ST -
I am shifting from 23 to 25mm tires. Welcome your input on what tire pressure you use on your 25 mm tires. I ride Conti GP 4000sII on my race wheels and Conti GP 4 Season on my trainer wheels. For 23 mm I rode 110psi/120psi (front/back). For 25 mm I dropped 10 psi to 100psi/110psi. Can I drop another 5psi without risking any flats?
Thanks.
ST -
I am shifting from 23 to 25mm tires. Welcome your input on what tire pressure you use on your 25 mm tires. I ride Conti GP 4000sII on my race wheels and Conti GP 4 Season on my trainer wheels. For 23 mm I rode 110psi/120psi (front/back). For 25 mm I dropped 10 psi to 100psi/110psi. Can I drop another 5psi without risking any flats?
Thanks.Im 200lbs, rode Raleigh 70.3 today with 25mm and latex tubes at 120psi. No flats or issues.
How much do you weigh? What are road conditions? What inner rim diameter? What tubes?
.
On this chart, I should be riding on 100 psi on 23’s and 87 psi on 25’s. I ride more like 85-90 psi on 23 for training and 70-75 psi for 25’s. That’s for training. for racing, I go around 95 psi on 23’s depending on pavement. At Wildflower and St. Croix I go around 85-88 psi on 23’s. Pavement is just too rough.
Too much!
As another poster mentioned depends on the rim (specifically the inner rim width) you are mounting those on.
I would strongly advise you to inflate them to 100psi and then measure actual width versus printed on tire… 25mm GP400Sii 's as many a previous poster has discovered to their dismay measures more like 29-30mm on today’s ‘wider’ rims when inflated to 100psi.
FYI mine (25mm GP4Ksii) mounted measure 29.5mm and I run them at 75psi (weight 180lbs ish)
Regards,
D.
As another poster mentioned depends on the rim (specifically the inner rim width) you are mounting those on.
I would strongly advise you to inflate them to 100psi and then measure actual width versus printed on tire… 25mm GP400Sii 's as many a previous poster has discovered to their dismay measures more like 29-30mm on today’s ‘wider’ rims when inflated to 100psi.
FYI mine (25mm GP4Ksii) mounted measure 29.5mm and I run them at 75psi (weight 180lbs ish)
Regards,
D.
I found the Conti4000SII on my Bonetrager Aeolus 70’s was waaaay up in the balloon tire range. The 23’s run more like 25’s on those rims.
Here’s a range of rims with internal rim width and tire actual widths checked with vernier gauge calipers…
Pacenti SL23 ’15 Rim = 20.3mm inside track width
Vittoria Corsa Speed 23mm:
Rear 26.2mm 95psi
Specialized Turbo Cotton 24mm:
Front 26.3mm 95psi
Vittoria Corsa CX 23mm:
Front 26.6mm 95psi
Conti GP Force 24mm:
Front 27mm 95psi
Vittoria Pave III 25mm:
Front 27mm 94psi
Clement LCV 25mm:
Front 27.6mm 95psi
Conti GP4000 SII Reflex 25mm:
Front 28.3mm 95psi
Kenda Karv (CX) 28mm:
Front 28.5mm 94psi
Specialized Roubaix Pro 25/28mm:
Front 29.7mm 95psi
HPlus Son TB14 = 17.5mm inside track width
Clement LCV 25mm:
Front 26.2mm 96psi
Specialized Roubaix Pro 25/28mm:
Front 27.6mm 95psi
Clement LGG Strada 28mm:
Front 28mm 95psi
Challenge Parigi-Roubaix 27mm:
Front 29.5mm 95psi
Challenge Strada Bianca 30mm:
Front 30.7mm 95psi
Rear 30.8mm 95psi
**Flo 30 rim = 19.3mm inside track width: **
Panaracer Gravel King 23mm:
Front 24.3mm 93psi
Conti GP Attack 22mm:
Rear 24.5mm 95psi
Conti GP4000 SII 23mm:
Front 25.3mm 93psi
Specialized Turbo Cotton 24mm:
Front 25.5mm 95psi
Specialized Roubaix Pro 23/25mm:
Front 25.7mm 95psi
Vittoria Pave III 25mm:
Rear 26.1mm 95psi
Conti GP Force 24mm:
Rear 26.7mm 94psi
Conti GP4000 SII 25mm:
Front 27.7mm 93psi
Rear 27.5mm 95psi
HED Belgium+ Rim = 20.6mm inside track width:
Vittoria Diamante Radiale 22mm:
Front 24.6mm 95psi
Panaracer Gravel King 23mm:
Rear 25.6mm 95psi
Vittoria Corsa CX 23mm:
Front 26.6mm 93psi
Specialized Turbo Cotton 24mm:
Front 26.6mm 95psi
Specialized Roubaix Pro 23/25mm:
Front 27.1mm 95psi
Conti GP4000 SII 23mm:
Front 27.2mm 94psi
Vittoria Pave III 25mm:
Front 27.2mm 95psi
Panaracer Gravel King 26mm:
Front 27.7mm 95psi
Conti GP4000 SII 25mm:
Front 28.6mm 95psi
Specialized Roubaix Pro 25/28mm:
Front 29.5mm 95psi
Clement LGG Strada 28mm:
Front 30mm 94psi
Challenge Parigi-Roubaix 27mm:
Front 31mm 93psi
Challenge Strada Bianca 30mm:
Front 32.5mm 94psi
Too much!worked out this time:)
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So if this chart is correct and I am reading it right, if I am 155 lbs I should be at about 95psi? I am on continental gp4 25’s
I weigh about 160lbs. My training wheels are HED Belgium C2s (on a 2015 Specialized SHIV Pro). Road surfaces in N. VA are pretty good, but not perfect. From the posts it looks like I could drop 5 PSI (95/105).
At 160 with 25’s I would probably drop more than 5 PSI.
I run 25mm GP4K’s on Begium C2 rims at 80-85 and I can probably go lower. I rode that pressure when I was up around 185 and never had a pinch flat. I’m now around 170.
We need your weight and what inner rim width you are riding to make a good estimate, but I’d most likely say that you are already riding too much pressure.
J
Once again, thanks to everyone for your input. At the risk of exposing my technical ignorance, what is the relationship between inner rim width and correct pressure? Rider weight is pretty straight forward : more weight → more pressure. However, would appreciate insight on rim width / tire pressure.
So the bead width changes the effective tire width and height. A 25mm GP4000s on a 13mm bead width rim (the old standard) measures at 25.6mm wide and on a 17mm bead width (common new carbon wheels) it measures at 27.1mm wide and on something very wide like an ENVE 7.8 with 19.5mm bead width, that same tire measures, 28mm wide at 100psi! Effectively, the tire is able to act as a larger diameter than listed on the casing as the bead widens.
J
Where is this chart from? Whom is the source for the data? Look’s pretty accurate from my experience.
On this chart, I should be riding on 100 psi on 23’s and 87 psi on 25’s. I ride more like 85-90 psi on 23 for training and 70-75 psi for 25’s. That’s for training. for racing, I go around 95 psi on 23’s depending on pavement. At Wildflower and St. Croix I go around 85-88 psi on 23’s. Pavement is just too rough.
Seems pretty good if you use the graph for (1) racing conditions on (2) good pavement.
Not racing? Go lower.
Poor pavement? Go lower.
Where is this chart from? Whom is the source for the data? Look’s pretty accurate from my experience.
Pretty sure that it is a michelin bike tire graph.
Not sure how they generated the data though …
Where is this chart from? Whom is the source for the data? Look’s pretty accurate from my experience.
It’s from Michelin, for their tires.