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Old 01-04-2013, 10:57 AM   #1
Whymee
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I Need Softer Forks!!!

Hiya Cats & Kittens!
First post here. Been lorking for some time.

This is going to seem like an odd request, bear with me.

I have a 85 RZ350 Yamaha that I have modified extensively. I have a 99 R1 front end on it. The forks are way too stiff.

I have looked around & I see no posts here or other places that deal with my problem. I understand that usually the average R1 owner wants, at the very least stiffer suspension.

Can anyone point me in the right direction for springs or a DIY cure for my "disease"?

Thanks!!

Stan

Here is a old pic of my machine.

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Old 01-04-2013, 11:56 PM   #2
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What are your current compression and rebound settings on the forks? Also, what about the pre-load and sag measurements?

Finally, what is your weight?

If everything is functioning correctly, you should be able to make the suspension pretty compliant/plush.

If you aren't able to correct things by adjusting the damping settings, you can alter the oil weight and/or level inside the forks. You could also change the springs as well as the valving. However, before getting into those areas, you should ensure that you have exhausted everything with the OEM adjustments and also that you are well versed with building suspension, etc.

Finally, what tire pressure(s) are you running? Sometimes simply adjusting the tire pressure can have a nice impact on the ride.

Ray


Quote:
Originally Posted by Whymee View Post
Hiya Cats & Kittens!
First post here. Been lorking for some time.

This is going to seem like an odd request, bear with me.

I have a 85 RZ350 Yamaha that I have modified extensively. I have a 99 R1 front end on it. The forks are way too stiff.

I have looked around & I see no posts here or other places that deal with my problem. I understand that usually the average R1 owner wants, at the very least stiffer suspension.

Can anyone point me in the right direction for springs or a DIY cure for my "disease"?

Thanks!!

Stan

Here is a old pic of my machine.

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Old 01-05-2013, 02:22 PM   #3
Race Engineer
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Try 26psi front, 34 rear....
Rider sag at 33% total travel...

Racetech website will give you spring rates with their calcuator ;-)
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Old 01-05-2013, 09:39 PM   #4
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Quote:
Originally Posted by RayJohns View Post
What are your current compression and rebound settings on the forks? Also, what about the pre-load and sag measurements?

Finally, what is your weight?

If everything is functioning correctly, you should be able to make the suspension pretty compliant/plush.

If you aren't able to correct things by adjusting the damping settings, you can alter the oil weight and/or level inside the forks. You could also change the springs as well as the valving. However, before getting into those areas, you should ensure that you have exhausted everything with the OEM adjustments and also that you are well versed with building suspension, etc.

Finally, what tire pressure(s) are you running? Sometimes simply adjusting the tire pressure can have a nice impact on the ride.

Ray
change the springs the wet weight for your 350 is 149 kg / 328 lb and the wet weight for the 99 r1 (thats what the forks look like they are off ) is 192 kg
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Old 01-10-2013, 10:27 AM   #5
Whymee
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Thanks for the replies gents.

Sorry I have not posted back sooner. With rebuilding a 76 Trans Am, assembling a big RC airplane & the new year the RZ has not had a high priority. Its time to throw some love at it.

I do not consider myself a suspension "guru". Quite the opposite. My background on street suspension is nil. Most of my knowledge is with conventional MX forks. I did replace seals in MX USD forks before. Whoopee.

I have not had these forks apart, yet. I am going on some assumptions here. Therefore, I believe these to be stock 99 R1 forks.

Springs - .92
Oil height - unknown
oil weight - unknown
preload - all the way out at the adjuster
clickers - Do not remember
tire psi - 40 - 42
Tire - Michelin Pilot
Tripples - Attack Racing

There is no free sag under the bikes weight. Frankly the forks do not sag under my weight either. I know the springs not right. Race tech recommends .83's. Closest they have is .85's.

And yes if I change springs I know my compression & rebound is not going to be correct. Maybe, just maybe, the stock range (with .83 springs) will get me in the ballpark.

Does any other company make springs for these forks other than RT? Is there a spring from another bike in the range (.80/.83) that I need that would work?

I have tried to call Race Tech for some info but Louies mailbox is full, so tech support is out for the time being.

I wanted to run my situation across some more knowledgeable peeps than I in this area. To get your opinion before I throw bad money after good at theses forks.

Thanks for your time & effort.

Stan
WV
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Old 01-10-2013, 01:12 PM   #6
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Quote:
Originally Posted by Whymee View Post

Springs - .92
Oil height - unknown
oil weight - unknown
preload - all the way out at the adjuster
clickers - Do not remember
tire psi - 40 - 42
Tire - Michelin Pilot
Tripples - Attack Racing

There is no free sag under the bikes weight. Frankly the forks do not sag under my weight either. I know the springs not right. Race tech recommends .83's. Closest they have is .85's.
Hi Stan,

Here is what you might want to try. Using the clickers for rebound and compression, run them all the way in (very gently, as you are bottoming a needle valve into a seat). Then back them out until they stop clicking. Count the number of clicks. That will give you the range.

While they are backed all the way out, test ride the bike and see how it performs.

The pre-load being all the way out, doesn't really make the springs harder or softer, per se. It adjusted the initial ride height mainly and controls the free sag (and to some degree rider side).

Changing the spring rate will match the stiffness of the springs to your weight (and also affect rider sag, as well as total sag).

Changing the compression and rebound damping is really watch controls the "stiffness" of your ride however, so until you check the current settings and see how the bike responds to different settings, I would be careful changing too much else.

With the compression and rebound valves dialed all the way in, they are turned off and the suspension basically would be stiff like it wasn't even there. With them all the way open, then it should be very plush (even if the springs are off a bit).

Try those things, then see what sorts of results you end up with.

40+ PSI is a bit high I think. That's going to translate into a rougher ride. Have you tried something more along the lines of 32 to 35 PSI to see how the bike handles and feels?

Ray
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Old 01-10-2013, 02:06 PM   #7
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Quote:
Originally Posted by Whymee View Post
Thanks for the replies gents.

Sorry I have not posted back sooner. With rebuilding a 76 Trans Am, assembling a big RC airplane & the new year the RZ has not had a high priority. Its time to throw some love at it.

I do not consider myself a suspension "guru". Quite the opposite. My background on street suspension is nil. Most of my knowledge is with conventional MX forks. I did replace seals in MX USD forks before. Whoopee.

I have not had these forks apart, yet. I am going on some assumptions here. Therefore, I believe these to be stock 99 R1 forks.

Springs - .92
Oil height - unknown
oil weight - unknown
preload - all the way out at the adjuster
clickers - Do not remember
tire psi - 40 - 42
Tire - Michelin Pilot
Tripples - Attack Racing

There is no free sag under the bikes weight. Frankly the forks do not sag under my weight either. I know the springs not right. Race tech recommends .83's. Closest they have is .85's.

And yes if I change springs I know my compression & rebound is not going to be correct. Maybe, just maybe, the stock range (with .83 springs) will get me in the ballpark.

Does any other company make springs for these forks other than RT? Is there a spring from another bike in the range (.80/.83) that I need that would work?

I have tried to call Race Tech for some info but Louies mailbox is full, so tech support is out for the time being.

I wanted to run my situation across some more knowledgeable peeps than I in this area. To get your opinion before I throw bad money after good at theses forks.

Thanks for your time & effort.

Stan
WV
Stan , e mail k tech enquiries@k-tech.uk.com for springs they will im sure give you the correct spring and advice they make and supply suspension for ama bsb and wsb . As the forks are from a 99 bike if it were me the first thing i would do is strip them down and service and clean the internals as over time the pistons and valves get blocked with alloy sludge from inside the fork legs im not sure what std air gap or oil weight is for the 99 but in my 05 i run with 5 weight (but i do have k tech 20mm piston kit and re valve ) you need to remember you have fitted forks that are designed to cope with a bike that is around 110lbs heaver than yours so its springs ,oil weight and air gap . re comp and rebound you would have to reset that anyway to get the best from the forks good luck .http://www.k-tech.uk.com/
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Old 01-10-2013, 03:04 PM   #8
Whymee
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Again, Thanks for the replies.

Since it is winter here in West Virginia, USA and my bike is tore apart for upgrades, I cannot test at this time.

Certainly a lower psi in a tire will translate into a softer ride. I would think I would get it as best as I can with springs/revalve/rebuild etc. & then play with air pressure. Fine tuning, if you will.

I just know I have to change springs at least, before I can get a warm fuzzy for the dampening.

You guys have given me a starting point. #1 springs. #2 rebuild (I would have done that anyway) #3 to be determined as I talk with RT or others "in the industry".

If anybody has any other words of wisdom I am all ears!

I will report back as this progresses.

Mucho thanks.

Stan
WV
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Old 01-10-2013, 03:13 PM   #9
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Old 01-10-2013, 03:22 PM   #10
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Quote:
Originally Posted by Whymee View Post
Again, Thanks for the replies.

Since it is winter here in West Virginia, USA and my bike is tore apart for upgrades, I cannot test at this time.

Certainly a lower psi in a tire will translate into a softer ride. I would think I would get it as best as I can with springs/revalve/rebuild etc. & then play with air pressure. Fine tuning, if you will.

I just know I have to change springs at least, before I can get a warm fuzzy for the dampening.

You guys have given me a starting point. #1 springs. #2 rebuild (I would have done that anyway) #3 to be determined as I talk with RT or others "in the industry".

If anybody has any other words of wisdom I am all ears!

I will report back as this progresses.

Mucho thanks.

Stan
WV
For all suspension understanding watch |Dave moss on you tube lots of vids
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Old 01-10-2013, 03:42 PM   #11
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Quote:
Originally Posted by Whymee View Post
I just know I have to change springs at least, before I can get a warm fuzzy for the dampening.
That's not really 100% correct. The springs are important, sure, but it sort of strikes me that you are operating in the dark here to some degree.

Here is how you should approach this:

1. set the compression and damping in the mid range. Check to see the rebound of the suspension (by compressing and releasing) and get a feel for how the bike reacts (either by riding and/or by pushing the springs down and releasing).

2. Once you have done that and have the compression and rebound in the ball park. Then measure the static sag, free sag and rider sag (with the preload completely off).

At that point, you can figure out what you need. Even with incorrect springs, you should be able to setup the suspension so it will operate pretty nicely. It might be a bit stiff and your sag settings might be a bit out of whack, but I think you should try to dial in the current suspension first, before you start making a lot of changes. That will teach you a lot in the process and help you understand what you are trying to accomplish here.

Again, having the correct springs for your weight and the bike's weight is a great idea, but you are remiss to completely skip the compression and rebound settings at this stage - in order to see what you are working with and learn about where things stand currently.

Also, keep in mind, OEM suspension is a compromise. Even with better springs and valving, it will never be as good as true after market suspension. Valving will help and so will springs, but for what you are dealing with (i.e. swapping suspension between bikes), I think you should step back and learn a lot more before you start making modifications.

BTW, I have a video up on youtube (where I change springs on my Ohlins forks). You might enjoy watching it if you are about to tear into your forks. It has some helpful tips and will give you an idea of what you are in for! :-)

As always, if you have any specific questions, just fire away. Sounds like you are on a fun project for sure

Ray

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Old 01-10-2013, 03:51 PM   #12
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There are some very good videos about setting sag on youtube, btw. Do some searches and you should be able to find them. I have some book marked in my files down stairs (I'm on the laptop right now). If you are interested in watching them, let me know and I can find the links and post them for you.

However, if I'm reading everything correctly, you are only talking about going from your current springs (which are 9.2 N/mm ??) to springs which are 8.5 N/mm correct? That's not exactly a huge change.

On my Ohlins front forks, I went from 9.75 N/mm (9.5 + 10.0 N/mm) down to 9.5 N/mm. On the back, I changed from 100 N/mm to 95 N/mm. It was a very minor adjustment in sag and ride quality. Yes, you could feel it, but mainly because the bike is super sensitive to any minor change.

I still think you'd be better off starting by properly dialing in your current suspension (and this includes tire pressure), before jumping into changing spring rates.

Also, can you post your current sag settings? Without those, you are pretty much guessing on a lot of this.

What is static sag, free sag and rider sag? You need two people to measure this typically. If you have front/rear stands (a front head stand), you can measure everything but the rear rider sag yourself using wire ties, etc.

Ray
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Old 01-10-2013, 04:20 PM   #13
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Old 01-10-2013, 04:33 PM   #14
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Dave Moss' video is excellent (and well worth the $5 or so he charges to view the entire thing). I used that as a reference when rebuilding mine.

Ray
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Old 01-10-2013, 04:50 PM   #15
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dave moss for free http://feelthetrack.com/?page_id=881 or facebook https://www.facebook.com/dave.moss.1466?group_id=0 or you tube http://www.youtube.com/user/Catalyst...?feature=watch
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Old 01-10-2013, 06:31 PM   #16
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I will try to do some measuring this weekend & report back.

Thanks guys!
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Old 01-10-2013, 07:28 PM   #17
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Quote:
Originally Posted by Whymee View Post
I will try to do some measuring this weekend & report back.

Thanks guys!
Best thing you can do is dial the compression & rebound all the way off (or very close to it), adjust the tire pressure down a bit and then (carefully) ride the bike and assess what the soft end of the spectrum is like. That will tell you a lot. I did that on my bike, when I start set about upgrading the suspension and dialing in the bike, etc.

The bike will probably ride like a po-go stick, but at least you'll know what the soft end of the suspension feels like (adjust the rear shock also). Then adjust it back to where it's ride-able and see how it feels there. Go one or two clicks at a time.

Handling and comfort tend to be a bit of a trade off in my experience. But with good suspension (setup properly), you should be able to get it to where you have good feed back and moderately comfortable ride. On my bike, I have full race suspension and have it dialed in a bit on the soft side for comfort when riding on the street (10mm less oil / 10mm more air spring).

Once you get the feel where you like it, then measure your sag. The sag will tell you if you need to change the springs (as will how the ride feels when the compression and rebound are adjusted where you like it).

Just remember, you can take any suspension and make it "too hard" or "too soft" if you adjust the compression far enough in the wrong direction. That's why you should check the damping settings first and foremost here.

Ray
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Old 01-10-2013, 07:39 PM   #18
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Great advise guys, makes me want better suspension too!
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Old 01-10-2013, 07:45 PM   #19
RayJohns
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Springs are definitely most important as far as starting point. I just wonder - because it seems the suspension barely moves now - if maybe part of the issue might not be compression damping that is almost turned completely off. That's the only reason I was saying to adjust it out and see how the bike responds.

Also, given the current stiffness, what's your view on moving down less than 1 N/mm in the spring rate? Is that going to have enough of an impact?

Ray

Last edited by RayJohns; 01-10-2013 at 07:48 PM.
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Old 01-12-2013, 09:32 AM   #20
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rebound is easy, compression is personal choice..!
If you cant get the springs exact go for the next closest.

Tyre pressure is high, tyre pressure effects suspension as well.

Try contacting Dave Moss, i had numerous very very in depth emails with him when i was learning about set up and im in the UK. Dave will reitterate what ive stated.

There are many variables to take into account and it can blow your mind if you try to go to deep...
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