Tire size change.8R19.5's to 225/70R19.5
I just purchased new tires for my 1984 29' Brougham. with the advice of the tire salesman I bought the B F Goodrich 225/70r19.5's to replace my old 8R19.5's. He said that a lot of people were conver...
Forum Discussion
If anyone wonders why I bother posting, this thread is a good example. No one has given a correct or complete answer.
An 8-19.5 is 8.0" wide on a 6.00" rim, with an allowable rim width range of 5.25 to 6.75, an overall diameter of 33.8", a minimal dual spacing of 9.1", and a load carrying capacity of 3195# at 95 psi (Load Range E).
A 225/70R19.5 is 8.9" wide on a 6.75" rim, with an allowable rim width range of 6 to 6.75, an overall diameter of 31.9", a minimal dual spacing of 10.0", and a load carrying capacity 3195# at 80 psi (Load Range E)
So not only are the tires 2" different in diameter, they are also different widths and don't completely share the rim width compatibility.
Summarizing:
If the rims you have a 5.25", then you can not change from an 8-19.5 to a 225/70R19.5.
If there isn't 3/4" clearance around the 8-19.5 in all positions (Including the front suspension completely collapsed AND the steering wheel fully turned), then a 225/70R19.5 is likely to rub. Very bad.
Note: Collapsing the suspension to verify clearances is very difficult to do. It can be estimated by someone with experience - and if you don't have that level of experience, seek help.
For those who are interested, the width difference when mounted on the same rim width is 0.6".
So if there is only 0.6" between the duals, then you CAN NOT use a 225/70R19.5 in place of an 8-19.5. In the OP's case, depending on how he measured the 3/4", he might be OK.
And lastly, use the same Load Range with 15 psi less.
An 8-19.5 is 8.0" wide on a 6.00" rim, with an allowable rim width range of 5.25 to 6.75, an overall diameter of 33.8", a minimal dual spacing of 9.1", and a load carrying capacity of 3195# at 95 psi (Load Range E).
A 225/70R19.5 is 8.9" wide on a 6.75" rim, with an allowable rim width range of 6 to 6.75, an overall diameter of 31.9", a minimal dual spacing of 10.0", and a load carrying capacity 3195# at 80 psi (Load Range E)
So not only are the tires 2" different in diameter, they are also different widths and don't completely share the rim width compatibility.
Summarizing:
If the rims you have a 5.25", then you can not change from an 8-19.5 to a 225/70R19.5.
If there isn't 3/4" clearance around the 8-19.5 in all positions (Including the front suspension completely collapsed AND the steering wheel fully turned), then a 225/70R19.5 is likely to rub. Very bad.
Note: Collapsing the suspension to verify clearances is very difficult to do. It can be estimated by someone with experience - and if you don't have that level of experience, seek help.
For those who are interested, the width difference when mounted on the same rim width is 0.6".
So if there is only 0.6" between the duals, then you CAN NOT use a 225/70R19.5 in place of an 8-19.5. In the OP's case, depending on how he measured the 3/4", he might be OK.
And lastly, use the same Load Range with 15 psi less.
