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Added shock shim, need help matching the front...

Old 05-29-2011, 04:06 PM
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Added shock shim, need help matching the front...

OK...

I added a 5.5-5.75mm shim to the rear shock, and over the last few day's I've been trying to tweak the front end to make the bike feel the same...

Prior to the shim, I had the bike handling amazing! Turn in was great, rear felt like ****, but was stable... Could transition from front straight at Nashville at high speeds and fell good about it... But I was dragging header on certain turns...

What I'm trying to figure out, is if I wanted to match the old rake of the bike with this shim added... How much should I move the forks to match that...

Someone said a 6mm shim was more like 8.5mm rise with swing arm angle and such... My front was originally lowered to compensate for the new spring rate, so i've got room to move them down to raise the front some...

I've played around and right now i'm +8mm from the way it was, and it doesn't feel the same... Wondering if i should go to 6mm... But I keep thinking thats gonna make the bike more raked than prior to shim...

thoughts?
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Old 05-29-2011, 04:19 PM
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Not sure on your specific question, but this thread may be good to start:

https://www.superhawkforum.com/forum...e-trail-24041/

What part of the handling do you not like right now? I would think that you would like the turn in better with the new geometry...
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Old 05-29-2011, 06:42 PM
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Well... I guess its hard to describe... I had raised the forks when I got my forks sprung, which was to put them back at stock height... I raised them a little more to give me a sweet spot... It just worked well... Which is why i would love to try and match it.

I guess I should have taken some measurements before adding the spacer, that way I could have been more accurate in moving the front.

I think part of it is the swing arm angle... I'm betting that its reacting differently now. I would suppose at the angle vs almost level before, it almost acts like a shock in not wanting to squat, so I'm feeling the bumps more than ever, which makes the *** end not feel planted like I would want it...
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Old 05-30-2011, 07:37 AM
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Interesting, I've found that a lower front ride height has helped even with an increase in the rear. My front is about -25mm and the rear +75mm. That's a little much for most people, and I'd probably be better suited to lower the rear some. You are sitting at about +25mm rear ride height right now, so you should be fine up front.

So, your problems are with front end turn-in or rear feel?
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Old 05-30-2011, 12:40 PM
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OK,

It appears as I found a sweet spot for me...

I made changes a few mm at a time, but right now I'm at 21mm from top of clip on to lock ring on the forks... And the just under 6mm spacer in the rear...

Now... Prior to today, i was running at preload 7 on the stock shock, which was giving me a the tallest ride height i could get... It was stiff, but not uncomfortable... I'm assuming the changed swing arm angle to be the reasoning why it feels more stiff than before.

There is a turn not far from my house that sweeps into a bridge while turning and the transition from pavement to bridge is not smooth... I have always felt comfortable with this spot before. I think i'm partially looking for imperfections right now because of the changes, but it feels less smooth now transitioning...

I dropped the shock preload to 6, which seemed to give me more movement in the rear, however it every so slightly changes the ride height, and is enough to not feel right again...

So... Question... With stock shock and my 215lb ***... How much sag should i really have? Because I can tell you for sure, I'm not getting the widely suggested 30mm, and don't think i ever have.

I'm starting to think my best option at this point is to find the best sag setting i can get with this damn shock, then add more spacer to recreate the ride height I want...

I could probably take tail fairing, and under tail back off, and with just seat on, take a sub frame to ground measurement with me on the seat now... Then set my sag, then add spacing to the shock until I reach the current ride height measurement with shock set as close to OK as i can get...

but then again... 30mm sag on this shotty shock? really? I'm having bad thoughts about how it would respond with that much movement anyway... i would hate to come off a bump and think its got to much damn movement and be loosing control...

i wish i had time to get a modded shock adn have it set up before the 4th!!!!!!!!!

thanks for the help guy's...
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Old 05-30-2011, 03:23 PM
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Thanks everyone for the help....

I just got back from a spirited run on 255, and i'm happy...

i was really happy with turn in at 6mm shim, but it felt stiffer than before, which i'm blaming on swing arm angle...

i backed the preload down to get some more sag.... Still not buying into this 30mm sag thing... i think i'm at 22 and it feels good...

Then i added more shim to recreate the ride height that i was at after sag before...

As it sits... i'm back to 3rd notch on shock preload adjustment, and have a 10-10.5'ish mm shim (sorry, didn't mic it) Front is at +21mm clip on to lock ring, which keep in mind my forks where sprung already, so not suggesting +21 on stock springs unless your half my weight lol...

I may still not half understand everything i've done today... But what I can tell you... Is my bike sits taller now, and after these last adjustments... i rode a very fun road and felt GREAT about the ride!!!

Now Saturday at the Alpine... If I can still put knee down with the taller set up, I'll be thrilled!!! Especially if I hear or feel no header grinding all day...

Thanks everyone.... Really appreciate it...

oh, BTW... 22mm rear sag, is that ok?
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Old 05-30-2011, 04:08 PM
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28mm rear sag is the sweet spot on mine. The reason for some of your problems is you have put more weight on the front end by changing your geometry.

Though it does sound like you are making many changes at once which really isn't a good idea. It does take a while to get a good set up and a lot of note taking to really get it right.
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Old 05-30-2011, 04:18 PM
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I have made many changes over the last few days true... But I've made one change at a time, and I'm riding the bike between each change...

I have what I call the test track road right down the road from the house... Wonderful back country road, thats clean, low traffic, and has TONS of turns...

I think i'm gonna run it like this on Saturday, then get with Jamie on modding a shock for me... not sure if i need to buy a F4i shock or mod stock one... but i guess i will find out.

I think before i was somewhere around 18mm sag, now i'm a 22... hopefully I can find a ever sweeter spot with Jamie's shock soon...
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Old 05-30-2011, 09:36 PM
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To give you the quick "rule of thumb" for sag numbers, take the total travel of the suspension and divide it by 4 and that is your starting point.
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Old 05-31-2011, 02:10 AM
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22, 28... It's close enough... None of the numbers I have quoted, or the others are set in stone... They are just somewhere to aim at, it's all about personal preference... But if you have it stiff enough that you have no sag, then you have no controlled movement... And like it has been said, with weight moving forward, you need to lighten up the rear spring...
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Old 06-01-2011, 03:57 AM
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I think what is happening is that you are finding the limitations of the stock parts. You are fighting the poor damping characteristics of the forks and shock and trying to compensate with geometry. That's really only going to get you so far, as you have clearly seen!

The inherent problems with the forks and rear shock is that the valving is harsh - providing too much damping over bumps. The higher rate springs up front have only increased those loads which is driving up the demand on the rear.

You can continue to tweak the geometry but pretty soon (if not already) you will be splitting hairs trying to get improvements. What you really need is a full revalve of both ends - I think you'd find that makes a world of difference!
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Old 10-22-2011, 09:57 PM
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Originally Posted by JamieDaugherty View Post
Interesting, I've found that a lower front ride height has helped even with an increase in the rear. My front is about -25mm and the rear +75mm. That's a little much for most people
OMG, I thought my geometry was radical. Did you have to add 3" to your kickstand?

The most i can go on the front is -10mm because of the risers and bar position. I have your modded F4i shock and I believe it's +6mm and I shimmed it another 3mm, so that's a total of +9. 9mm at the shock is supposed to be approx. 14mm at the wheel I believe. The 190x55 Q2 adds another 12mm, so that's 26mm up in the *** end. The sprocket is 44 tooth with 2 links removed which moves the wheel up closer, so this affects these measurements in ways I can't calculate.

this results in front -10mm, rear + 26mm and whatever mm the 2 link chain reduction/44t sprocket amounts to.

What I can calculate is that I have added a 17mm shim under the sidestand and the bike sits at a reasonable angle. So would it be safe to assume that real net geometry would be somewhere in the area of 17mm when looking at -10mm front and +26mm rear(+ chain sprocket effect)?

Whatever the numbers mean, I'm not sure. What i do know is that it feels very good to me.

3mm shim atop shock:



forks up 10mm:



17mm shim under sidestand:



Bike sitting at reasonable angle with 17mm shim under side stand:


Last edited by nath981; 10-22-2011 at 10:12 PM.
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Old 10-23-2011, 08:20 AM
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Originally Posted by nath981 View Post
OMG, I thought my geometry was radical. Did you have to add 3" to your kickstand? ......9mm at the shock is supposed to be approx. 14mm at the wheel I believe.
No, I haven't added any to my sidestand. My bike sits over more than I would like but it's ok. The drop in the front helps, plus the rear ride height is about half at the middle of the bike where the stand is.

The leverage ratio of the VTR's is about 4:1. That means 1mm at the shock is 4mm at the axle. Your +9mm shock length is actually closer to 35mm at the axle - FYI.
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Old 10-23-2011, 05:25 PM
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And while changing the wheel might add some, moving the wheel forward actually lowers the bike (the wheel essentially moves "up" the angled swingarm), so those should about cancel each other out...

Still, you are in the 30-40 mm range in the rear... And with a lower front, you are essentially rotating the bike around the middle, not exacty where the stand is, but close...

So no, the net increase in the rear remains, but since you have raised more in the rear than lowered in the front, the net result at the stand is around 15-20 mm or so, ie around where you have shimmed the stand to... So your geometry changes is actually a bit farther than you thought...
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Old 10-23-2011, 07:38 PM
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Originally Posted by JamieDaugherty View Post
No, I haven't added any to my sidestand. My bike sits over more than I would like but it's ok. The drop in the front helps, plus the rear ride height is about half at the middle of the bike where the stand is.

The leverage ratio of the VTR's is about 4:1. That means 1mm at the shock is 4mm at the axle. Your +9mm shock length is actually closer to 35mm at the axle - FYI.
I can't imagine how you have added so much to the rear where the side stand is and you are still able to use it. Unbelievable!

Anyway, it's interesting that the raw numbers of +9mm at the shock and +12mm at the rear tire equals 21mm, and then today I added another shim under the side stand, which makes it 21mm also, and now the bike is sitting perfectly. Probably has nothing to do with anything other than it might be a good rule of thumb for adjusting side stand height. haha

leverage ratio doesn't mean anything to me, probably since i've always sucked at geometry. And even if i did understand, there doesn't seem to be a viable consensus on the numbers. Tweety at one point wrote 1.6 to 2 to 1 if i recall correctly, sport rider wrote 3 to 1, and now your at 4 to 1 ratio. Whatever it is, I'll take your word on it, but I know my present set-up works, and with the 190 Q2, the handling is the best it's ever been so i have no need to change anything.

Oh, incidentally, when I was telling you about the way I adjusted rebound(by sitting backwards on the bike and pumping the passenger pegs), and i said that i had detectable rebound with no adjustment, that was correct when I had a 180 Power Pure on; however, When i went to the 190x55. i had to follow your advice and add a 1/2 turn rebound to keep the bike from getting out of shape when leaned over on undulating pavement. Thanks for a great shock.

Originally Posted by Tweety View Post
And while changing the wheel might add some, moving the wheel forward actually lowers the bike (the wheel essentially moves "up" the angled swingarm), so those should about cancel each other t...

Still, you are in the 30-40 mm range in the rear... And with a lower front, you are essentially rotating the bike around the middle, not exacty where the stand is, but close...

So no, the net increase in the rear remains, but since you have raised more in the rear than lowered in the front, the net result at the stand is around 15-20 mm or so, ie around where you have shimmed the stand to... So your geometry changes is actually a bit farther than you thought...
well this is the most drastic I've gone relative to geometry changes which coincidentally was precipitated by the unstable conditions of the 190x55 michelin power pure. That tire on a 5.5" rim becomes scarier(you predicted this in another thread) as the front crown grows, esp in quick transitions, and then i discovered that I had too little rebound for the bigger tire which was exacerbating the unstable condition. The added rebound got the some of the high speed instability at lean on curves with humps.

Like i mentioned above, these changes along with the 190 Q2 have resulted in a great set up, so i'll not be touching anything right now. I'll have to leave the technical interpretation of why this should or shouldn't be to you experts. And why Dunlop has chosen to make a 190x55 that is preferred for the 5.5" rim when no other manufacturer has is baffling to me, but I can say unequivocally that i'm glad they did.
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