[Healeys] Speed to RPM ratio?

[Bob Haskell]

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
>>>
>
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