After wrestling for over a week with the question of what to do about my final drive ratio and what sprockets and chain to get, I have finally made a decision and pulled the trigger. I’m glad this is over. I’m always stressing over price/value and which way to go. Should I go cheap or should I go for quality? It is true what they say about getting what one is paying for, but trying to strike a balance between going all out and keeping it reasonable and less painful on the bank is what creates an elevated risk for an embolism in the grey matter.
First, there was the gearing to consider. I’ve never been to the Nashville Superspeedway. I couldn’t find a decent track map online and the scarce info that can be gleaned off of message boards and various web sites is suspect at best; at least to me. Then there is the slight hangup I have about owning my solution and a tendency of not listening to people whose credibility cannot be verified. Not to mention that there is a bunch of contradicting info out there. And I’d rather mess up of my own volition than play the victim without a clue to somebody else’s BS. In short, I can deal with my own mistakes and their consequences. Nobody to blame but myself. That’s the way it should be. Since I don’t know jack about gearing and cannot yet distinguish the utter crap from the useful information, I have to be very selective about my sources.
I’ve learned this much in racing school:
- Gearing is track specific.
- The vast majority of stock street bikes are geared wrong. It is very rare for stock gearing to be correct for the race track.
- Navigate the race track using the top half of the gearbox, meaning gears four through six; the gears are closer together there and hence RPM variances are less, making it easier to find the correct gear for any given corner.
- You should be able to hit red line in sixth gear somewhere on the track, usually at the end of the longest straight.
- Gear your bike to always be in the optimum power band.
With that said, I know I am missing essential information. How long is the longest straight at Nashville Superspeedway? Or at least what is the average top speed attained on a liter bike? I suppose I could leave well enough alone and go there with my stock setup. But I don’t work this way. Now that I have learned about this neat little morsel of racing info, I have to try and apply it. I’ve been doing fairly well lugging through some corners or screaming around in others or on the straights. Yes, I’m lazy. My shift light rapidly blinks to inform me it’s time and all I can think of? “I’m almost there… almost… I can make it… I don’t want to upshift just now, because ah… right here I would have had to downshift.” Most of the time, I street shift anyway… I am nowhere near the power band… I tool around the track in fuel saving mode. That tendency has to stop. No wonder I suck at going fast in a straight line. By the time I get the Pirate into her sweet spot where she pulls hard, it’s time to get on the binders again and stuff her into the next corner, where I –yet again– get to go around all those people who just passed me in the straights. I would like to get to a point in my riding where I only pass people ONCE. Less work that way. Unless I’m lapping them… then twice would be good. 😉
And why am I always catching up with them in the corners? Seems to me that I shouldn’t be… but that is a different blog post altogether.
I have finally decided to just wing it and go with theoretical values and bring my top speed down to my personal best, which somewhat coincides with values flung around online.
Now, where exactly would my shift points be on the S1000RR? That’s determined by the power band. To be scientific about it, I would have to get the bike on a dyno and see where she’s got what. I don’t have the money for that, nor do I know where to find one of those around here. Lastly, I just don’t feel up to finding out at the moment. My bike is stock, properly broken in, and dyno figures are a look at estimated real-world performance. Dyno figures do not translate directly. Not that simple. I just make it easy on myself and look at a few stock dyno charts. 9.5 – 13K. Good, that kind of meshes with my subjective experience and perception. The red line is at 14.5K and the front wants to come up around 11K. Further, BMW suggests to bring the revs up to 9K for a proper race start. Good enough. Now, I have a range.
I plug in some values into an online tool called the Gearing Commander and am torn between running 16/46 or 16/47, which would be -1/+2 and -1/+3 from stock respectively. I don’t like even/even distribution on teeth, so I opt for the 16/47 choice which seems better on overall wear and gets me a theoretical 4 MPH closer to that red-line moment I’m supposed to have at some point.
But it isn’t over quite yet. Should I stick with the stock 525 setup or go with a 520 conversion? 520 is obviously lighter since it isn’t as wide. The first number denotes pitch, which is the distance between two pins; the second number is the width of the chain. After sitting on the fence for another day, not being able to make up my mind one way or the other, the deciding factor came in the form of my LSR meet at the Maxton Mile in May. Weight matters there, never mind that I’m not going to be running these sprockets, but I want to keep everything the same size, so I can swap stuff at the track if I really need to. Another monetary consideration, definitely.
I’m not fast enough yet to even consider tweaks such as weight reduction to the point of measuring my fuel, ripping unnecessary parts off my bike, or to be concerned about the minute differences in chain acceleration, tension, and sprocket sizes. I’ll get to that when it is necessary. Right now I have other concerns. 520 it is. Cheaper also, less materials involved. And most of the good price/value ratios can be found in that size, too.
After checking that I have the necessary adjustment room on the rear axle and hoping that I have the clearance required to actually run a 47-tooth rear, it is time to order two sprockets and a chain. Two more days are spent wrestling with compromise between price and value and I finally decide on the following and pull the trigger before I can change my mind three more times:
- Vortex Racing 520 16T countershaft sprocket
- Vortex Racing 520 47T rear sprocket
- RK 520 GXW XW-Ring chain (118 links, I will need to cut one)
This will give me a final drive ratio of 2.94 as supposed to the stock ratio of 2.59.
The theoretical top speed would be 159 MPH as opposed to 181 MPH with stock gearing.
Theoretical shifting speeds at 9,500 RPM: 56, 70, 85, 98, 108, 117 through the six gears.
Yeah, I’m going to have to wear a diaper to stay in the top three gears. =D But it should be an improvement over the stock gearing. Now, wish me luck so I don’t wad that shit.
My work here is done. Come what may. I will own it.
I’ve never given much thought to proper gearing. I’ve heard about it, but the most I really knew about the final drive ratio was that it was just another of many a brilliant way to screw up a perfectly good ride. I knew that changing sprockets could be used to manipulate the power delivery characteristics of the engine, add top speed to the detriment of low-end torque or sacrifice some off the top for more of that awesome arm-stretching pull down low. Want your bike to sound like an Osterizer going down the road but don’t have a 250? Bring that final gear ratio down for more of that “I’m so much faster and exponentially cooler than you” engine sound. Really gives that new $600 rip-roaring loud slip-on a ton of street cred. You’re wound up tight but get there quicker. You’re also shifting quite a bit more, because the gears are closer together at the top of the box. But be aware that you now only sound fast. Your engine is working harder and your bike’s maximum speed just took a nose dive below the need of that TRE you just bought off eBay.
Note: A Timing Retard Eliminator aka de-restrictor is a device designed to remove or circumvent the artificial top speed restriction to 186 mph imposed on Japanese-made sport bikes capable of going faster. This practice is known as the “Gentlemen’s Agreement” between the USA government and the four major Japanese manufacturers: Suzuki, Kawasaki, Yamaha, and Honda.
Want to pop those wheelies on your ‘Busa, but having a hard time getting it up? Drop a few teeth in the front and be ready for that Viagra moment!
It didn’t dawn on me when Ed Bargy addressed the issue and said that most stock sport bikes are not geared properly for the track. They are geared way too tall. You should be hitting red line in top gear somewhere on the track, usually that means the end of the longest straight. You should be using the upper three gears negotiating the track, since the gear ratios of the top gears are closer together, not as tall. This will enable you to stay in the optimal power band more easily and gear selection for any given corner is simplified since you run less of a chance of getting stuck between the choices of “lug ‘n bog” or “scream and bounce (off the rev limiter)” because your gears are too tall, meaning they are too far apart in the RPM range. Acceleration is also much better when you’re in the “sweet spot”, too. The sweet spot is the point in your engine’s power band where horsepower and torque are at their peak.
Blah… blah… blah… I listened, in that store-for-analysis-later semi-disinterested way, made a mental note of “each track usually has its own unique setup requirements for your bike”. I muse that this final drive ratio bit falls into the same category with dialing in proper suspension settings and tire selection. Who has the money for that? Not that this matters at my level. I’m still 16 seconds away from having to worry about stuff like this, or so is my conviction. For an anal retentive and recovering borderline-pathological perfectionist, I can be pretty blasé about some things. OK, I promise I’ll worry about it in 10 seconds.
I’ve forgotten all about gearing until I watched my onboard track videos. Good grief! The stuff you never knew you did wrong! Blaringly obvious! I shifted like I was tooling around on the back roads, stuck behind a gaggle of cruisers and worrying about my fuel economy! I short-shifted…. No, you can’t even call it that. I shifted so early, I had to pre-register the request with my transmission. No wonder I lost several runs on the straights, even when I didn’t forget to get on the gas coming out of a turn! I felt like I was going backwards in time when I was waiting for the bike to accelerate, it took so long for the engine “to kick in”. Shifting too soon in the RPM range and not being at full throttle are only two of reasons.
The third, it had finally sunk in, is my gearing. The words of Mr. Bargy came rushing back to me. All that information I didn’t think I needed just yet suddenly seemed a lot more important. And my bike wasn’t all that happy in the lower gears. Like I always have said, she doesn’t like to be in too tall a gear. Not that the S1000RR lugs, she just feels vibey and discontent. I can definitely feel when she is in “her range”. The buzz in the bars lessens; the bike seems to settle and is more responsive, like a cat readying herself to pounce, if that makes sense. She feels like she is on rails when you’re up in the RPM range and giving it throttle in the turns… not so much when you’re “coasting” through the corners at 5,000 RPM at quarter throttle singing la-dee-da-dee-da… it’s a beautiful day… whistling and thinking happy thoughts. Yup, I caught myself riding it like a girl out on a Sunday drive, not a care in the world and feeling fi-iiine. Gawd! I’m less of a Miss Daisy on the street. At least it seemed that way. Holy hell. I guess I was having so much fun, I forgot I was there for roadracing training, not for a stroll down the track in the beginner group.
I did watch the novice group and it was almost like they were going in slow motion. I saw one control rider going around the fast part of the track in standard street pose. You know, upright, kind of cockeyed on the bike, clutch hand resting on the upper thigh. Poor guy probably drew the short straw at that morning’s staff meeting. Bummer! And to think I almost signed up for the novice group because I thought I wouldn’t be able to keep a constructive pace in the intermediate group.
I also watched the expert group for a while. I mentioned to Mr. Slow how freaking fast they look. He nodded and said it was fun to watch these guys duke it out in the corners. I asked him that we must be crawling compared to them. He nodded in agreement: “Those guys look at you like you look at the novice group.” Wow! That’s kind of neat when you think about it. My first ever track day w/o instructors and class room sessions and I’m mid-pack in the mid-pack. That is freaking cool beans. For some reason I didn’t think I was “that fast” already.
Speed is a strange critter. Well, not speed… the perception of speed. When you are on the track you seem pretty fast to yourself. Of course you do, because you’re riding at the upper third of your skill range, or at least should be when you’re learning and concentrating on technique and being smooth, but still pushing boundaries and feeling for the limits. When you watch the POV video from that same session, you’re so embarrassingly slow, you only watch it alone, in the dark, behind a closed door. When you watch others go by who are riding at about the same speeds with comparable skill you think you’re out of your mind and can’t believe you’re actually out there doing the same. Yeah, baby!
What does this mean to me? I am at work studying the fine art of gearing selection with the help of Ed Bargy’s book “Introduction To Motorcycle Roadracing” and this handy little online tool called “Gearing Commander”. Stay tuned… this subject has the smell of walkthrough about it. I engage my brain this much while studying a subject matter, I have to put it in concise and organized form to remember it all and make sure that I have actually grasped the concept. For now, I better stick my nose back into the books and figure this thing out. I’m not going to Nashville to hit the Superspeedway just so I can do a little street riding around 6,000 RPM. I’m going to have this sorted. I already have to change my tires after every track weekend, and put the bike back into street trim. What’s adding two more sprockets to the task going hurt?
I really need a dedicated race bike… Nah! I’m the girl who wears knee pucks on the drag strip. I’m also the girl who rides her S1000RR 285 miles in full race gear just to hit the track. I wrestle drag bikes through the twisties and abuse supersports on the drag strip. Did I mention I am the first person in the world to do the entire BRP (Blue Ridge Parkway) end-to-end on a BMW S1000RR in second gear, observing the speed limit (more or less)? Why start and be normal now? =D