Tyre pressure confusion?

on-yer-bike

Im using Vittoria Open Corsa 320 tpi clinchers for the first time. I usually inflate my tyres to 105 psi. However, looking at the Vittoria tyre pressure app it tells me that the pressures should be 125 front, 130 rear. Ive never used this kind of pressure. Also, the tyres are 25 mm and I thought these were run at lower pressure? The recommended tubular pressure is even higher at 130F, 135R. Could this be why they kept puncturing before I switched to Conti Comps? What should Conti Comps be inflated to?

simon_masterson

Just use a chart. 90-100 should be ample if you're fairly light; and even if you aren't, I can't see why you'd need to run a 25mm clincher that hard unless you're carrying luggage on it.

ai_1

Simon Masterson wrote:

Just use a chart. 90-100 should be ample if you're fairly light; and even if you aren't, I can't see why you'd need to run a 25mm clincher that hard unless you're carrying luggage on it.

125psi+ seems hugely excessive on 25mm even if you were carrying luggage. If you only ride the most luxuriously smooth of roads that might not be a provlem bur I suspect on normal Ireland & UK roads that's going to be unpleasant. I've been playing around with pressures on 25mm Mavic Yksion tyres and I'm finding approx 85psi front and 95 or 100psi back to be a good comfort/firmness compromise.
I weight about 86kg and the bike's about 7kg

charlie_potatoes

davidmt83 wrote:

Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33
Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67

Is this for front, rear or both tyres.
Can it be correct for both?

Dippydog2

Charlie Potatoes wrote:

davidmt83 wrote:

Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33
Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67

Is this for front, rear or both tyres.
Can it be correct for both?

The above is for the rear. Front is 10% less.

kajjal

The balance is not too low so you get pinch punctures and the tyres deforming enough to effect handling. And not too high so you get a lot of road vibration.

mercia_man

Vittoria have always recommended really high minimum pressures for Open Corsas. But for ordinary riding (rather than time trialling) on rough British roads they work better with lower pressures. I have found 23mm ones are good for me at 100-105 psi. A search on the internet showed other people feel the same as me. I reckon you could try 25mm Open Corsas at 95-100 and increase a bit if you get a snake bite puncture.

mercia_man

davidmt83 wrote:

Mercia Man wrote:

Vittoria have always recommended really high minimum pressures for Open Corsas. But for ordinary riding (rather than time trialling) on rough British roads they work better with lower pressures. I have found 23mm ones are good for me at 100-105 psi. A search on the internet showed other people feel the same as me. I reckon you could try 25mm Open Corsas at 95-100 and increase a bit if you get a snake bite puncture.

How can we not be taking the riders weight into account?!

I agree weight is a consideration. But the OP hasn't given his weight. Different tyres have different make-ups. Some like Vittoria Open Corsas are very flexible with high tpi counts and require higher pressures for the same size than, for example, Vittoria Randonneurs which are thicker and less flexible with lower tpi. That's why a chart like the above based solely on weight and nominal size is only helpful if it's for a specific tyre.

It's also worth pointing out that many people recommend using slightly lower pressures with the new breed of wider rims such as Archetypes.

I'm fairly light - 70kg including cycle clothing, helmet and shoes - and find 23mm Open Corsas are good for me on UK roads at 100f/105r on Campag Neutron Ultra wheels (old school narrow). I'm currently using 23mm Schwalbe Ones on Archetypes. I found 90/95 was too low as I got a snakebite puncture. Now using 95/100.

Old_Timer

davidmt83 wrote:

Mercia Man wrote:

Vittoria have always recommended really high minimum pressures for Open Corsas. But for ordinary riding (rather than time trialling) on rough British roads they work better with lower pressures. I have found 23mm ones are good for me at 100-105 psi. A search on the internet showed other people feel the same as me. I reckon you could try 25mm Open Corsas at 95-100 and increase a bit if you get a snake bite puncture.

How can we not be taking the riders weight into account?!

One reason for not taking the rider's weight into account could be the need for each individual rider to adjust the pressures to best suit their riding location's roads, their weight and their riding needs (speed, endurance, comfort, etc.) I'd take the tables, such as provided above, as a guide and use these as a starting point to determine what to use that day/each ride. Just my thoughts, feel free to critique 8)

Personally, for my Continental Gatorskins, 25mm width, I tend to run right at 110 rear and 100 front for the regular routes I take. I'm 178lbs, moderately smooth roads with a few "cobbled", rough sections, on a CAAD 10. Adjusted each ride for what I'm planning on doing that day. So far no pinch flats with these tyres and pressures.

on-yer-bike

Im 72 kg + bike. Vittoria dont make any allowances for tyre width in their App. The App is free if you want to check it out. Also a warning came with the tyres not to inflate them lower or higher than the amounts stated on the tyre wall. The minimum pressure written on the tyre is 115 psi. The app gives pressures depending on the thread count and wet or dry conditions.

mercia_man

I'm a similar weight to you. I've been riding Open Corsas on and off for about 15 years. I used to follow the recommended minimum pressure on the sidewalls - 8 bar or 115psi. Then I found out on the internet that many people run them at lower pressures. I tried it at 7 bar (just over 100 psi) and this works well for me. More comfortable and a feeling of more grip on damp or rough roads. No apparent downside. Try your tyres at that sort of pressure and see what you think.

Open Corsas with latex tubes are a sublime combination but you obviously have to accept they are a relatively fragile race tyre. Stiffer training or light touring tyres like Gatorskins are not comparable.

declan1

I'm 73kg and running 25mm Michelin Pro4 SC on Archetypes (fairly wide rims) and I'm running 80F 85R. 120psi is definitely excessive unless you're very heavy.

on-yer-bike

declan1 wrote:

I'm 73kg and running 25mm Michelin Pro4 SC on Archetypes (fairly wide rims) and I'm running 80F 85R. 120psi is definitely excessive unless you're very heavy.

But why does the tyre manufacturer recommend it?

on-yer-bike

OK, Ive been out on the Vittorias pumped up to 120F, 125R and they feel much better than at 105 psi. I thought it would be bone shaking but it wasn't and the bike felt faster. The higher the thread count the higher the pressure according to the app.