How fast?

[Mars]

I have a 1930 Desoto 4dr sedan, straight 8. Runs great,good brakes. I usually cruise at about 35-40 mph. Feels and sounds like about as fast as I want to take it. But didn't they go much faster when they were newer? Would I be pushing my luck pushing the throttle ? The rear gear doesn't help either. Also the ocasssional front end shimmy. Just wondering .

[Vintageben]

Well I'm a little surprised that nobody has replied to this already so I will give my humble opinion although I have no experience with Desoto I do have a 1929 Chrysler 65 sedan. Now I would have thought your vehicle should do much better then 35-40 mph but maybe the diff ratio is a bit low and if you're getting a front end shimmy I would pay some attention to the front end before trying to go faster also check what revs your engine is doing at different speeds. Another thing is is it a restored car or a original old girl my Chrysler would do 45mph comfortably with a very tired engine and felt stable on the road. So I would take some check things over before trying to go faster any way hopefully someone with some Desoto experience will chime in 

[Mars]

Thanks for the reply. I am surprised more folks havnt chimed in. To the best of my knowledge its original. The rear gear makes a big difference I think. What part of the front end should I pay most attention to? It passed state inspection. It will go faster, but I don't know how far to test this 88 yr old girl.

[keiser31]

My 1931 DB DH6 will do a smooth 45mph and once in a while I will take it to 50mph. I will NOT do freeways with it ever again. I did that once and a semi almost blew me into a ditch. My '31 had a shimmy and "death wobble" so I took it around the corner to the alignment guy. He found two wedges at each spring to front axle mounting area and there was one broken on each side. He took the broken ones out and realigned the car and all is well....no more wobble.

Edited February 26, 2018 by keiser31 (see edit history)

[ply33]

The legal maximum speed in California from 1931 to 1941 was 45 MPH. I'd expect that a mid-market or upper middle market car like a 1930 DeSoto that was only a year or so old when the 45 MPH limit started in 1931 would have been able to do the speed limit.

 

A number of years ago, I followed a friend to a car meet. He drove his stock (older restoration) '31 Plymouth PA down US 101 from the SF Bay area to Santa Maria a distance of about 200 miles. I was pretty surprised that he kept a pretty constant speed of between 50 and 55 MPH. Seems that if a lowly Plymouth in good condition can do that a bit more upscale Dodge or DeSoto should be able to do it too.

[Mars]

I guess I just need to get use to the "mechanical "sounds. As opposed to today's quietness.

[Guest]

My 1930 Pontiac can run all day on the interstates as long as I keep to the truck lanes.  55 is no trouble and I have no problem with 60 or even 65 to pass.

Will run at these speeds with hands off the wheel since I did an alignment.

Edited February 27, 2018 by Guest (see edit history)

[Bloo]

2 minutes ago, Tinindian said:

My 1930 Pontiac can run all day on the interstates as long as I keep to the truck lanes.  55 is no trouble and I have no problem with 60 or even 65 to pass.

Will run at these speeds with hands off the wheel since I did an alignment.

 

What is your gear ratio and tire size?

[Guest]

41-9 -- 4.55-1  The largest circumference 550/19 tires I could find.  Approx 2900 revs at 60 mph.  According to the optimum piston feet per second travel (1200) optimum speed for the engine is 40 mph.  400,000 miles (3 engine overhauls and 3 C&Ps) since becoming my daily driver in 1959.  99,000 miles when my Grandfather gave me the car.  Going from 475/500/19 tires made quite a difference.

Edited February 27, 2018 by Guest (see edit history)

[Mars]

Tire size-4.50x19.   Rear gear is 4.6 or 4.9 I believe .

[Mars]

So, am I about right with the 40 mph speed?

[Guest]

That is what is called the optimal piston travel in feet per second.  It is/was considered the most efficient speed of the engine in order to get the best performance/life/economy out of the engine.  A Desoto is a higher priced/quality car than a Pontiac.  More like an Oldsmobile.  I would see no reason not to drive your Desoto at closer to 50mph and if it were my car with that ratio I would consider up to 55 to pass.

When I was buying tires I found that there was a much as 1 1/2 inch difference in the loaded height of tires of the same size.  So there is the possibility of getting 3 1/2" to 3 1/4" more distance with every revolution.

Having your brakes and alignment is important if you want to run with the big trucks on the interstate.  I always favoured the main highways over the back roads if I was going a long distance (350-450 miles per day) because of the fewer stops and starts.  Each person should drive and enjoy their car their own way.  If you get half as much enjoyment out of your car as I have out of mine you will have a great time.

Happy hobbying.

[hchris]

All things being equal, with due attention to details already mentioned, my own experience with a CF8 is that 50mph is quite comfortable on the open road.

 

 

As to front end shimmy, almost invariably it's the wedges under the front springs that set the castor which are the main culprits, ever had a shopping trolley go rogue on you? ?