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Freeway cruising speed RPM

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

zwh02
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zwh02

Freeway cruising speed RPM

Post by zwh02 » Wed Dec 25, 2019 2:42 am

Just recently got a new set of tires on my 97 850 base sedan (automatic). I previously had 195/65/15 sized tires but I went with the stock size 195/60 for my new set.

Naturally, I knew I would likely see a slight increase in engine speed with the smaller ratio sized tire.

Now I am just a little under 3k rpm while cruising @ 65mph on the freeway, I find I'm anticipating it to shift into another final (higher) gear to lower the engine speed. I'm often sticking to the slow lane staying @ 60mph for the slower (quieter) engine speed. I also worry about the increased fuel consumption with the higher engine speed but this is stock configuration after all..

Is this typical gearing/rpm range for a stock tire(d) auto 850?

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callahanoffroad
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callahanoffroad

Re: Freeway cruising speed RPM

Post by callahanoffroad » Wed Dec 25, 2019 4:41 am

So I run 196/65/15's as well. The circumference difference is 3.62% which is basically nothing.

When you run the 65's if your speedo says "100 mph" you were actually doing 103.62mph.

When you run the 60's when your speedo says 100mph, you are actually doing 100mph.

So what's happening is that your speedometer is actually correct again.

As for the shifting point of an automatic that has to do with engine speed, throttle position, and some kind of unholy voodoo magic. I have a 5-speed so I'm not entirely familiar with the automatic transmission's. That being said though the car should not be driving any differently than it was on the 65's. The car never knew that you had outfitted different tires. So to the car 65mph with 65's is the same rpm and speed display with the 60's. You could track the actual vehicle speed with a gps based speedometer. But the car doesn't know and never did.

Now I'll also tell you that there is no power in these non-turbo motors under 3,000 rpms. If you're going over hills and such the car HAS to downshift and increase engine speed to keep the road speed.

Hope that answers your question.

Merry Christmas :-)
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1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

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befarrer
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befarrer

Re: Freeway cruising speed RPM

Post by befarrer » Thu Dec 26, 2019 9:24 pm

I likely have different gearing, but I'm doing 2500RPM at 65MPH, but I have a 98 V70 LPT AWD. (not XC or R)
98 V70 GLT AWD
01 Focus Wagon SOHC 5-speed
93 Mazda B2200 with 13B swap
Works on Volvo Trucks

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