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Speedo gear 32 vs 31 tooth #2679829
07/21/19 05:35 PM
07/21/19 05:35 PM
Joined: Jan 2003
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So Near, Yet So Far
topside Online content OP
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According to Brewer's, I need a 31 tooth for 3.23s & 28" tire
According to the Interweb, a 32-tooth.

I have a mint 32, a mint 39, and a used 31 with a few teeth knocked off, of course laugh2

What's 1 tooth worth in MPH on this setup?
FWIW, I tend to drive by the tach on the highway, but around town I'd like to know my speed.

Re: Speedo gear 32 vs 31 tooth [Re: topside] #2679831
07/21/19 05:45 PM
07/21/19 05:45 PM
Joined: Jan 2003
Posts: 28,389
Hamtramck, PA
Alaskan_TA Offline
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Check your email & you will be able to compare a 31 & a 32 against your GPS soon. ;-)

Re: Speedo gear 32 vs 31 tooth [Re: Alaskan_TA] #2679833
07/21/19 05:48 PM
07/21/19 05:48 PM
Joined: Jan 2003
Posts: 14,103
So Near, Yet So Far
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Thanks, Barry, you Da Man.

GPS ?! laugh2

Re: Speedo gear 32 vs 31 tooth [Re: topside] #2679834
07/21/19 05:50 PM
07/21/19 05:50 PM
Joined: Nov 2003
Posts: 35,516
Lincoln Nebraska
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RapidRobert Offline
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Lincoln Nebraska
I'd want the mint 32 toother in there just cuz how bad the 31 toother is but it'd show the MPH a hair low than actual MPH (might cost you a ticket, might not). The archives has a chart & someone posted a link for a comprehensive chart but I dont have that info. EDIT measure your actual tire dia to get it as dead on as possible (might change what tooth count you need). MORE EDIT the chart someone posted had a MPH/RPM chart that was very helpful & there was something about an Excel worksheet. EVEN MORE EDIT the Excel worksheet in the 2 links are right there on the same page, right in front of me, I missed it.

Last edited by RapidRobert; 07/21/19 06:51 PM.

live every 24 hour block of time like it's your last day on earth
Re: Speedo gear 32 vs 31 tooth [Re: RapidRobert] #2679853
07/21/19 06:29 PM
07/21/19 06:29 PM
Joined: Jan 2003
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Yeah, I have the Brewer's chart.
Barry & I are trading my 39 for his spare 31.
Was just curious what the difference would be between 32 & 31...

Re: Speedo gear 32 vs 31 tooth [Re: topside] #2679861
07/21/19 07:00 PM
07/21/19 07:00 PM
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Posts: 3,953
Prospect, PA
BSB67 Offline
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About 1 mph at 31 - 32 mph

Re: Speedo gear 32 vs 31 tooth [Re: BSB67] #2679901
07/21/19 09:27 PM
07/21/19 09:27 PM
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So Near, Yet So Far
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Thanks.

Re: Speedo gear 32 vs 31 tooth [Re: topside] #2679974
07/22/19 03:57 AM
07/22/19 03:57 AM
Joined: Aug 2007
Posts: 5,410
Caracas, Venezuela, SouthAmeri...
NachoRT74 Offline
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There is an XLS table on tech section here where makes the exact maths. You could get maybe a 31,45 result. So you decide which one is the best for you based on that ( rounding up or not )

Re: Speedo gear 32 vs 31 tooth [Re: NachoRT74] #2679990
07/22/19 07:03 AM
07/22/19 07:03 AM
Joined: Jan 2003
Posts: 966
Richmond Twp. Mi.
Mr340 Offline
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I recently went from a 28 to a 29 and the speedo went from 4mph low to 3mph high. this was with a 2.76 and 26" tires and a 4 speed.

Re: Speedo gear 32 vs 31 tooth [Re: Mr340] #2680033
07/22/19 09:14 AM
07/22/19 09:14 AM
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Posts: 5,479
Downtown Roebuck Ont
Twostick Offline
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Originally Posted by Mr340
I recently went from a 28 to a 29 and the speedo went from 4mph low to 3mph high. this was with a 2.76 and 26" tires and a 4 speed.


Maybe go up a tire size or 2 to get it dead nuts.

Kevin

Re: Speedo gear 32 vs 31 tooth [Re: Twostick] #2680035
07/22/19 09:19 AM
07/22/19 09:19 AM
Joined: Jan 2003
Posts: 966
Richmond Twp. Mi.
Mr340 Offline
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Originally Posted by Twostick
Originally Posted by Mr340
I recently went from a 28 to a 29 and the speedo went from 4mph low to 3mph high. this was with a 2.76 and 26" tires and a 4 speed.


Maybe go up a tire size or 2 to get it dead nuts.

Kevin


I usually drive 5-7 over so the 3 hi gives me an extra cushion drive

Re: Speedo gear 32 vs 31 tooth [Re: topside] #2680039
07/22/19 09:30 AM
07/22/19 09:30 AM
Joined: Nov 2003
Posts: 5,103
Fort Worth, Texas
3hundred Online work
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IIRC, when I did the arithmetic years and years ago, each tooth was worth ~ 1.67%. Which meant you should be able to get it within 1% either way +/- if your speedo head is working correctly. FWIW, YMMV, ect. 2ยข

Roibert


'68 Fury Convertible
'69 300 Convertible
'93 Ramcharger 5.7 Hemi
'93 Ramcharger 318 sold
'01 3500 4x4 Cummins 6 speed sold
'13 300 S sold
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