Tyre pressures

[Pale Rider]

50psi in the front; 70 psi in the rear would be my recommendation.

Depends if you think 'snake bites are bad, because I'll take a level bet that that's what would happen to the OP if they rode a rear tyre inflated to only 30psi, the first time they hit a significant edge/pothole.

Could be, although don't under-estimate the power of podginess.

A 40c mountain bike tyre is a vastly different pressure prospect to a 25c rubber band roadie tyre.

I reckon the majority of flat bar riders don't check their tyre pressures from one month to the next.

That's not for me, but most of us on here are cycling anoraks and very much in the minority of cyclists generally.

 

[smutchin]

I usually refer to the oft-cited piece from Bicycle Quarterly for guidance on tyre pressure if I'm unsure - though I tend to go slightly lower than the pressures suggested on their chart...

(NB load should be calculated as the total of bike weight, rider weight and luggage weight, split proportionally front/rear as indicated - you can estimate figures, no need to work them out precisely)

 

[Ajax Bay]

I usually refer to the oft-cited piece from Bicycle Quarterly for guidance on tyre pressure

So do I, citizen, but not this time. Perhaps you (@smutchin ) could just help to OP by reading off from the graph what he should use (Rear/front) if he weighs 125kg and the bike weighs 15kg with 42mm wide tyres, and the weight is split 60/40?

 

[smutchin]

So do I, citizen, but not this time. Perhaps you (@smutchin ) could just help to OP by reading off from the graph what he should use (Rear/front) if he weighs 125kg and the bike weighs 15kg with 42mm wide tyres, and the weight is split 60/40?

Ha! OK, fair point. I missed the post where the OP mentioned his weight and tyre size.

By a process of extrapolation and guesswork, though, I would say 67psi is on the high side. Assuming a total load of 140kg, split 60/40, I would suggest something in the region of 50psi front, 60psi rear.

 

[SkipdiverJohn]

I'd go with 50 front/65 rear. Given the OP is a big bloke and tyres do slowly lose pressure, it isn't going to hurt to have a couple of PSI extra to begin with, as it allows for it losing a bit by the time it's next checked & pumped up.

 

[stuarttunstall]

Thank you all for the advice

 

[Ajax Bay]

700 x 42c Schwalbe Smart Sam and I am 125KG

Tyre pressure spec for these tyres:
"PSI: 30-55"
So probably best not to put more than 55psi in the rear tyre.

By a process of extrapolation and guesswork, . . . Assuming a total load of 140kg, split 60/40, I would suggest something in the region of 50psi front, 60psi rear.

By extrapolation (from the graph) and taking into account the stated max pressure, I'll amend my recommendation to 55 rear and 45 front for this width of tyre (and weight of bike + rider).

 

[smutchin]

By extrapolation (from the graph) and taking into account the stated max pressure, I'll amend my recommendation to 55 rear and 45 front for this width of tyre (and weight of bike + rider).

I'll go along with you on that.

@stuarttunstall There's arguably a case for changing your tyres for something rated for higher pressures. Besides, Smart Sams are offroad tyres, so if you're mostly riding on the road, you'd probably be better off with something like Marathons anyway - these would not only roll faster on tarmac (even if it's less-than-perfect tarmac), and have better grip, they would also have much better puncture protection.

 

[T4tomo]

There are a number of professors on here who will confirm but 67 sounds low to me if you are a big bloke.

Yes if 23-25mm road tyres, but not if on some.wide recreational rubber

 

[stuarttunstall]

I'll go along with you on that.

@stuarttunstall There's arguably a case for changing your tyres for something rated for higher pressures. Besides, Smart Sams are offroad tyres, so if you're mostly riding on the road, you'd probably be better off with something like Marathons anyway - these would not only roll faster on tarmac (even if it's less-than-perfect tarmac), and have better grip, they would also have much better puncture protection.

That had crossed my mind... the roads I use are not the best so I was looking a slightly narrower Marathon Greenguards, more for puncture protection

Tyre pressure spec for these tyres:
"PSI: 30-55"
So probably best not to put more than 55psi in the rear tyre.

By extrapolation (from the graph) and taking into account the stated max pressure, I'll amend my recommendation to 55 rear and 45 front for this width of tyre (and weight of bike + rider).

Looking at the tyre on the bike the max shown is 80 PSi

 

[stuarttunstall]

Hi

I have just checked my tyres again, 3 weeks ago I set the tyres to 67 PSi, I have not used the bike as I have been away for a couple of weeks...

Going out in the morning so I thought I would check them, bot around 49-50 PSi, so lost about 17 PSi over 3 weeks, does that sound right? I have read they can loose 1-2 PSi per day so I suppose on that basis done well

 

[Salty seadog]

Hi

I have just checked my tyres again, 3 weeks ago I set the tyres to 67 PSi, I have not used the bike as I have been away for a couple of weeks...

Going out in the morning so I thought I would check them, bot around 49-50 PSi, so lost about 17 PSi over 3 weeks, does that sound right? I have read they can loose 1-2 PSi per day so I suppose on that basis done well

Yep, all tyres will lose pressure over time. No worries, just put some more in.