Thinthatch

The above has 700 x 38 wheels and the tyre wall shows max 75 psi.
I have a 'thing' about my tyres being solid to the touch when pumped up.
My pump won't allow me to go above the recommended pressure, no doubt for good reason but when riding the bike on the flat, for example the tyres make that slurping sound as if they are (almost) flat.
I only weigh about 11.5 stone or 160 pounds.
Am I doing something wrong or expecting too much?

hokiefyd 

I presume you're hearing some sort of tread noise on smooth surfaces. At or above 75 psi on a 38mm tire for a rider of only 160 pounds means you're likely riding on only the very top of the tread pattern, and you're likely to experience some sort of tread noise that most wouldn't experience just because only the tops of the tread features are in contact with the pavement.

I don't know what tires you have on your Giant. Are they the stock Crosscut tires, as shown below?

roam08 by jnjadcock, on Flickr

subgrade

I'd say you're putting too much pressure in your tires. I weigh 85 kg/190 lbs, and have found that the optimal pressure for my 700cx38 Schwalbe CX Comps is around 55-60 psi, depending on the road conditions. It may vary a bit for each tire, but I don't think the difference would exceed 10 psi.

travbikeman

Actually there have been many tires out there in the past that could vary a great deal more than 10psi's. My Trigger Sport tires 700x38 have a 75-100psi rating. It was a harsh riding tire, and one of the reasons I have changed them out.....now if I can just get someone on facebook market place to buy them from me!!!

jskash

My Specialized Crossroads Armadillos run the same 75-100 PSI. Specialized made a new version of the Crossroads Armadillo that has much lower PSI. 700 x 38mm, psi 50-80.

Thinthatch

Thanks for the responses.
The tyres are the Giant Crosscut AT ERT 700x38C tubeless, and the tyre wall shows the maximum pressure at 75psi.
To me, at that level they feel under inflated..

I can't post a photo of the tyres because of a ridiculous rule that I must have made 10 posts first.

hokiefyd 

I'm 240 pounds, and I ride my 38s at about 40 psi in the front and 55-60 psi in the rear. I promise you that 75 psi is not underinflated. If you're used to road bike tires, which have smooth tread surfaces, you may just be feeling tread squirm from the taller tread features.

DorkDisk

Max pressure is not the recommended pressure. Its the maximum pressure for the rated weight of the tire, so about 300 lb of load, at your weight you should be much much lower. No knobby is meant to be pumped up that high, thats the realm of 25c slicks. No matter how much you pump it up, the squirminess of the knobs will not change; I suspect that is what you are hearing. You are running the wrong type of tire IMO for high pressure. I run these 38s (rated for 50-90psi) at about 60 at 150lbs. They are light, quick, and comfortable. They will roll faster, accelerate faster, and hold speed easier than your knobbies.

Wanderer

Once you wear the square leading edge off those knobs, they will be quieter, and have less buzz!