[Healeys] Speed to RPM ratio?

[Jim Ryan]

Am I missing something?  I just check accuracy with the GPS on my phone.

On Sun, Jun 13, 2021, 3:25 PM i erbs via Healeys <healeys at autox.team.net>
wrote:

> My tach is driven by my distributor gear
> Speedo comes off my transmission.  Not sure about the relationship to
> accuracy.
>
> Ira Erbs
> 1959 AH 100-6
> 1967 MGB
> Milwaukie, OR
>
> On Sun, Jun 13, 2021, 11:50 AM banjojohn <banjojohn at cox.net> wrote:
>
>> Thanks.
>> 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 the indicated speed and the tach should be consistant
>> since they are both driven by actual engine or output shaft speed.
>>
>> John
>>
>>
>> Sent from my T-Mobile 4G LTE Device
>>
>>
>> -------- Original message --------
>> From: Bob Spidell via Healeys <healeys at autox.team.net>
>> Date: 6/12/21 12:25 PM (GMT-06:00)
>> To: Bob Haskell <rchaskell at earthlink.net>, healeys at autox.team.net
>> Subject: Re: [Healeys] Speed to RPM ratio?
>>
>> That's it!
>>
>> On 6/11/2021 4:31 PM, Bob Haskell wrote:
>> > http://longstonetyres.co.uk
>> >
>> > Cheers,
>> >
>> > Bob Haskell
>> > Austin Healey 3000 BN7/BT7 registrar
>> >
>> > On 6/11/21 7:01 PM, Bob Spidell wrote:
>> >> Note there is a not insignificant difference in diameters of tires
>> >> with the same nominal size (e.g. '165/80-15'). The English tire
>> >> site--can't think of the name offhand--has (had?) a table comparing
>> >> the diameters of different brands/models of the same size tires, and
>> >> IIRC they could differ by as much as half an inch. I'd say to measure
>> >> the actual diameter of your tires, but it's kinda hard when moving;
>> >> the 'flat spot' goes away--partially, at least--and the tires 'grow'
>> >> some from centrifugal force (anyone seen film of top fuel dragsters
>> >> launching; the rear tires must expand a few inches or more?).
>> >>
>> >>
>> >> On 6/11/2021 3:36 PM, John OBrien wrote:
>> >>> Thanks to all who replied.  These will give me something to work with.
>> >>>
>> >>> John
>> >>>
>> >>> On 6/11/2021 4:26 PM, John OBrien wrote:
>> >>>> Hi Guys and Gals
>> >>>>
>> >>>> I am trying to calibrate my tach.  I installed a Spiyda RVI - RVC
>> >>>> conversion board, because my tach was acting wierd. Anyway, I am
>> >>>> still trying to get this setup to read correctly.  My question is,
>> >>>> on my BJ8 with standard 3.9:1 diff. what should my RPMs be in
>> >>>> fourth gear going 50 MPH , without overdrive engaged.  I'm running
>> >>>> 165/80R15 tires. I'm just looking for a reference point to compare
>> >>>> what should be, and what I am reading.
>> >>>>
>> >>>> Any help is appreciated.
>> >>>>
>> >>>> Thanks
>> >>>>
>> >>>> John
>> >>>>
>> >>
>>
>> _______________________________________________
>> Support Team.Net http://www.team.net/donate.html
>> Suggested annual donation  $12.75
>>
>> Archive: http://www.team.net/pipermail/healeys
>> http://autox.team.net/archive
>>
>> Healeys at autox.team.net
>> http://autox.team.net/mailman/listinfo/healeys
>>
>> Unsubscribe/Manage:
>> http://autox.team.net/mailman/options/healeys/banjojohn@cox.net
>>
>> _______________________________________________
>> Support Team.Net http://www.team.net/donate.html
>> Suggested annual donation  $12.75
>>
>> Archive: http://www.team.net/pipermail/healeys
>> http://autox.team.net/archive
>>
>> Healeys at autox.team.net
>> http://autox.team.net/mailman/listinfo/healeys
>>
>> Unsubscribe/Manage:
>> http://autox.team.net/mailman/options/healeys/eyera3000@gmail.com
>>
>> _______________________________________________
> Support Team.Net http://www.team.net/donate.html
> Suggested annual donation  $12.75
>
> Archive: http://www.team.net/pipermail/healeys
> http://autox.team.net/archive
>
> Healeys at autox.team.net
> http://autox.team.net/mailman/listinfo/healeys
>
> Unsubscribe/Manage:
> http://autox.team.net/mailman/options/healeys/ryan@jimryan.com
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/healeys/attachments/20210613/c05cc7ed/attachment.htm>