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6 mm Shim? NO!

20K views 142 replies 39 participants last post by  Mayfield07 
#1 ·
2003 'Bird with 20,400 miles. And I will always be thankful to the seller for admitting he had fitted the bike with a 6 mm shim placed above the rear shock. I knew nothing about this mod. He'd heard that it increased handling responsiveness.

If so, it would have been hard to tell during my initial, 3 mile test ride. But I bought the bike. Took it to a local, reputable shop for a full - and I mean FULL - service. New fluids, tires, brakes and a thorough shake-down ride. They blessed it as a solid, low-mileage machine.

Okay. Fast forward; 20 canyon rides and a few thousand freeway miles later.

I didn't like this bike.

It was twitchy, nervous at all speeds - always wanting to fall in to or out of a turn . . . refusing to maintain a steady line through fast sweepers . . . requiring constant correction at the bars. In my memory, the only bikes I owned that ever handled worse were an 82 Kaw LTD with that "spaghetti" frame, and an 84 gPZ that wanted to stand up if the brakes were touched while leaned over.

But this wasn't a Kawasaki. It was a Honda. 30 years of experience has taught me that shade-tree engineers and quick-buck aftermarket supply houses are no match for the engineering acumen and testing resources of a billion dollar manufacturer. There was something better there, waiting for me. I needed to get this bike back to stock. Yesterday.

So the shim came out. Chain, reload and damping re-adjusted. Tires set to spec. Couldn't wait for Sunday.

As the tires warmed and we re-acquainted ourselves with the Angeles Crest, a slight smile turned to a grin. The bike now held its line through the turns, tightening or expanding the radius ONLY in response to my input at the bars. No more nervous, twitchy behaviour. This CBR 1100 xx - this Blackbird is now the bike it always could have been. . . the bike it once was.

I'd offer you a free 6 mm shim for the cost of shipping. Unfortunately, I have no idea where it is at the moment. And I don't care.
 
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#80 ·
Correct sag, preload, compression and rebound settings for your size and riding style are more important than a "shim".

Suspension gets "tuned" just like anything else. What is optimal for touring can never be optimal for twisty roads - period. What is optimal for the track will never be optimal for one or two up sport touring - period.

Suspension is a combination of geometry, leverage, and hydraulic function. It's not magic.

Correct tuning of a "shim" for performance has absolutely not the slightest thing to do with your height. Period. Your foot is not on the ground when you're going around a corner. And it shouldn't be.

Everything that we're talking about here is about what compromises make the most sense. That's even more a matter of personal opinion.
 
#97 ·
Another thought: If I were an aftermarket supplier, I would be very, very leery of supplying this particular mod. Why? (1) Honda has already stated that it will affect the bike's handling adversely. (2) When that poor 19 year old wrecks his modified bike in a turn and later tells his lawyer-daddy that the bike was "twitchy", his angry lawyer-daddy will look for a scapegoat with money. Honda Motor Corporation would be the obvious choice, but they've made it clear that suspension mods like this one (and we're NOT talking about an aftermarket, like-butter Ohlins rear shock here) may make the bike unsafe. So that avenue is lost. So, who is left to sue? Guess.
 
#99 ·
"Before the shim, i had to fight her, steer her (as in countersteer of course), force her with the body, it was a physical exercise. But with the shim that isn't necessary."

I see. So - BEFORE the shim, you understood that a counter-steering force was required to initiate and maintain a turn. But AFTER the shim was installed, counter-steering was no longer required, or not much required anyway.

Fascinating.

One thing. I don't know what was wrong with your bike in stock trim but there must have been SOMETHING amiss. In stock trim, I have never. EVER. . . felt like I was fighting the bike in any way. Nor have I known anyone who KNOWS of anyone who thought the stock bike required exceptional physical effort to steer. With new tires, fork oil and proper suspension setup, this bike is just . . . intuitive. Which is what you would expect from a Honda-engineered product. "Force her with the body?" That is absolutely NOT my experience nor (I warrant) the experience of other motorcyclists here. MIne is a 2003 model, whcih I believe was its last year of sale here in the states. (Could Honda have revised the rake and trail specs in the model years between introduction and end-of-production? That's the only thing I can think of that might explain your bad experience with the stock setup.)

Enter the turn on the outside. Initiate the turn with a slight press to the inside grip (or a slight pull on the outside grip - same thing). Maintain slight, continuous pressure to maintain the line through the apex. Look to the impending straightaway and accelerate while reducing pressure on the bars, allowing the bike to return to vertical as you sight into the next bend.

And repeat.

That 6mm shim does two things for the bike, neither of which Honda intended. 1) Front end "rake" (look it up) is reduced. 2) Front end trail is also reduced. Purchasing my 'bird with that horrible thing installed, I experienced its negative effects first-hand during a 150 mile loop through Angeles Crest and over to Mulholland. This was with new tires properly inflated and suspension sorted for my 190 lb. weight. I traded bikes with a friend for part of the ride (He's on a Triumph.) He loved everything about my bike - smooth power, controls, instruments, etc. - all of it EXCEPT the handling. "It doesn't care to stay on line in the bends, does it?" Then, chagrined: "Not BAD, mind you!" :) The shim was removed the following week.

Like linked braking, that 6mm shim is the answer to a question that no one asked. In my opinion. :)
 
#101 · (Edited)
One of 3 things happened here:

- you didn't understand;
- you don't want to understand;
- my english is so bad, we are lost in translation (most likely)

Regards :thumb:

EDIT: when quoting someone, you should quote the entire sentence or signal that some parts were hidden with (...)

"Before the shim, i had to fight her, steer her (as in countersteer of course), force her with the body, it was a physical exercise. Nothing wrong with it, i assume it. But with the shim that isn't necessary, or should i say, it's necessary but in a more relaxed and natural way."

or

"
Before the shim, i had to fight her, steer her (as in countersteer of course), force her with the body, it was a physical exercise. (...)But with the shim that isn't necessary,(...)."
 
#100 ·
I've been watching this thread for some time now and all I have gleaned from it is that some like the shim and some don't.
We all ride on different roads, we all ride differently.

My daily Bird works for me* but I have no doubt that if some other members of this forum tried it a % would describe it as unrideable/dangerous.

Is any new ground going to be covered? If not I have a feeling the thread will be closed ......

*I don't like the tyres that I've got fitted at the moment but they are loved on this forum, another story.
 
#102 ·
I am not into the fancy suspensions or terminology, I run a stock suspension, 75,000 Kays on my current Bird,
I tried the 6 MM shim after reading about it on a few BB forums, And I liked it, Its been in there for 100,000 Kays, and I still like it,

Counter steering is pushing the left bar away with your left hand to turn the bike to the left, So its opposite to what you think it does,

Best way to find this out, Is to go in and out of the dotted white line on the road, It exagerates the counter steering so you can physically notice it,

Higher speeds, Its minimal, So most people wouldnt notice that they are actually doing it,

The best examples of Counter Steering to watch in action are Flat Trackers or Speedway bikes racing, The front end is facing hard right and the bike is going hard left,

Tyres and Pressures are personal preference also, But they do effect the bike critically, If they are not right, your bike will handle like a pig,
 
#108 ·
Thats a good Video,
 
#111 ·
Duck....not often I disagree with you but I do on this one!
The 6mm shim subject is lost...one guy starting with a shim and removing it and most others starting with stock and adding the shim...
depends on your riding style and experience...meh!
but...
**There's some good information about "counter steering" a lot of riders don't seem to know much about.
I've had discussion with some friends that ride more upright touring bikes and Harley style motorcycles their whole lives that don't know anything
about counter steering. I don't think about it normally but I use it all the time.
You're the boss but I'd let it ride a little longer :popcorn:


QUOTE=TheDuck;466234]I've been watching this thread for some time now and all I have gleaned from it is that some like the shim and some don't.
We all ride on different roads, we all ride differently.

My daily Bird works for me* but I have no doubt that if some other members of this forum tried it a % would describe it as unrideable/dangerous.

Is any new ground going to be covered? If not I have a feeling the thread will be closed ......

*I don't like the tyres that I've got fitted at the moment but they are loved on this forum, another story.[/QUOTE]
 
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#112 ·
Duck....not often I disagree with you but I do on this one!
The 6mm shim subject is lost...one guy starting with a shim and removing it and most others starting with stock and adding the shim...
depends on your riding style and experience...meh!(...)
You could split the posts and began a new thread. ;)


(...)but...
**There's some good information about "counter steering" a lot of riders don't seem to know much about.
I've had discussion with some friends that ride more upright touring bikes and Harley style motorcycles their whole lives that don't know anything
about counter steering. I don't think about it normally but I use it all the time.(...)
And yet we all menage to ride our bikes, guess what, i managed to take her today to the mech... happily steering her like a lory (sure weights like one)! :cool:

Funny you mentioned uprght touring and Harleys, to me, they are the ones who require more inputs to the bars.
 
#113 ·
Found some random specs on rake and trail:

RAKE - the angle of the steering head. The smaller the number the steeper the angle. Steeper (smaller) rake = more responsive steering, but at the expense of stability. Sport bikes thus have a relatively steep (small) rake, cruisers have a higher rake angle.

TRAIL - the distance between (a) a vertical line extending from the front axle tot he floor, and (b) another vertical liine extending from the steering head to the floor. The greater the trail, the more "kicked out" the front end will act and feel. Cruisers have a relatively high trail number. Sport bikes do not.

2008 GSXR600, a small sportbike. Rake = 23.25 deg. Trail = 3.7 inches. Both of these numbers are relatively short, to provide immediate response to turning input. You just don't want to take your hands off the bars to scratch an itch. :--)

2008 Honda Valkerie, a big cruiser/tourer. Rake = 26 degrees, trail is 3.9 inches. Larger steering head angle, slightly greater trail. Go ahead, fish around in the glovebox for your cell phone; the front end won't go anywhere.

2008 Indian Chief, a V-twin cruiser. Rake = 29 degrees, trail is 6.1 inches. This is a bike built for long straightaways, requiring great effort to initiate and maintain a turn. You don't want to herd this bike through the turns of Mulholland canyon. It keeps demanding that you visit the sagebrush on either side instead.

2003 Honda 1100xx Super Blackbird: Rake = 25 degrees, Trail = 3.8 Our bike.

Note that the Blackbird's steering and trail are only slightly more tame than a small hyper-sportsbike: less than 2 degrees difference in rake, and only one-tenth of an inch difference in trail. This statistic sort of negates the statement of just a few others here, that

(a) the stock bike is designed primarily to remain stable at 175mph. No, the rake and trail numbers are closer to sport bike spec than straight-line spec.

or

(b) the stock bike is truckish or requires "great effort" to initiate a turn. It doesn't. See above.

Adding a shim will reduce both rake and trail. And clearly, it doesn't take much to alter a bike's handling. The mod WILL quicken the bike's response to steering input. No argument there. Whether that's desirable on a bike of this size is the crux of this discussion. Honda says "Don't do it." Me? I just find the stock setup to be much more relaxing and confident. Thanks.
 
#114 ·
(...)
Note that the Blackbird's steering and trail are only slightly more tame than a small hyper-sportsbike: less than 2 degrees difference in rake, and only one-tenth of an inch difference in trail. This statistic sort of negates the statement of just a few others here, that

(a) the stock bike is designed primarily to remain stable at 175mph. No, the rake and trail numbers are closer to sport bike spec than straight-line spec.

or

(b) the stock bike is truckish or requires "great effort" to initiate a turn. It doesn't. See above.

Adding a shim will reduce both rake and trail. And clearly, it doesn't take much to alter a bike's handling. The mod WILL quicken the bike's response to steering input. No argument there. Whether that's desirable on a bike of this size is the crux of this discussion. Honda says "Don't do it." Me? I just find the stock setup to be much more relaxing and confident. Thanks.

So, a Valkirie is a sport bike? Just 1 degree more than the BBird and one-tenth of a inch diference in trail...


 
#116 ·
"So, a Valkirie is a sport bike? Just 1 degree more than the BBird and one-tenth of a inch diference in trail..."


Not at all. The Valkyrie is a large touring bike that can willingly navigate a set of twisties, while staying rock solid on straightaways. Just like the Blackbird, but with softer numbers (i.e., slightly slower handling, slightly more stability).

Small differences in rake and trail apparently make noticeable differences. As I learned after removing the shim. :) There is NOTHING in the 'bird's stock specs to suggest "truckish" handling, or a bike that doesn't want to respond to rider input. It handles wonderfully well in stock trim (although an Ohlins shock is on my wish list).

I'm not smart enough to calculate the reduction in rake between a stock 'bird and the shimmed 'bird. It's a function of lifting the bike's back end, then calculating the trigonometric reduction in rake angle based on the unchanging wheelbase and altered steering head angle. But the change is most certainly there. Now, IF that change reduces the rake of the 'bird to an angle that is equal to or (shudder) LESS than the angle of the GSXR 600, it absolutely explains why I and others find the steeper steering head angle to be annoying at best. Thanks.
 
#118 ·
"So, a Valkirie is a sport bike? Just 1 degree more than the BBird and one-tenth of a inch diference in trail..."


Not at all. The Valkyrie is a large touring bike that can willingly navigate a set of twisties, while staying rock solid on straightaways. Just like the Blackbird, but with softer numbers (i.e., slightly slower handling, slightly more stability).

Small differences in rake and trail apparently make noticeable differences. As I learned after removing the shim. :) There is NOTHING in the 'bird's stock specs to suggest "truckish" handling, or a bike that doesn't want to respond to rider input. It handles wonderfully well in stock trim (although an Ohlins shock is on my wish list).

I'm not smart enough to calculate the reduction in rake between a stock 'bird and the shimmed 'bird. It's a function of lifting the bike's back end, then calculating the trigonometric reduction in rake angle based on the unchanging wheelbase and altered steering head angle. But the change is most certainly there. Now, IF that change reduces the rake of the 'bird to an angle that is equal to or (shudder) LESS than the angle of the GSXR 600, it absolutely explains why I and others find the steeper steering head angle to be annoying at best. Thanks.
And there is nothing wrong with the shim (as many of us can tell) but you said, it almost handles worst than a 82 Kawasaki... :crap:

Maybe we could all use a grain of salt when reading each others posts.

About your BBird photos, (best colour no doubt), i asked because i saw you still had the hero blobs, which could explain your ridding habits, and use of the BBird. Hence, the dislike of the shim.
 
#121 ·
I think we agree more than we don't.

If the Blackbird were my only bike and if I spent every ride dicing through tight canyons with friends, I might appreciate, and even keep, that shim. Well, not really - but I do get your point. Thanks.
 
#129 ·
Admin will do what it wants. But before they close it down, here is a summary of what I've learned on this thread:

1. Contrary to claims by a few, the Blackbird's stock geometry - rake, trail and wheelbase - place it near the sport-touring side of the sportbike category.
2. It was NOT designed solely to remain stable at 175 mph. If it were, rake, trail and wheelbase would be significantly larger.
2. For reasons of safety and stability (and liability), Honda recommends AGAINST the use of a 6 mm shim or other mods that would change its geometry.
3. Contrary to claims by a few, a number of riders here have had the same experience as me. In essence: with the shim installed, the bike is more responsive to input. But that responsiveness comes with the requirement for more frequent input at the bars to maintain a chosen line, whether heeled over or vertical. Removing that shim - and returning the bike to stock - provides (for us) a superior sport-touring experience; precise control through the turns, and stability on the straights. Just as the manufacturer intended. Many of us have other bikes more suited to being thrown back and forth through switchbacks.
4. Tire choice, shim thickness (many have reduced the thickness and liked the results), tire inflation, rider weight, experience and a host of other factors ALSO contribute to the way in which this modification has been and will be viewed.

Some, of course, prefer the modified traits outlined in #3 above. I don't. But fortunately and unanimously, we also find this bike to be a daily joy to ride.

Thanks, all. Keep enjoying this incredible machine.
 
#135 ·
What about adding shim to DMR shock?

On a more serious note, or perhaps just more on topic, I've recently received a rear shock from DMR, which I'm looking forward to trying next season.

In speaking with Jamie when purchasing, he mentioned the modded shock was 3mm taller.......question is, would/should I add an additional 3mm shim
when installing the shock?

Any experience here? Certainly no shortage of opinions, myself included :)
 
#137 ·
Re: What about adding shim to DMR shock?

On a more serious note, or perhaps just more on topic, I've recently received a rear shock from DMR, which I'm looking forward to trying next season.

In speaking with Jamie when purchasing, he mentioned the modded shock was 3mm taller.......question is, would/should I add an additional 3mm shim
when installing the shock?

Any experience here? Certainly no shortage of opinions, myself included :)
Personally - I would fit it WITHOUT a shim - make sure the sag is set correctly for you - then spend time getting to know the bike again.

When you know the bike - you could try a 3mm shim - and see if you like it. If not - you take it back out. Simple
 
#139 ·
If you havent had one before, and all this work is happening at once, i would suggest starting with no shim, so you can guage how everything else has worked. Then, let it bed in, do a few 1000kms, and see what you think. Would you want/need it? At least then you know the effect all the other mods have had without a variable in the mix. You might well think that your riding style/riding environment doesn't require it.
 
#140 ·
Well, I'm not sure to be honest (if I want/need), just like a sharp handler, and already have an FJR, so this is my
toy for quick day rides, and twisties are always top priority, which is why I'm upgrading some bits, learned on last
couple bikes that suspension is the absolute best place to add resources which yields the most amazing returns.
 
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