Hi to all that may read this , Being the stuck in the 80's old fart that I am , I just ran into a major info problem !.......

I am just about to order some new michelins for the old fantic and I went to order up some heavy duty new tubes to go with

them I found out they don't list tube sizes the same anymore !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!ARGHHHH

what would the proper tube sizes be for a 4.00x18 and a 2.75x21 respectivly ! these 110/90x18 mean nothing but confusion

to me !!!!!!!!!!!

Or can some one point me to a conversion chart ???

Thanks for the help !!!!

Glenn

Michelin list trials tubes in 4.00x18 & 2.75x21 on their website http://two-wheels.michelin.com/2w/front/af...804〈=EN

Edited March 5, 200719 yr by Grib

HEY MOST NEWER STYLE TUBES CHANGED TO THE METRIC SYSTEM, AND MOST TUBES ARE CONSIDERED COMBINATION TUBES, WHICH MEANS THEY WILL FIT MORE THAN ONE TIRE SIZE, THEY ARE EASIER TO INVENTORY THAT WAY, I WORKED IN A TIRE SHOP FOR 10 YEARS AND NEVER COULD FIGURE IT ALL OUT, ONE NUMBER IS VALVE STYLE, METAL , RUBBER, IMPLEMENT, OR TRUCK/ BUS, THE OTHER WILL TELL THE SIZE, FROM MY EXPERIENCE JUST ABOUT ANY 18 INCH OR 21 INCH TUBE WILL WORK, AS LONG AS YOU HAVE THE METAL THREADED VALVE STEM, AND TRY FOR A SMALLER SIZE TUBE, IT IS EASIER TO STRETCH A TUBE THAN TO HAVE IT TOO BIG, THEN IT WILL CREASE INSIDE THE TIRE AND YOU RISK A BLOW OUT, CAUSE THERE ISN'T ENOUGH ROOM FOR A BIGGER TUBE TO FULLY TAKE SHAPE, ANOTHER THING PUT SOME TALC OR BABY POWDER IN THE TIRE AND ON THE TUBE, IT HELPS TO LET THE TUBE AND TIRE STAY SEPARATE FROM EACH OTHER SO IT ROLLS INSIDE INSTEAD OF FLEXING AND YOU WON'T PINCH THEM AT A LOW PRESSURE, WELL I HOPE THIS HELPS AS LONG AND DRAWN OUT AS IT SEEMS....................................................JOHN

Typing in upper case on forums is considered SHOUTING and impolite.

Typing in upper case on forums is considered SHOUTING and impolite.

I wondered why my ears are ringing?

Hello Glenn,

I haven't needed to buy tubes for years so my old ones are all 4.00 x 18 (4 inches wide by 18 inches diameter). The newer figure you have of 110/90 x18 is the metric equivalent. Divide the metric millimetre figure by 25.4 (1 inch = 25.4mm) so that 110 becomes 4.33 inches wide with a 90% margin as far as I can make out. Maybe then the 90% equates to a usable range of 3.897 ins to 4.33 ins. A 2.75 x 21 inch tube would therefore be 2.75 x 25.4mm = 70mm wide, or 70 x 21 in metric terms.

Bye, PeterB.

90% is the aspect ratio of the tyre that the tube is meant for - the nominal height of the tyre is 90% of 110mm. You could just buy Michelin Trials tubes in the correct sizes of course