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--></style></head><body lang=3DEN-US link=3Dblue vlink=3D"#954F72" style=3D=
'word-wrap:break-word'><div class=3DWordSection1><p class=3DMsoNormal>The T=
ach is an accurate way to determine vehicle speed and can be more accurate =
than the speedometer but you need to know these variables:</p><p class=3DMs=
oNormal><o:p> </o:p></p><p class=3DMsoNormal>Tires =E2=80=93 either Re=
vs per Mile or loaded radius (this is different than the nominal diameter a=
nd usually available on the tire manufacturers website)</p><p class=3DMsoNo=
rmal>Rear End Ratio =E2=80=93 for a Healey there are limited options usuall=
y 43/11 =3D 3.91, 41/10 =3D 4.10 or 39/11 =3D 3.55</p><p class=3DMsoNormal>=
<o:p> </o:p></p><p class=3DMsoNormal>If you do the check while driving=
in 4<sup>th</sup> without the overdrive engaged the math is easier. One co=
mplication is the tire manufactures do not report Revs per Mile consistentl=
y and sometimes a conversion is required. Assuming =C2=A0Vredestein Sprint =
Classic=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 165HR15 and 4.10 rear end ratio this =
table will work:</p><p class=3DMsoNormal><o:p> </o:p></p><div><table c=
lass=3DMsoNormalTable border=3D0 cellspacing=3D0 cellpadding=3D0 width=3D20=
4 style=3D'width:153.0pt;border-collapse:collapse'><tr style=3D'height:12.7=
5pt'><td width=3D91 nowrap valign=3Dbottom style=3D'width:68.0pt;padding:.7=
5pt .75pt 0in .75pt;height:12.75pt'><p class=3DMsoNormal align=3Dcenter sty=
le=3D'text-align:center'><span style=3D'font-size:10.0pt;font-family:"Arial=
",sans-serif'>MPH <o:p></o:p></span></p></td><td width=3D113 nowrap valign=
=3Dbottom style=3D'width:85.0pt;padding:.75pt .75pt 0in .75pt;height:12.75p=
t'><p class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><span st=
yle=3D'font-size:10.0pt;font-family:"Arial",sans-serif'>=C2=A0RPM <o:p></o:=
p></span></p></td></tr><tr style=3D'height:12.75pt'><td nowrap valign=3Dbot=
tom style=3D'padding:.75pt .75pt 0in .75pt;height:12.75pt'><p class=3DMsoNo=
rmal align=3Dcenter style=3D'text-align:center'><span style=3D'font-size:10=
.0pt;font-family:"Arial",sans-serif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A030 <o:p></o:p><=
/span></p></td><td nowrap valign=3Dbottom style=3D'padding:.75pt .75pt 0in =
.75pt;height:12.75pt'><p class=3DMsoNormal align=3Dcenter style=3D'text-ali=
gn:center'><span style=3D'font-size:10.0pt;font-family:"Arial",sans-serif'>=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A01,670 <o:p></o:p></span></p></td></tr><tr =
style=3D'height:12.75pt'><td nowrap valign=3Dbottom style=3D'padding:.75pt =
.75pt 0in .75pt;height:12.75pt'><p class=3DMsoNormal align=3Dcenter style=
=3D'text-align:center'><span style=3D'font-size:10.0pt;font-family:"Arial",=
sans-serif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A040 <o:p></o:p></span></p></td><td nowrap v=
align=3Dbottom style=3D'padding:.75pt .75pt 0in .75pt;height:12.75pt'><p cl=
ass=3DMsoNormal align=3Dcenter style=3D'text-align:center'><span style=3D'f=
ont-size:10.0pt;font-family:"Arial",sans-serif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A02,230 <o:p></o:p></span></p></td></tr><tr style=3D'height:12.75pt'><t=
d nowrap valign=3Dbottom style=3D'padding:.75pt .75pt 0in .75pt;height:12.7=
5pt'><p class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><span =
style=3D'font-size:10.0pt;font-family:"Arial",sans-serif'>=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A050 <o:p></o:p></span></p></td><td nowrap valign=3Dbottom style=3D'pad=
ding:.75pt .75pt 0in .75pt;height:12.75pt'><p class=3DMsoNormal align=3Dcen=
ter style=3D'text-align:center'><span style=3D'font-size:10.0pt;font-family=
:"Arial",sans-serif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A02,790 <o:p></o:p></sp=
an></p></td></tr><tr style=3D'height:12.75pt'><td nowrap valign=3Dbottom st=
yle=3D'padding:.75pt .75pt 0in .75pt;height:12.75pt'><p class=3DMsoNormal a=
lign=3Dcenter style=3D'text-align:center'><span style=3D'font-size:10.0pt;f=
ont-family:"Arial",sans-serif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A060 <o:p></o:p></span>=
</p></td><td nowrap valign=3Dbottom style=3D'padding:.75pt .75pt 0in .75pt;=
height:12.75pt'><p class=3DMsoNormal align=3Dcenter style=3D'text-align:cen=
ter'><span style=3D'font-size:10.0pt;font-family:"Arial",sans-serif'>=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A03,350 <o:p></o:p></span></p></td></tr><tr style=
=3D'height:12.75pt'><td nowrap valign=3Dbottom style=3D'padding:.75pt .75pt=
0in .75pt;height:12.75pt'><p class=3DMsoNormal align=3Dcenter style=3D'tex=
t-align:center'><span style=3D'font-size:10.0pt;font-family:"Arial",sans-se=
rif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A070 <o:p></o:p></span></p></td><td nowrap valign=
=3Dbottom style=3D'padding:.75pt .75pt 0in .75pt;height:12.75pt'><p class=
=3DMsoNormal align=3Dcenter style=3D'text-align:center'><span style=3D'font=
-size:10.0pt;font-family:"Arial",sans-serif'>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A03,910 <o:p></o:p></span></p></td></tr></table></div><p class=3DMsoNormal=
><o:p> </o:p></p><p class=3DMsoNormal>if it would help anyone send me =
your tire make and size and rear end ratio and I will sent a chart like the=
above.</p><p class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>H=
arold<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p><div style=3D=
'mso-element:para-border-div;border:none;border-top:solid #E1E1E1 1.0pt;pad=
ding:3.0pt 0in 0in 0in'><p class=3DMsoNormal style=3D'border:none;padding:0=
in'><b>From: </b><a href=3D"mailto:banjojohn@cox.net";>banjojohn</a><br><b>S=
ent: </b>Sunday, June 13, 2021 3:51 PM<br><b>To: </b><a href=3D"mailto:ryan=
@jimryan.com">Jim Ryan</a>; <a href=3D"mailto:eyera3000@gmail.com";>i erbs</=
a><br><b>Cc: </b><a href=3D"mailto:healeys@autox.team.net";>Ahealey help</a>=
<br><b>Subject: </b>Re: [Healeys] Speed to RPM ratio?</p></div><p class=3DM=
soNormal><o:p> </o:p></p><div><p class=3DMsoNormal>Jim, you are right.=
I have used GPS and my speedo is not accurate, but close enough for =
me. My point was that the speedo is mechanically linked, from the tra=
nny, to the engine, and my tach gets its signal from the coil, which also i=
s directly linked to engine speed through the distributor. <o:p>=
</o:p></p></div><div><p class=3DMsoNormal>Regardless of my actual speed, my=
speedo and tach should maintain a direct relationship in any given gear.<o=
:p></o:p></p></div><div><p class=3DMsoNormal>Thanks again for all the opini=
ons and various charts and facts provided by the list members.<o:p></o:p></=
p></div><div><p class=3DMsoNormal><o:p> </o:p></p></div><div><p class=
=3DMsoNormal>John<o:p></o:p></p></div><div><p class=3DMsoNormal><o:p> =
</o:p></p></div><div><p class=3DMsoNormal><o:p> </o:p></p></div><div i=
d=3D"composer_signature"><div><p class=3DMsoNormal><span style=3D'font-size=
:9.5pt;color:#575757'>Sent from my T-Mobile 4G LTE Device<o:p></o:p></span>=
</p></div></div><div><p class=3DMsoNormal><o:p> </o:p></p></div><div><=
p class=3DMsoNormal><o:p> </o:p></p></div><div><p class=3DMsoNormal><s=
pan style=3D'color:black'>-------- Original message --------<o:p></o:p></sp=
an></p></div><div><p class=3DMsoNormal><span style=3D'color:black'>From: Ji=
m Ryan <ryan@jimryan.com> <o:p></o:p></span></p></div><div><p class=
=3DMsoNormal><span style=3D'color:black'>Date: 6/13/21 4:17 PM (GMT-06:00) =
<o:p></o:p></span></p></div><div><p class=3DMsoNormal><span style=3D'color:=
black'>To: i erbs <eyera3000@gmail.com> <o:p></o:p></span></p></div><=
div><p class=3DMsoNormal><span style=3D'color:black'>Cc: banjojohn <banj=
ojohn@cox.net>, Ahealey help <healeys@autox.team.net> <o:p></o:p><=
/span></p></div><div><p class=3DMsoNormal><span style=3D'color:black'>Subje=
ct: Re: [Healeys] Speed to RPM ratio? <o:p></o:p></span></p></div><div><p c=
lass=3DMsoNormal><span style=3D'color:black'><o:p> </o:p></span></p></=
div><div><p class=3DMsoNormal>Am I missing something? I just check ac=
curacy with the GPS on my phone.<o:p></o:p></p></div><p class=3DMsoNormal><=
o:p> </o:p></p><div><div><p class=3DMsoNormal>On Sun, Jun 13, 2021, 3:=
25 PM i erbs via Healeys <<a href=3D"mailto:healeys@autox.team.net";>heal=
eys@autox.team.net</a>> wrote:<o:p></o:p></p></div><blockquote style=3D'=
border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margi=
n-left:4.8pt;margin-right:0in'><div><p class=3DMsoNormal>My tach is driven =
by my distributor gear<o:p></o:p></p><div><p class=3DMsoNormal style=3D'mar=
gin-bottom:12.0pt'>Speedo comes off my transmission. Not sure about t=
he relationship to accuracy. <o:p></o:p></p><div><p class=3DMsoNormal>=
Ira Erbs<br>1959 AH 100-6<br>1967 MGB<br>Milwaukie, OR<o:p></o:p></p></div>=
</div></div><p class=3DMsoNormal><o:p> </o:p></p><div><div><p class=3D=
MsoNormal>On Sun, Jun 13, 2021, 11:50 AM banjojohn <<a href=3D"mailto:ba=
njojohn@cox.net">banjojohn@cox.net</a>> wrote:<o:p></o:p></p></div><bloc=
kquote style=3D'border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in=
0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=3DMsoNorm=
al>Thanks.<o:p></o:p></p></div><div><p class=3DMsoNormal>I am actually just=
comparing the tach with the speedometer indicated speed, which, I believe =
reads a little high due to tire size. But the relationship between th=
e indicated speed and the tach should be consistant since they are both dri=
ven by actual engine or output shaft speed.<o:p></o:p></p></div><div><p cla=
ss=3DMsoNormal><o:p> </o:p></p></div><div><p class=3DMsoNormal>John<o:=
p></o:p></p></div><div><p class=3DMsoNormal><o:p> </o:p></p></div><div=
><p class=3DMsoNormal><o:p> </o:p></p></div><div id=3D"m_-861204074283=
8000386m_-7997059852725315655composer_signature"><div><p class=3DMsoNormal>=
<span style=3D'font-size:9.5pt;color:#575757'>Sent from my T-Mobile 4G LTE =
Device<o:p></o:p></span></p></div></div><div><p class=3DMsoNormal><o:p>&nbs=
p;</o:p></p></div><div><p class=3DMsoNormal><o:p> </o:p></p></div><div=
><p class=3DMsoNormal><span style=3D'color:black'>-------- Original message=
--------<o:p></o:p></span></p></div><div><p class=3DMsoNormal><span style=
=3D'color:black'>From: Bob Spidell via Healeys <<a href=3D"mailto:healey=
s@autox.team.net">healeys@autox.team.net</a>> <o:p></o:p></span></p></di=
v><div><p class=3DMsoNormal><span style=3D'color:black'>Date: 6/12/21 12:25=
PM (GMT-06:00) <o:p></o:p></span></p></div><div><p class=3DMsoNormal><span=
style=3D'color:black'>To: Bob Haskell <<a href=3D"mailto:rchaskell@eart=
hlink.net">rchaskell@earthlink.net</a>>, <a href=3D"mailto:healeys@autox=
.team.net">healeys@autox.team.net</a> <o:p></o:p></span></p></div><div><p c=
lass=3DMsoNormal><span style=3D'color:black'>Subject: Re: [Healeys] Speed t=
o RPM ratio? <o:p></o:p></span></p></div><div><p class=3DMsoNormal><span st=
yle=3D'color:black'><o:p> </o:p></span></p></div><p class=3DMsoNormal =
style=3D'margin-bottom:12.0pt'>That's it!<br><br>On 6/11/2021 4:31 PM, Bob =
Haskell wrote:<br>> <a href=3D"http://longstonetyres.co.uk";>http://longs=
tonetyres.co.uk</a><br>><br>> Cheers,<br>><br>> Bob Haskell<br>=
> Austin Healey 3000 BN7/BT7 registrar<br>><br>> On 6/11/21 7:01 P=
M, Bob Spidell wrote:<br>>> Note there is a not insignificant differe=
nce in diameters of tires <br>>> with the same nominal size (e.g. '16=
5/80-15'). The English tire <br>>> site--can't think of the name offh=
and--has (had?) a table comparing <br>>> the diameters of different b=
rands/models of the same size tires, and <br>>> IIRC they could diffe=
r by as much as half an inch. I'd say to measure <br>>> the actual di=
ameter of your tires, but it's kinda hard when moving; <br>>> the 'fl=
at spot' goes away--partially, at least--and the tires 'grow' <br>>> =
some from centrifugal force (anyone seen film of top fuel dragsters <br>>=
;> launching; the rear tires must expand a few inches or more?).<br>>=
><br>>><br>>> On 6/11/2021 3:36 PM, John OBrien wrote:<br>&g=
t;>> Thanks to all who replied. These will give me something to=
work with.<br>>>><br>>>> John<br>>>><br>>>=
;> On 6/11/2021 4:26 PM, John OBrien wrote:<br>>>>> Hi Guys =
and Gals<br>>>>><br>>>>> I am trying to calibrate m=
y tach. I installed a Spiyda RVI - RVC <br>>>>> conversio=
n board, because my tach was acting wierd. Anyway, I am <br>>>>>=
; still trying to get this setup to read correctly. My question is, <=
br>>>>> on my BJ8 with standard 3.9:1 diff. what should my RPMs=
be in <br>>>>> fourth gear going 50 MPH , without overdrive en=
gaged. I'm running <br>>>>> 165/80R15 tires. I'm just loo=
king for a reference point to compare <br>>>>> what should be, =
and what I am reading.<br>>>>><br>>>>> Any help is =
appreciated.<br>>>>><br>>>>> Thanks<br>>>>=
><br>>>>> John<br>>>>><br>>><br><br>______=
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