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1966 Oldsmobile 98 J78-14 tires?


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Good day fellow Oldsmobile collectors,


Reaching out to learn of availability of a correct, whitewall, J78-14 tire for my 1966 Oldsmobile 98.

The original tires are no longer safe, yes they are the originals with under 10,000 miles and I would like to change them for safety reasons.


I recall, back in the day, that the J78-14 was unique to Oldsmobile and Buick and not a common size - when compared to the H or L size tires.

Can anyone point me in a direction?    I would prefer to buy new wheels and leave my original tires on the original rims for HPOF reasons.

Has anyone gone to a 15" rim to allow a better size selection for daily use?     Seems 225/75/15 is available but seems small for a 98.


Thank you and let the banter begin!  :)


All the best,


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J78-14s have an 8.80" section width and a 28.20" outside diameter. 225/75-15s are nearly identical at 8.86" section width and 28.29" outside diameter. There are plenty of 15x6 and 15x7 steel wheels with your 5 x 5" bolt pattern. One easy option is the wheels used on the 1971-76 GM full size cars. Also the 1977-1990 B-body wagons. Obviously your stock wheel covers won't fit.

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Throw away your old J78-14 tires.  They are not factory originals but a replacement set.  Your correct size is 8.55x14 bias ply.  For judging, even though they are bias ply, they are the wrong size and would warrant the same deduction as a radial replacement.


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