Front Suspension Upgrade Questions

[outasight20]

Hey all,

I know there are a million threads similar to this one and I already read through a lot of them. I am simply looking for some clarification.

My only gripe with the FZ6 is the loose unsettled feeling I get when I hit bumps in turns and the front end dive under hard braking. Does changing just the front fork springs and oil fix this problem?

Racetech sells their gold emulator kit, does anyone do this when they change their springs and oil? What if any difference does it make?

I replaced my fork seals and fork oil with 10wt less than 6 months ago. I would prefer to not remove the seals to change the springs. Do the seals have to be removed to change the springs? If I remember correctly, I could remove the springs by just removing the fork cap.

Can anyone who has done the Racetech spring upgrade share their experience with both the process and improvement to handling and braking?

I weigh 180, about 205-210 with gear. Racetech recommends .90 kg/mm springs, however I've read most people around my weight go with the .95 kg/mm.

Finally, when changing to Racetech springs, is the stock rear shock still adequate, or does the front upgrade highlight the weakness in the rear? I'm not looking to race my bike, I just want more confidence in the corners and a more stable feeling over bumpy roads.

 

[Ben sIII]

It is an amazing change on the bike, it is quite a simple job, maybe a couple hours max, and you don't have to remove the seals to replace the springs, just take the forks off, remove the cap, and pull out the old springs and replace with the new ones.

I went with the 0.95 springs and i weigh a few kgs more than you and i find them comfortable, gives you far more confidence under brakes and turning. As for the rear shock, i havent felt the need to change it, though i did up the preload by 1 point.

Hope this helps, i also ran 15wt oil for what its worth

 

[outasight20]

It is an amazing change on the bike, it is quite a simple job, maybe a couple hours max, and you don't have to remove the seals to replace the springs, just take the forks off, remove the cap, and pull out the old springs and replace with the new ones.

I went with the 0.95 springs and i weigh a few kgs more than you and i find them comfortable, gives you far more confidence under brakes and turning. As for the rear shock, i havent felt the need to change it, though i did up the preload by 1 point.

Hope this helps, i also ran 15wt oil for what its worth

This is just what I was looking for. I will probably go with the .95 springs. Once my tax return comes in, they are getting ordered along with some 15wt shock oil.

 

[iSteve]

You may want to go with the recommended .90's. If you are looking for control over bumps lighter springs will be preferred. Likewise if you are looking to ride high speeds on a smooth surface heavy spring will be better.

Think of riding a bicycle. A road bike with no suspension is super unstable over bumps and potholes while a mountain bike with suspension feels much more in control and comfortable.

 

[outasight20]

Now I'm a little confused. If lighter springs are preferred for control over bumps, wouldn't going with stiffer springs (ie: Racetech vs. stock) make the sloppiness over bumps in the corners worse? I understand the ride will be harsher with the heavier rate springs, much like a sports car has a harsher ride than a minivan. Will there really be that much of a difference between the stock .77 kg/mm spring and the .90 kg/mm spring? I am just looking to tighten up the front end as like we all know, it is very sloppy in stock form.

 

[darius]

I'm trying to setup my suspension right now as well, but with Hyperpro springs (progressive rate).

From my research so far:

• Spring weights should be chosen according to rider weight w/ gear.
• Too light and you get front end dive and unsettled feeling in corners the harder you take them. Might get harsh as the forks near bottom out.
• Too heavy and the suspension will resist compression and send the shock to the rider. Firmer suspension is needed for fast cornering as the bike is pressed into the corners.
• The spring weight just needs to match the rider close enough to be able to get the sag into the right range for their riding style.
• A sag of 30-35mm is recommended for street riding.
• Sag is set by adjusting the preload. Our FZ6 unfortunately has no fork preload adjusters. It has to be set internally using the right length preload spacer that sits on top of the spring under the fork caps.

Check out vids from Dave Moss. He is the suspension guru:
Motorcycle Suspension - Setting Sag - YouTube

 

[Yasko]

Let me know what works. This is a mod that I'd like to do this summer.:thumbup:

 

[Neal]

Hey all,

I know there are a million threads similar to this one and I already read through a lot of them. I am simply looking for some clarification.

My only gripe with the FZ6 is the loose unsettled feeling I get when I hit bumps in turns and the front end dive under hard braking. Does changing just the front fork springs and oil fix this problem?

Racetech sells their gold emulator kit, does anyone do this when they change their springs and oil? What if any difference does it make?

I replaced my fork seals and fork oil with 10wt less than 6 months ago. I would prefer to not remove the seals to change the springs. Do the seals have to be removed to change the springs? If I remember correctly, I could remove the springs by just removing the fork cap.

Can anyone who has done the Racetech spring upgrade share their experience with both the process and improvement to handling and braking?

I weigh 180, about 205-210 with gear. Racetech recommends .90 kg/mm springs, however I've read most people around my weight go with the .95 kg/mm.

Finally, when changing to Racetech springs, is the stock rear shock still adequate, or does the front upgrade highlight the weakness in the rear? I'm not looking to race my bike, I just want more confidence in the corners and a more stable feeling over bumpy roads.

I have tried that very change and I give it the thumbs down. Yes, the front diving down in breaking was improved. However, the improvement was not enough overall in my case my bike was better before the change.

The bike would hunch under acceleration and the front would tend to push out wide giving a sensation of the losing the front and making the bike run wide in turns. I actually ran my bike off the road and crashed with-in a week of making this change after having ridden without incident for over a year.

My advice is get a real suspension not a micky-mouse band aid. You need forks that have adjustable damping and compression to have real handling and confidence in the turns.

 

[bob808]

I've replaced my springs with Racetech '90 ones and I'm about 80kg without gear. For me the improvement has been huge. Also I have replaced the bars with FZ1 bars and also got braided brake lines. The overall handling is much better but I felt the need to preload the rear shock some more. Still not enough, I feel my back end is wobbly now (not jello but still). The bike stops faster with less nose dive and feels firmer under heavy acceleration.
This mod has security issues, as easy as it seems there are a few factors to be taken into account:
If you only replace the springs then it's not so bad but you need to be sure that the oil has the exact same level in both tubes. Keep in mind that when you take out the old springs you take out some oil as well. But if you replace the seals then it means that you have to dissasemble the forks from the bike. Putting them back may not be as easy as it seems. I spent a lot of time after installing them back in because I felt the bike wasn't stable in turns. It seems that it's not that easy to allign the forks with the triple, and they may twist a little bit when you torque everything down. Harder to explain in words but I could make a drawing. Now the front end is ok after alot of adjustments. Also I felt the need for a rear shock after some riding with the new springs. I don't know if you'll feel this while commuting but if you like the weekwnd fun on twisties you'll feel the need for a nicer rear shock.
Mishandling the forks and messing with different oil levels or proprer allignment of the forks can mean the difference between life and death. The operation itself is not complicated if you follow the service manual to the letter.
Ride safe!

 

[motojoe122]

This is just what I was looking for. I will probably go with the .95 springs. Once my tax return comes in, they are getting ordered along with some 15wt shock oil.

This is exactly what I did before I did the R6S fork swap. I liked it but eventually wanted more control and convience of having the adjusters on the forks instead of having to change oil and spacer stock.

 

[Erci]

I don't have personal experience experimenting with FZ6 front sus, but from many years of downhill mountain biking (where suspension plays a critical role), I can tell you that no matter what spring weight / oil weight you go with, there is no way to gain the same control one would gain from having a fork with adjustable rebound and compression damping.

Getting rid of fork dive, without compression, would require heavy springs. Heavy springs will minimize dive, but suspension will end up being less compliant and overall harsh on normal bumps.

If I still had my FZ6 and wanted to improve front feel, I would go straight for fork swap.

 

[nivag]

I changed mine to Ohlins linear springs and fork oil to 12.5W

http://www.600riders.com/forum/fz6-performance-mods-section/46348-suspension-upgrade.html

Great improvement, the lack of fork diving was most noticeable. I was always using the rear brake to balance the bike under heavy breaking.

 

[dpaul007]

I'll be doing springs and oil here within the next week, maybe even this weekend if I have time. I got .90 springs and 5w oil. There aren't too many smooth roads where I am, so I chose to stick with lighter weight oil. Also, I'm 193ish lbs.

Something I found about oil viscosity and level:
Standard forks without adjusters can also be tuned by altering the fork oil viscosity and level. On non-cartridge forks ( like TY350 ), the level of the oil generally affects compression damping and the oil weight/viscosity affects the rebound damping. Keep in mind, with cartridge forks, that unless your forks have a rebound cartridge in one side and the compression cartridge in the other, like Fantic Marzocchi, Gas-Gas, and most new forks, a change in oil viscosity and level will have some affect on BOTH rebound and compression damping. Heavier oil viscosity will give more compression and more rebound damping. On the other hand, a higher oil level will give you more compression “damping” ( resistance to the fork compressing ) but less rebound damping as the reduced air pocket inside the top of the fork tube will exert more pressure to extend the fork. That air pocket inside the top of the fork tube acts as a secondary spring as it is compressed when the bottom slider moves up. Raising the fork oil level makes for a smaller air pocket that takes more energy to compress ( per inch of travel ) than a larger one and will exert more pressure to assist the spring extending. The advantage of having different cartridges in each fork for rebound and compression damping is that they can be adjusted separately, which you could not do if the cartridge handled both rebound and compression as most motocross forks do.

 

[FinalImpact]

Compression rate is controlled by the damping system not the spring. So you can't fix a "DIVE" issue with a spring alone. You will be disappointed.

In short - spring rates are set by load imposed and the damping control does not effect the springs ability to carry a given load. That is - once you sit on the bike stationary - it is the springs that keep the bike suspended at a given ride height not the oil damping components (on our bikes).

Also, the stock fork springs are not a continuous (fixed) rate as they start at one value 0.77 mm/kg and rise to something like 1.2mm/kg under full compression. The biggest issue here is they need the preload adjusted to fix the initial sag of 45mm and reduce it 30 ~ 35 mm.

I urge you not to go crazy with the spring rate trying to fix a damping issue. Lack of damping is what is hurting the nose of the Fizzer. The lighter folks could likely get away with running emulators and fresh oil of higher viscosity if they adjust the springs pre-load for proper sag (I say this only from money saving stand point).

IMO - if you just cruise and want a smooth ride, shim the front spring, add emulators, and change the oil. If you ride aggressively I'd suggested a fixed rate for increased predictability (also the rear is a fixed rate) and run a front rate 0.9 mm/kg for geared rider of 215 or less.

Best money spent: if you can swing it - upgrade the forks to R6 or better. Its worth the effort and expense as it truly transforms the bike making it a pleasure to ride. Control in the corners and over uneven terrain will be improved substantially.

JJD952

 

[Erci]

Compression rate is controlled by the damping system not the spring. So you can't fix a "DIVE" issue with a spring alone. You will be disappointed.

In short - spring rates are set by load imposed and the damping control does not effect the springs ability to carry a given load. That is - once you sit on the bike stationary - it is the springs that keep the bike suspended at a given ride height not the oil damping components (on our bikes).

Also, the stock fork springs are not a continuous (fixed) rate as they start at one value 0.77 mm/kg and rise to something like 1.2mm/kg under full compression. The biggest issue here is they need the preload adjusted to fix the initial sag of 45mm and reduce it 30 ~ 35 mm.

I urge you not to go crazy with the spring rate trying to fix a damping issue. Lack of damping is what is hurting the nose of the Fizzer. The lighter folks could likely get away with running emulators and fresh oil of higher viscosity if they adjust the springs pre-load for proper sag (I say this only from money saving stand point).

IMO - if you just cruise and want a smooth ride, shim the front spring, add emulators, and change the oil. If you ride aggressively I'd suggested a fixed rate for increased predictability (also the rear is a fixed rate) and run a front rate 0.9 mm/kg for geared rider of 215 or less.

Best money spent: if you can swing it - upgrade the forks to R6 or better. Its worth the effort and expense as it truly transforms the bike making it a pleasure to ride. Control in the corners and over uneven terrain will be improved substantially.

JJD952

A big +1! (mainly the fact that attempting to fix dive with firmer spring is a bad idea)

 

[outasight20]

I'm glad I started this thread. I'll hold off on the Racetech springs for now. I already have the 15wt oil which tightened up the feel a llittle but made the ride a little more bumpy too. I'll probably just leave it stock for now. If I ever take it to the track and find the suspension inadequate, I will consider the R6 fork mod.

 

[dpaul007]

I urge you not to go crazy with the spring rate trying to fix a damping issue. Lack of damping is what is hurting the nose of the Fizzer. The lighter folks could likely get away with running emulators and fresh oil of higher viscosity if they adjust the springs pre-load for proper sag (I say this only from money saving stand point).

But they should have the correct springs in there that are the proper rate for the riders weight, right? I read this in an old thread from another forum and it makes sense:

the springs are the starting point... Once the springs are appropriate for your weight then you should start with the recommended fork oil weight and height. After that you can experiment with different heights, varying the fluid, and weight (a tiny bit). If you still don't like it then maybe you are a good candidate for a revalve job, which should come with a new fork oil weight recommendation.

 

[FinalImpact]

DP this true. I'm just saying throwing springs in there alone will not fix the issue. If cost is the turning point, start with the emulators if your under 200lb.
Hint my r6 springs are 0.88mm/kg. Work great even on the heavier fizzer.

 

[outasight20]

I've done some reading on cartridge emulators and their huge advantages over fixed damping rods. It seems that at my weight of 175, my money would be best spent on the Racetech emulators, some shims to get the sag right, and some fresh 10 or 15 wt oil. I will leave the springs stock for now. As I understand simply adding the emulators will reduce front end dive significantly as well as make the bike much more compliant over bumps in the road. The more I read about the emulators, the more they make sense. Damping rods are so old tech!

 

[iSteve]

If you're going to go through the trouble of adding emulators you should do the springs also. The stock progressive springs are a compromise by Yamaha and pretty much don't work for most riders.

I live in MA also and ride on some of the worst roads the state has to offer "and some of the best". I found just changing the springs and a little experimenting with preload and oils made for a great improvement in ride and handling.