Date: Sun, 3 Jul 2016 22:08:08 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Speedometer is off
In-Reply-To: <CAEwp_cRnwHEnf10oXGTj=DxzbkY39e49i1BpeqTtsoKYe9oGgA@mail.gmail.com>
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The 195/75-14 tire is not a larger diameter than the 185/80-14, it may actually be smaller. Do your really have 195/75 or 195/80's.
The 87's were still notorious for speedometers/odometers be overly optimistic. Usually over reading by almost 4%. The number at the bottom indicates the revolutions per mile. Compare that with the listed revolutions per mile listed for the tire you are using. A typical 185/80-14 (~25.5") is around 830 RPM. Your speedometer is probably 805. If you speedometer is really under reading the needle is probably sticking and needs lubrication of repair or the rotor is moving far enough away from the stator that the magnetic drive is not working as it should.
On either of those tires with stock gearing 3,800 engine rpm is about 68 mph.
As for the phone apps there are those that use GPS and those that triangulate off of the cell towers. The GPS tend be dead on except for the reaction time.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Marc Perdue
Sent: Sunday, July 3, 2016 3:35 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Speedometer is off
Hi all,
I have an '87 Westy, auto, with Yokohama LT 195/75R-14 Y356 D tires.
Being as they are bigger than the 185s, I always figured that the speedometer was a few mph off. When I picked up my van yesterday, something felt very wrong to me. I felt like I was pushing the van really hard to get up to Interstate speed, 70 mph, and I was passing a lot of people at 63-65 mph.
Today, I had my wife download a speedometer app to her phone and we checked our actual speed against what my speedometer was reading. We found it was off by 5 mph at lower speeds and off by 7 mph at higher speeds.
So, I assume that I have three options here:
1) Adjust my speed according to what I know the discrepancy to be;
2) Change the gearing so that my speedometer is accurate once again?;
3) Change the size of my tires.
Since I just bought 2 new tires, that last option is not one that I'm going to pursue any time in the near future, but may consider when the time comes to replace tires.
In any event, I thought this information might be useful to anybody who's running this size tires on their vans.
Drive safe, y'all!
Marc Perdue
PS--This was a real eye-opener for me when I considered the time or two when I actually thought I got up to 85-90 . . . =8^O
