Can you cruise at 80+mph in your truck?

[Larry]

Really?

Not that I doubt you've passed a diesel truck before, but that mentality is asinine. 25 details on both trucks are more important than diesel vs. gas.

Wind and speed friction will pretty much affect any truck equally and it's exponential. New trucks are better in wind tunnels etc. but higher speed in a truck pretty much equals lower MPG.

I can run my K30 at 80+ easily but it's not worth the MPG loss to me (12V Cummins and 5 speed, 4.10's and 37's). If $$$ for fuel doesn't matter to you, do what you want. If it does, do the math. You lose a LOT of efficiency at higher speeds in a full size truck.

Yes, really and that it not about gas vs. diesel. It is just an observation when passing someone in a diesel truck where so many of the owners seem to think only a diesel can push wind down the highway or rolling up Wolf Creek Pass at speed limit, etc. Figure most of the out of state diesel guys are pulling big 5th wheel trailers that do not take mountain curves very well and the drivers could be watching EGTs while they drag their house on wheels on long grades. Then there are the diesel guys like my buddy from CA where his 2005 Dodge/Cummins that is geared to the point it is only good for about 84 MPH before the governor plateaus his engine RPM/ road speed. More than once has some guy craned his neck out the window of his diesel rig at us in a 70’s truck with a popup camper as I pass them on the highway. And, I never said I was getting great fuel economy at that speed while doing so. I’m most definitely getting single digits at 85+ with the aerodynamics of a drive in movie theater screen. In fact, the K10 does best on the highway with fuel economy at 55 to 65 MPH but the sweet spot where the pedal, my ankle and my goofed up hip like to sit is right at 73 MPH. So many times I look down at we’re going 73 MPH like that is where everything is comfy. 73 is typically our Interstate rolling speed.

That said, the picture I posted of us rolling 87 MPH was the year we did Death Valley. We left home in a major snow storm where it took is 6 hours just to get from Pueblo West to Springer, NM which is only about 120 miles from home. Then from Springer to Albuquerque we were in crazy hurricane-like crosswinds but once we got West of Albuquerque the hammer was down all the way to Flagstaff as we were running late to meet up with the rest of the crew in Kingman, AZ. I didn’t feel bad about 8 MPG at 85 MPH as we got great fuel mileage at 20 MPH for 6 hours straight. But no, I don’t drive the old girl like a bat out of hell everytime it is on the Interstate but it is nice to know it will safety do it if I want or need to. [FONT=&quot]Plus when I take the K10 on long distance trips I gauge fuel economy by the total amount of fuel used and total amount of miles driven. Doing fuel economy based on tank by tank is a waste of time for what I use this thing for. The Death Valley trip came in an average of 11.72 MPG for the entire trip, which isn’t too bad for what it is. [/FONT]

 

[Blue85]

big key is QUALITY springs / shocks / steering components / alignment / and they be good to go .

The FIRST thing I think of is tires, because I've dealt with various tire issues over the years. Now back when I had 35" radials on alloy wheels I never thought much of tires except the road noise. Then I would put springs and shocks as #1 for comfort because I've never had major steering problems. But once you go to bigger tires or anything bias, their roundness and balance are the dominant factor in how fast you can cruise comfortably.

 

[black dawg]

Also thinking about tires, it is surprising how low the speed rating can be on certain tires. A tire blowout at 80+ would be ugly....especially in one of these old trucks.

 

[Larry]

Also thinking about tires, it is surprising how low the speed rating can be on certain tires. A tire blowout at 80+ would be ugly....especially in one of these old trucks.

Indeed! = in pants

 

[nvrenuf]

Reach 80, yes. Cruise at 80, nope.

 

[thatK30guy]

My K30 will reach 80 but as I get older now I get a little more nervous even driving it 55-60 because I've developed a small fear of 16.5" tires and the bead popping.

 

[Blue85]

After driving my truck to Michigan the past two years in two different configurations I will say this.

Trip number 1 was with 35's, 10 bolts, 3.73's and a 700R4. My brother and I could easily do about 80 and not worry about it. It wasn't all that bad of a drive, and I would do it again.

Trip number 2 was this year. Only difference was 37's and a 14BSF. I got beat up on this trip. I would not, and could not, go above 75 due to the feeling that the truck would explode. Now, I think this has a lot to do with the tires I have, but still, I wouldn't be comfortable going much faster than 70.

This is exactly what I'm talking about, and I also lived with OZ radial beatings for a few years. When the tire isn't round you can't have a smooth ride no matter what you do, except maybe 55MPH and below. When you run street tires (like 33" all-terrains or even 35" mud radials) you don't even think about tires being a factor.

 

[85 Burb]

When I first got my suburban even doing 55 was scary. But everything in the front end was shot (ball joints, tie rod ends, u- joints on both sides of the axle, steering gear box) it memory steered real real bad and every bump in the road was an adventure or reeling the steering wheel left and right a couple times before finding center. However with a completely rebuilt front end and new steering gear box it is pretty nice to drive on the highway. With the addition of the NV4500 im optimistic cruising 80 will be very possible.

I guess to echo the others, with quality parts, replacing what is worn out, and an overdrive, 80 should be doable.

 

[dhcomp]

Mine will cruise at 80 if its not loaded down. Its a power problem more than anything.

Got a ticket doing 80 downhill into reno this morning

Was doing 65 the whole way, and let it coast down the hill.



I'm spinning about 2500 rpm at 80, thats about as high as i like to cruise it.

Its spent time at 85 though.

So, in general, yes.

I've got old springs, but good shocks, bushings, ball joints, steering stuff.

Just wish my New steering box was tighter. I see a preload snug down session in my future on this box.


The big thing at 70+ is how straight it likes to stop. If it wants to be all over the road under hard braking, its best to keep the speeds down.

Mine is pretty squirly right now with the looser steering box, and i've been keeping it at 70 or so max a lot more recently.

 

[diesel4me]

Reach 80, yes. Cruise at 80, nope.

Ditto for my truck!...it might reach 80+,but I'd be lucky to maintain that speed for long before I'd be picking up shrapnel.....

65 mph is plenty scary enough for me,thank you...especially if you needed to stop fast,square bodies aren't noted for great rear brakes,they tend to lock up and skid easily..

 

[y5mgisi]

Personally I think the squirlly breaking issue is caused by spring wrap during breaking. If the axle rotates, it will throw off the steering geometry at the drag link. I think it normally exposes itself in the form of a right hand pull. I think a front anti wrap bar would be the ticket to stopping that. Although yes, a worn steering box isn't helping things. I REALLY want a red head steering box. But they are so expensive!

 

[ashman]

Personally I think the squirlly breaking issue is caused by spring wrap during breaking. If the axle rotates, it will throw off the steering geometry at the drag link. I think it normally exposes itself in the form of a right hand pull.

hmmm, I have that problem and I haven't been able to figure it out. Maybe you're onto something...

 

[y5mgisi]

Even in the motor trend tests of a brand new 89 blazer they talked about the "unsettling right hand dive under hard breaking. Cause if you think about it, if the pitman arm stays stationary, and the axle" wraps" under hard breaking, the steering arm would rotate closer to the pitman arm, but since it's stationary, it effectively makes the axle steer to the right.

 

[y5mgisi]

Here,

 

[6.2Blazer]

When I first got my '90 K5 it was only 4 years old with 49k on the ticker and all stock besides for 32" radial mud tires. Point being it was in the intended factory condition and not all worn out. Freeway speed limits were only 65 mph back then but I regularly drove 75+mph, including a couple of tickets in it. I also regularly drove 60-65 mph down the country roads.

 

[Aquafbody]

81 K5 with a 454 and sm465 on 31's. Spedo go up to 80 and I can peg it with petal to go.burnout

 

[yellowK20]

I can and do cruise 80-85 in all my radial tired trucks , I would never run that fast on Bias ply mud tires for long lol . As for handling if the suspension is tight and the steering is properly aligned and in good shape then its a non issue.

Overdrive, good door/window seals, and some soundproofing go along way in boosting confidence on the highway.

 

[yellowK20]

Ok so not all my trucks , my 90 hits defuel somewhere around 70mph indicated lol but its still rocking the TH400

 

[82355]

I've developed a small fear of 16.5" tires and the bead popping.

Why???

Martin

 

[82355]

I cruise my 1988 V10 Suburban down the interstate with an SM465 and 4.10 gears on 315/70R17 tires. The speed limit in Nebraska is 75. The only issue is it burns a lot of fuel at that speed. I try to keep it at 70, but I always catch myself hitting 75-80.

Martin