Author Topic: Tuning the New B1250 Suspension (Read 4717 times)

ZenMan · « **on:** April 01, 2007, 03:04:34 PM »

Everybody has their own methods and preferences for tuning their suspensions. Being this is a brand new bike and one of the first of the '07's in the U.S., I thought I'd post my approach and include some pics for anyone interested.

Managed to get out between rainstorms today, getting the suspension dialed in some more. The rear shock has a 7 position preload adjustment (#7 is stiffest), and comes from the factory on position #4. I'm a big guy (260 lbs.) and so yesterday morning I notched it up to position #5 and left the rebound dampening alone, at 50%.

Spring preload adjustment (arrow shows indicator on #5 position):

Rebound dampening adjustment (slotted with indent marks):

Sorry for the blurred pics, I guess my camera wasn't adjusted for close-ups!

The front forks have preload reference marks from 0 to 5 (#0 is stiffest) with the factory setting at #3. I turned the forkspring preload up to the #2 line, jumped on and put a hundred miles on her yesterday.

Front fork spring preload (shown at position #2):

I noticed the ride height increase only slightly when putting both feet down. Handling was still neutral, but input response was a bit quick on countersteer and I felt a slight wobble entering reduced radius curves on the brake, and the rear was a hair loose under exit power. Straightline stability was slightly decreased. Going up one position on the rear and one position on the front results in a steeper chassis angle with the nose a bit lower, decreasing the rake and trail slightly. It's a pretty hefty rear spring. I also noticed slightly better braking compression up front, but a bit more rear push.

So this morning I cranked the rear up to #6 and the front up to halfway between #1 and #0 reference. The fork springs react less to adjustment because of their longer length, so to balance it out I stiffened up the front a half increment more. This brought the front up to a little more even chassis angle with the rear, but still slightly lower in front than the factory settings, with the ride height a little higher overall than stock.

So today I found the countersteer just right... not race-track quick but responsive enough to change lines mid-turn with minimal effort. Nice and stabile entering and braking before the apex, good traction accelerating on the exit, points well. Straightline stability is acceptable and tracks good, no wandering. Brake compression is firm and predictable, no excessive rear push. Ride height is good, I can barely flat-foot it at a stop, though normally I only put my right foot down anyway.

Tomorrow is supposed to be gorgeous so I'm gonna fill the tank and get the rebound dampening dialed in on the rear shock. It feels just a bit light so I'll start at 60% and go from there. Keep ya'll posted.

JamieK · « **Reply #1 on:** April 01, 2007, 03:06:07 PM »

Keep 'em coming Zen!

ZenMan · « **Reply #2 on:** April 01, 2007, 03:14:33 PM »

Dread, your '06 has the same setup, doesn't it? Do these pics look familiar? Have you done any suspension tuning on yours yet?

JamieK · « **Reply #3 on:** April 01, 2007, 04:46:02 PM »

Yeah its exactly the same in the suspension dept...I haven't had to adjust as it seems that at 185lbs fully dressed I'm right at the factory setup weight

Once the roads clean up some more and I get the jetting sorted I'll be able to push the bike a bit harder and see if the suspension needs to be adjusted

ZenMan · « **Reply #4 on:** April 01, 2007, 06:34:09 PM »

OK, I thought so. One difference I do know of is the '07 swingarm is 1" longer, the frame is 1" shorter because of the new engine, so the wheelbase comes out the same. But the chassis angles will be slightly different so you may not get the same results from your adjustments.

185 lbs. seems like it would be just right for the factory settings. I've got about 80 lbs. on ya, so mine needed some stiffening up. I like it a bit on the firm side anyway, I tend to get a little aggressive in the twisties at times.

I could probably go with #5 on the rear and #1 on the front and be fine, but this way when the ol' lady jumps on the back it might not need any more tweaking. She's only 120 lbs... Of course, it we throw another 80-100 lbs. of gear on there, the rear will go to #7 for sure.

By the way, the rebound dampening felt real good today, I put on another 110 miles this afternoon. 50% is 1-1/4 turns counterclockwise from full clockwise stop, and I set it at one full turn out. I figure that's about 60%, and it's fine right there for now.

Happiness is a fine-tuned suspension!

JamieK · « **Reply #5 on:** April 01, 2007, 07:45:53 PM »

Quote from: "ZenMan"

OK, I thought so. One difference I do know of is the '07 swingarm is 1" longer, the frame is 1" shorter because of the new engine, so the wheelbase comes out the same. But the chassis angles will be slightly different so you may not get the same results from your adjustments.

That's somewhat true over the 05 but the 06 has the same swingarm as the 07, the wheel bases are also the same 58.3". I believe the swingarm is actually 2" longer than the 05 models....

Quote from: "ZenMan"

185 lbs. seems like it would be just right for the factory settings. I've got about 80 lbs. on ya, so mine needed some stiffening up.

I'm guessin' you have some height on me too (I'm ony 5'7") although I think you mentioned a 30" inseam which is the same as mine...I'm hoping to drop another 10-15lbs by summer so I may have to soften the bike up a bit.

Quote from: "ZenMan"

By the way, the rebound dampening felt real good today, I put on another 110 miles this afternoon. 50% is 1-1/4 turns counterclockwise from full clockwise stop, and I set it at one full turn out. I figure that's about 60%, and it's fine right there for now.

Happiness is a fine-tuned suspension!

Good to hear...that is one thing I may adjust but I need to get a better feel for the bike first...there may be a track day here near the end of the month, if so I may take the beast out and get comfortable with it

ZenMan · « **Reply #6 on:** April 01, 2007, 08:29:20 PM »

Quote from: "Dreadnought"

Quote from: "ZenMan"
OK, I thought so. One difference I do know of is the '07 swingarm is 1" longer, the frame is 1" shorter because of the new engine, so the wheelbase comes out the same. But the chassis angles will be slightly different so you may not get the same results from your adjustments.

That's somewhat true over the 05 but the 06 has the same swingarm as the 07, the wheel bases are also the same 58.3". I believe the swingarm is actually 2" longer than the 05 models....

Well, here's what they had to say in the Two Wheels Only review:

"Forks and shock get harder springs and a re-valve for firmer damping, plus a longer swingarm is made possible by the shorter engine and stacked gearbox."

Page 2: http://tinyurl.com/2koucw

They were talking about the difference between the '06 and '07 models... but who knows, magazine writers can make mistakes just like anyone else, aye?

Quote from: "Dreadnought"

there may be a track day here near the end of the month, if so I may take the beast out and get comfortable with it

Yeah, definitely go for that! here's nothing like a day at the track to get your suspension dialed in right!

Plus you'll have a freakin' blast being able to open 'er up with no traffic, no cops, and no speed limit.

JamieK · « **Reply #7 on:** April 01, 2007, 08:59:55 PM »

Yeah I'm pretty sure they duffed up their specs...I've been keeping a close eye on the differences between the 06 and 07 and some of the e-zine articles I've read don't quite add up...I'm still looking forward to lining mine up with an 07 to do a side by side comparo

As for track days, they are what got me out of riding sport bikes...having that much fun on the track took the thrill out of riding on the street...so now I have the sedate B12 my world is in balance...I'll be able loaf around the track with it or take it to the strip and turn some respectable times...then back on the street its a capable sport tourer or commuter

ZenMan · « **Reply #8 on:** April 02, 2007, 12:47:58 AM »

Quote from: "Dreadnought"

Yeah I'm pretty sure they duffed up their specs...I've been keeping a close eye on the differences between the 06 and 07 and some of the e-zine articles I've read don't quite add up...I'm still looking forward to lining mine up with an 07 to do a side by side comparo

Well heck, Dread... we can sure figure this swingarm thing out for ourselves can't we?

Let's go measure our swingarms and see what's up. I'll take my tape measure tomorrow and get the length from the center of the rear axle to the center of the swingarm pivot shaft, you measure yours the same and we'll know for sure what the real deal is.

Screw the dang magazine writers, who needs 'em?

ZenMan · « **Reply #9 on:** April 02, 2007, 03:10:55 PM »

OK, the distance between the center of the swingarm pivot shaft and the center of the rear axle is exactly 23-1/4 inches.

What'd you come up with on your '06, Dread?

JamieK · « **Reply #10 on:** April 02, 2007, 03:15:26 PM »

I'll measure it when I get home tonight

ZenMan · « **Reply #11 on:** April 02, 2007, 08:02:35 PM »

I just thought of something.

Measuring to the center of the rear axle won't give us a true comparison... the axle moves in the sliders when you adjust the chain! Duh!

So I went back and measured from the center of the swingarm pivot shaft to the rearmost edge of the swingarm... 24-1/2 inches.

Whaddya got?

JamieK · « **Reply #12 on:** April 03, 2007, 11:25:55 PM »

OK...I'll give you three guesses my swingarm is and the first two don't count

JamieK · « **Reply #13 on:** April 03, 2007, 11:27:29 PM »

Time's up...its 24.5 inches from the center of the pivot to the end...who'd a thunk it

ZenMan · « **Reply #14 on:** April 04, 2007, 12:51:51 AM »

Not what I would have guessed... but so much for all the mag writers, huh?

I wonder what's up with all the reviews and spec blurbs, even SuMoCo all saying the whole point of the compact staggered-shaft tranny on the new engine is to give the '07 a shorter frame and longer swingarm?

Well now we know better, aye?