Subject: Re: [TR] RPM speed calc

From: Dave MacKay <[email-masked]>
Date: Mon, 1 Jun 2020 14:41:08 -0400

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>Date: Sun, 31 May 2020 16:52:23 -0500

>From: bill beecher <[email-masked]>

>Subject: [TR] RPM speed calc

>Came across this calculator with all the right input fields.  But, I
wonder how accurate it really is given the following input.

>TR3 with a 3.7 rear, OD at redline of 5,000rpm.  Vredestein 165R/15 tires,
25.4? diameter.   Should be moving along at 124mph!

>https://wahiduddin.net/calc/calc_speed_rpm.htm

>Anyone get a different answer?

>Bill

Here (attached) is a spreadsheet that I wrote to calculate speed versus rpm
given different parameters. I wrote it to check my speedo after I installed
an HVDA transmission. If the spreadsheet doesn=E2=80=99t make it through th=
e list
as an attachment, just e-mail me directly and I=E2=80=99ll send it to you.

With a standard Triumph gearbox + overdrive, and the parameters you gave, I
calculate speed at 5000 rpm in top gear (with overdrive) as being 124.5
mph. Note that, I think that the tire diameter is 25.25=E2=80=9D, slightly =
less
than you indicated.

I hasten to add that calculating a speed and believing it=E2=80=99s achieva=
ble are
two different things!

Regards,

Dave MacKay

1960 TR3A s/n 68639L

near Toronto, Canada

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div class=3D"WordSection1"><p class=3D"MsoPlainText">&gt;Date: Sun, 31 May =
2020 16:52:23 -0500</p><p class=3D"MsoPlainText">&gt;From: bill beecher &lt=
;<a href=3D"mailto:[email-masked]">[email-masked]</a>&gt;</p><p=
 class=3D"MsoPlainText">&gt;Subject: [TR] RPM speed calc</p><p class=3D"Mso=
PlainText">&gt;=C2=A0</p><p class=3D"MsoPlainText">&gt;Came across this cal=
culator with all the right input fields.=C2=A0 But, I wonder how accurate i=
t really is given the following input. </p><p class=3D"MsoPlainText">&gt;TR=
3 with a 3.7 rear, OD at redline of 5,000rpm.=C2=A0 Vredestein 165R/15 tire=
s, 25.4? diameter.=C2=A0=C2=A0 Should be moving along at 124mph!</p><p clas=
s=3D"MsoPlainText">&gt;=C2=A0</p><p class=3D"MsoPlainText">&gt;<a href=3D"h=
ttps://wahiduddin.net/calc/calc_speed_rpm.htm">https://wahiduddin.net/calc/=
calc_speed_rpm.htm</a></p><p class=3D"MsoPlainText">&gt;=C2=A0</p><p class=
=3D"MsoPlainText">&gt;Anyone get a different answer? </p><p class=3D"MsoPla=
inText">&gt;Bill</p><p class=3D"MsoNormal">=C2=A0</p><p class=3D"MsoNormal"=
>Here (attached) is a spreadsheet that I wrote to calculate speed versus rp=
m given different parameters. I wrote it to check my speedo after I install=
ed an HVDA transmission. If the spreadsheet doesn=E2=80=99t make it through=
 the list as an attachment, just e-mail me directly and I=E2=80=99ll send i=
t to you.</p><p class=3D"MsoNormal">=C2=A0</p><p class=3D"MsoNormal">With a=
 standard Triumph gearbox + overdrive, and the parameters you gave, I calcu=
late speed at 5000 rpm in top gear (with overdrive) as being 124.5 mph. Not=
e that, I think that the tire diameter is 25.25=E2=80=9D, slightly less tha=
n you indicated.</p><p class=3D"MsoNormal">=C2=A0</p><p class=3D"MsoNormal"=
>I hasten to add that calculating a speed and believing it=E2=80=99s achiev=
able are two different things!</p><p class=3D"MsoNormal">=C2=A0</p><p class=
=3D"MsoNormal">Regards,</p><p class=3D"MsoNormal">=C2=A0</p><p class=3D"Mso=
Normal">Dave MacKay</p><p class=3D"MsoNormal">1960 TR3A s/n 68639L</p><p cl=
ass=3D"MsoNormal">near Toronto, Canada</p></div></body></html>

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Archive: http://www.team.net/pipermail/triumphs  http://www.team.net/archive

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From: Q <[email-masked]>
Date: Mon, 1 Jun 2020 11:46:15 -0700

The factory claims 21 MPH per 1,000 RPM in 4th no OD for TR3 and TR4 
with 165 x 15 tires.

Edward Hamer

Petaluma CA

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From: Brian Kemp <[email-masked]>
Date: Mon, 1 Jun 2020 17:43:38 -0700

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Bill - Here is a 20 year old article that I wrote with all the math 
regarding TR6 tire sizes.  Note that this is an obsolete portion of the 
site that has not been cleaned out.  Most of the links are probably dead.

http://www.sctoa.org/tech.htm

Brian

On 5/31/2020 2:52 PM, bill beecher wrote:
> TR3 with a 3.7 rear, OD at redline of 5,000rpm.  Vredestein 165R/15 
> tires, 25.4” diameter.   Should be moving along at 124mph!
>
> Serenity Now......
> Donate: http://www.team.net/donate.html
> Unsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/[email-masked]

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    Bill - Here is a 20 year old article that I wrote with all the math
    regarding TR6 tire sizes.  Note that this is an obsolete portion of
    the site that has not been cleaned out.  Most of the links are
    probably dead.<br>
    <br>
    <a class="moz-txt-link-freetext" href="http://www.sctoa.org/tech.htm">http://www.sctoa.org/tech.htm</a><br>
    <br>
    Brian<br>
    <br>
    <div class="moz-cite-prefix">On 5/31/2020 2:52 PM, bill beecher
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:[email-masked]">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      Came across this calculator with all the right input fields.  But,
      I wonder how accurate it really is given the following input. <br>
      <div dir="ltr">
        <div>TR3 with a 3.7 rear, OD at redline of 5,000rpm.  Vredestein
          165R/15 tires, 25.4” diameter.   Should be moving along at
          124mph!</div>
        <div><br>
        </div>
        <div><a href="https://wahiduddin.net/calc/calc_speed_rpm.htm"
            moz-do-not-send="true">https://wahiduddin.net/calc/calc_speed_rpm.htm</a>
          <div><br>
          </div>
          <div>Anyone get a different answer? </div>
          <div>Bill<br>
            <div dir="ltr">Serenity Now......</div>
          </div>
        </div>
      </div>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <pre class="moz-quote-pre" wrap="">** <a class="moz-txt-link-abbreviated" href="mailto:[email-masked]">[email-masked]</a> **

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</pre>
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From: Q <[email-masked]>
Date: Tue, 2 Jun 2020 12:27:03 -0700

All the TR series came with 3.89 ratio rear axles as stock. If you 
ordered the optional OD you could then order a optional 4.10 rear axle.  
The 4.10 axle was not available without overdrive.  Not a popular option 
for the street, it really is only good for racing.

Edward Hamer

Petaluma CA

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