Tyre pressures

[Two-Wheels]

I know a lot of this will be "it depends" but I'll ask anyway.
I am guessing it'll be depending how heavy you are, the surface you're cycling on & they're just the two obvious variables that I can think of. Perhaps weather conditions. I suspect there'll be god knows how many more.

Tried having a search but got very wishy washy responses really. Basically I'm looking to see what I should be inflating the tyres to rather than just putting them to somewhere a bit below maximum 'just because'.

I'd have to go outside & check to be 100% but I'm fairly sure my tyres are 700x35c. The bike is a Trek FX2 hybrid bought in 2017.

I cycle pretty much on the road for 99%. That 1% may be me having to go over a bit of rough ground as I pass from 1 section of road to another but generally it's just your standard road surface. Some good quality, some not so good.

I weigh about 170lbs & put about 80psi in the rear with 70psi up front. Again I'd have to go outside and check to be 100% sure but i think the max is 90psi.

There's surely a (loose guide) formula for it so that I'm not asking the exact same question when I buy an actual road bike as the hybrids replacement?

Just wondered how you figure it out is all.

 

[mjr]

I start from the BQTireDrop graph. 80psi in a 37mm rear would be far too rough for me.

 

[ianrauk]

I weigh a few more pounds then you and go for somewhere in-between what the tyres minimum and maximum pressures state to what I find comfortable.

 

[Sittingduck]

Trial an error... or
something like this online calculator
If it was me I would brave that sunny and mild outdoors and go and confirm tyre specs and take it from there. I would guess around 60 is better.

 

[Ming the Merciless]

Look up 15% tyre drop and if you have an iPhone there is an app you can put your weight and width tyres with weight distribution and it’ll throw out some pressures for front and back.

 

[GuyBoden]

Less pressure is needed on a cold Winter day, than a hot summer day.

 

[cougie uk]

I use roughly the figures in this. This is the weight per wheel - front wheel has less weight on it than the rear wheel.

I don't change because of temperature but if it's wet I will lower the pressure slightly for better grip.

You're definitely using too much pressure anyway.

 

[Deleted member 1258]

I'm 170 lb and on 700c x 25 I'm running 65 psi front and 75 psi rear, any higher than that on the roads round here and I'm at risk of loosing my filings.

 

[Ming the Merciless]

Less pressure is needed on a cold Winter day, than a hot summer day.

I get my thermometer out before every ride and adjust pressures

 

[Twilkes]

100kg and 70psi still feels a bit harsh on 28mm tyres.

IIRC the max rating on a tyre is half the pressure required to blow the tyre off the rim, it's nothing to do with rideability. And the minimum pressure is always overstated to try to avoid you pinchflatting, you can safely ride them lower than this. The exception is tubeless where there can be rim compatibility issues, especially on hookless rims.

 

[GuyBoden]

I get my thermometer out before every ride and adjust pressures

Less pressure is also needed in the wet, so if it starts to rains, you need to get off your bike, then let some air out of your tyres.

 

[Ming the Merciless]

Less pressure is also needed in the wet, so if it starts to rains, you need to get off your bike, then let some air out of your tyres.

I just find a suitable flint to embed in the tyre for that.

 

[All uphill]

I weigh about the same as you, OP, and use 45 front and 50 rear in my 35c tyres. The ride is still poor because I allowed myself to be persuaded to fit Marathon plus! The flippin' things just won't wear out either!

 

[Two-Wheels]

I'm 170 lb and on 700c x 25 I'm running 65 psi front and 75 psi rear, any higher than that on the roads round here and I'm at risk of loosing my filings.

For the most part I'm not too bad. If the road surface gets a bit iffy though then yeah there is that.
I was also on a long decline on the day of my accident. It was a long straight & I was going all out for me to see if I could tip 40mph as hadn't done it before (usually max out about 35-38). As I hit the 40 marker the bike certainly got all wibbly-wobbly.

Now i'm not sure if that's the tyre pressure playing its part, rider (in)experience, whether the bike itself or the gears can't handle that speed or what. Perhaps a combination of the lot. It didn't feel great that's for sure so I had to ease off.

 

[Grant Fondo]

I weigh about the same as you, OP, and use 45 front and 50 rear in my 35c tyres. The ride is still poor because I allowed myself to be persuaded to fit Marathon plus! The flippin' things just won't wear out either!

I always find Marathon Plus are best with no air in at all, and snow-chains fitted when it gets a bit icy.