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Hello to everybody. I am looking for information and opinions on rake and trail measurements pertaining to land speed racing my Destroyer at El Mirage ( and someday Bonneville).

Here's where i'm at:
I took a stock destroyer, made the following mods, went 154mph at El mirage with what felt like very little traction
-Steering damper
-added VRSCR wheels and tires
-had a few rear sprockets made
-took off the seat (i'm 6'3" so i needed to scoot back)
-added K&N

Next, addressing traction issue:
-added 50lbs of lead inside swingarm
-removed radiator shroud
-geared lower
Went 162mph still spinning the wheel

Then the SCTA/El mirage tire rules changed, so I swapped the VRSCR wheels for a set of 17" PM Billet wheels from an X1 Buell

SO.......with my new 17" wheels I ran in Sept. and had a strong speed wobble. Went 147mph after I rolled off throttle.

A SCTA official told me that a trail issue caused this, so I went home to measure (didn't measure before, dumb, I know)

I get a trail measurement of 1 1/2 inch......NOT GOOD.
I understand it should be 2-4 inches to be safe.

so, now I guess a set of triple clamps could correct this. Any thoughts?
Any ideas where I can get some off the shelf, or get some made?
 

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i know that some of the ahdra racers use custom triple trees that do increase the front end trail.. you might find out where they are available calling somebody who races the vr class or maybe eagle hd..
 

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The Tin Man
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Jesse,
I have drag raced VRods since 02 and did 3 years of LSR but with a ZX14 - on rough asphalt at Maxton and did one Bub event in 07 - with wet slippery and rutted salt. I considered building a turbo Vrod as well as almost went with a Destroyer. I ultimately went with the 14 as I decided to do it on my nickel - which was much cheaper on the 14 and I was concerned about the VRods engieering - especially related to handling with sustained high speed - my goal was 185 to 200MPH range.

After playing the game - I concluded that my judgement was correct. It is very difficult to get the HP required - I run around 200RWHP and even more of an issue - the VRod seems to have handling demons that have proven very nasy at this game. I have known of some that have gone down and others that scared the life out of the riders.

I think there may be multiple issues here - all around high speed dynamics. My guess is it has to do with lift. One theory I have is Gumby's casket (i.e. radiator shroud) is bad and causes lift. Number 2 - I think the open aerodynamcis of the bike is also causing lift. Both Kaz and the recent venture = - I believe the member is Sideways - have broken 200 without mention of handling problems - both had fairings. Fairing dehigned properly will put a down force on the front end and also elliminate some of the uplift around other components such as the pertruding engine - you, etc.

ALso - it is my understanding that heavy wheel help with both traction and stability as it increases the inertia - so if your wheels are getting too lite - that could be an issue for both traction and inertia. Tires do funny things also - I used Battleax 208 with combined race/street compound at 45PSI with Nitrogen...... These tires seemed to provide good traction and held together in both situation - i.e. asphalt and salt.
 

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The Tin Man
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Also too note is that wheel balance is really important. Check and double check as well as wheel alignment - set on rack with a string.

Now weight in the swing arm - it is my understanding can sometimes help traction but at the same time can impact stability in a negative fasgion - having something to do with change the monement of inetria of the bike..... most of these things do not play out in drag racing as it is a flsah of momentary speed - on really smooth and sticky pavement. Salt, dirt and rough runways introduce a another set of problems - complicated by the duration - sustained speed and stress on engine
 

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The Tin Man
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The 14 is probably as stable handling of a bike at high speed as one can get..... but at Bonneville - running the 9 mile international course - on wet salt with lots of ruts...... I would break lose whenever I went above 185 - I concluded that this was an aero issue - experiencing lift that would take it beyound the friction coefficient. When that happened - drama would follow complete with the rear end wagging (fish tail style) and rooster tails of salt. Ruts would also cause the bike to shutter and front end to move to and fro...... very uncomfortable with multiple "you are GOING DOWN" alarms going off at the worst moments. At this point I would stand on the pegs and lift my butt off the seat 2an inch or 2 and it would settle down and bite again - and also learned to gently roll off a bit on the throttle to help minimize the impact of loss of traction - a tip from an old road racer that was running that year and managing the same issue. Staying loose on the bars was important as trying to stop the head shake could have transfferred the movement into the chassis and that is when the bike tends to play catapult.

I guess my point is that my guess is that aeros are a major consideration as well as various set-up issues - I do not understand the impact of rake and trail and therefore do not have an opinion..... but do be careful - btw - the headshake I am talking about was NOT a tankslapper - which is beyond my safety threshold to deal with.
Kevin
 

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I can see how weight in the swing arm would increse traction because it is heavier, but as mentioned above it would cause all kinds of issues on anything but a very smooth surface. You hit the bump and the mass starts moving which results in a lot of work for the suspension components to keep in check.

The stock triple clamps have rake which reduces trail. Good for lighter steering, not so good for stability. Just switching to zero rake triple trees (yokes) will increase your trail and make the bike more stable.

You didn't mention what steering dampener you use. Maybe an adjustment is needed as well.
 

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added weight shouldn`t be on the suspension.as mentioned above adding inertia to the suspension makes controlling the wheel travel and traction more difficult..as bikerider58 said zero rake trees will increase trail and i know that many vr class racers use them so they should be available..kspz may be correct about the radiator housing causing lift at speed..fixing that might be a challenge..
 

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I can see how weight in the swing arm would increse traction because it is heavier, but as mentioned above it would cause all kinds of issues on anything but a very smooth surface. You hit the bump and the mass starts moving which results in a lot of work for the suspension components to keep in check.

The stock triple clamps have rake which reduces trail. Good for lighter steering, not so good for stability. Just switching to zero rake triple trees (yokes) will increase your trail and make the bike more stable.

You didn't mention what steering dampener you use. Maybe an adjustment is needed as well.
We make the trees with 0 rake and move the fork tubes much closer to the steering stem, (inward) or in any configureation for that matter our trail is 6.7 the stock geometry is just plain unsafe in LSR. Our bike is super stable at speed.
My opinion on ballast is simply, its a complecated issue, since you want what is called the center of pressure to move forward at speed. I try my best to keep the bike (as realistly possibl) light which gives us the option of adding wieght ballest where its needed, which can be in the front of the bike versus say the swingarm or both which can actually sometimes inhance the handleing. Steep steering heads are not nessesary if the trail is right. Also you are getting into a suiside mission trying to put excessive dampning if the front is too tight you run the risk of the back end coming around, if the bike is set up correctly you need very little dampning. Tim
 
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