Anybody ever notice how the speedometer reading increases slightly at the 
bottom of a deep bump (that is, as the wheels travel up relative to the 
vehicle body), and decreases as the suspension is unloaded (i.e., as the 
vehicle is "unweighted")?

Wave-like road surfaces where it takes a second or more to travel 
crest to crest at speeds of at least 45 mph seem to show this effect 
best.  Sometimes the speedo will waver as much as 4 - 5 mph as the 
suspension loads and unloads.  

We have a 76 westy, so maybe it's something to do with the design of the 
speedo cable etc.  Our speedo, contrary to what most other folks on the 
list have found on their own busses, is really, really close to 'actual' 
speed: I drove at exactly 60mph along 4 miles of an 'odometer test 
section' on I-5 near Mt. Vernon, WA, and was only maybe a second off of 4 
minutes.  Yippee!  

Tobin
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Tobin T. Copley                  Currently              =============  
(604) 689-2660                    Occupationally       /_| |__||__| :| putta
tobin@freenet.vancouver.bc.ca      Challenged!        O|             | putta
                                                       '-()-------()-' 
Circum-continental USA, Mexico, Canada 15,000 miles... '76 VW Camper! (Mango)