Author Topic: Low tyre pressures  (Read 726 times)

ourclarioncall

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Low tyre pressures
« on: December 16, 2021, 01:34:24 AM »
Anyone experimented with low or really low tyre pressures on say a 2.0 or wider tyre ?

Wondering ..how low , can you go ? And what are the pros and cons

Moronic

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Re: Low tyre pressures
« Reply #1 on: December 16, 2021, 07:55:32 AM »
I'll get to this over the next few days in the Gippsland Tour report that I've started in the Tours section.

In short, with 45F/50R in the 50mm Schwalbe G-One Speeds on my loaded Mercury, the bike was all but unrideable on this road, resonating over the corrugations so violently that the front panniers partly demounted and my ride companion could see daylight under the rear tyre. Even at quite low speeds - say 15kmh.




Reflection led me to drop pressures for a similar section of road two days later. I dropped them until a two-handed thumb squeeze made a big impression - down to about 25-30psi it seemed when I reconnected a floor pump at the of the trip.

Result was the bike rode the corrugations like they didn't exist, even at high speeds on descents. Rolling resistance on bitumen increased marginally - my bike still rolled faster than my companion's on its 26x1.5-in Marathons at 80 psi. No other downside that I could determine.

If you cut pressure enough, it appears the tyre will lose its profile when cornered hard. Mine didn't.
« Last Edit: December 29, 2021, 01:06:49 AM by Moronic »

JohnR

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Re: Low tyre pressures
« Reply #2 on: December 16, 2021, 09:57:02 AM »
I've used 50mm tyres with less than 30psi to smooth out indifferent road surfaces although if you've got tubes then low pressures increase the risk of a snakebite puncture. To me, 40psi is a very high pressure. Tyres are, after all, the primary suspension.

See also pages 33-35 of the "bible" http://www.sjscycles.com/thornpdf/thorn_mega_brochure.pdf .

Andre Jute

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Re: Low tyre pressures
« Reply #3 on: December 16, 2021, 09:06:59 PM »
There's a large thread on the subject (and several others!) at
http://thorncyclesforum.co.uk/index.php?topic=3798.0
called "In praise of riding low pressure tyres fast"
That will give you an overview and further links to investigate.

steve216c

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Re: Low tyre pressures
« Reply #4 on: December 19, 2021, 03:01:48 PM »
Tyres generally have a minimum and maximum recommendation on the sidewall. This can be quite a range. Too low a pressure can lead to more frequent punctures. But a good choice of tyre and tube can reduce some of that risk.

Lower pressures on uneven surfaces and on slippery surfaces can increase traction and even make the difference of being able to ride or having to push the bike.. If you have a pump when you are riding, you can always adjust for the conditions as you ride. Cycling is not always about going fast.

I personally prefer the upper end harder pressures when on good roads and commuting. But my Rohloff bike has suspension. There is a lot to be said about suspension being overrated and unnecessary if you have good wider tyres. I have to confess, my similar geometry derailleur trekking bike has no suspension, and if I am on 4-5 bar rather than 6, just as comfortable on longer rides. On 6 bar and over cobblestones, the non-suspension bike does make me feel like my fillings might get shaken out though  :o
If only my bike shed were bigger on the inside...