To measure the tyres they will at least have to be mounted. Even mounted there will be great variations due to different width rims. What if all the syncro owners measure the rolling diameter of their tyres and we can make an accurate chart. To find the rolling diameter put a mark on the tyre and on the road, then drive the van for a few revolutions of the tyre and measure back to the original mark and divide by the number of revolutions. Then divide this (C) by 3.142 and you will have your loaded diameter.

Here is the data from my syncro;

BFG 215/75X15 464.7 revs per kilometre, loaded dia 685mm (27") *Michelin 205CR14 (originals) 481 rev/km, loaded dia 661mm (26")

*These are the original tyres fitted to Australian spec syncros with 14X6 wheels.

When talking of the ET of a wheel please include the width of the rim as this will change the clearance. To find the ET, Width/2-inset (measured from the bolt face)=ET. A 6X15" wheel with 215/75X15 tyres needs an ET from 12 to 37mm for clearance. A 7X15" wheel with 215/75X15 tyres needs an ET from 24 to 26mm for clearance.

----- Original Message ----- From: "Derek Drew" <derekdrew@rcn.com> To: <Syncro@yahoogroups.com>; <vaNAGON@GERRY.VANAGON.COM> Sent: Tuesday, January 30, 2001 2:22 AM Subject: [Syncro] Need Help For Forthcoming Article

> As part of the article I am writing on tires/gearing/wheels, etc., I found > that I was making assumptions about the height of the wheels we use that > appear to me subsequently to be in error. > > That is, I assumed the stock Michelins were 25.3" tall and that the BFG 27 > x 8.50 All Terrain Radials were 26.3" tall. > > On remeasuring these tires, I now feel they are 25" and 26.15", > respectively, going by the tires I have around here. > > Could those of you who run these tires who have a moment measure them > yourselves and let me know what you think is a reasonable assumption about > diameter? > > The proper determination of their actual diameter is critical to > assumptions that flow through many calculations, and therefore I would > rather find out before the fact rather than after that there is an error in > my assumptions on this. > > I am thinking that I will use measured tire height as the basis for > diameter assumptions because, even though actual measured rolling > circumference results might be more accurate, these are more difficult to > extrapolate to new tires under consideration due to the difficulty in > conducting rolling resistance testing of the possible new tires. In other > words, by sticking with actual measured tire height for input data one can > more easily extrapolate data that is useful for selecting tires, which is > the diameter that the tire measures. > > For the purposes of the measurements, I judged that the best method was to > measure the tire at the edge, and discount about half of the bulge in the > middle of the tread, if there is any bulge, as being something that will be > squished flat when the wheel has weight bearing on it. > > In other words, the diameter data that I collected was for tires which did > not have weight on them. > > Again, this makes it more easy for us to walk into a tire warehouse and > measure the diameters of various tires off the vehicle, knowing that the > measuring methodology matched the input assumptions. > > If nobody sends me back any opinions to the contrary, then I am going to > use 25" and 26.15" as the baselines for the calculations. > > > > > > _______________________________________________ > Derek Drew New York, NY > CEO & Co-Founder > http://www.ConsumerSearch.com/ > =========================== > "Best Expert Review Site" > for product reviews on the Internet > Jan. 2001, PC World Magazine > ========================== > 80 South Street, 2nd Floor > New York, NY 10038 > derekdrew@rcn.com > 212-580-6486 > > Alternate numbers for the industrious phone caller that wants to try every > avenue: 917-848-6425 (cell); 202-966-7907 (Work), 212-580-4459 (Home), > 202-966-0938 (Home), 978-359-8533 (fax [efax]), 212-269-3188 (Seaport > office), 212-269-3188 (Seaport main number). > > > If you would like to modify your subscription settings (including unsubscribing), visit: > http://groups.yahoo.com/group/Syncro > Please remember that rude or offensive language is not allowed on the Syncro list. Please try your best to resolve differences privately and keep them off the list. > > > > > > > > > > > > > > >