Tire Pressure?

[Eiron]

I usually run my car tires at higher pressures than what the owner's manual recommends (in order to get even wear across the tread).
But I usually run my road bicycle tires lower than generally-accepted recommendations (in order to get a faster ride & better traction).

Are folks running their PCX tires at the recommended pressures (F=29psi, R=36psi), or something different?

[j.d.b.]

Honda specs 29 front, 33 rear from their development work. That's where I run them with no trouble.
As to my bicycle, I run the pressure up to get more speed (less rolling resistance), just as running car tire pressure higher results in better fuel economy or efficiency.

[Eiron]

Thanks for the correction on the rear psi j.d.b. I was reading the pressure for the max load rather than for a single rider.

I also used to ride narrower bicycle tires at high pressures, but due to the recent studies on bicycle tire pressure & rolling resistance, I now run wider tires at lower pressures. (I know, it doesn't fit what we've been told for years!)

[iceman]

I usually run my car tires at higher pressures than what the owner's manual recommends (in order to get even wear across the tread)

Wouldn't higher pressure mean the centre of the tyre gets most wear compared to slightly under pressure and thus more width of the tyre in contact with the road (more resistance).

[Eiron]

Yes, too high of a pressure would certainly wear down the center of a car tire. But I'm only talking about a few extra lbs of pressure. On my FWD cars, that usually means a change from the recommended 32psi up to 35psi on the front tires. Otherwise, I always end up with the shoulders of the tread worn down long before the face of the tread is worn. If I were to run them with slightly low pressure, the wear problem increases for me.

[dasshreddar]

I keep my oversized scoot tires around the stock recommended psi 28-30 front 32-35 rear...
fwd car tires i do 38 all around

[homie]

I keep my oversized scoot tires around the stock recommended psi 28-30 front 32-35 rear...
fwd car tires i do 38 all around

I have let out 3-4 pounds under the listed psi to get even better ride. If I ever buy better shocks I would pump it back up.

[honkerman]

I keep my oversized scoot tires around the stock recommended psi 28-30 front 32-35 rear...
fwd car tires i do 38 all around

I have let out 3-4 pounds under the listed psi to get even better ride. If I ever buy better shocks I would pump it back up.

Yeesh. I hear ya on the shocks. Did over 300 miles in one day from Westfield Mass to Lancaster County PA on Wednesday. It wasn't a terrible ride, but cushier shocks would have been nice.

[gn2]

I always end up with the shoulders of the tread worn down long before the face of the tread is worn.

That means your tracking is out.

[you you]

I always end up with the shoulders of the tread worn down long before the face of the tread is worn.

That means your tracking is out.

I'm not so sure this is always the case but then again I'm not an expert Don't some cars have more positive camber than optimum so as to produce a safe level of understeer. Push on a bit and start using this and it wears the outside of the tread first.

[gn2]

All fwd cars understeer, which is partly why nearly all cars are fwd.
If both shoulders of each tyre are wearing its pressure related, if one shoulder is wearing on a fwd car the geometry is out.

[honkerman]

All fwd cars understeer, which is partly why nearly all cars are fwd.
If both shoulders of each tyre are wearing its pressure related, if one shoulder is wearing on a fwd car the geometry is out.

I prefer oversteer myself, but then, I know how to drive. Let's face it, the majority of drivers have no idea what they are doing and can barely keep the vehicle between the lines. Here in the U.S., few drivers know how to drive stick, which is, I believe, a huge reason that they can barely drive at all. Of course, they think they can text, apply mascara, eat a full course dinner with a knife and fork, and even read the newspaper while behind the wheel...

Funny thing, I drove my mom's VW Jetta the other day. it's still relatively new, with only 2k miles on the clock, but when I used the auto gearbox to downshift and use engine braking, she about swallowed her tongue: "They told me I can't shift this car!" she tells me...Really? why do you think the option is there? For looks? For something to chat about over tea and cookies?

sheesh. Alright, venting complete.

[you you]

All fwd cars understeer, which is partly why nearly all cars are fwd.
If both shoulders of each tyre are wearing its pressure related, if one shoulder is wearing on a fwd car the geometry is out.

Quite a generalisation (sic)

Both worn is rarer but it could be say....undersized stretched tyres or worn tie rod bushes or...


so both can be "geometry' and not simply pressure

[Eiron]

I always end up with the shoulders of the tread worn down long before the face of the tread is worn.

That means your tracking is out.

I disagree.
On my Saabs (the FWD vehicles with which I have the most experience), they run positive camber, caster, & toe. This naturally forces higher wear on the outer edges of the tires at the factory-recommended pressures. The only way to counter this is to slightly increase the pressures by a couple of pounds. This, of course, changes the handling & ride characteristics a little bit. But the differences are small enough (for my typical driving patterns) to be of no concern to me.
___________________

Thanks to everyone for the helpful tips & advice!

[Mister Paul]

On a right-hand drive car, the outside of the nearside tyre will wear more quickly than the right. It's not about pressure, but camber and cornering.

I'd be interested to see what evidence suggests that fatter, lower-pressure bike tyres make you faster. Hadn't we better tell the Tour riders?

[Eiron]

Cool! Here's one

And here's another

There's more info out there (Jan Heine's got a lot of test data posted), but these are nice starters.

Let me know what you think!

[iceman]

Not sure that applies to anything other than thin cycle tyres (and even then it was minisucle and probably made up for by them cycling harder without knowing as it is only a few %) - those on this forum that have put wider tyres on or tyres with apparently more grip lose some mph and mpg but get better grip - which is what they wanted. Which makes sense, if you have more contact and more friction it will slow you down - that's the point, as long as you do not go silly and have very under-inflated tyres which is very bad - they get hot (I had a puncture once and the tyre had almost melted as I drove for a long way), and can come away from the rims.

[Eiron]

You are correct: those links only apply to bicycle tires. But, that was my original example (slightly higher for car tires, slightly lower for bicycle tires).

I wasn't trying to say that wider, lower pressure scooter tires would make you faster, I was only asking what the general rule was for the PCX.

[j.d.b.]

I doubt there's much to compare between car and bike tires aside from the most elemental characteristics.