What's the starting point for raising your fork tubes? - Wrist Twisters
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post #1 of 24 Old 12-06-2018, 01:25 AM Thread Starter
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What's the starting point for raising your fork tubes?

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Suspension:

The most important adjustments are setting the correct sag front and rear. This should be done while wearing your riding gear. A good reference is
Motorcycle Suspension set-up.

The total travel on a 04' - 07' 919 is:
Suspension Front: 43mm cartridge fork; 4.7 inches travel
Suspension Rear: Single shock with seven-position spring preload adjustable; 5.0 inches travel.

The rear shock preload at 1/3 of 5" = 1.66" (1/3/8" is a nice round number.) You can convert to mm for a more accurate reading.
The front forks preload at 1/4 of 4.7" = 1.175" (1/316" is a nice round number)

I use a tie wrap secured around the front fork to get precise measurements. In fact I keep it in place year round to get readings from my spirited rides.

Rebound damping:
Once your suspension has compressed over a bump, rebound damping determines how fast the suspension can extend and keep the wheel in contact with the ground. Too much rebound damping will keep the suspension compressed when it should be extending to follow the road on the downside of a bump, and the wheel will lose contact with the ground. Too little rebound damping and the suspension will extend fast enough to push the bike up forcibly, giving it a loose feeling. Because rebound damping plays such a big part in how well the tire stays in touch with the ground, it gives you the feeling of traction and the confidence that comes with it.

The rebound damping should be set midway for starters, I found this adjustment to be adequate for street riding. You can play with it only after you have logged a few miles with the correct sag adjustments.


Do you want your 919 to turn in a little quicker without compromising stability? Raise your fork tubes.

Raise the fork tubes 10 mm as shown below.

How- To:
You don't need a stand to do this.
Just do one side at a time.
The other fork leg will keep it from falling down.
Loosen the top clamp bolt first, then the bottom. hold the fork tube firmly & twist a little as it moves up,Once there, snug the top bolt.
Finish the first one before moving on to the second.

Torque the bottom pinch bolts to 29 ft. pounds and the top pinch bolts to 16 ft. pounds.

It is now time to take your bike for a test ride preferably in the twisties.

NOTES: This modification should be used in conjunction with a 70 profile front tire. Greater than 10 mm, proceed at your own risk!!!
Found this in the chain length thread, noticed the 3rd part where he talks about "Raise the fork tubes 10 mm as shown below".

So that would assume you know where the factory settings are. If you got the bike used, it might already be moved.

Just to be sure, what is the factory height? Mine has always had a bit showing, just the tip

So 10mm would be from the very top of the fork?

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post #2 of 24 Old 12-06-2018, 01:27 PM
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Quote:
Originally Posted by KarlJay View Post
So 10mm would be from the very top of the fork?
I'd treat the position where the top outer edge of the fork tube is flush with the top triple clamp as being your zero starting point

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post #3 of 24 Old 12-06-2018, 09:40 PM
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Agreed, Stock location is flush with triple clamp. People pitch them down to keep the front end from rising but this bike is not quick to wheelie. People also do it when they track the bike to get a slightly more aggressive angle.

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post #4 of 24 Old 12-07-2018, 02:10 PM
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Quote:
Originally Posted by tedheiman View Post
Agreed, Stock location is flush with triple clamp. People pitch them down to keep the front end from rising but this bike is not quick to wheelie. People also do it when they track the bike to get a slightly more aggressive angle.

More aggressive angle of what?
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post #5 of 24 Old 12-07-2018, 03:13 PM
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Quote:
Originally Posted by tedheiman View Post
Agreed, Stock location is flush with triple clamp. People pitch them down to keep the front end from rising but this bike is not quick to wheelie. People also do it when they track the bike to get a slightly more aggressive angle.
Mine came new with the tubes a bit proud of the top deck of the clamp.
Basically, the end of the straight diameter of the tubes were in line with the deck, while the lead in taper of each tube stood proud of the deck.

Either way, it's just a couple of mm difference.

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post #6 of 24 Old 12-07-2018, 03:23 PM
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Raising tubes in the clamps:
-Decreases trail and therefore sacrifices some front end tire feel.
-Reduces the lean angle at which grinding out begins.
-Sound like a great recipe for spirited or track day riding...........................................

IF one simply wants reduced effort steering and cares not about anything else, then of course the tubes can be raised some.

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post #7 of 24 Old 12-07-2018, 03:48 PM
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Quote:
Originally Posted by LDH View Post
More aggressive angle of what?
By lifting the fork tubes you pitch the front of the bike down. This positions the bike in a slightly more aggressive stance. Whenever I track a bike I always lift the forks. It also helps with wheelie control.

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post #8 of 24 Old 12-07-2018, 06:13 PM
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Quote:
Originally Posted by tedheiman View Post
By lifting the fork tubes you pitch the front of the bike down. This positions the bike in a slightly more aggressive stance. Whenever I track a bike I always lift the forks. It also helps with wheelie control.

That's great except for the fact that almost every modern supersport bike made in the last 10 years needs more Trail in the geometry not less. Basically we either raise the front end up or install offset triple clamps to get those numbers. With that we use fork cap extenders which are VERY common on most modern sportbikes.
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post #9 of 24 Old 12-07-2018, 08:00 PM
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Quote:
Originally Posted by LDH View Post
That's great except for the fact that almost every modern supersport bike made in the last 10 years needs more Trail in the geometry not less. Basically we either raise the front end up or install offset triple clamps to get those numbers. With that we use fork cap extenders which are VERY common on most modern sportbikes.
Yes, and even MotoGP bikes have added steering head angle in addition to bigger trail numbers.

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post #10 of 24 Old 12-07-2018, 11:40 PM Thread Starter
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Now I'm kinda lost. Two questions:

Q1. There's always a trade off. If we raise the forks, and if it makes it turn in quicker, then what do we give up? Is it the "neutral" feeling?

Q2. Is 10mm the agreed reasonable limit?

Q3. Does it change the tar snake chasing? (I've never been a fan of chasing tar snakes).

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post #11 of 24 Old 12-07-2018, 11:59 PM
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Tar snake chasing? I'm not sure what that means. Generally if there is a tar snake and my tire touches it, my tire immediately moves itself off the tar snake. If I had to imagine, the trade off would be that you have less ground clearance, and everything that comes along with putting more weight on the front tire. Probably more outright front end grip, but also easier to stoppie.

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post #12 of 24 Old 12-08-2018, 03:05 AM Thread Starter
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Quote:
Originally Posted by nathanktm View Post
Tar snake chasing? I'm not sure what that means. Generally if there is a tar snake and my tire touches it, my tire immediately moves itself off the tar snake. If I had to imagine, the trade off would be that you have less ground clearance, and everything that comes along with putting more weight on the front tire. Probably more outright front end grip, but also easier to stoppie.
Basically tar snake chasing is any kind of tracking that the tire does when there's small changes. Seems that some tires will shift around more when the road isn't so smooth. Some, you can't help, like a mini sink hole or a tar wave, can't do to much about those but to avoid them.

This was discussed before and my old GT501 didn't like the ribbed roads and small tar snakes. I think it has to do with the center line grove dancing on the road groves.

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post #13 of 24 Old 12-09-2018, 08:50 AM
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They raise the front end now days? I always thought you lowered it. (I won't touch the geometry of a bike. Very delicate balance.)

Have the manufacturers gone too far in making bikes steer quickly?


The more I learn, the more confused I get.

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post #14 of 24 Old 12-09-2018, 10:04 AM
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Quote:
Originally Posted by Sniper-x View Post
They raise the front end now days? I always thought you lowered it. (I won't touch the geometry of a bike. Very delicate balance.)

Have the manufacturers gone too far in making bikes steer quickly?


The more I learn, the more confused I get.
The manufacturers don't simply raise the front nowadays.
Generally, the very steep steering tube angles of not so long ago have been replaced by less extreme ones. There's much inter-related complexity in this aspect of the geometry, mostly chassis and tires I think.
Past that, the trend for some years now has definitely been towards way more trail, and triple clamp offset is used for that.
My understanding is that this is primarily a front tire "feel" at race pace issue.
To put it in perspective, I have read that 92 mm or less of trail puts one in the "front tire no feel" zone. Meanwhile our 919's come with 98, and 110 is not out of the ordinary for road racing, be that from a current chassis or using aftermarket offset triple clamp kits.
The bigger trail numbers might also be being used to more advantageously relocate the C of G, perhaps within the confines of a target maximum wheelbase and who knows what else.

Past that, it seems to me that extremely few proponents of "raising the tubes" as a matter of course, are even aware of the also resultant reduced trail, reduced feel, and lowered C of G, none of which are advantageous in terms of serious road race track use of a motorcycle.

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post #15 of 24 Old 12-09-2018, 12:10 PM
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Some of the bikes that I have/had

Honda 919: Rake 25 degrees, trail 3.9 inches.
Honda 599: Rake 25.5 degrees
Ducati 848 Streetfighter 24.5 degrees
KTM 990 Super Duke 23.9 degrees, trail 4 inches

The Super Duke is easily the most twitchy of that group. The 919 has been gone too long, I don't remember for sure how stable it was, but I'm thinking pretty stable. The Ducati is by far the most stable, almost slow steering of the bunch. The 599 has an Ohlins in back, which raises the rear a tiny bit, maybe a 1/4". It's somewhere in the middle.

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post #16 of 24 Old 12-09-2018, 12:44 PM
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Quote:
Originally Posted by Sniper-x View Post
Some of the bikes that I have/had

Honda 919: Rake 25 degrees, trail 3.9 inches.
Honda 599: Rake 25.5 degrees
Ducati 848 Streetfighter 24.5 degrees
KTM 990 Super Duke 23.9 degrees, trail 4 inches

The Super Duke is easily the most twitchy of that group. The 919 has been gone too long, I don't remember for sure how stable it was, but I'm thinking pretty stable. The Ducati is by far the most stable, almost slow steering of the bunch. The 599 has an Ohlins in back, which raises the rear a tiny bit, maybe a 1/4". It's somewhere in the middle.
That's a fun looking stable you've had over time!

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post #17 of 24 Old 12-09-2018, 02:49 PM
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Oh, that's just a partial list. I have 2, 990 Super Dukes. I'm on my second 929, sold the first one. There was an Interceptor, a CBR 600RR, a '98 CBR900RR, a KLX 250, a couple of WR250s, a Ninja 250.

Buy in the fall, sell in the spring spring, a year or or 2 later, and motorcycles are a fairly cheap hobby. I made a couple hundred off the Interceptor, and 900RR. Broke even on the 6. Still have the WRs.

I'm going to have a (used) Ducati 939 SuperSport some day. May buy one of the KZ900s (used) in a few years.
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post #18 of 24 Old 12-09-2018, 04:29 PM
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Quote:
Originally Posted by Sniper-x View Post
Oh, that's just a partial list. I have 2, 990 Super Dukes. I'm on my second 929, sold the first one. There was an Interceptor, a CBR 600RR, a '98 CBR900RR, a KLX 250, a couple of WR250s, a Ninja 250.

Buy in the fall, sell in the spring spring, a year or or 2 later, and motorcycles are a fairly cheap hobby. I made a couple hundred off the Interceptor, and 900RR. Broke even on the 6. Still have the WRs.

I'm going to have a (used) Ducati 939 SuperSport some day. May buy one of the KZ900s (used) in a few years.
You Sir, have it figured out!

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post #19 of 24 Old 12-09-2018, 06:25 PM Thread Starter
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Quote:
Originally Posted by Sniper-x View Post
They raise the front end now days? I always thought you lowered it. (I won't touch the geometry of a bike. Very delicate balance.)

Have the manufacturers gone too far in making bikes steer quickly?


The more I learn, the more confused I get.
"Raising the fork tubes" is lowering the front end. It's confusing, but it means that the tube are higher up in the clamps. Stock seems to be near dead even at the top.

Lowering the front (by raising the tubes) by 10mm seems to be the limit. I was just wondering what the starting point was. Seems it's where the bevel of the top of the forks starts.

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post #20 of 24 Old 12-09-2018, 07:01 PM
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But LDH sells fork tube extenders to Lower the tubes, thus Raising the front.
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post #21 of 24 Old 12-09-2018, 07:49 PM
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Quote:
Originally Posted by Sniper-x View Post
But LDH sells fork tube extenders to Lower the tubes, thus Raising the front.
Yes indeed.
For example, a really tall tire in association with a good swing arm angle will drive a chassis tuner to lift the front to maintain overall chassis geometry, instead of shortening the rear shock to compensate for the taller rear tire.
Or, one might minimize their installed front preload to 5 mm or less, but want to maintain rider on geometry, and use the extended fork caps to drop the tubes down in order to do so.

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post #22 of 24 Old 12-10-2018, 02:10 AM Thread Starter
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Quote:
Originally Posted by Sniper-x View Post
But LDH sells fork tube extenders to Lower the tubes, thus Raising the front.
I really have no idea about why someone would do that, I'm very far from a suspension expert. I'm just wondering about what happens when you lower the front by 10mm.

Seems it's faster turn in, but what about the stability?

I'd imagine LDH knows all about this stuff, but maybe doesn't apply as much to the 919 or maybe less for street use and more for track use.

I guess lowering the front 10mm wouldn't hurt to try out.

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post #23 of 24 Old 12-10-2018, 08:40 AM
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On the 919 lowering the front didn't do anything positive for me except when I had a passenger on the back. Other than that, standard height was better as the front was already super soft and compressed substantially just under normal cornering forces even without braking input. You also have to understand that my riding style on the 919 was closer to a 2-stroke gp bike than a UJM... I learned to carry way more cornerspeed and trust the front instead of relying on acceleration which the 919 simply does not have at least not compared to the bikes I was riding along side. I've mentioned it many times before. The 919 has one of the vaguest front ends in the business, but it is sure-footed.

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post #24 of 24 Old 12-10-2018, 08:55 AM
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Quote:
Originally Posted by KarlJay View Post
I really have no idea about why someone would do that, I'm very far from a suspension expert. I'm just wondering about what happens when you lower the front by 10mm.

Seems it's faster turn in, but what about the stability?

I'd imagine LDH knows all about this stuff, but maybe doesn't apply as much to the 919 or maybe less for street use and more for track use.

I guess lowering the front 10mm wouldn't hurt to try out.
Many bikes that are taken to the track have fork extenders added so the forks can be lowered further than is possible with stock... I'm not knowledgeable enough to know the reasoning behind it but my suspension guy seems to know what he's doing so I just listen to what he says and give him feedback when it doesn't feel right ...

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