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Author Topic: perfect sprocket size?  (Read 5622 times)

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Offline fabr

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Re: perfect sprocket size?
« Reply #45 on: August 21, 2009, 09:56:20 AM »
I don't disagree with that at all but I'd say  comparing calculating top speed and needed gear ratios to calculating  spring rates are just a bit different. I fully agree with you on the springs but calculating for gear ratios and speeds ,to me anyway, it's not a guess so calculating instead of guessing is the only way to go.
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LiveWire

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Re: perfect sprocket size?
« Reply #46 on: August 21, 2009, 11:35:12 AM »
Your still starting with a WAG as to what the car will actually pull for a top end. If you guess high and the engine can't pull it, top speed may be limited even more by the engine not being at peak power. If you guess low, I guess you'll be RPM limited and at leas the calculations will be correct.

Most people don't do roll out. Hell, most people don't even measure the tire, they use the rated size.
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Offline fabr

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Re: perfect sprocket size?
« Reply #47 on: August 21, 2009, 01:04:20 PM »
Quote from: LiveWire on August 21, 2009, 11:35:12 AM
Your still starting with a WAG as to what the car will actually pull for a top end. If you guess high and the engine can't pull it, top speed may be limited even more by the engine not being at peak power. If you guess low, I guess you'll be RPM limited and at leas the calculations will be correct.

Most people don't do roll out. Hell, most people don't even measure the tire, they use the rated size.
I agree completely but as you have shown the calculations  are correct for everything but the ultimate top speed. That's pretty good for me anyway and a far cry from a WAG. Also with engines you can assume somewhere in the 80% of redline for 6t h gear max rpm. Yes, a WAG but one that will make very little difference in the results for our purposes.

I SURE can't disagree with that either. That's why I added it to the discussion. I'm betting it is totally new to most. Now THAT is something that can really skew your results!
« Last Edit: August 21, 2009, 01:05:56 PM by Masterfabr »
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but something else also, isn't an American at all.  We have room for but one
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the English language... and we have room for but one sole loyalty and that is a
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Offline Carlriddle

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Re: perfect sprocket size?
« Reply #48 on: August 21, 2009, 06:19:22 PM »
Agreed this is not figuring in drag??  Did the math on Master's link.... 102mph.  Shiot if I hit 80% of that I'm bailing out. :o :o I think this formula apllies more to the lower end, and that is what most are looking for, get up and go!!!!!!!!!
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Offline fabr

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Re: perfect sprocket size?
« Reply #49 on: August 21, 2009, 07:25:20 PM »
Quote from: Carlriddle on August 21, 2009, 06:19:22 PM
Agreed this is not figuring in drag??  Did the math on Master's link.... 102mph.  Shiot if I hit 80% of that I'm bailing out. :o :o I think this formula apllies more to the lower end, and that is what most are looking for, get up and go!!!!!!!!!
It's dead on mathmatically.WE have to allow for what the top rpm will be based on a WAG based on experience tho. No it cannot figure in drag either.These calculators give you good information to make an informed guess not a complete WAG.
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Offline Voodoochikin04

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Re: perfect sprocket size?
« Reply #50 on: August 28, 2009, 07:03:57 PM »
im trading out my 72 for a 60 through doug which im sure you all know..  but out of sheer curiosity, and a fear of "how will i ever know" type thing..  i rigged up an idler and managed to get a chain on that mammouth 72tooth sprocket..  i took it for a short spin..  punching the gas in 1st 2nd 3rd 4th, i can rooster tail and pitch it sideways..  it just pulls solidly from 1st to 2nd to 3rd to 4th, tames up in 5th.. hits redline in 6th no problem.. i can easily accelerate in 6th..  this is with the 14 front and 72 tooth rear..  in all actuallity it is to steep... lol.. not by much though..  6th gear now feels how 4th used to.  only put about 4 minutes on it and disassembled as to not have any wear on the sprocket.. but i just had to know..  crazy..  punching it in 1st lifts the front end to full droop, (by watching the shocks).    so im really hoping that with my 13tooth front and 60 rear, i will still like the ratio, and be satisfied.    ;D ;D


i was looking back on fabbers post with my mph at those gear ratios..   i was doing about 85 at redline in 6th today... holy cow.. it felt fast..  maybe this is the perfect setup, but hell it just cant work.. cant have an adjustable idler..
« Last Edit: August 28, 2009, 07:12:09 PM by Voodoochikin04 »
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Offline fabr

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Re: perfect sprocket size?
« Reply #51 on: August 28, 2009, 07:11:29 PM »
5.14:1(72/14) compared to 4.61:1(60/13). You won't even notice a difference. Well,MAYBE just BARELY, but I'm betting you won't.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

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Offline Doug Heim

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Re: perfect sprocket size?
« Reply #52 on: August 29, 2009, 09:32:32 AM »
Im glad you got to try it out though. Just knowing and trying it since you had it anyway was a great expierence because as you said, otherwise you would not know. 60 is going out Monday.

Thanks Doug
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