A few questions

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Aug 18, 2001
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#1
Here is a copy of an e-mail that i sent to jer, but i was hoping to get a quicker answer to some of my questions. At least the questions that anyone else here can answer.

"Mr. Wilkey,

I have used the spring rate gen. on your site and am a little confused about my spring rates. I race motocross and supercross and am looking for a compromise in spring rates. Based on the facts that i ride a 2002 yz426 and i weigh 180 lbs (190 with full gear), your generator suggested running .45 fork springs and a 5.3 shock spring. My stock fork springs are .46. Am i really going to feel the difference between a .45 and a .46 average spring rate? Since noone makes .45 springs would i buy one .44 and one .46 (since the average will be .45)? I can see where i might feel the difference between the recommended 5.3 rear shock spring compared to the stock 5.5 spring; however, you only make 5.2 and 5.4 shock springs. On what side should i err: softer or harder? For supercross your generator suggested the stock fork rate of .46 and a 5.4 rear spring. Since i do ride some supercross, should i just stick with the stock springs in the forks and get a 5.4kg rear spring?
Now, on to the valving questions. I am aware of the old saying "The best that you know is the best that you have had", but is there really a big difference from stock suspension to suspension that is revalved for me? I guess what i am asking is: What will the new suspension "feel" like compared to the way that the stock suspension handles things? And the final questions are reguarding the subtanks. I understand that by running the sub tanks, the forks physically have a higher oil level, but due to the restrictive barrier at the sub tanks, the higher the fork shaft velocity the "lower" the fork oil level feels like. The tanks should therefore make slow speed bumps feel soft and plush, while high speed hits, such as landing from a big jump, feel firm, as though the forks had no tanks and a really high oil level. But, do the tanks really work like all of the "theory" makes them out to be. They sound like the next best thing since sliced bread. I am an amature rider, money is tight and best spent on products/services that pay the biggest divedends at the end of the day. Is all of this suspension mumbo-jumbo as good as everyone says that it is?

Sorry for the longwindedness, but very thankfull for the answers (and the questions) that are sure to come.

Future customer and fellow DRN member,
Yz426King
Phillip Hutchinson"

Any answers to my questions would be helpfull.
 

marcusgunby

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#2
On springs i always go on the soft side of the spring rate generators answer.On the sub tanks-most riders say they work and even after a few months they seem happy with them.
 
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#3
The following is the reply that i recieved form Jer about the email that i posted above. I'm sure that he wont mind me posting this because it has some really good info about subtanks. The reply is nested, so to distinguish what he said from my original i will put his replys in "quotation marks".

Mr. Wilkey,

I have used the spring rate gen. on your site and am a little confused about my spring rates. I race motocross and supercross and am looking for a compromise in spring rates. Based on the facts that i ride a 2002 yz426 and i weigh 180 lbs (190 with full gear), your generator suggested running .45 fork springs and a 5.3 shock spring. My stock fork springs are .46. Am i really going to feel the difference between a .45 and a .46 average spring rate? Since noone makes .45 springs would i buy one .44 and one .46 (since the average will be .45)? I can see where i might feel the difference between the recommended 5.3 rear shock spring compared to the stock 5.5 spring; however, you only make 5.2 and 5.4 shock springs. On what side should i err: softer or harder? For supercross your generator suggested the stock fork rate of .46 and a 5.4 rear spring. Since i do ride some supercross, should i just stick with the stock springs in the forks and get a 5.4kg rear spring?


"Run the stock springs.. You'll be fine.. I generally round down for MX, but again you'll be 100% fine with stock.."

Now, on to the valving questions. I am aware of the old saying "The best that you know is the best that you have had", but is there really a big difference from stock suspension to suspension that is revalved for me? I guess what i am asking is: What will the new suspension "feel" like compared to the way that the stock suspension handles things?

"You will feel a big difference, stock suspension is inefficient in its ability to produce the proper total valve area over the wide range of speeds that are seen during use. A good revalve is far from stiffer or softer but rather more more efficient and really both stiffer and softer at different parts of the speed spectrum. In simple terms the suspension when set-up properly offers more control and stability, better or equal bottoming resistance and less harshness."


And the final questions are reguarding the subtanks. I understand that by running the sub tanks, the forks physically have a higher oil level, but due to the restrictive barrier at the sub tanks, the higher the fork shaft velocity the "lower" the fork oil level feels like. The tanks should therefore make slow speed bumps feel soft and plush, while high speed hits, such as landing from a big jump, feel firm, as though the forks had no tanks and a really high oil level. But, do the tanks really work like all of the "theory" makes them out to be. They sound like the next best thing since sliced bread. I am an amature rider, money is tight and best spent on products/services that pay the biggest divedends at the end of the day. Is all of this suspension mumbo-jumbo as good as everyone says that it is?

"Good question and well your the inspiration to finally put this one to the key pad.. So here goes.. Heres one for DRN as well as your reading...

As many of you have seen I've been a proponent of the Ross Maeda designed subtank system, and as anyone I know of who has asked my personal feeling everyone will hear.. "I won't ride a bike without a subtank system".. Yes I believe it does that much for a front suspension system.. So what's really going on.. Ross posted some stuff up for me on my web site a long time ago and I was excited to post it up.. It was a begging of a great friendship, that has made me a better tuner regardless of a few differences in approach.. But something was always a little off about what was going on inside the subtanks and that has left me uncomfortable.. Well one day, quite a while back it came to me as I was working on a Interceptor gas shock with my 12 ton press.....

So the subtanks work by regulating air through the restrictive barrier... Ok.. We run more oil which means that the fork will have a higher compression ratio and that will allow us to regulate the additional flow.. No worries.. But how does the system work as an advantage when we brake?(The subtanks feel much plusher than non-subtank fork when braking.) Like any fork with a higher oil level we should see more resistance to compression as we get deeper in the stroke..Interestingly enough many have said well its simple really the fork is not moving fast enough so the air can go through the restrictive barrier without much resistance.. And reason number two air is compressible and acts as a buffer...Humm.. This never set well with me.. Bottoming resistance is clearly slower in shaft speed than the huge (high speed) bumps at the bottom of the Reb-Bud ski jump, that you hit taped, before you brake.. That should spell death for the rider with a ultra high fork oil, and unlike a damping issue only that might help this is an ugly position sensitive... (this is not a prevention of packing going on..) Well I accepted common perspective till the VFR revealed something stupidly simple.

The tanks work because the forks are not fully extended for any length of time before the impact, and then have time to distribute a significant volume to the subtank without having time to refill the main chamber.(so it gets better the more bumps you hit if they are spaced closely and you've been in a wheelie for instance) So the pressure rise from static is not as nearly as significant as when we ride off into the air allowing the tanks to equalize and then land and force the almost complete volume into the tank..Its just a time delay.. The subtanks allow for a buffering, and bottoming resistance is increased because the forks fully extend and we are in the air long enough to empty any positive pressure back into the main fork volume.. How cool is that? So what else should this tell you? Don't buy anything with a check valve.. It will give the same bottoming effect, but you're not going to get the same plushness factor as the tanks will equalize more quickly and if your in big bumps, or you carry your wheel in the air too long your going to have issues.. It amazes me how designs can be so much more than they where intended for by chance alone..

BR,
Jer"



Sorry for the longwindedness, but very thankfull for the answers (and the questions) that are sure to come.

Future customer and fellow DRN member,
Yz426King
Phillip Hutchinson
"I think thats all the questions.. Let me know if I an help with anything else..

BR,
Jer"
 

bclapham

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#4
i think the stock springs are fine, i have a freind withe the same bike at 195lbs and the stock setup works fine for him- heck, even after 2 seasons we are reluctant to start messing, but alas a fork seal has gone so we will take them apart- sometimes its like the old pair of shoes theory- they may be a bit sloppy in places, but there is nothing like knowing that old pair of shoes feel, LOL.

btw- eibach makes 0.45's, but stick with the stockers