fork springs

[greg]

Had a quick look and there's a couple of threads but nothing that specific..


I'm thinking of upgrading the front suspension to some linear springs, as it's a bit soft and bottoms out under hard braking.

What are peoples opinions on this who have done the mod? Also what weight would I need, the bike is naked so I assume it's a little lighter than the standard Fazer? My weight is around 75kg without gear on (maybe around 80-82 with gear as I mostly wear textiles and have a top box).

Will I find the back a bit too soft after doing this? Also what weight oil do people recommend with linear spings?

Also anybody in the UK recommend a good place to buy some?

Cheers

 

[YZF73]

I changed out my fork springs a few months back, here's the run down;


I purchased linear rate Racetech springs on Amazon from Powersport Superstore over in the US, I could only find progressive springs for sale over here in the UK, however it still worked out cheaper to get them from the US even after the extra shipping costs and taxes etc, took 2-3 weeks to arrive if I remember correctly.

I used Racetech's spring calculator (RT - Digital Product Search) to determine the correct rate for my body weight, at 71kg without gear, the calculator showed that the rear spring was correct, and that either 0.85 or 0.90kg/mm fork springs would be suitable for me depending on application (I generally ride more aggressively than most, and also ride on track quite often), hence I went for the 0.90's.


As your bike is an '06 model, and Yamaha supposedly revised the damping of the front forks for '07, I can provide information on what I've found to be true with my '07 model when it comes to oil viscosity and damping, however the figures won’t necessarily apply directly to your bike.


Oil weight, well...

Damper rod forks are really sensitive to oil weight, and it took me multiple tries to get the rebound where it needed to be in different ambient temperatures. I finally settled on Putoline HPX 17.5wt for summer, and 15 or 12.5wt for the winter (not sure which yet).

SAE oil weights are not consistent between brands, for example a 20wt Putoline has a similar viscosity to 30wt Belray, its well worth using Viscosity Index Tables to compare oil viscosities, here are the ones I use;


Suspension Fluid - Pvdwiki

Comparative Oil Weights Table


The compression damping of the forks is a real compromise, with the compression damping orifices having been made large to prevent harshness under high speed compression, removing the majority of the low speed compression damping. (I believe this may have been the main focus of the damping revision between the '06 and '07 models)

I am looking at fitting Racetech Gold Valve Emulators for this very reason, however if you just want to go with springs, you can effectively utilise air gap to aid in compression damping, I'm currently running a 115mm air gap, which I feel is quite effective on my '07 model.


More information on Racetech's Gold Valve Emulators can be found here if you want to read up on them;

Emulators



Hope this helps, please feel free to ask any other questions if you wish.

Yamahaboyz

 

[greg]

how much did you pay for them then? looking the other day they seemed to range from £80 to £130

i've seen a few different air gap values as well for the fz6

 

[YZF73]

Just over £80 including shipping, plus £12 taxes and an £8 handling fee.


Here's the ad for the ones I bought;

[ame="http://www.amazon.com/gp/product/B000GV2DQW/?tag=5336337973-20"]Amazon.com: Race Tech Fork Springs - .90 KG/MM FRSP S3732090: Automotive[/ame]


Yamahaboyz

 

[FinalImpact]

FWIW: Me @ 185lbs (84kg) + gear 22lbs (10kg), and using 0.88kg/mm linear springs (stock R6 Springs & forks) are perfect. I would not suggest .95 as it'll likely be too harsh.

Remember the stockers are 0.7 to 1.25 at full compression so the sweet spot for most in this weight range is going to be about 0.90 kg/mm rates.


As you were on the rest as I swapped the whole fork set for a R6 vs emulators!

 

[greg]

tbh i can't be arsed with the expense and effort of swapping r6 forks in, i only use the bike for commuting now. Would just like it a bit firmer up front so I have better stopping power

Is there a significant weight difference between the FZ6N and the faired FZ6?

Would a 0.85kg spring maybe be better for me, or would that be too soft?

 

[YZF73]

According to Wikipedia, not the most reliable of sources, the FZ6N is approximately 6 Kilos lighter than the FZ6S, you could say that this makes your bike slightly less 'nose heavy'.

Racetech's spring calculator recommends a 0.85kg/mm spring for your weight on the street, this would probably be your best bet as my faired bike is a little harsh on the road with 0.90's, however I wanted the bike to perform on the track aswell as on the street, so I was happy to accept the stiffer ride on the road.


Yamahaboyz

 

[FinalImpact]

tbh i can't be arsed with the expense and effort of swapping r6 forks in, i only use the bike for commuting now. Would just like it a bit firmer up front so I have better stopping power

Is there a significant weight difference between the FZ6N and the faired FZ6?

Would a 0.85kg spring maybe be better for me, or would that be too soft?

I was just trying to give a perspective from a heavier point of view just in case you had some strange urge to go higher than 0.9 kg/mm. 0.85 would likely be pretty good for you.

So how ya doin after that tumble?

 

[slowlane]

I put some yacugar progresive springs in my forks, i weigh about 12.5 stone,springs are too firm, only had 26mm static sag,which raised the front too much,ended up cutting 6mm off the spacer tubes. Now have 33mm sag & forks feel great,hope this helps.

 

[PhotoAl]

A thread on another approach which looks interesting.

http://www.600riders.com/forum/fz6-general-discussion/33191-ricor-intiminator-fork-mod.html

 

[mongol777]

I wanted to do springs as well but decided to try heavier oil first. Put it 15W Belray - night and day. Bike is much more planted, no more diving when breaking, etc. Just oil change was enough for me - $15 for oil + 30 min. I don't think I'll be doing springs.

 

[greg]

I was just trying to give a perspective from a heavier point of view just in case you had some strange urge to go higher than 0.9 kg/mm. 0.85 would likely be pretty good for you.

So how ya doin after that tumble?

sorry i wasn't having a go

hand is getting better, but still got a lot of problems with my shoulders, especially my left



i think i did try heavier oil last time, i think there's a risk of popping oil seals if it's too heavy though, plus it doesn't really help with slow speed damping