Clydesdales/Athenas (200+ lb / 91+ kg) - Hi Everyone. returning back to biking/full of stupid questions.

I just bought a crosstown 3.0 (fuji). how flat should the tire look when i sit my heft on it? I don't feel that fat, but the back tire just seems to flatten out. I hesitate to ride it.

and of course, I never notice these things when i buy something.

Have you checked the tire pressure? Is it correct? I don't notice any appreciable flattening of my tires, but I'm at the low-end of the Clydesdale spectrum (~200lbs)...

Get a pump. Get a tire gauge. Check the pressure regularly, and keep the tires pumped up. The tires are marked with a range of pressures to use. If you're heavy, you should probably have them pumped up to near their maximum.

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

I'm a large fella and run my tires at max and a *bit* above if they are good quality tires. They do tend flatten a bit but you get used to it. As long as the pressure is good you should be good, unless your running really skinny tires? The smallest I run are 28s' on my Panic and they work great...

his bike (if it is a 2008) is a 700 x 35c, keep them pumped up near the max. esp the back tire (assuming you are bigish). for my 23c my back tire flattens a slight bit the front tire hardly at all for my 32c tires the back buldges slightly. some run the front lower than back, but not by much.

I did that & went on a short ride, not as bad as I thought. I think I'm just compulsive about making a mountain out of a molehill.

Check the pressure on the tire, air it up to that, and ride. How it looks is how it looks. (If it's actually too squished, you may get flats from it, but don't worry till it happens).

Check the pressure, don't guess. Check the pressure regularly...every time you ride, at least to start with, until you get a feel for how quickly the pressure drops. Bike tires lose pressure rather quickly, enormously faster than car tires.

Consider an idealized case, with some rather crude approximations: Take a tire inflated to 100psi, and touch it to the ground with absolutely no weight on it, not even its own. It'll touch the ground at a single point, with no flattening at all. Now, apply some force...say, 100 lbs. The tire will flatten somewhat to support that force. How much? Well, neglecting most of the real world, it'll flatten to the point where the contact patch touching the ground is about 1 square inch (it's mainly the air pressure that's supporting things). Now increase the force to 200 lbs, and the tire will flatten more, until the contact patch is 2 square inches. The tire has to flatten in order to support any weight.

Most tires supplied on stock bikes, especially lower end bikes are pretty much junk. They flat easily, the cut, tear and wahtever else. When I buy a new bike, I toss the stock tires befoe the bike even leaves the showroom floor.

I bet if you dish out a few bucks for some good tires, you'd have a better feeling about the tires. Continental makes good tires, spend about $25-$35 for something decent even if only the rear tire first if on a budget. Front usually not as much an issue as the rear. Stock Bontrager/Cheng Shin and a few others on low end bikes usually have issues.

I just switched my 700 X 35c's out for 28's on my 2007 Crosstown 2.0. Im 315 lbs. and was using 75 psi on the rear, and 70 psi on the front

I understand being worried, a new bike is a big investment especially if it is your first bike shop quality bike. No biggie :thumb:

So how about some pictures of this bike? It's a rule round these parts ya know.

I did that & went on a short ride, not as bad as I thought. I think I'm just compulsive about making a mountain out of a molehill.

You're among friends...

You're among friends...

That said, let me make the standard offer to the OP. If he's in the Philadelphia, PA, area, I'll ride with him if he likes. PM me.

It is IMPOSSIBLE to have a tire stay completely round once weight is added. Only worry about tire pressure during a ride when the steering/handling gets sluggish. If you can break the laws of physics and chemistry, let us all know.