In the thick of it
I have a problem with my 2006 Honda CBR1000RR. Recently I noticed some oil dripping down one of the tubes on my forks. Being a mechanic, I didn't think much of it, dropped the forks, and replaced the seals. I had some 15-weight fork oil on the shelf, so I used that to refill to factory level. Before that, everything was gravy. I had fine tuned the suspension a few weeks ago. However, when I reassembled everything and went for a test ride, after the tires were warm I pushed it around a little bit. The bike now understeers like one of those cheesy Smart cars. I have the preload topped out on the front (I'm a big guy, topped out is exactly factory sag) compression is at about 80 percent of max, and rebound 45 percent (the rebound damping on this bike is very overpowering I've noticed, even more with the 15-weight). I'm using Pilot Power 2CT tires. The only other change I've made is raising the forks a negligible amount. They used to be 4mm from the top, and now they're topped out. Turning down the damping for the 15-weight oil isn't helping much. If you tip the bike in the corner, it washes pretty well, but throw in some throttle and you can get into a hellacious drift. What in the world is causing this?
Eric Beebe
San Gabriel, CAinline_mediumwraptextright26714378/tech/146_1003_cbr_forks_engine_damage_and_race_tires146_1003_01_z+ask_the_geek+honda_CBR.jpgTrue

I ♥ Acceleration
Re. "The Traction Circle" (RSS, Sept. '09). Andrew, this is a great article which struck at the heart of the matter (pun intended), and possibly uncovered a deeper philosophical reason why we love riding so much-all those 3-dimensional G-forces plotted on a graph form a heart-a sign of love.

More Nakedness
When you did the R1 naked bike, where did you relocate the coolant reservoir to? I want to do my ZX-10R naked but it looks ugly without fairings.
Ray D
Via the internetinline_mediumwraptextright24855683/tech/146_0909_sportbike_nakedness_chains_bearings146_0909_01_z+ask_the_geek+R1_naked_bike.jpgTrue

Dear Geek:
You guys are always talking about changing a bike's front ride height when you change tires. How do I do that, and how do I know how far to go, eh?

Tony Moonen
Dorchester, Ontario, Canada

PS: Love the bow tie!

Hey Geek:

What is the best product and process for cleaning your chain? I ride daily, and spend about one hour per week cleaning my chain due to excessive build up. I lube my chain anywhere from 3 to 4 times a week depending on how much and what type of riding I am doing.

Eric D. Hatch
Garland, Texas

Hey Geek:

What is the best product and process for cleaning your chain? I ride daily, and spend about one hour per week cleaning my chain due to excessive build up. I lube my chain anywhere from 3 to 4 times a week depending on how much and what type of riding I am doing.

Eric D. Hatch
Garland, Texas

Give Me A Brake
I have a 2004 GSX-R600 with 7850 miles on the odometer-I live in Alaska, the bike and I hibernate for half the year. I started to have a handling problem about a year ago. When the bike is coming to a quick stop under fairly hard braking at speeds under 30mph, the handlebars will start to bounce up and down like you're using a jackhammer to break concrete. You hear a really nasty sound kind of like Godzilla's roar and your fillings literally fall out of your teeth. Now at that point you decide to let go of the brake lever and the vibrations instantly stop. A gentle application of the brake lever causes no vibration or noise all the way to a complete stop. And above 30mph even squeezing the brakes hard enough to lift the rear wheel causes no problems.

20 Questions In One
My friends and I were curious about why race teams use magnesium wheels and not carbon fiber. Carbon fiber is lighter and stronger, right? When molded into that certain application, is magnesium superior? Does it have anything to do with the limited availability of rim designs in carbon fiber or is it more cost related because of the R&D time it would take to test and produce?

What's all this ruckus about suspension these days? It seems everyone is clued in that suspension setup can be a key to riding fast and safely, but how do you do it? No matter what shock or fork you have, they all require proper adjustment to work to their maximum potential. Suspension tuning isn't rocket science, and if you follow step-by-step procedures you can make remarkable improvements in your bike's handling characteristics.

Dry Weight Confusion
Am I missing something here or does the dry weight that is listed by the motorcycle companies include oil and radiator weight? Or is it the gas that makes it "wet"?
B. David Bland
Germantown, MD

Wobbling Kawasaki
I have a Kawasaki ZX-14. In an effort to quicken/tighten the cornering abilities, I changed my rear tire to a 190/55-17 from a stock 190/50-17. Since the tire change I experience noticeable headshake from 45 to 55 mph. The dealership said the front tire balanced perfectly, and they are reluctant to do anything. The tires are smooth at all other speeds, and the bike handles well. Any comments concerning the tire swap and cause of the headshake would be appreciated.
Jim Cowan
Orting, WA

Thrust And Horsepower
When you look at a dyno chart, you see that a bike might have a horsepower rating of 65 at 4000 rpm. Say your primary drive ratio is 2.000, the final drive is 1.500 and the gear you are in has a ratio of 1.000. You multiply 2.000 x 1.500 x 1.000 and get 3 (which would be your overall gear ratio), then take that and multiply it by your 65 horsepower. Does that equate to 195 horsepower at the rear wheel? Is that what your bike is putting down, or is it already figured in when you look at the dyno chart? Can you compare two dyno charts and gear ratios to see which bike might be faster? If this is the case, then a higher dyno number does not always equal a quicker bike, right?
James Patterson
Erin, TN

Hoop Dreams
Why are many aftermarket wheels labeled as racetrack only? Wouldn't a carbon or magnesium rim work just as well in the canyons as it would on the track? And why do racebikes have smaller wheels than stock bikes? How do the smaller hoops affect performance?
Vince Davis
Los Angeles, CA

In Our Last Two Installments Of Art & Science we covered the basics of data acquisition (Jan. '08) and analyzing engine rpm data (Mar. '08). Speed and rpm, generally considered the two most important channels, are almost always given dedicated inputs on data acquisition systems and provide plenty of information on their own. As always, however, more data from other sources can allow you to better analyze that speed and rpm info, as well as look at other aspects of setup and riding that speed and rpm traces on their own can't reveal.

We Never Get Tired Of Tire Questions
I ran Michelin Pilot Power 120/70-17 and 190/50-17 on my '99 GSX-R750. The grip level and the mileage of this tire were pretty impressive and I was determined to use it again. However, when the tires were finished I changed to a used set of Bridgestone BT-002 Race 120/70-17 and 190/55-17, which I had been using on another bike for track days. With the Bridgestones on my GSX-R it feels like 20kg less. Steering is so much lighter and it's lot more fun to ride, although stability is compromised. Now I am lost. The BT-002 Race is not street legal, and I do not know if I can get the same feeling with the BT-002 RS in the same dimension. Or is the different feeling mainly due to the change in dimension from 50 to 55? In such case I could use the Pilot Power 190/55-17 or the 190/50-17 and adjust the ride height (I have an adjustable hlins rear shock).
Robert Schuhmayer
Austria

In last issue's Art & Science we discussed the basics of data acquisition and different ways to interpret speed data. Speed-whether recorded by a GPS-based system or a unit that measures wheel speed-is generally the base channel and offers plenty of information on its own. Adding more channels, however, allows a more in-depth analysis of the motorcycle's and rider's behavior on the track. That higher level of analysis can in turn result in quicker development and improved overall performance from both the bike and rider.

Y= MX + B
I'm an avid track-day rider and I have a chassis geometry question. My pace at the track has really improved over the last year, and I'm trying to understand more about my suspension and chassis. To make a bike turn in better and feel lighter, you can either lower the front or raise the rear. I don't believe it matters which way you go, as the end result is the same chassis geometry (except that if you lower the front, the bike's chassis is lower, and if you raise the rear, the bike's chassis is higher).

In the first three installments of this series we looked at data gathered by various sensors attached to the acquisition system: speed, rpm and throttle position. In this segment we'll deal with channels derived from position data collected by GPS-based systems that don't require any additional sensors. GPS setups, which calculate ground speed based on the change in position over time, can use that data to calculate acceleration forces in any direction, a helpful addition when it comes to evaluating performance.

Dave's Saggy Shock
I've got an '03 GSX-R1000 with a bit over 14K miles on it. The shock has started feeling a little mushy, and I'd like to get it back to how it felt originally. I remember reading that a shock would typically need to be rebuilt at around 15K miles. I've also heard that simply changing the fluid in the shock should restore its prior performance. Unless this is something that can be done by your average shade-tree mechanic, I'm probably going to just remove the shock myself and have someone else do the work on it.

Recommended Suspension Settings

These tables show suggested suspension settings for each bike. You can also use the tables to find which issues of Sport Rider each bike was tested. For more information on suspension, check out the Suspension Tuning Guide.

Richard Was Busy This Month
Of the three motorcycle magazines I currently subscribe to, Sport Rider invariably delivers the best comparison information and test data of the three, period. I especially like the performance data you provide with your model comparisons. Rather than a lot of seat-of-the-pants subjective opinions, your staff provides graphs and charts to show why one bike is faster or laps quicker than another. As an engineer, this is the stuff that makes your comparisons meaningful and provides objective credibility to your bike recommendations.

While the general public was eagerly awaiting Internet spy photos of the new '08 Hayabusa, the team at Velocity Racing had already taken delivery of an actual example of the breed and was busy building the bike it would soon be using to campaign in the AMA Prostar Pro Street class. Anyone who follows motorcycle dragracing knows of Velocity's reputation for constructing race-winning machinery since bursting onto the scene in '01. Under the leadership of Barry Henson (owner and rider), Velocity has had an impressive string of nine national championships, and it's not out of the question to believe it will be adding more in '08.

With the new era of 800cc MotoGP well underway, our spies in the paddock have managed to snap some pictures of the new bikes. Here is a sampling from the first few races of '07.

Twenty-two thousand miles. That's the sad tale told by the odometer of Brad Roller's 1996 Yamaha YZF600. Trevitt likes to cast a supercilious glance down the flanks of such two-wheeled stalwarts and proclaim each a "creaky old pile." That's to say his tastes run toward the still-smells-of-new, preferably owned by someone else. (Don't ask about his dusty GSX-R600.)

In the March issue's "Technicalities," we started to delve into the "Witches' Brew" of suspension systems with damping. Specifically, we discussed rebound damping. This month we will continue to unravel the mysteries by looking at the most misunderstood, and possibly the most critical, component of suspension: compression damping.