Mixing spring rates in your forks? - Wrist Twisters
 
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post #1 of 22 Old 12-13-2011, 08:40 PM Thread Starter
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Mixing spring rates in your forks?

Whats the concensus of mixing spring rates? I know mixing a .90 kg and a .95 kg spring in either leg to give you an average .925 rate is practiced by some but how far can you take the mix and match? Whats the result of mixing, say a 1 kg spring with a .90...does that feel the same as a .95 matched set? Is there too big a difference in rates? Handling issues? ...just curious really.

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post #2 of 22 Old 12-13-2011, 08:53 PM
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My GUESS is that without a fork brace to tie the fork responses together, you might get some wiggle on hard bumps. However, I don't claim to be knowledgeable enough about it to advise anyone to take my guess as a fact.

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post #3 of 22 Old 12-14-2011, 07:26 AM
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Others have mixed .900's and .950's to get .925 without a problem. Mcromo will speak up here as he has done it. Keep in mind that many fork designs have the dampening duties split between the legs, i.e. rebound in one leg only and they don't utilize a brace.

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post #4 of 22 Old 12-14-2011, 08:25 AM
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Quote:
Originally Posted by Ottawa919 View Post
Keep in mind that many fork designs have the dampening duties split between the legs, i.e. rebound in one leg only and they don't utilize a brace.
Ah, yes, that's true! I've never ridden one. Do they wiggle in response to severe surface abnormalities?

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post #5 of 22 Old 12-14-2011, 09:55 AM
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The axle is a brace...

Fork spring rates are mixed every single day to custom tailor the sag settings to the riders weight.

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post #6 of 22 Old 12-14-2011, 05:03 PM
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Quote:
Originally Posted by LDH View Post
The axle is a brace...

Fork spring rates are mixed every single day to custom tailor the sag settings to the riders weight.

I knew I didn't know much about it!

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post #7 of 22 Old 12-14-2011, 05:58 PM
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Quote:
Originally Posted by LDH View Post
The axle is a brace...

Fork spring rates are mixed every single day to custom tailor the sag settings to the riders weight.
Absolutely spot on.
Mixed rates are proven and valid.
For the particulars of a 90/95 for a net 925 that has 15 mm of internal preload, in a condition of 35 mm of sag , the difference in spring force between the 2 legs would only be a mere 5.5 pounds force

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post #8 of 22 Old 12-14-2011, 06:05 PM Thread Starter
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Quote:
Originally Posted by LDH View Post
The axle is a brace...

Fork spring rates are mixed every single day to custom tailor the sag settings to the riders weight.
LDH, while waiting on lighter springs to correct my oversprung front end (1 kg springs and im 160 lbs.). Since the stokers are mushy, and my racetechs are over stiff, whats the net result of mixing a stock spring n a 1 kg racetech spring? Disaster?

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post #9 of 22 Old 12-14-2011, 06:41 PM
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honda,
While I know this question is somewhat off-topic, I'm really curious. I've been to Manila within the last few years. With the nature of a lot of the streets and congestion, where do you ride a large bike like the 919?
No disrespect intended, I just never saw anything except very small bikes when I was there.

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post #10 of 22 Old 12-14-2011, 06:57 PM Thread Starter
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Quote:
Originally Posted by RichT View Post
honda,
While I know this question is somewhat off-topic, I'm really curious. I've been to Manila within the last few years. With the nature of a lot of the streets and congestion, where do you ride a large bike like the 919?
No disrespect intended, I just never saw anything except very small bikes when I was there.
Haha, inner city is totally hopeless for a large capacity bike. Thats what my drz is for you have to head out of town on the weekends, there are twisties within half an hr. of the city...and did i mention we have $11 trackdays?

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post #11 of 22 Old 12-14-2011, 06:59 PM
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Quote:
Originally Posted by honda ng gingsa View Post
Haha, inner city is totally hopeless for a large capacity bike. Thats what my drz is for you have to head out of town on the weekends, there are twisties within half an hr. of the city...and did i mention we have $11 trackdays?
That makes sense.

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post #12 of 22 Old 12-14-2011, 07:07 PM Thread Starter
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Quote:
Originally Posted by RichT View Post
That makes sense.
Are you in Manila often? Look us up if ever you're in town again.

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post #13 of 22 Old 12-14-2011, 07:46 PM
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400 pesos for track days huh?

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post #14 of 22 Old 12-14-2011, 07:57 PM Thread Starter
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Quote:
Originally Posted by andrewebay1 View Post
400 pesos for track days huh?
Ok, its 500 pesos for a 4 hour session... Special rate just track access to ride as much as you can between 8-12, no marshals or first aid on standby.

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post #15 of 22 Old 12-15-2011, 10:56 AM
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Quote:
Originally Posted by honda ng gingsa View Post
LDH, while waiting on lighter springs to correct my oversprung front end (1 kg springs and im 160 lbs.). Since the stokers are mushy, and my racetechs are over stiff, whats the net result of mixing a stock spring n a 1 kg racetech spring? Disaster?

Hey if it works it works... Just remember that you might have special sized spacers for an aftermarket spring versus an OEM spring and thus would need to make sure you match the spacers to the springs etc...

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post #16 of 22 Old 12-15-2011, 07:31 PM
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Quote:
Originally Posted by LDH View Post
Hey if it works it works... Just remember that you might have special sized spacers for an aftermarket spring versus an OEM spring and thus would need to make sure you match the spacers to the springs etc...
Go for it !
The effective rate should be somewhere in the low 90s (depending where you are in the stroke, noting the dual rate stock spring)
Suggested is 15 mm of internal preload.
Take your oil level to 125 mm at the same time.

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post #17 of 22 Old 12-15-2011, 08:52 PM Thread Starter
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Quote:
Originally Posted by mcromo44 View Post
Go for it !
The effective rate should be somewhere in the low 90s (depending where you are in the stroke, noting the dual rate stock spring)
Suggested is 15 mm of internal preload.
Take your oil level to 125 mm at the same time.
Worth a shot eh? Meantime, Ive ordered a .925 setup like yours as were about the same weight range. Im already running 130 on the oil.

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post #18 of 22 Old 12-15-2011, 08:57 PM
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There are new forks out that have ALL the spring in one leg & ALL the dampening in the other. That is a 100% difference.

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post #19 of 22 Old 12-16-2011, 12:18 AM
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And my BMW has nothing but oil in both legs.

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post #20 of 22 Old 12-19-2011, 10:36 AM
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Quote:
Originally Posted by honda ng gingsa View Post
Worth a shot eh? Meantime, Ive ordered a .925 setup like yours as were about the same weight range. Im already running 130 on the oil.
130 is fine.
5 mm difference is greater as you increase the level, so keep the last 5 in reserve in case you want to try it.
Do not go less than 125.

Suggested is 15 mm of internal preload for your 0.925 setup.
Given the rear spring you are running on the Ohlins, you might want to later try going to 10 mm of internal preload.

You are going to do serious track lapping on a regular basis.
You really do want to know how much fork and shock stroke you are using.
A
Zip tie your shock shaft.
B
When doing the front springs, when they are out, slowly fully bottom out one fork leg, put a zip tie on the fork tube so its edge is resting on the top of the dust cover lip. Then put a wrap of tape right above the zip tie.
The tape tells you the relationship between fork stroke and hard mechanical bottom out - which you do NOT want to hit !
You really don't want to see less than a 7 mm gap between the zip tie and the tape (assuming a 3 mm wide zip tie). Once you are into the last 10 mm or so of fork stroke, you're into the hydraulic cushion zone which is there as protection against hard mechanical bottoming. The hydraulic cushion zone has a tendency to keep the fork compressed when the front end forces are released, in other words behave like an uncontrolled excessive rebound device.
There are things you can do to reduce the hard front braking induced fork stroke.
Slide back on the seat.
Grip the tank as hard as you can.
Keep down low.
Do not lock elbows.
Use your gut and lower back muscles to keep you in place and NOT your arms !
Feed in the front brake, don't jump on it.
Once you master all the above, then add in beginning with some rear brake before you even touch the front, it must be before in order to be effective.
Use of the rear with hard front braking on a 919 is for chassis pitch control and nothing else but, it's not the rear braking power you are after, just the chassis reaction it gives you.

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post #21 of 22 Old 12-19-2011, 07:47 PM
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Quote:
Originally Posted by honda ng gingsa View Post
Worth a shot eh? Meantime, Ive ordered a .925 setup like yours as were about the same weight range. Im already running 130 on the oil.
I'm ballparking your mix of early stock with 1.0 as yielding an effective rate of 0.875 kg/mm in the normal stroke zone, not the braking dive zone.
You'll be far better off with your 0.925s and maybe Santa will speed them along for you.

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post #22 of 22 Old 12-19-2011, 08:57 PM Thread Starter
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Super tips and info, mcromo. Thanks!

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