[Healeys] Speed to RPM ratio?

[Bob Spidell]

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
>>>>
>>