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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by jeremyshaw[/i] [br]I looked into this for my own Series 5. It's getting the correct rolling radius which is important; it has quite an effect on the overall gearing. So its the height of the tyre which is more important than the width. Crosslplies where pretty much 100% ratio width to height, so a 6" wide tyre was 6" tall. Trouble comes when you fit a 6" wide (155mm) radial which is at most 80% of the height. (155/80) The rolling radius is too small and you end up with a speedo reading high and too many revs for a given speed. Also, it just looks wrong, the wheels don't fill the arches, a bad enough problem with 13" wheels to start with. I ended up fitting 175/80 13 van tyres from Formula 1 Autocentes and they give, as near as dammit, the correct rolling radius. They look better, handle fine, reduced the revs at speed and the speedo is not (so) wildly inaccurate! The correct rolling radius in the Rootes manual is 29.56cm for a C41 Nylon crossply. Somewhere close to that is what I wanted. There are various websites that you can go to and put in your tyre details and it will give you the rolling radius, speedo error and all kinds of confusing data! I'm sure there are other arguments against my reasoning but it works mathematically and that's good enough for me! Happy motoring, Jerry. [/quote]    Insert an Image File Check here to include your profile signature.