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Installed the 700R16AD Auburn Deluxe Radials last year on my 37 120C, they are a tight fit on the front and had to do a slight adjustment on both front fenders, the Radials made a big differance as the car really handles so much better compared to the Bias Ply tires.

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Everyone happy with the Diamondback Auburn radial tires? It seems like the other classic tires are made by Coker. Are the Diamondbacks a better tire than Coker? Being this '40 is destined to operate in some road rally events like Great Race, it might be driven a little harder than most 40 Packard out there. Would you say the DB Auburn 700-16 are a good choice or should I look for something different? Perhaps a light truck tire?
Joe, is your only preference with the 700-16 because it fits the side mount covers better than the 750-16? Or do you find a drivability difference?
(I still haven't decided whether I will be using the dual side mount or smooth fenders. Chances are both sets will be painted.)


thanks,
Mark

You do realize that different springs were used if side mounts were originally fitted, yes?

Mark, take Joe Santana's and Chuck's advice, go with Diamond Back bias-sized radials. You want a runner, but you'll never be happy with the "off" look of a 215/225 SUV radial. They won't look kosher in the fenders' opening. If you want an understated, elegant, international look, get Diamond Back Auburns in black wall. Your car will be, after all, a serious road car, not another local car show/cars'n' coffee tart.

The identical spec Michelin/Bridgestone/Yokohama LT 7.00 x 15 bias-sized radials used by many 1941-47 Buick Century/Roadmaster, Cad Series 61/61/60S, Chrysler New Yorker/Saratoga, Hudson Commodore Eight, Packard '41 and 1942-47 160/180/Super/Custom Super Clipper 2003/2006/2103/2106, call for pressure 8-10 lbs. over bias ply's 32 psi max cold.

Radials' sidewalls have more give than bias ply, so probably not much harder on your suspension components, but have yet to read any serious tech study or SAE-worthy reports on this.

Diamond Back was until recently vulcanizing a wide whitewall on the above Yokohama 7.00 x15, 7.50 x 16 LTs. Since Yokohama has joined Michelin and Bridgestone in no longer offering these LT (light truck) bias-sized 7.00 x 15 radials, Diamond Back has been crafting, or having someone craft for them, bias-sized 7.00 x 15 radials under their Auburn line.
We don't know if these are automotive or LT tires, but if the former, would like to know what pressure Diamond Back themselves are recommending.

It used to be said that radials, or at least belted radials, gave a harsher ride than bias tires. But many people are reporting better ride and handling with bias-look radials on older cars not originally designed for them. I would try to keep tire pressure at or below 30 PSI on 1930s thru mid 1950s cars. It is not necessary nor is it a good idea to run tires on passenger cars at the maximum pressure rating on the sidewall.
On the other hand, Packard recommended tire pressures as low as 22 PSI on late 1930s 120 cars. I run 24 to 26 PSI cold on my '37 120 conv. coupe with Firestone bias tires. That gives good results overall, and so far, tread wear seems to be normal at 3,000 + miles. The tires run only slightly above ambient temperature at sustained speeds around 50 MPH. I don't know whether the bias-look radials are belted or not, but I'd think a belted radial tire would need about 28 PSI cold on a 3600 lb car. Excessively low pressure might cause belt separation issues.

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My 40 did originally have dual side mounts. If I decide to not use them, we'll find out how high it sits without them. Springs aren't too pleasant to change, but can be done later if needed.


thanks,
Mark

Without the dual sidemounts I expect the front springs to feel pretty harsh, in addition to sitting high. The sidemounts add quite a bit of weight.

I have the Diamond Back Auburns on my '54 (not the bias-ply look because they weren't out yet). I love them. Excellent handling, quiet, good looks (whitewalls are still nice and white after 4 years) and reliable. They aren't cheap. I haven't yet put them on my '56 because the budget is going to other needs on that car.

My dad's '38 Super has Toyo tires, with whitewalls and beauty bars. I'm pretty sure they are truck tires. They are impossible to turn when the car isn't moving, and still really hard to turn when it is moving. At some point I'll probably be switching those out to Diamond Back's also.

Clarification to mine above.

Radials do have a higher first cost, but they can be expected to out-last bias ply tires by 30% or more, and they offer better handling and lower rolling resistance, which gives better gas mileage. It's said that radial tires have about 10% less rolling resistance than similar bias tires. That could be expected to improve MPG and free up some horsepower.