Pressure too low in tyres
- Thread starter Sunny Portrush
- Start date
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- tyres
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Ajax Bay
Guru
- Location
- East Devon
The 25 M+s will actually come up as 26mm or even a bit more. Measure your tyre with 90psi in.
If you are 88kg (I'm not suggesting you are but it makes the maths easier) and the bike is 12kg all up, then the rear wheel is bearing 55kg and the front one, 45kg.
Using the Tyre Pressure calculator graph in the Bicycle Quarterly (by Jan Heine) article attached, your 26mm wide (assumed) rear tyre should be run at 105psi and the front at 85psi. Drop about a psi (in each tyre) for each kilo you are less than 88. By the way this is a useful rule of thumb for carrying weight eg luggage: for every kilo, run one psi more. The other rule of thumb is: 5psi less for each mm of extra width. But the graph in the article is easy to read.
Bear in mind that the M+s are 700+g each as opposed to 280g (say) for the tyres you've replaced, and their rolling resistance is greater; about 50% worse.
If you are 88kg (I'm not suggesting you are but it makes the maths easier) and the bike is 12kg all up, then the rear wheel is bearing 55kg and the front one, 45kg.
Using the Tyre Pressure calculator graph in the Bicycle Quarterly (by Jan Heine) article attached, your 26mm wide (assumed) rear tyre should be run at 105psi and the front at 85psi. Drop about a psi (in each tyre) for each kilo you are less than 88. By the way this is a useful rule of thumb for carrying weight eg luggage: for every kilo, run one psi more. The other rule of thumb is: 5psi less for each mm of extra width. But the graph in the article is easy to read.
Bear in mind that the M+s are 700+g each as opposed to 280g (say) for the tyres you've replaced, and their rolling resistance is greater; about 50% worse.
Last edited:
Salty seadog
Space Cadet...(3rd Class...)
yep, thats what I run, on the 28's on the Whyte I run 100psi
raleighnut
Legendary Member
- Location
- One of the 'Elite'
I'd say 60psi was too low, have a look on the sidewall at their 'Max Rated' pressure, I generally run mine at close to that on the rear and 10psi less on the front.
EasyPeez
Veteran
- Location
- Cottingham, East Yorkshire
I didn't even realise M+ came as narrow as 25mm. But yes, as stated above the benefit that they offer in sturdiness and puncture protection has to be paid for somehow, and that's in weight and rolling resistance. They will feel a hell of a lot more 'treacly' than your Rubinos I'm afraid. But 60psi is too low. I'd be thinking around 80-85psi for my needs, off-road. @Ajax Bay 's link is dead useful for working out your own set up.
smutchin
Cat 6 Racer
- Location
- The Red Enclave
Me neither.
Yes, very good. I run my 25mm tyres at about 90psi on the road, which looks bang on according to the chart (for a total load of nearly 90kg). I'd probably go a bit lower for trails and towpaths but not as low as 60psi.
byegad
Legendary Member
- Location
- NE England
That's what I found with these tyres.
OP
OP
Sunny Portrush
Guru
- Location
- Musselburgh
Thanks all - I`ll try pumping them up to about 90psi and see how they roll. I`m not expecting to do anything serious off-road - as mentioned at the start, it`s just for the local towpath which seems to be made up of tiny stones and the old converted railway lines which is built from red-ash - both surfaces would wreck the Rubino`s I would suggest!
And Smutchin, i`m blonde, blue eyed and 13st....................and male lol
And Smutchin, i`m blonde, blue eyed and 13st....................and male lol
Ajax Bay
Guru
- Location
- East Devon
83kg. 80 on the front; 100 on the rear.
biking_fox
Guru
- Location
- Manchester
As other said. They really are very heavy and feel very different. Worth their weight in time saved fixing punctures though.
Lpoolck
Veteran
This may be more road specific but 80PSI if your a 90kg rider, 65PSI for 70kg according to Keith Bontrager.
View: https://www.youtube.com/watch?v=NpxUcfZhxLk
I have recently dropped mine from 95 to 75 (I weigh 75kg) and the bike rides to much better over the rough road surfaces and my backside is also thankful for the the smoother ride!
View: https://www.youtube.com/watch?v=NpxUcfZhxLk
I have recently dropped mine from 95 to 75 (I weigh 75kg) and the bike rides to much better over the rough road surfaces and my backside is also thankful for the the smoother ride!
raleighnut
Legendary Member
- Location
- One of the 'Elite'
Just don't buy the inner tubes with his 'brand' on them .................................absolute bloody rubbish, overpriced too.
ozboz
Guru
- Location
- Richmond ,Surrey
Got to say this is interesting stuff , I cannot seem to get tyre pressures sorted , I was riding M+ on my Surly CC , I recently got some Land Cruisers ( £17 for two ), Ive not had a good ride on them yet , but I will try and work out from the info on here what they maybe should be , but low pressure in the M+ was bordering on disaster , it was all over the place ,
OP
OP
Sunny Portrush
Guru
- Location
- Musselburgh
As the OP, just a wee update. Pumped back tyre up to 100psi and the front to just over 80 and it made the world of difference. Still takes more effort to get them cruising in the same manner as the Rubino`s but that`s not bad thing - I may even develop some thigh muscles by the end of winter!
