K8 suspension - setting sag and new spring?

[Simonp]

Been having a play with suspension on the K8. From the go, front felt good but rear feels OK with Mrs on board but a bit bouncy solo, 2 clicks extra rebound solved that.

Decided to do the smart thing and measure suspension sag properly. All measurements are difference between rider on board and bike raised off ground with no load on suspension

I have read that for street riding 35-40mm front and 30-35mm rear is about right, so on with the riding gear and out with the tape measure.

Front is right on 35mm on stock setting so looks good, and feels pretty good on the road.

Rear sag is only 21mm - Figure I might need to loosen off preload, but there is only about 5mm above the top locking ring. So my question is, if I loosen up by around 3mm (to leave some thread for the ring to grip), is that going to get me another 14mm of travel, or so I need a softer spring? I weigh in at about 165lbs (or 75kgs) in gear, so quite light.

If I need a new spring, I assume this means whole new shock? Would not upset me too much as I would love to be able to easily change preload when Mrs gets on the back, she probably adds 145lb and sag is therefore probably about right with her on board

. Used to have a Honda VFR with a dial for preload, was so simple to give it a couple of turns to switch from solo to 2 up and back again. Ohlins is an obvious but expensive route, are there other recommended alternatives? I do a mixture of fairly calm 2 up riding plus some more sspirited solo riding, but no knee down heroics

 

[busaziggy]

I can only respond to part of your question. You do not need to replace your rear shock to change the spring.

I did not notice where you are located. I have a spare stock K8 rear shock if you would prefer to have a spare shock re-sprung so you don't have any downtime for your bike. PM me if interested.......Ziggy...........busaziggy

 

[kml]

Stage 4 Sportsbike Shock Absorbers | www.elkasuspension.com

 

[Jza]

I dont think you will need a new spring at each end...

Wind the preload off at the front till you get to the desired level.. the jack the back up and wind a ring of preload off.... im 270lbs and although not perfect i can play with settings to get to a "liveable" setup... im sure 165lbs isnt too light! Check the Jinksters post on how to get it right?

J

 

[Tufbusa]

At 165 lbs your stock springs should work quite well. Your progressive linkage and spring on the rear should take appropriate care of your 145 lb passenger.

The goal of setting sag by adjusting preload is to place the working area of the suspension in the middle one third of suspension travel. This is the area where the suspension is most compliant. Keep in mind the rear suspension should have between 5 & 10mm of free sag (Bike weight only) once the proper sag (Rider Sag) numbers are achieved. If you have less than 5mm your spring is most likely to soft. Conversely, if you have more than 10mm of free travel you may want to look into a softer spring.

Your stock suspension will work very well for street riding applications with a rider weight of 120 - 200 pounds.

Proper suspension set up is the ticket to miles of happy riding!

 

[Simonp]

Good to know that stock equipment should work. Do you think I can get another 14mm of sag with only 3 to 4 mm of adjustment left on the top of the locking ring? (by the way only have 4mm of free sag at present)

 

[E Zurcher]

How about 250 lbs? Recommendations?....other than lose weight fatass!

 

[Tufbusa]

I'd have to play with your suspension to see exactly what you have.

The distance your shock threads travel is multiplied several times over due to the short distance from the swingarm pivot to the shock. I don't know the fromula but one mm of shock travel should be several mm of distance at the axle.

I'd try turning the collar out a ful turn and see what effect it has on your sag number and adjust from there.

 

[sixpack577]

I weigh 175lbs, (and 195lbs in leathers, it does make a difference) and I was able to get 32mm of rear sag on my 08.
I can still get a little more too, I just haven't fooled with it any more as it rides very good(front is perfect also, sag is mid 30's).
I have 3 threads visible above the lock ring on top of the rear spring, if that gives you a ballpark idea of what you have left to work with.
Stock suspension settings made the Busa awful to ride, with the sag set properly it's a different bike and rides great.
I also have no problems taking my wife riding with me either.
TufBusa is the man to ask your suspension questions to!

 

[Tufbusa]

How about 250 lbs? Recommendations?....other than lose weight fatass!

I like your style!

At 250 you may want to look into heaver springs, especially fork springs. I'd suggest setting your sag as best you can and see what you end up with. If you don't ride twisties agressively and use your bike for commuting, you may be able to reach a satisfactory result with the stock suspension?

The issues with going with heavier springs it's sometimes necessary to upgrade the valving due to the heavy springs over whelming the OEM valving. Depends on how heavy the springs end up being to haul your "Fatass" (I'm still giggling over that one ) around.

 

[E Zurcher]

Thanks Tufbusa, I think they cranked down the spring when they sold me the bike cause it's about halfway down. So far I haven't had any issues so I will experiment a bit and see what happens. So far everything is at stock recommended settings.

 

[Tufbusa]

E Zurcher, have a couple friends over to help you check your sag numbers as is. Then adjust both ends accordingly and try to get both ends as close as possible to each other. If you can get your front sag down to 40mm or less, that's a good thing and satisfactory.

Work on the rear and I'd bet you can get the rear down to 35mm or so which will be good also. I'd be interested in hearing what you came up with. When you are doing the deed if you need help drop me a note, I'll be happy to guide you through the process.