YellowDuck

Off-season philosophical question (this place is a bit dead lately!). 2014 will be my first race season, after three years of track day riding. Last year I used Dunlop Q2s which were wonderful. I never used warmers and it only took one lap to heat them up. They did get pretty hot and melty at times though... For this season, I will be on race slicks (Bridgestone V01-R) with warmers. Here's my question...given that, at my pace I rarely if ever slid the Q2s (excluding cold tracks, damp asphalt, etc), will I likely go faster on the slicks? In other words, if the tires weren't clearly holding me back, can "better" tires be of any use? Do we somehow sense the limits of the tires even when they don't actually slide, and (usually) stay within those limits, or does no sliding = you don't need better tires yet? It seems that nowadays the high performance street tires are so good that you can be near the limits of cornering on them anyway (near ground-clearance-limited lean angles with decent body position), so why the need for race tires? Also, on street tires with good technique braking force seems to be limited by geometry (endoing the bike), not traction, so its hard to see how race tires help there either. I am thinking that the biggest benefit might be the ability to get on the throttle harder exiting corners without spinning up the rear (if there is any benefit at all). Maybe club racers at my level are just fooling themselves that they can benefit from DOT race tires or slicks? Opinions?

I think any person would be biting off a big chunk of physics and mechanics to adequately confirm or disprove what you are saying. However what I know to be correct from what I have studied and tried in practice, your impression is at least partially wrong. Go through a longer corner with a constant throttle reach forward and gently apply the brake. In most instances, if not all, the bike will stand up. Ok we already agree on this. Applying the brake pulls the contact patch in more, pro-steering the bike up. "Pro-steer" means to rotate the bars further into the turn. When actively doing this, the bike stands up. Applying the brake when leaned seems to have this effect. Thanks for this explanation. I think I almost get it, just one more question....what do you mean "pulls the contact patch in more"? Which way is "in" in this case? Towards the inside of the corner, or backwards towards the bike in a longitudinal direction? I expect the former but want to be sure I get it.

Nice. One point I am confused about though. I thought the main physical reason that a cornering bike tends to stand up under braking is that the extra compression of the front suspension brings the center of gravity lower and to the outside of the corner. It is like the rider suddenly started hanging off less, bringing his weight inwards towards the bike. This article mentions a completely different effect (which I don't totally understand) about the effect of braking on the tire contact patch. Is my preconception wrong, or are there two different things gong on here? And how exactly does the one mentioned in this article work?

Oh poor Michael. I am very upset about his current predicament. It is a funny picture though, and his racing experience explains the "ho-hum" expression on his face. Panic management...

Let me know when the petition is ready for my signature.

Wow, that should be illegal...for the same reason that movable aerodynamic components are illegal in formula 1 auto racing (except of course for DRS). What does it mean now to find the right setup, if the "setup" is adjusting itself every 10 m, with no input from the rider? Whoever has the best computer algorithms wins. Blech.

Not to change the topic, but another thing I noticed is that the fastest lap (by far) in that video is the one where I brake the latest and hardest at the end of the straight (braking starts about 10:00) - you can see the front tire getting pretty squirmy, and I actually bump the zip tie on the fork a smidge. I know CSS is not big on super hard late braking, but in my case when I get that right it seems to make a difference. Probably that's just a measure of how poor my braking points normally are. Especially at the end of a long straight I have a tendency to coast or at least not brake very hard at some point during the setup for the corner. I think I need to work a lot harder at identifying braking markers, and moving them forward when possible. If there is time to coast, then there was room to brake later!

Nearly there....lost 10 lbs already (weightwatchers - very educational experience, keeping track of everything you eat and drink). I am actually going to try for another 10 before the season starts. I am making sure to also get lots of exercise (gym, and also cross country skiing) to ensure that I am not shedding too much muscle mass.

Interesting discussion. I think I am a little more with Eirik than rchase on this one. For me, I love the feeling of having it all under control. I guess the fact that, on a motorcycle, not having it all under control brings with it big consequences, makes it more satisfying to do it right? Maybe that is the desire to "live life with actual consequences" that rchase describes. But those rare moments of spiking adrenaline when things don't go as planned and I am momentarily not sure if I really do have it all under control - I don't like those. They don't add to the excitement in a good way, they are scary and proof of my failure to do what I wanted to do, and make me feel reckless. In all of my track riding I seek to minimize those experiences. I am actually curious to see if that will still be possible when I make the switch from track days to racing this season. If it isn't, I doubt I will enjoy it.

Ha, you're right, and I am already getting it right sometimes! Just reviewed some track footage from this year showing the front fork action, and even when I am turning it in hard I am not experiencing much fork rebound between braking and turn in. For example check out the three corners beginning at 8:45 in this video: The one at 8:50 is a bit of a slow turn-in (big braking corner after a long-ish straight) but the next two I think I flick it in pretty quick (by my standards) but there is no real rebound from the compression under braking. Of course it can get better but it is working better than I expected just thinking about it.

Never realized that you had to "time" your slipper clutch releases with the actual turn. Cool tidbit there. Does it just keep slipping when you start your throttle roll on? No, it would never slip in any scenario where you were accelerating, even slightly. It is the back torque in the driveline that activates the slipper. But I find that when it is slipping because of a big mismatch between wheel speed and engine speed, then there is very little engine braking at all, but at a certain point as you are slowing down and the two get to be nearly matched the clutch reengages and the engine speed has to rise a bit, producing a momentary increase in engine braking. Better to have all of that happen before you turn in, so get the downshifting done early.

I like the idea posted earlier in this thread that the best possible timing is to be quick-tuning at the precise moment that you have fully released the brakes, so that the front suspension does not have time to decompress, but I have my doubts about my ability to do it in practice. I expect a few tenths of a second lag (at least) from releasing the brake to turning, and another few tenths to get the bike cornering hard enough to maintain that suspension compression. With a normal rebound setting I will have lost at least 50% of the fork compression in the interim, and possibly more like 75%. We are still a few months away from getting to put any of this into practice up here in Canuckistan, but this is all good food for thought. Before last season I was riding "mentally" with you folks for several months before the season started, then jumped on the bike in May and instantly went faster than ever before.

I liked his comment about getting all of the downshifting done in one hit, and then having the clutch all the way out with the engine and wheel speeds matched before he turns it in. That's also my goal, but of course I am not doing the fancy clutch + throttle rev matching. At my level there is enough weight on the rear wheel that I can do my downshifting early in the braking zone, dump the clutch way before turn in and let the slipper handle it. I find this has to happen early because if I wait too late the slipper might not reengage fully until after I have started to turn which really can make a mess of things, with the sudden little pulse of back-torque engine braking after I am already off the front brake.

I think the proportions of your body and, perhaps even more, your flexibility strongly affect what body position you can achieve. There are few young, fit guys that I ride track with who have body positioning that I would love to emulate, but I know for a fact that that is not going to happen unless I lose, like, 50 lbs and also take up yoga in a big way. On the other hand, watching race results (at least at the club level) proves that there is more than one way to skin a cat, and lots of different body positions can achieve excellent results.

Up here in southern Ontario I have been doing track days at Toronto Motorsports Park operated by a variety of groups, and at Grand Bend as well as Mosport operated by Ducati Owners Club of Canada. Last year I started doing a lot more at Grand Bend, Run by Racer 5 and / or SOAR (Southern Ontario Association of Racing), and I intend to start racing with SOAR this year. That likely means I will do most or all of my track riding at Grand Bend, with maybe an early season test-and-tune kinda day at TMP (got to get used to the warmers and slicks!). Even though we are just a bunch of middle-aged guys starting racing for fun, our endurance team has a website: http://www.prairie-dog-racing.com/ In addition to the endurance racing I will run in Battle of the Twins. I will likely post on-board videos of the races on youtube if anyone wants a good laugh this year!

You will get more technically competent answers I am sure, but one thing I can tell you for certain is that having a passenger aboard seriously messes with the bike's geometry and rear ride height. The added compression of the rear spring alters the swingarm angle, bike attitude (front to rear ride height difference), steering geometry (rake) and stroke position of the the suspension (more compressed in the rear, more extended in the front). You can compensate for this to some extent by adding rear preload. All this does is extend the shock from its current, more compressed stroke position towards a more natural position, which also solves your basic geometry problem (swingarm angle and front rake) under steady state conditions (neither accelerating nor braking). You will likely find that if you add enough preload to restore the normal bike attitude with a passenger aboard you will have zero free sag left (i.e., with no rider aboard the rear suspension will be topped out). This is not an issue but when riding solo again you will want to remove the additional preload. What the preload adjustment can *not* do is make the spring stiffer. To really set up a bike for performance two-up riding you would want a stiffer rear spring, but on most bikes swapping the spring out is a pretty big job so that's not really practical unless the bike is always ridden two-up. What I am saying is that there is really no way to optimize suspension adjustment for two-up performance riding unless you change the springs (at both ends), so don't expect to find a perfect setup with the stock hardware. With your passenger aboard you are always going to be compressing the rear more under acceleration even if you get the preload right - that is, you will have more backwards pitch - and you will also more front compression on braking. I'll bet you could remedy this somewhat by adding both compression and rebound damping at both ends, but that is still not the same as having the correct spring rates.

Not being able to use up all of the available room at the corner exit? (BTW, great topic - I am eager to hear some answers on this because line selection is going to be important for me this year as I start racing and need to learn a few new tracks fairly quickly.)

In street riding (or driving) part of it is just lane position. In right turns you are apexing near the shoulder, which is usually yours alone. On lefts you are apexing near the center line which could easily be occupied by oncoming traffic. The need to keep your head and upper body well within your own lane complicates things a bit turning left...

I recognize a lot of rchase's points in my own experience. I would add to that the simple lack of awareness that track days even existed in my area. Cost is certainly a factor for many. If you don't own full leathers for instance, that is pricey. If there is a "no sidestand rule" then you need to buy a sport chock or something. Some will want to install frame and axle sliders, etc, and of course there is the whole trailer thing....it all adds up so there is a certain cost threshold that keeps people away. It's a lot to invest at the outset in an activity you aren't even sure you are going to like. We have an outfit around here called Racer 5 that offers complete bike and equipment rentals and several stages of training (similar to CSS I guess but on CBR125s instead of superbikes). It is very reasonable and has turned out to be a great entry into track riding for many. Offer a day with equipment, training and a bike for under $400 and they show up in droves.

Lose 15 lbs before season starts. Get my race license. Get accustomed to using slicks and warmers. Get more coaching and drop 2 seconds. Complete the endurance season (6 rounds) no lower than 2nd place in our class. Run at least four rounds of Battle of the Twins Lightweight and make at least one podium (sounds like a lofty goal but it is a small class with our association - only 5 or six riders typically). How's that sound for middle-aged guy in his first race season?

I don't ride on the street anymore but when I did I would never have done this. No way, never. Admittedly, on those *really* long and boring stretches I sometimes sang to myself inside my helmet. Often "Born to be Wild" (or course) but also "After the Goldrush" for no apparent reason and also a brutal rendition of "Seven Bridges Road".

Here you go - best riders in the world on the best rain tires available. Plenty of amazing riding but not much knee-down stuff! http://www.youtube.com/watch?v=tv4_425K8r4

Maybe on a goldwing, and with poor body position. Sorry, on a bike with decent lean angle potential, I am not buying this. We are talking about corning forces in the 1 G range. I can't see doing that on wet pavement but I stand to be corrected if someone proves otherwise!

I am a suck in the wet on the track. For me it is not the lower level of traction that is the problem, it is the inconsistency in the available traction. If it were uniform you could approach the limits pretty safely. But it generally is not, so a much wider margin of safety is necessary. x 2 if we are talking about street riding.

I am not 100% sure the question makes complete sense as written, because I think that normally you would be totally off the brakes (done trail braking) before *reaching* your maximum lean angle for the corner. So, I am going to say that, ideally, you are at maximum lean angle during that moment of zero throttle, because once you got on the throttle the suspension extends a bit, moving your center of gravity higher so you don't need quite as much lean angle to carry the same corner speed on the same radius.