fork spring rate

[chiller]

So I'm trying to figure out the spring rate I should get for my bike.

I put my details of rider weight and bike weight into the Racetech calculator and get 1.076 kg / mm (the stockers are .829kg / mm aka really mushy). Having done that I went back thru and added the weight of luggage as part of the bike and the recommendation is 1.17 ...

Racetech has either a 1.0, 1.1, or 1.2 ... what would I feel for the difference between 1.0 and 1.1 and 1.2 ? would it be overly harsh without luggage if I went to the 1.2 ? and conversely overly soft if I 'only' went with 1.1 with luggage ? I'm trying to understand what I might feel. Luggage on the bike is there 50% of the time.

thanks for input anyone.

 

[mxs]

Have you tried to call Racetech? Their techs will be able to help over the phone to make the right decision. They have seen and dealt with all possible scenarios I can imagine.

 

[omnivore]

For a streetbike, I would err on the soft side. Traction and comfort.

 

[Brian P]

Go with the 1.1 as a happy medium.

 

[Ikan]

Go with the 1.1 as a happy medium.

^+1. Since luggage is approximately 50% of the time.

Like Little Red Riding Hood, not too soft and not too hard, just right!

 

[LGdrama]

Buy Ohlins.....

 

[kellen]

use one 1.1 and one 1.2 and voila, you have 1.15

 

[kellen]

Buy Ohlins.....

and yes, if you are set on doing fork springs, get ohlins...they are only like 20 or 30 dollars more and they are model specific. Race tech springs are generic and you have to add spacers for different models.

 

[elton_t]

For a streetbike, I would err on the soft side. Traction and comfort.

same here. i only check for sag for front and back, then make sure the rebounds are balance. if it feels good then it is good

for track it is different.

 

[RockerGuy]

Can you not get a stiffer spring and dial down the preload?

 

[Stewart]

what weight of oil are you using? , makes a big differance.

 

[Franko!]

What is the front sag with you on the bike? The mushy feeling may be the hydraulics (compression/rebound).
When was the fork oil last changed?

 

[chiller]

and yes, if you are set on doing fork springs, get ohlins...they are only like 20 or 30 dollars more and they are model specific. Race tech springs are generic and you have to add spacers for different models.

Buying Ohlins is something I thought about and looked into but I can't find out anything about how to get the correct spring rate. When I look here :

http://www.ohlinsusa.com/us/catalog/Reclist2010_07506-10_1.pdf

It only lists part numbers for springs not the actual spring value... is there something else that isn't mentioned on the page ?

 

[chiller]

use one 1.1 and one 1.2 and voila, you have 1.15

interesting Idea, I never thought about doing that... would I need to buy a 1.1 and a 1.2 kit to make this work ? or do you know of any companies that would sell only 1 spring and 1 spring ?

 

[chiller]

Can you not get a stiffer spring and dial down the preload?

If you got the 1.2 and you dial it to minimum preload you will still be at 1.2 ... which is a bit stiffer then I think I need... I'm actually leaning towards a 1.1

what weight of oil are you using? , makes a big differance.

the stock weight of 10wt right now because it is the stock fork, i might up to it to a 15w

What is the front sag with you on the bike? The mushy feeling may be the hydraulics (compression/rebound).
When was the fork oil last changed?

fork oil changed a year ago, or about 5k. the bike has no compression adjuster, only preload and rebound control on the fork. i believe front sag is about 1.5 or 1.75 inches right now, which is way too low...

 

[caboose56]

If you got the 1.2 and you dial it to minimum preload you will still be at 1.2 ... which is a bit stiffer then I think I need... I'm actually leaning towards a 1.1

the stock weight of 10wt right now because it is the stock fork, i might up to it to a 15w

fork oil changed a year ago, or about 5k. the bike has no compression adjuster, only preload and rebound control on the fork. i believe front sag is about 1.5 or 1.75 inches right now, which is way too low...

If you run a 1.1 and add 10mL (or so) of fork oil to each fork you will get a more supple ride while cruising but the extra oil will serve to stiffen up the forks towards the bottom of their travel. Use the 10W, stick with what is specified, just add an extra 10mL or so.

 

[chiller]

If you run a 1.1 and add 10mL (or so) of fork oil to each fork you will get a more supple ride while cruising but the extra oil will serve to stiffen up the forks towards the bottom of their travel. Use the 10W, stick with what is specified, just add an extra 10mL or so.

Interesting, I did not know that ... thanks for the tip

 

[caboose56]

There is a finite amount of air in the forks above the oil. When the forks compress that volume of air decreases, so the pressure increases and acts like an air spring. If you add 10mL of oil in each fork you'll have a smaller volume of air above the oil. So when you compress the forks there is a larger pressure increase in that air spring, effectively making the air spring stiffer.

 

[JohnnyP636]

If you run a 1.1 and add 10mL (or so) of fork oil to each fork you will get a more supple ride while cruising but the extra oil will serve to stiffen up the forks towards the bottom of their travel. Use the 10W, stick with what is specified, just add an extra 10mL or so.

+1 the valves are designed to work with that specific weight of oil, changing to a thicker oil will stiffen up the forks but at the same time affect all the characteristics of them...Keep the oil stock and do the springs and see where that gets you, stiffer oil and springs at the same time might not get you the results your after and make a mess of tuning for you...Play with the air gap like caboose said first before changing weights