Ah, but to further mess things up - the old sizes (4.00, 3.50) were 100% sidewalls (so 4.00x4.00). The 4.10 (or anything else with a .10 increase from the standard size such as 3.60) was designated as a "low profile" tire, so a 4.10 was a 4.00w x 90% sidewall, 3.60 was a 3.50w x 90% sidewall. Which is why a modern 110/90 replaces the old 4.10, but a 100/100 would replace a 4.00.
bk --- [EMAIL PROTECTED] wrote: > SOHC4 Digest 4712 > > Topics covered in this issue include: > > 1) Resubscribe? > by "Frogspawn Inc" <[EMAIL PROTECTED]> > > ---------------------------------------------------------------------- > > Date: Wed, 24 Mar 2004 21:18:36 +0200 > From: "Frogspawn Inc" <[EMAIL PROTECTED]> > To: "sohc4" <[EMAIL PROTECTED]> > Subject: Resubscribe? > Message-ID: <[EMAIL PROTECTED]> > > Nothing from the list for some time - have I been de-subscribed? > Going through my huge pile of old Classis Bike magazines - often > read and > re-read - I found some tyre size conversions that puzzle me. > Old Size Modern Metric > 2.50/2.75 3.10 80/90 > 3.00/3.25 3.60 90/90 > 3.50 4.10 > 100/90 > 4.00 4.25/85 > 110/90 > 4.70 none > 120/90 > 4.50/5.00 5.10 130/90 > > A bit of arithmetic shows that all is not equal. There are 25.4mm > to one > inch. Old sizes and modern are expressed in inches whilst metric > is, well, > metric. Thus 4.00 (as in 4.00X18) is 101.6mm. 110/90 is 110mm width > and 90% > aspect ratio equals 99mm height a smidgeon less than 101.6mm. > Modern 4.25/80 > is size, 4.25" and 85% aspect ratio that calculates to 3.61" so it > seems a > little small although the width is larger. The 3.25X18 is 3.25" > equals > 82.55mm. The said equivalent is 90/90 that to me works out at 90mm > X 90% > equals 81mm equals 3.18". Working this way and assuming a 90% > aspect ratio, > I get a theoretical 113/90 to replace a 4.00 and a 92/90 for a > 3.25. OK so > now that all is clear,I'll just go into my local tyre shop and > demand a > 113/90X18. > Regards > Paul (non metricated and still thinks in thou) H > > > ------------------------------ > > End of SOHC4 Digest 4712 > ************************ __________________________________ Do you Yahoo!? Yahoo! Finance Tax Center - File online. File on time. http://taxes.yahoo.com/filing.html
