New Tyres - Necessary To Inflate To Manu. Recommended PSI??

[woodbine]

I ride a mid 80s British Eagle MTB. The old slick/road tyres I had were Tioga city slickers, which I used to inflate to around 65 PSI rear and 60 front which was within manufacturer's recommended pressures. All was well.

I had to replace these and bought a pair of Schwalbe City Jets 26 x 1.5". On the sidewall, it says to "inflate to 85 PSI". I thought this was a bit extreme, so inflated to approx. 75.

Bearing in mind it's an old bike with no suspension, the ride is now very hard and uncomfortable. Every slight bump and pothole is transmitted through the frame and the bike is now uncomfortable to ride and rattles along.

If I reduce the pressures further below the maker's recommended pressure to around what I was using in the old tyres - will this affect the tyres? Will it cause them to wear quicker or be damaged? Are all slick tyres like this these days - needing very high pressures? Do others ignore the maker's pressure recommendations? Are there other slick MTB tyres that would be better for my needs?

When I was growing up, I can't think that we would ever have pumped up bike tyres to such high pressures. I'm sure that a traditional, frame-mounted tubular tyre pump would have been incapable of inflating a tyre to anything like 85 PSI. Why are such high pressures needed now?

 

[Yellow Saddle]

The high pressure is not needed, but better construction techniques and materials allow higher pressure. Ride them at whatever pressure below max that you feel comfortable with.

 

[Tanis8472]

It actually say 85psi max 6 bar.
It's the max pressure allowable.

Inflate to what feels comfortable without feeling squidgy if you know what I mean. Iirc mine are about 50psi

 

[Pale Rider]

The Schwalbe tyres I have state a pressure range, rather than 'inflate to'.

Lower pressures are fine, but the higher the pressure, the better the puncture resistance, so you may need to find a compromise there if you start getting lots of punctures at your preferred pressure.

 

[Markymark]

It feels bumpy at first but try and stick with it. You'll get used to it and it'll be faster a fewer punctures (probably)

 

[Yellow Saddle]

I don't see how higher pressure produces less punctures other than snake-bites which are technically not punctures.

In all the scenarios I can envisage, higher pressures will increase the likelihood of punctures.

 

[woodbine]

Thanks for all your replies. Reduced the pressures to 65 rear and 60 front - which is what I ran the old Tiogas on. Seemed a little less harsh to ride on a quick ride this afternoon. Will see how it goes.

Do some slick tyres ride harder than other makes? Or, would having a more modern tyre like the Schwalbe with some type of puncture protection built in, versus tyres with no protection, mean that they ride harder or differently?

 

[Yellow Saddle]

Thanks for all your replies. Reduced the pressures to 65 rear and 60 front - which is what I ran the old Tiogas on. Seemed a little less harsh to ride on a quick ride this afternoon. Will see how it goes.

Do some slick tyres ride harder than other makes? Or, would having a more modern tyre like the Schwalbe with some type of puncture protection built in, versus tyres with no protection, mean that they ride harder or differently?

You ask all the hard questions.

"Hard" w.rt. tyres can be interpreted in two ways: a) low compliance and, b) higher rolling resistance and hence harder to pedal.

Compliance in a tyres can be found in two places: a) low air pressure and, b) soft, thick rubber. Therefore, to answer your first question, yes, some slick tyres can technically be harder than others but this is not executed by any manufacturer in such a way that you would notice. However, some slick tyres are much harder to pedal than others. All things being equal, the tyre with the thinnest rubber and casing will be the easiest to pedal, but harder to prevent punctures in. Puncture protection always implies harder to pedal. There is no exception to this rule.

 

[Pale Rider]

I don't see how higher pressure produces less punctures other than snake-bites which are technically not punctures.

In all the scenarios I can envisage, higher pressures will increase the likelihood of punctures.

https://www.cyclescheme.co.uk/community/how-to/how-to-prevent-punctures

 

[Yellow Saddle]

https://www.cyclescheme.co.uk/community/how-to/how-to-prevent-punctures

That's a naïve piece of pseudo-science.

"Firmer, higher pressure tyres puncture less often. A tyre at, say, 80psi has half as much rubber in contact with the road as a tyre at 40psi, so it's less likely to encounter shards of glass or flint in the first place. When it does so, the glass/flint/whatever is less likely to press into (and be picked up by) the tread of a firm tyre than a soft tyre."

Firstly, the relationship between pressure and contact area is not linear, as stated. This is simple to ascertain even with a simple thought experiment.

Secondly, as contact area goes up, so pressure goes down. Pressure is what presses the rubber into shard. By their own analogy, they are wrong.

Thirdly, the assumption that a shard will be less likely to stick to and penetrate a firm tyre is nonsense. Stickyness is again a function of pressure and a firm tyre will make it stick better than a soft tyre.

Lastly, it is not the air pressure that prevents a tyre from being penetrated, it is the hardness, thickness and lubricity of the rubber, none of which is affected by air pressure.

A harder tyre will present a shard with a firm target. Since all the shard has to overcome in that case is the hardness of the rubber, it will penetrate. A soft tyre is a soft target which will bulge inwards and not allow the shard to penetrate as easily.

Don't acquire your wisdom from brochures and marketing bumph.

 

[Pale Rider]

That's a naïve piece of pseudo-science.

"Firmer, higher pressure tyres puncture less often. A tyre at, say, 80psi has half as much rubber in contact with the road as a tyre at 40psi, so it's less likely to encounter shards of glass or flint in the first place. When it does so, the glass/flint/whatever is less likely to press into (and be picked up by) the tread of a firm tyre than a soft tyre."

Firstly, the relationship between pressure and contact area is not linear, as stated. This is simple to ascertain even with a simple thought experiment.

Secondly, as contact area goes up, so pressure goes down. Pressure is what presses the rubber into shard. By their own analogy, they are wrong.

Thirdly, the assumption that a shard will be less likely to stick to and penetrate a firm tyre is nonsense. Stickyness is again a function of pressure and a firm tyre will make it stick better than a soft tyre.

Lastly, it is not the air pressure that prevents a tyre from being penetrated, it is the hardness, thickness and lubricity of the rubber, none of which is affected by air pressure.

A harder tyre will present a shard with a firm target. Since all the shard has to overcome in that case is the hardness of the rubber, it will penetrate. A soft tyre is a soft target which will bulge inwards and not allow the shard to penetrate as easily.

Don't acquire your wisdom from brochures and marketing bumph.

I cannot be bothered to argue with you - whatever source I post you will dismiss as worthless - but your repeated misinformation posted on here is becoming a liability.

You think you know everything about a bicycle, but you do not.

 

[Yellow Saddle]

I cannot be bothered to argue with you - whatever source I post you will dismiss as worthless - but your repeated misinformation posted on here is becoming a liability.

You think you know everything about a bicycle, but you do not.

Posting a dubious link and not substantiating it or defending it is not a debate and will get you nowhere. I dismissed your "source" with substantiation.
"repeated misinformation" - I'll leave it up to others to decide for themselves whether my arguments hold water or not.
Good bye.

 

[Moderators]

This thread is turning into a fight outside the chipshop at closing time, so locking it. Nothing to see here.