I know its not motoring, but it is green motoring!
I have a new bicycle with 700 x 35 tyres (it says so on the sidwalls). I have fitted a trip computer but need to know either the tyre circumference in millimetres or the size in inches.
I think the circumference is 2200mm which makes a 27.5" tyre. Does that sound right for the sidewall markings?
TIA
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piece of chalk plus tape measure required. Mark tyre and pathway - wheel machine forward -stop when chalk mark on tyre comes around - mark pathway - measure distance. Job done.
Usually most cycle computers are not terribly acccurate. Tyre sizes vary with Manufacturer.Within one or two per cent is ok unless you intend to ride the RAAM at some future date.
Happy Cycling with great cost savings on fuel.:-))
Phil I
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As Phil I said, but sit on the bike when wheeling forward for the most accurate measurment.
ps, The Cateye website suggests 2168mm for a 700x35 tyre.
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That makes sense as the flattening of the tyre at the bottom will reduce the distance travelled each revolution.
Thanks
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700mm is about 27.5"
Does the size you enter need to include the sidewall height?
2200 is approximately the circumference of a circle with a diameter of 700mm, does the computer make allowance for the sidewall height, or do you need to actually measure the circumference of the tyre?
I struggled to get a 27" tyre during the week, seems like 700 is the popular size now for a road bike.
Chris
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"I struggled to get a 27" tyre during the week, seems like 700 is the popular size now for a road bike."
www.tyresatlast.com - UK-based. I needed 28 x 1.75 - which I thought were only possible in Germany, but they came 48 hrs later. The bike I need them for is about 90 years old!
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700 metric replaced 27inch for wired-on tyres (like they have seperate inner tubes) about 1983 ish but 27inch was available for years later now theyve gone.
But, even in the 1960s the real racing wheels where you glue the tubular tyre to the rim (all one item no tube) have always been 700 metric
incidentally at the top level glue ons called "sprints & tubs" are still the best.
OK wired ons have got techy and better but if you try good tubulars youd never want to go back to wired ons.
used to race on these myselff best advantage was apart from fact they anf the sprint type rims are so light is we pumped the tubulsar tyres to 160 PSI for used on fast road courses.
I thinkythe glued on tubular tyres which we always used even for training went out for 2 reasons.
Folk today want convenience and glue on tyres was a time consuming job and was a skill
and modern houses are so tiny and folk dont have places to do these things in anymore
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Quite right Oldlag , tub sales declined because of the convenience / skill factor involved with prepping and mounting them correctly on the wheel, you could use 'tub'tape' instead of glue but this was never as reliable (as in the tub could roll off the rim in certain circumstances - wet/cold conditions!) however I believe that the main reason for the change is because decent modern wire-on tubed tyres now easily match the performance of the best tubulars even for racing.
Espada III, the easy way to measure your wheel circumference is with a seamstresses flexible tape measure wrapped around the tyre, remove the wheel first though!
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Espada III the easy way to measure your wheel circumference is with a seamstresses flexible tape measure wrapped around the tyre remove the wheel first though!
That will give the circumference of the tyre when off the bicycle, but doesn't take into account deflection of the tyre at the contact point with the ground. Espada III needs the rolling radius when he's sat on the bicycle. Phil I and Andy T have the right idea.
Edited by L'escargot on 10/08/2008 at 10:52
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How much deflection is there are on a HP front wheel? Not much I reckon compared to the rear, the seamstresses tape method is fine.
Btw I have had a max of 55mph out of my road bike speedo down a greasy Yorkshire Dales hill, was pretty scary!
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I know it soecifically refers to cars but this website may be of assistance. tinyurl.com/69pkmk
Edited by L'escargot on 10/08/2008 at 10:29
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How about using a bit of 'o' level maths, if only to compare results.
From memory, circumference = pi (3.1416 or 22/7) X diameter.
Handy too, if you only had a retractable steel rule which wouldn't easily measure circumference.
Edited by ifithelps on 10/08/2008 at 11:27
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How about using a bit of 'o' level maths if only to compare results. From memory circumference = pi (3.1416 or 22/7) X diameter.
The trouble with that method is that cycle tyres commonly come up slightly over or undersize. Everytime I change a front tyre on the bike I need to re-set the computer, the circumference method is the most accurate way to set it up.
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