youngoldbloke
The older I get, the faster I used to be ...
Could be the overall diameter is the same as before - did you measure it?
New version of tyre is (much) smaller than outgoing model... am I within my rights to return them?
- Thread starter I like Skol
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Ajax Bay
Guru
- Location
- East Devon
It's a sign! The tyres are the same outside diameter.
Ajax Bay
Guru
- Location
- East Devon
What is the actual (ie you measure it accurately) width of these Vittoria Zaffiro "25s" at, say, 100psi? What was the width of the previous 23s you had? On what width rim?
OP
OP
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
That is what I am getting at. The rolling circumference of the old v new tyres must be the same because the mileometer is reading the same
OP
OP
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
As it happened I did measure the tyres 'accurately' using a Vernier caliper and taking measurements at several points around the tyre. The rim width isn't relevant as I am comparing tyres when mounted on the same rims and the pressures were at 100psi but I don't think road bike sized tyres really stretch much between 60-120Psi.
I didn't write the results down but both tyres measured around 23.something wide and were within 0.2mm of each other (the 25c was the narrower). Height measured including the rim depth was also within the same 0.2mm of each other with the 25c being tallest but considering the fact that the 23c tyre had around 1000 miles on it and a pronounced flat worn by the many hours of rolling along in the vertical I would suggest that were the 23c tyre brand new out of the wrapper just like the 25c tyre then the 23c would have just stood marginally taller to match it's slightly greater width.
If I were a cynical man I would swear they are both made using the same carcass but the 25c has slightly less rubber on it!
Anyway, it is all irrelevant now because I am using the new tyres and have effectively replaced like-for-like except the sizes shown on the sidewall are wrong.....
Elybazza61
Guru
It's probably something to do with a new construction,presumably tyre makers are altering things to keep up with the trend for wider rims and the newer 25's just don't bulge out as much as your old 23's did.
My 23 Schwalbe pro-ones come up at 26 on the wide rimmed Hunt wheels(25's would be too wide for the Helium) but the Hutchinson Sectors stay at the quoted 26 on the Archetypes(narrower rim) on the cross bike.
My 23 Schwalbe pro-ones come up at 26 on the wide rimmed Hunt wheels(25's would be too wide for the Helium) but the Hutchinson Sectors stay at the quoted 26 on the Archetypes(narrower rim) on the cross bike.
potsy
Rambler
- Location
- My Armchair
It's probably more to do with them selling a 23c tyre and labelling it a 25c, they can then claim their '25c' tyre only weighs X amount of grammes
Get yourself some M+ and stop being such a weight weenie speed freak
Get yourself some M+ and stop being such a weight weenie speed freak
OP
OP
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
This week I have ordered a 0.5 guard for my Wahl clippers to replace the 1.0 guard I was using previously. Using this should be the final action needed to get down to my competition weight......Get yourself some M+ and stop being such a weight weenie speed freak
dan_bo
How much does it cost to Oldham?
Can you not just write 700x23 on the sidewall and get on with your life?
potsy
Rambler
- Location
- My Armchair
OP
OP
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
With my closet OCD?
potsy
Rambler
- Location
- My Armchair
I do a similar thing with my jeans, cross out 40" waist 29" leg and write in permanent marker the correct figure of 32" waist 32" leg
Poacher
Gravitationally challenged member
- Location
- Nottingham
So 25 really is the new 23!
Ajax Bay
Guru
- Location
- East Devon
It maybe irrelevant to you, @I like Skol , but besides your (perfectly reasonable) parochial interest the knowledge (of variable and non-assured quality) these threads contain may be useful to others. Spurred on by your thought that " I don't think road bike sized tyres really stretch much between 60-120Psi."
I decided to test this.
I've measured the width of the new Continental GP 4 Seasons 28-622 I've just mounted on 622-15 Mavic MA3 rims (NB 15mm inside bead, butyl inner) at pressures from 40psi to 120psi (NB max rating is 115psi).
psi width (mm)
40 25.2
50 25.3
60 25.45
70 25.6
80 25.8
90 25.95
100 26.1
110 26.2
120 26.4
Comment: Fairly straight line, perhaps steepening after max specified pressure.
Note that @andrew_s 's measurement on 13mm rims @ 100psi was 25.7mm.
Experimental method and constraints:
Uncalibrated track pump (but the intervals were 10psi + or - 0.5 psi, so can assume equalish intervals). Done over short period indoors so temperature and atmospheric pressure would not have significantly changed.
7 width readings per pressure level taken by digital calipers; two outliers discarded and remaining 5 averaged, avoid measuring adjacent to valve.
Digital calipers calibration checked against steel rule (accurate to within 0.1%).
OP
OP
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
Jeez, have you not got a job? You may need help.
As I said, not a lot of pressure related stretch and it should be correspondingly less for the narrower 23 & 25mm tyres. Your figures suggest most people will experience less than 0.5mm difference when running in the 80-110psi band (this seems to be the most popular pressures for 23c tyres) and 0.5mm is diddly squat when we are talking about rings of inflated rubber mounted imprecisely on a 2ft diameter metal ring.
All I wanted was something 2-3mm taller/wider.......
