Tyre Pressures
 

I'm currently riding a hybrid with 700 x 38c tyres inflated to the max 70 psi front and rear.

I've been feeling on some rougher patches of road with lots of small dips and seams in road that the front is very light and almost out of control.

Found the 15 % tire drop online and decided to give it a go. Figures came out at 67 psi rear and 44 psi front.

Decided to go 70 rear and 50 front this week and see how it goes.

Anyone have any experience of either overinflation or the 15% drop method.

Novice commuter anyone with a more experienced opinion would be welcomed.:)

With no suspension, reduced tyre pressure can give a slight spring effect. This will reduce the effect of the unsprung weight of the bicycle bouncing around and occasionally lifting from the road. The rear wheel generally carries more weight than the front, so the effect is less pronounced and ideally you should run a slightly higher pressure in the rear. The softer front tyre will slow you down somewhat compared to a rock-hard one, but for commuting and general riding the other benefits may be worth it.

I usually put 1 bar less in the front tire, i.e. about 15 psi lower. For a 700x38 tire, I would inflate to 5 bar (73 psi) in the rear, and 4 bar (58 psi) in the front.

The bike is rigid aluminium frame without any suspension, I climb about 300 ft on commute so I figured a rigid bike would waste less energy, hard enough trying to get a decent speed up them.

Will see how I go with 70/50 with week, might go to 45 if its ok on front.

Are you referring to this article about tire pressure?
http://www.bikequarterly.com/images/TireDrop.pdf

I am running 700x28 (front 70 rear 80) so I can't really compare with your 38c. The article gave me the confidence to go lower than the suggested sidewall rating of 105 psi!! My wrists/hands thank me!!

That's the one.

Dropped 20 posi off the front and going to see how it goes this week. Hopefully more cushiony.:)

My hands (and butt) have thanked me a lot after trying out the guidelines in that article a few months ago. :thumb: No reason to inflate all my tires to max when I only weigh 150lbs...

Lol me + luggage adds 100lbs to that.

Got a goal of losing 40 lbs eventually, lost 5 so far:rolleyes:

I am currently running Conti Sport Contact 700x37c and like about 60 psi rear and 55 front. I run them a little harder sometimes, but it doesn't improve my times any.

Try using this calculator put out by Michelin based on an old true and tried formula; just use the middle calculator not the first or third one; see: http://www.dorkypantsr.us/bike-tire-...alculator.html also follow the links if you want to know which percentage ratio to use. Make sure you include your total bike weight including bottles, seat bag etc and then your clothed weight.

What will work best really depends on the weight of the rider. A heavier rider will cause too much deflection (and pinch flats) if the pressure is too low. If the rider is very light, inflating to max pressure will have you bouncing all over the place.

Interesting calculators. I've always run 40 psi in front and 60 psi in back. I'll give the online calculator recommendations a shot as well.

Tried the front lowered to 50 psi today, no discernable drop in speed or increase in drag/effort required. Front tyre hummed a bit more which I guess is an indication of better contact with the road and it felt a bit more stable at speed.

Steering still feels a bit light not sure if this is due to the more upright geometry of the hybrid or not.

You reported what most others have reported. A few like their tires rock hard but in reality their loosing performance on street use due to the tire actually hopping or skipping over road imperfections, rock hard tires only work on very smooth surfaces like a velodrome and even there you don't want them to hard due to loss of cornering traction. Sheldon Brown I believe talks about the fallacy of using too high of pressure. And that Michelin calculator formula had been around a very long time, I used the formula back in the 80's! We had a chart instead of a calculator.

The steering feeling light could be the bike, it could be the brand and model of tire, tire width, if it's a new bike you may not be use to it yet.

Michelin calculator gave results within 1 psi of bike quarterly's calculator. 67 and 44 psi. Did another commute home via a rougher trail and again the bike feels more planted to the ground, cornering feels much safer and vibration is very much reduced.

I'll let it drop naturally to 45 psi and just maintain it from that pressure.

The tyres I'm using aren't the best but as I can't justify simply replacing them I'll have to wear them out first. They are 700 x 38mm almost slicks with a very shallow tread cut in them and the lightest of dimples printed on the shoulders.

Ideally as I ride a mix of road and rough cycle tracks I'd like a tyre with a smooth centre centre section for road use but with bigger shoulder tread for the rougher stuff.

Something like the Continental Top contact.

Recently returned to cycling after 10 years out and am just about to cross the 20 mile mark on the bike in 5 weeks so still getting used to things again.

I like my tire pressure to be closer together. For my 700x35's I like 55 psi in the front, 60 in the rear. Surly crosscheck with rack and bag, rider at 230lbs. I do travel some dirt and double track as well.

i like my tires pretty hard, near the upper limits of the max. recommended pressure.

- 700x37 conti sport contacts on my hybrid: 85 psi

- 700x23 vittoria rubino pros on my road bike: 130psi


when i finally wear-out the sport contacts that came with my hybrid, i'll likely drop down to something in a 32 that can take 100+psi.

You may have trouble finding such an animal. On our higher end 700x32 tires we have a recommended max pressure of 95psi. I looked at some of the other brands, and the tires that I looked at had a max pressure of 85-90 psi. That's not to say that you couldn't experiment a little, but do so carefully. Sheldon Brown writes on this particular topic here:

http://www.sheldonbrown.com/tires.html#pressure

^ well in that case, 95psi is close enough to 100.

or i could consider something in a 28, though as my hybrid is my foul weather bike, i don't want to get too narrow and high pressure. a 95psi 32 is probably the sweet spot for me on that bike.

FWIW my specialized armadillo nimbus are 700x35 and rated 75-100psi.

But man, I wouldn't run them that high personally.
I'm used to running 80 rear / 70 front and 100 is just super harsh in comparison.