Bike is a 2003 cbr600rr. stock gearing is 16f/43r previous gearing was 15f/43r current gearing is 15f/45r I use a 520 chain...will count the links tomorrow and post if need be. As I installed the bigger rear sprocket this evening, I noticed my wheelbase shortened by a good deal (more than I had expected). I bet I had moved the rear axle about 10mm in. Doing a bit of search I came up with -8.56mm based on http://www.xs4all.nl/~ator0437/gc/ My question(s) is: 1) I do not have the ability to adjust the swing arm angle to give the rear more anti-squat. Should I stiffen the rear (increase preload and/or compression damping) to deal with the increased torque that will be exherted under WOT? How will this affect traction in your experience? I will make sure to have apropriate chain slack so as to allow the shock to do function throught it's stroke range. 2) I have a Ohlins triple w/ 12mm ride height adjustability; should I make any changes in this department (tires are the same, Metzeler Racetecs)? 3) Should I increase rebound damping in the front to help cope with quicker weight transfer? Anything else I'm not considering to even ask about? Thanks for your responses in advance! regards, IG
In #1, you say that you don't have the ability to adjust the swingarm angle. And in #2, you say that you have an Ohlins shock with ride height adjustability. Something doesn't compute. ???? To increase the swingarm angle, add ride height in the shock. To decrease swingarm angle, remove ride height in the shock.
You're right, I contradiceted myself in the statement. I will increase the ride height some, perhaps at 3mm intervals, then test. What I meant is that the bike does not have the ability to change / adjust swingarm angle at the pivot. Is there a rule of thumb of hom much ride height/swingarm angle one should add / take away based on the amount of change in rear axle location / wheelbase? Thanks! I.G.
Why not get a second, longer chain that will keep your wheelbase the same? For swingarm angle, find what the ideal eye to eye length should be. That will help get you the correct swingarm angle.
Time constraint - will be running the bike this weekend and do not have time to order new, get delivered and installed. Anyone else wanna chime in and share the wisdom?
from picture (just using torque for static, not a dynamic equation). It doesn't appear to make a big difference. If you supply the red numbers I can give you a more detailed result (those are just guesses). I thought the excel file I made was very interesting, and it might be entirely wrong, so someone can check my math if they want. It actually says for a larger sprocket there is a small additional force on the axle (negative in this case meaning downward) you can try raising the ride height a few mm to compensate for the lower rear caused by moving the axle up the swingarm your rebound settings should be based off of other more significant things than what this small change would do to your bike IMO. no problem, I wouldn't worry too much about it unless you are a top expert or going for the AMA crown, because unless you are a top top echelon rider you might not notice a handling difference anyway. The biggest difference you will notice will be a change in geometry (slight), the bike might handle a tick slower..but barely noticeable.
Dude, your trying too hard to engineer your motorcycle's performance, when you should engineer your enjoyment instead. Go out and ride it. On top of that, most of the people in this forum are not experienced suspension technicians and are guessing or chest puffing or calculating based on the abstract. Would you trust your bike setup to guys with less experience than you? Some of them are giving you advice and you can count on this forum providing lots of that, although there are some clever folks on here, too. Chill. Go ride. 10mm is noticeable to a pro rider, but most of them would just gas it anyway. Worry about things like how much gas in in the tank instead.
Firstly, thanks to all who offered their input. I am not a top echelon rider, far from it in fact but I do enjoy reading about how my bike works ... the science of it all in general. I do know a bit from all the study-up I've done, but even those who's opinion should be taken with a grain of salt (average rider) can sometimes offer things which one had not considered before and so I value their opinion, even if I may not take it "to the bank". I won't worry about it all, but will instead just ride the thing but generally speaking I try to make the thing as safe as possible because for me safe = fun (crashing does not = fun). My hopes in posting is also that occassionally someone with mucho credentials will decide to disect the subject for us mere mortals and then others like me will benefit as well. Again, thanks for all the inputs and let's hope the beaver stays dry this weekend. I.G.
that's the spirit . The only way to learn is to keep discussing things and throwing new ideas out there, if they are 100% right or not is part of the debate. That's one of the main points of this forum really. If only top experts answered it wouldn't be a forum, it would be a pay-for-answer site.
I think I disagree with this point. When you move the axle closer to the swing arm pivot you are effectively raising the ride height and increasing the swingarm angle. True, if you measure the ride height/rider sag from the center of the axle to a fixed point on the bodywork it will register a shorter reading because you moved the axle forward and up. But if you take the same measurements from the farthest point on the swingarm (away from the swingarm pivot, not the axle) you will find the ride height is increased. Why? Because when you moved the axle forward you decreased your leverage, which will now take a higher moment of enertia to get that same deflection against the rear shock spring. So, my theory is to just to measure your rider sag before and after to the furthest point on the swingarm towards the back of the bike (not the axle) and make sure it stays the same no matter what sprockets you run. Just remember, when you shorten the wheel base you move the total bike/rider weight bias towards the rear of the bike, and towards the front when you increase it. So, you may have to click the damper settings accordingly, as someone stated, if you moved the axle a good bit from your base settings.
