Max cruising speed

[66bugguy]

I have a 66 bug, 1500 single port with stock transmission. a guy told me that if you try to go over 65 you begin to get to the point where you will overheat the engine and start melting pistons and stuff, does this sound right? The owners manual said you could cruise at 75 max, so not sure where it came from. Anyone know what a good cruising speed actually is? My bug will do 70 no problem, just not sure if its good to keep it there for long periods.

[richparker]

I cruise 70 all the time.

The hotter the ambient temperature, the hotter the engine is gonna run.
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[6T5 square]

70-no problem.
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John
65 square 1500S (weezer) sold but always on my mind
60 beetle (Ned)

Quoting John Muir -- Open the rear boot. Get out the stool and sit down. Contemplate the air-cooled beauty before you. - How to Keep Your Volkswagen Alive -- Step-By-Step Procedures for the Compleat Idiot

[Max Welton]

I think the Germans, when they wrote the owners manual, had no concept of Americans driving across the south-west for hours at a time.

Max
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[slayer61]

Doesn't max cruising speed depend on RPM? Gear ratios? Rear tire size etc. Rather than merely speed?
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[Cusser]

[runamoc]

when I had 40hp I used a brick for cruise control on the Interstates.
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[Bobs67vwagen]

Many variables to be considered here, such as temperature, engine condition and tune, and condition of all cooling related items. That being said, as Cusser pointed out you have a 66 which had a 1300 originally and a trans axle with gearing set up to to help the 1300 get the car moving easily. When the 67 came out with the 1500 they changed the transaxle to use the additional power of the new engine. I put about 125,000 miles on a 66 with stock 1300 and mostly kept the speed in the 60 to 65 range, and it took me across country 3 times. I think keeping it at 65 or so for extended periods is probably safer-just my opinion for whatever that may be worth.

[viiking]

Many, many years ago, I drove my Dad's 68 (1500 single port, unvented lid) from Sydney to Adelaide around 900 miles (before freeways) in mid summer with temperatures over 100F during the day.

We had three adults and two small children on board and a roof rack with an un-aerodynamic storage box on top. Due to a major time constraint we had to do the normal 2 day trip in one go over about 16 hours of driving.

The relatively new car (4 years old) was easily able to drive at 65mph for hours on end, occasionally reaching 75 when needing to overtake. Fortunately the terrain was very flat and the roads had little traffic.

The car was certainly heavily laden and therefore under some stress. No-one in those days ever concerned themselves that the car couldn't handle these speeds for hours on end. In fact I can vividly remember that the advertisements always said the VW had a "maximum and cruising speed" of 72 mph for the earlier 1200 and 78(?) for the 1500. None of the drivers ever considered slowing down in case the "pistons melted".

Now admittedly the car was in excellent shape, serviced by VW and all the seals etc were in place.

Now the ONLY problem we had was on one refuelling stop, when for some reason I went to check the oil as soon as I stopped and opened the engine lid. For some reason (and I don't know why now) I removed the air cleaner and woosh, the carburettor caught fire. Not a big fire, but enough to give me a fright.

Obviously the heat soak from the engine ignited the fuel left in the carburettor throat. The fire went out as quickly as it appeared. No leaks were visible, I put the air cleaner back on and we went on our merry way with no issues and no repeat. Perhaps in hindsight one should not stop the car immediately after a long drive, but allow it to idle for a while, a bit like early turbo engined cars, to allow the cooling system to reduce the temperature.

Would I drive that same way today? No. The car, regardless of how well the engine has been rebuilt etc is till over 50 years old. It cannot be as good as it was new.

However, 65mph is not an excessive speed to do for shorter freeway commutes now. I'd be more concerned that a 50 year old stub axle or steering box would fail or I get hit by a gargantuan pickup truck these days.
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1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3

[rcooled]

[mukluk]

In my opinion, the answer to maximum cruising speed is "it depends": depends on the weather, depends on the engine's state of tune, depends on the terrain, depends on how many more miles you want to go before needing to rebuild the heads or long block.

Will you melt pistons just because you cruise over 65mph? Not likely, or at least not if you aren't trying to race up a very long steep grade into a strong headwind in the middle of summer with your car that hasn't had a tuneup since before the Berlin Wall fell. In good tune and with a properly functioning cooling system, your Bug should be perfectly capable of performing just as the owner's manual states, all day long, driving conditions permitting. But do keep in mind higher speeds translate into more heat and faster wear in the long run.

Get to know how your car feels and sounds while driving. If you pay attention, it'll tell you if you're pushing things too hard and need to back off.

Of course there's also the thought that life's short, so why be in such a hurry to get to your destination? Slow down a bit and enjoy the scenery.
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1960 Ragtop w/Semaphores "Inga"

[Eric&Barb]

IOHO 3,000 RPM is best for longevity of the engine and much better MPG with only short burst above that in cases like when you are up shifting on a hill and do not want to go below 1,500 RPM in the higher gear which lugs the engine damaging bearings. Helps if one can add in a counter weighted crankshaft that will not flex as much as the stock crankshaft damaging the bearings + engine bores and a oil filter pump to protect the bearings from the normal metal flakes that occur in a internal combustion engine.

Having oil temp and oil pressure gauges are a must. 230F oil temp is generally by most the high limit, personally do not like to push it up to 220F. On rare occasion in 90+F outside temp we have slowed down about 5MPH below 3,000 RPM in third gear while climbing loooong steep hills to keep below 220F.
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[Max Welton]

[RWK]

I believe the manual says maximum AND cruising speed, especially in the older models, the cooling system works best at higher RPMs
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[Bobs67vwagen]

I think that since the manuals were written from the 50's to the 1970's, you have to consider the changes in gasoline that have occurred. Today's fuels are generally lower octane and contain other additives such as ethanol. Engineers and chemists please correct me if I am wrong, but I think this leads to a hotter running engine which spells trouble for an acvw if you are not careful.

[Eric&Barb]

[KingAir42]

I was wondering, I know they advertised the 1200's you could drive flat out all day. But what about the 13,15,and 1600s? Could you drive those flat out? Did vw advertise one was able to hammer down on the later engines? And if not, how did they let repeat customers of earlier engines know that driving WOT was not advised any longer?
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[mukluk]

@KingAir42
The maximum speed same as cruise speed thing carried on all the way through the years and engines.

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1960 Ragtop w/Semaphores "Inga"

[Eric&Barb]

[viiking]