new14rider
Novice Class
Posts: 76
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posted November 19, 2012 04:04 PM
Lowering the bike for Texas Mile. Suspension question
So I ordered a Trac Dynamics 2" internal lowering system for the front forks. The forks are already 1/2" slid up in the triple tree. I also have Brocks rear adjustable window links. Anyone know if it's better to have the front lower than the rear or have them about even (bike leven when sitting on it) I'm wondering if I have an improper rear-front height difference (rear lower than stock) will I affect the stability and aerodynamics at top speed. What would be the ideal ratio or rear lowering if I have lowered the front 2.5" from stock. How would you set the adjustments on the front and rear shocks for a rider who is about 209 lbs 6' tall. I do have an Ohlins steering damper as well.
Thanks!
  
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entropy
Moderator
Posts: 8671
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posted November 19, 2012 05:51 PM
"I'm wondering if I have an improper rear-front height difference (rear lower than stock) will I affect the stability and aerodynamics at top speed..."
this is a good thing to worry about.
Getting it wrong will induce a very unsettling "something is wrong" feeling as the bike wobbles at top speed. It happened on my 12 and on my Busa at the Texas Mile. I fixed it by keeping the same relative height as stock, i.e. a point on the front was x.x" lower (or higher) as the back.
Lower the front, then lower the back, keeping the same difference as stock, just lower.
Also, do not drag the plastic under any circumstances. I always keep a min of 2" under the front fairing lower.
Hitting the front brake hard and putting the plastic on the pavement when leaned over bc of the typical Texas crosswind, is NOT something you want to do.
karl
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toledoUPSguy
Expert Class
An old guy with a new toy
Posts: 320
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posted November 19, 2012 09:17 PM
I was looking at those Slammer cartriges too. Would only having 1.5" of travel cause any issues in LSR?
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The man on top of the mountain didn't fall there.
2014 ZX14r in nuclear sunset orange and black
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BobC
Pro
Posts: 1736
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posted November 20, 2012 12:48 AM
 Edited By: BobC on 20 Nov 2012 11:03
Suspension movement for LSR can be quite small, certainly a lot less than for the street. I found by trial and error that the best setting for the front forks was to lower through the triple clamps by no more than half-an-inch and then strap the front down. This still allows some suspension movement, as opposed to just strapping down to the same height and fully compressing the fork spring.
That small amount of suspension can be critical. I got one or two tank-slappers when the front came down after a gentle power wheely when my bike was just strapped down hard. This disappeared when it was lowered a little and then strapped. I lowered the rear to the middle hole on the three-hole links which was enough and the bike was very stable, down about three inches front and rear.
I prefer strapping the front for these events, rather than changing the fork internals because it's not only about lowering the bike for aerodynamics but also to stop the front from unloading when you launch. A strap prevents this and there's less chance of a wheely, so you can launch much harder. For one-mile events, as in quarter-miles, it's about how you launch the bike !
I think this image from a meeting a few years ago is interesting. Two bikes with identical tune, rider's of similar size, but the blue bike (mine) was lowered. My speed at the trap was 203, the grey bike was 11mph slower.
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Candy Thunder Blue 2006 ZZR1400
Stock wheelbase
Max: 205.4 mph in 1.25 miles
2012 ZZR1400 in Golden Blazed Green
Brock CT Full System. etc
Max: 203.1 in 1 mile (so far)
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GREYHOUNDMOSES
Expert Class
Posts: 324
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posted November 20, 2012 04:41 AM
quote:
I lowered the rear to the middle hole on the three-hole links which was enough and the bike was very stable, down about three inches front and rear.
It looks like Muzzy links in your picture?
They claim 1 1/2" with the middle hole?
You forgot to mention some of that 11mph came from you having a much better tuck!
Although, those pictures make me doubt if those leather "humps" are a good idea.
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BobC
Pro
Posts: 1736
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posted November 20, 2012 05:39 AM
Edited By: BobC on 20 Nov 2012 13:53
With the preload I was using and on the middle hole my bike was around three inches lower at the rear compared to the other bike. Yes my tuck was lower and I didn't have the toes of my boots stuck out in the breeze. It all helps. I'm not sure about the hump either, it would work better if I could get my chest lower and my head back more. What I need is a cut down tank. Some riders advocate sitting up on the tail of the bike to get more horizontal and I'm not sure about that. Anyone have a wind-tunnel I could borrow for a day? 
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Candy Thunder Blue 2006 ZZR1400
Stock wheelbase
Max: 205.4 mph in 1.25 miles
2012 ZZR1400 in Golden Blazed Green
Brock CT Full System. etc
Max: 203.1 in 1 mile (so far)
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