fish_antlers
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posted March 30, 2002 08:21 AM
Wheel spin percentages vs suspension setup?
I'm intrigued by Rob's comments in the Bear stacks thread re: missing speed being tied to wheel spin. I'm hoping for an explanation of wheel spin, how it is measured and determined and exactly which elements of the suspension settings have an effect on it etc...
thanks
   
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fish_antlers
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posted April 01, 2002 07:06 AM
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fish_antlers
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posted April 03, 2002 06:04 PM
anyone? Doug? Rob?
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psycho1122
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posted April 03, 2002 10:15 PM
I know this has something to do w/ the pivot point of the swingarm in relation to the angle at which the drive chain is to the swing arm. The more angle you have(chain less parallel to the swing arm from rear sprocket towards the front), the more the pull effect the chain will have on the rear suspention. So instead of squating under exceleration to improve traction, the rear end will lift up (like a Honda Shaft driven bike)and unload the rear tire, result:less traction under exceleration.
Am I making sense!? This is hard to describe......
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fish_antlers
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posted April 05, 2002 10:03 AM
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fish_antlers
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posted April 07, 2002 07:54 AM
doug?
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psycho1122
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posted April 07, 2002 12:56 PM
Doug wont give you a different answer.....maybe just a different explination of the same thing.
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fastestr1
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posted April 07, 2002 08:05 PM
So the straighter (or less angle) the chain is to the swing arm the less it will squat?
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fish_antlers
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posted April 07, 2002 08:08 PM
how do you arrive at the "percentage"?
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psycho1122
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posted April 08, 2002 06:17 PM
O.K......Watch a bike on a Dyno, especially in a lower gear...The Chain force will acctually "lift" the back of the bike. Thus the reason for adjustable swing arm pivot points on race bikes. If your bike is geared w/ a larger sprocket for a short track and you have excessive wheel spin on corner exits, your could effectively reduce it by lowering your pivot point. This will make the chain more parallel w/ the swingarm and reduce the "Tangent Force" it applies to the suspension and improveing traction.
Percentages are probably obtained from expensive "on board" telemetry.
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fish_antlers
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posted April 09, 2002 02:55 PM
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zx12zx11
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posted April 09, 2002 03:09 PM
I know of a few ways to improve traction at top speed. The only thig is that I promised a person that I would never tell what would help. I'm sorry but I can't help at this time.
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entropy
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posted April 09, 2002 03:40 PM
quote:
I know of a few ways to improve traction at top speed. The only thig is that I promised a person that I would never tell what would help. I'm sorry but I can't help at this time.
Zx12zx11
maybe i'm just in a bad mood or something, but that is bordering on the most ass-inine post I have yet read on this forum. Maybe you meant it as a joke?
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psycho1122
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posted April 10, 2002 06:55 AM
Why not share good info!!?, If it is valid and useful......
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dougmeyer
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posted April 10, 2002 07:05 AM
I'm not ignoring you but I don't have time to answer this properly. I'll get back to you when I have a minute to write it up coherently, but psyco's comments are correct.
As far as measuring it, figure the mathematical speed based on observed rpm and tire size, gearing, etc., and compare this to the actual speed measured by clocks at that rpm. The difference can only be wheelspin.
OR have a data aquisition system that compares front wheel speed to rear wheel speed.
Doug
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fish_antlers
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posted April 10, 2002 07:56 AM
thx Doug..... this really intruiged me... I wanted to sit down with a coffee and read your response.... I was excited to see it and then the board went down fer a few days..
hey... how was yer trip?
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zx12zx11
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posted April 10, 2002 08:00 AM
entropy I was fishing and got one. It was just a bad joke.
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entropy
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posted April 10, 2002 08:24 AM
zx11zx12,
I apologize for being such a shit. Yesterday was a bit of a pain, nothing major just "one of those days". Even my wife accused me of PMS...
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RobMuzzy
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posted April 10, 2002 08:28 AM
Wheel Spin
Fish- We measure the front wheel rpm and rear wheel rpm on the road race bikes. The rpm times wheel circumference gives you distance traveled (mph). The difference between the front wheel and rear wheel gives you slip. We use an on board computer that calculates all this data and converts it to final format. As I posted before there are many things that will effect top speed, wheel spin is one of them. Tire construction, air pressure, rear suspension, and track surface will all effect rear wheel spin. Four to six percent is normal at speeds around 180 to 200.
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RobMuzzy
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posted April 10, 2002 08:37 AM
Wheel spin and rear suspension
Fish- If you are looking for what we did in my story here is the answere. We decreased rear shock rebound dampening. The track had a lot of small bumps and the rebound setting we had was not letting the rear wheel return before it hit the next little bump. This caused the tire to deflect instead of following the surface.
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fish_antlers
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posted April 10, 2002 08:37 AM
pardon my being a thick plank... so the percentage of wheel spin is the amount of deviation between the front and rear wheel's spinning due to differences in circumferance, tire pressure etc?
(trying to understand... it's a bit of a leap from making sure my chain is lubed....  )
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RobMuzzy
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posted April 11, 2002 02:07 PM
Wheel Spin
fISH- The formula in the computer has the circumference of the front and rear wheel. Therefore the data for each wheel is accurate mph. So if the data says the front wheel is going 180 mph and the rear wheel is going 198 mph there is an 18 mph difference or 10%. This is due to rear wheel slip.
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fish_antlers
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posted April 11, 2002 02:14 PM
thanks...
very cool...
so this is corrected by tire inflation, tire size etc etc?
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