Great writeup, LA Dog, but maybe a thing or two should be clarified about the performance improvement. There will be a rear-wheel torque improvement in first gear, but you will also lose that improvement sooner, because you will need to shift to second gear sooner. For example, if one gears for a 15% rear-wheel torque improvement, one also needs to shift to the next gear at a 15% lower speed, at which point there is a big rear-wheel torque drop.

Except for first gear, ratios are largely rider-selectable. For example, if sixth gear is a little too tall (and has too little torque and horsepower) for the speed you're riding on the freeway, no problem, use fifth gear.

 

Thanks Warp but have to respectfully disagree on most all of that- We are talking mechanical change to the overall drive ratio. A 13% change in overall ratio is just that- and will increase or decrease TQ to the rear wheel depending on which way you went with that 13%.

This is based on math an calcs so it's not a nebulous science or guessing game. Think 1/4 mile cars & bikes. 3.11, 3.23, 3.50, 4.11 overall gear ratios are the norm- gets the vehicle through the gears faster is all.

There is no induced TQ dip at shift by having a shorter overall ratio, other than what might happen when you let off the gas to shift- or - if you purposefully shift outside of the engine's optimal powr band. like say you shift from 1st to 2nd at 1900 rpm. ya it will be a big TQ drop- with any overall gear ratio. if you remain shifting in the power band - say 3500-4500 rpm, baby is going to fly with each bang of the gears. If loss of TQ were the case, no one would shorten their overall gear ratio.

You are correct though about having to shift sooner at a lower RPM and that info is in my first few posts of this thread- that is a trade-off to getting to that rpm much sooner and going faster, quicker. We're not talking a big change going full 30/70, somewhere around 100-ish rpm at 1st and up to 300rpm in 6th.

Keep in mind too- we are not working from a "normal" and optimal starting overall gear ratio (2.79 - say what?). We are starting from a purposefully "too tall" crappy gearing ratio put down on us by the MoCo. So with the three available pulley upgrades, you get to un-do this to your preferred degree. if you look up older HD bikes pre-2006, they had more proper overall gearing ratios close to 3 and 30 front / 70 rear pulleys, etc. Some of the 883's had front pulleys as small as 27!

We're simply turning back the clock to the good 'ol days

 

I'll agree that it's mostly based on math and calcs. But one needs to include all the variables to get the right results.
There is always a rear-wheel torque drop when shifting to the next higher gear, regardless of the final drive ratio.

When you shift from first to second, you get roughly a 20 to 30% drop in rear wheel torque, depending on the rpm you shift at. So while you might get 13% more rear-wheel torque in 1st gear by switching to the 13% lower ratio, you also need to shift to second at a lower mph (or you'll run out of rpms), so you suffer that big torque drop from the shift sooner than you would have with the stock ratio. And the same goes for all the other shifts up through 6th gear.

Rear-wheel horsepower (which is a combination of both torque and rpm), stays roughly the same, regardless of what one does to the gearing.

 

Warp- respectfully, if you have data to support the claims of other variables to consider, please post it and source. If it measures up I will be first to agree. Even though I can be argumentative, I love new knowledge and I'm not one who always has to be right. But if I read something that strikes me odd I will poke at it .

All of the variables for gear changes are known and posted, online calcs, etc. - This thread is going to be based on factual data only, not theory guesstimations or unknown quantities, so lets try to keep it to that.

Horsepower is same / same regardless of gearing ratios- i don't think anyone is saying it is different.

 

Yes you have, and hats off to you for doing that. I'm really pressed for time, so I haven't responded to all your arguments. Just tried to pick some off the top.

Perhaps you're starting to get a bit emotional?
I've already given some examples of my drag racing experiences, on the track (including prepped tracks), and street racing.

I can understand if what you think you are hearing from me runs contrary to various kinds of internet myths. And I've spoken to and learned from many people who were way more knowledgeable than I am, and that's how I moved forward, learning to leave some of the old BS behind.

T[/QUOTE]

 

Nothing in this thread is a myth or BS so yes I'm not pleased that you would make these claims just to purposefully be inflammatory- A lot of work and verification has gone into the data presented here and the outcomes are based on years of previous results. So please stop negatively participating in something you have zero interest in doing, understanding, don't care for and have never done! I've seen you do this in other threads so I'm not sure what your deal is, but it's not cool. Trying not to use the "T" word..

 

Yes, you have presented some really good data, and I have acknowledged that several times already. And I disagree with some of your interpretations and conclusions from that data.

Maybe take some Midol, or some other menstrual medication, and you'll be better able to look at things more objectively tomorrow morning, without throwing a hissy-fit over someone expressing differences from your own opinions and beliefs.

 

Hrmm. Really tasteless personal comments there bud- but that's what I've seen you do before so I'm not surprised to see it again. So last post you say it is all internet myth and BS, and now this post, it is really good data. Sounds reasonable. Anyway I don't mind a disagreement if you have data to support your different claimed results on this specific upgrade, and that there is zero benefit. that would be helpful to add. But you don't have any.

I think the cam upgrade thread guys need you over there too. way too much crazy talk about getting more power from replacing cams?? That's nuts. Just downshift!

 

Are bikers suppose to be relegated to making only tasteful comments? If so, better tattle on me to your Mom. Maybe she'll tell my Mom, and I'll be punished by having to eat all my vegetables or somethin'.

However, I was quite polite till after you started getting pizzy. So you can take credit for the change, or for "drawing first blood", so to speak. If it bothers you, look first toward yourself for the solution.
Hello, I already used your own supplied data to support my differing claims. You can try to let it go in one ear, and out the other, or learn a little from it, or try to twist it into someone pizzing in your Wheaties. Which path you take is up to you.

 

Hey LA_Dog sorry to see this guy is trying to take a leak on your strawberries so to speak.
I think what you have written here is a great write up and will really help people to understand how a simple sprocket swap can effect the performance and feel of their bike.
As I've said before I've done sprocket swaps on chain driven motorcycles to great effect and all the info is out there for anyone wanting better knowledge of this as in principle it's exactly the same. What you have written here is based on fact and how these changes have worked on your bike. There really isn't any argument to be had. Cheers for taking the time to write it up in the first place, I learnt something new about what I can do to my bike to improve it.