Optimum tyre pressure?

[NickTB]

Hi all,
I’m looking for various ways to speed up my bike and one is tyre pressure. My bike is a Marin Lucas Valley which has the stock Kenda Kwest tyres it came with, 700 X 28C. I’m 96 kg. Can anyone give me an idea of the correct pressure? They’re currently 80psi
Cheers,
Nick

 

[vickster]

What’s the range on the tyre?

 

[NickTB]

What’s the range on the tyre?

When you say range, how do you mean?

 

[Ming the Merciless]

http://www.dorkypantsr.us/bike-tire-pressure-calculator.html

 

[vickster]

When you say range, how do you mean?

What does it say on the side of tyre for min/max?

 

[ebikeerwidnes]

The max pressure will be on the side of the tyre - if you are riding on reasonable roads then this seems to be the most efficient for rolling resistance

if you are somewhere more slippy then others will know more than me

 

[NickTB]

All it says on the sidewalk is min 50psi-max 85psi

 

[ianrauk]

Somewhere between the minimum and maximum indicated on the sidewall of your tyres. Try a pressure that you find comfortable with.

 

[silva]

On flat road the more pressure the faster.
At 80 psi you have 5 psi left within the tyres pressure range.
So it looks like that option is a goner.
Another way to speed up your bike is pushing harder.

 

[Sea of vapours]

You could refer to this graph. The idea behind this is to produce an optimum deformation of the tyre. Note that this will give you higher pressure on the back than on the front if you use this method. The rationale is in the attached document (the graph is from the document) . It's pretty convincing, but it's just a school of thought and the starting point should be 'between the min and max marked on the sidewall', as has been said.

 

[Drago]

Within the limits of the tyres max pressure rating, it's a very personal thing. Fiddle a bit until you find a pressure that you're comfortable at and which rolls well. We can't tell you what that might be.

 

[silva]

Within the limits of the tyres max pressure rating, it's a very personal thing. Fiddle a bit until you find a pressure that you're comfortable at and which rolls well. We can't tell you what that might be.

At a current 80 psi and a tyre spec of 50-85 he already sits near the optimum for the total weight on that chart.
So to go faster it doesn't look like tyre pressure is gonna make a difference.

 

[I like Skol]

At your weight (same as me) I would say 80psi is about right for a 28mm tyre. I would run that size around 65-80 depending on how much comfort i wanted.

 

[Ming the Merciless]

You’ll find unless you run stupidly low pressures that the pressure really doesn’t make that much difference to your average speed. On billiard smooth roads highest pressure might be better but roads are nowhere near smooth.

 

[Ajax Bay]

First measure the tyre width (at 90psi (say)). Just because it's sold as 622-28 doesn't mean on your rim it's 28mm wide.
At 96kg plus the bike @11kg divides up 65kg on the rear and 42kg on the front. If the tyre is a true 28mm then (from chart attached) 110psi on the rear and 70psi in the front (assumes tyres rated max is 110+).
"I’m looking for various ways to speed up my bike"
10psi here or there will make minimal difference to your speed.
The quickest way to 'speed up your bike' (apart from pressing a bit harder on the pedals) is to replace the Kendas with Continental GP5000s. This will save you at least 8W per tyre.
Then use this chart (or @SoV's upthread):