Front Spring Rate: 0.72 kg/mm (stock)"
 
We did have a couple of suspension guys discuss this in more detail
https://fz07.org/thread/4893/spring-rate?page=2
 
pattonme:
"I measured again (assuming merc16's forks are stock) and came up with 0.79-0.82kg/mm.
 
 

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I'm a researcher. If I don't know something about an upgrade, I read everything I can about it before deciding to buy something, call it methodical or whatever. when searching about info on front fork upgrades, the various solutions, cost etc. I found a lot of conflicting info on the stock front fork springs on the FZ/MT07. I present the following for everyone's benefit and also solicit any informed opinions  as well.
 
various unsubstantiated forum posts (not necessarily this forum):
 
"The stock front springs are for a 165 lb rider. If you weigh more than that....you need stiffer springs to stop the front end dive".
 
"I agree the stock forks are not too bad, especially if you are 150 lbs or under".
 
"Traxxion changed the front springs from .9kgs to 8.5kgs for my weight... 165 pounds with gear"
 
:
Now the facts from three trusted sources, but with 2 different opinions. They are three very well known manufacturers and or shops, I won't put them on the spot by mentioning names:
 
vendor A
At 175-180 lbs in gear, If your're in the market for front springs, I'd ditch the factory springs and go for the next lower rate of 0.85 kg/mm.
the stock rate is 0.875 kg/mm, which is only incrementally firmer. (so splitting hairs) The proper approach to fixing brake dive will be to address the damping.
 
Vendor B
we’d recommend trying it with the OEM springs. We rated the OEM springs in the FZ07 at .87 kg/mm.
VendorC
.875 is good for your weight.
 
Here is the kicker and it goes against the common opinion it seems, I am 175-180 pounds with gear, not a 150 pound Japanese rider. Is it possible the bikes are or have been supplied with different springs in different markets, or are people just mis-informed.
 

 
Go with the advice of vendors A-C, they are not far from the facts, the real issue is the weak damping. .87 stock springs have been tested to be true. You either need imulators or drop in valves from cogent dynamics at a minimum
Go to o sonic springs web site and use the spring calculator
It's more reliable than racetech
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Since others dropped names, the three vendors in order of listing in my post are Nick @ Stoltec, Todd @ Cogent, and Dan @ Traxxion. I assume they got it right.
BTW all three came up with .875 (stock spring rate) one just rounded off.
 

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  • 1 year later...
On ‎5‎/‎10‎/‎2017 at 7:05 PM, i28 said:

According to http://www.racetech.com/ProductSearch/2/Yamaha/FZ-07/2015-16
"Stock Front Spring Rate: 0.72 kg/mm (stock)"
 
We did have a couple of suspension guys discuss this in more detail
https://fz07.org/thread/4893/spring-rate?page=2
 
pattonme:
"I measured again (assuming merc16's forks are stock) and came up with 0.79-0.82kg/mm.
 
 

RaceTech has updated their web site: http://www.racetech.com/ProductSearch/12/Yamaha/FZ-07/2015-17

 

They now say:

"Stock Fork Spring Rate:0.88 kg/mm (stock)

Comments: First Year 2015 FZ-07/MT-07 Models may have lighter .75kg Rate Fork Springs"

 

I know can be difficult to distinguish soft springs from soft dampening. As soft as my 2015 front-end is, my static sag is only about an inch and all the spring-rate calculators I've used say I should be using 0.9 kg/mm so my stock springs are probably correct while it's just that my fork oil is way too thin (5wt should be 15wt).

I was tortured by the Japanese during the war, Jack. Not a pretty story. Strange thing is they make such bloody good cameras.

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