A '78-'89 911 D/E stock wheel question

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08-08-2009, 08:26 AM

#46

Chris M.

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[QUOTE=sig_a;6798050]

Quote:

Originally Posted by Chris M.

IAt Mid Ohio, the smaller wheels cause fewer shifts because you can't use 2nd gear in the Keyhole, Madness, and Carousel. At Putnam, they cause 1 extra shift between turns 4 and 5. "You don't have to use 5th gear at either track,"

I'm run out to max 6350 rpm in fourth just before seven at Mid Ohio on 17". Seems you would have to shift to fifth with 15". I recall you mentioning to me at Putnam a euro engine. That must be it.

Good thread.

Are you hitting a rev limiter at 6350? What engine? Sounds like a 3.2.

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08-08-2009, 10:54 AM

#47

sig_a

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[QUOTE=Chris M.;6798178]

Quote:

Originally Posted by sig_a

Are you hitting a rev limiter at 6350? What engine? Sounds like a 3.2.

3.2 USA/G50. Rev limiter sputters >7000. I've four 15" Fuchs, and I've wanted to try them at Putnam and Mid Ohio. I'm guessing 15's at MO would have me in 5th just beyond kink turn at six. I also wonder why my rev limiter doesn't kick in at redline?

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08-08-2009, 01:53 PM

#48

Astroman

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Quote:

Originally Posted by sig_a

I also wonder why my rev limiter doesn't kick in at redline?

Redline = 6250
Rev limit = 6500

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08-08-2009, 09:42 PM

#49

MUSSBERGER

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Quote:

Originally Posted by FredC

It seems that 15s are very popular down in Texas and Colorado. It's interesting to see how 1 particular shop can have such an impact. What's with Buckley's new exhaust system? I am curious.

Got to add 15's to the saying. "Steers,Queers and 15's"

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08-08-2009, 09:56 PM

#50

FredC

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Quote:

Originally Posted by MUSSBERGER

Got to add 15's to the saying. "Steers,Queers and 15's"

LMAO!!!!! Now that's real funny!

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08-08-2009, 10:04 PM

#51

Gary R.

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Gotta get a set of 15's to try, 245's and 225's... maybe move that back sway to the last hole. Imaging actually USING 5th gear?

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08-09-2009, 12:08 PM

#52

bauerjab

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You can take a lot of the guesswork out of the effect of moving to different sized wheels by doing a little math. Provided you know your gear ratios, differential ratio, tire diameter, rev limit, and exit speeds of each corner of the track, you can chart what will happen. See, e.g, http://www.fatboyraceworks.com/gears/

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08-09-2009, 12:16 PM

#53

Gary R.

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Anyone know stock SC gear ratios and final drive ratio?

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08-09-2009, 12:26 PM

#54

DanR

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Quote:

Originally Posted by Gary R.

Anyone know stock SC gear ratios and final drive ratio?

what do you need to know stock for? I did not think you D boys ran 'cough' stock anymore

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08-09-2009, 12:29 PM

#55

Gary R.

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Quote:

Originally Posted by DanR

what do you need to know stock for? I did not think you D boys ran 'cough' stock anymore

Ouch! Well, mine are stock but now you let the cat out of the bag for Sean and Fred! To think he mentored you too!

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08-10-2009, 08:54 AM

#56

Bill Verburg

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Quote:

Originally Posted by Gary R.

Anyone know stock SC gear ratios and final drive ratio?

different tires and rev limit will of course result in different speeds

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08-10-2009, 09:18 AM

#57

FredC

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Quote:

Originally Posted by Gary R.

Ouch! Well, mine are stock but now you let the cat out of the bag for Sean and Fred! To think he mentored you too!

here we go again...

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08-10-2009, 11:11 AM

#58

Gary R.

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Quote:

Originally Posted by FredC

here we go again...

Yep, I couldn't afford the "CT Stock" 915, spent all my money on a "CT Stock" 3.0!

Bill - thanks for the chart, i'll plug the numbers into the spreadsheet mentioned earlier and see the difference between 15's and 18's..

Transmission One -
Tire Size - 275/35/15 with 23" rolling diameter
Redline - 7000
Gear + Max MPH
1st Gear 38.86 MPH
2nd Gear 67.46 MPH
3rd Gear 98.06 MPH
4th Gear 123.66 MPH
5th Gear 150.62 MPH

Transmission Two
Tire Size - 275/35/18 with 25.5" rolling diameter
Redline - 7000
Gear + Max MPH
1st Gear 43.09 MPH
2nd Gear 74.79 MPH
3rd Gear 108.72 MPH
4th Gear 137.1 MPH
5th Gear 166.99 MPH

Last edited by Gary R.; 08-10-2009 at 02:49 PM.

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08-10-2009, 02:11 PM

#59

Chris M.

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Quote:

Originally Posted by Gary R.

Yep, I couldn't afford the "CT Stock" 915, spent all my money on a "CT Stock" 3.0!

Bill - thanks for the chart, i'll plug the numbers into the spreadsheet mentioned earlier and see the difference between 15's and 18's..

Transmission One -
Tire Size - 275/35/15 with 23" rolling diameter
Redline - 7000
Gear + Max MPH
1st Gear 38.86 MPH
2nd Gear 67.46 MPH
3rd Gear 98.06 MPH
4th Gear 123.66 MPH
5th Gear 150.62 MPH

Transmission Two
Tire Size - 275/35/15 with 25.5" rolling diameter
Redline - 7000
Gear + Max MPH
1st Gear 43.09 MPH
2nd Gear 74.79 MPH
3rd Gear 108.72 MPH
4th Gear 137.1 MPH
5th Gear 166.99 MPH

Did you mean to put "275/35/18 with 25.5" rolling diameter" under transmission two?

Quote:

Originally Posted by Gary R.

Gotta get a set of 15's to try, 245's and 225's... maybe move that back sway to the last hole. Imaging actually USING 5th gear?

245s on the rear will only be slightly shorter than the tires you're already running because they only come in one size; 245/50. This won't provide much of a change in gearing. You need to put the 225/45 or the 275/35 to get a significant change in height. The 225 is easy on an 8" Fuch but a 15x9 is rare...except in Texas!

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08-10-2009, 02:24 PM

#60

M_Weining

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Bill,

Nice template. Do you have this posted on one of your web pages? If so, where? If not, could you send to me at "kmweining at msn dot com"?

Mark

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