FDNewbie

iTrader: (10)

So I take it for all cars, you should run the manufacturer's recommended psi rating? Cuz in that case, I gotta find out what it is on the FB and the Camry too...

dgeesaman

iTrader: (7)

Yes absolutely. Driver door pillar.

Dave

DrPJM1

And be very careful when you get tyres mounted. I watched in disbelief as they inflated my tyres to 50psi "because it's the max". I even had to sign a waiver because I wanted my tyres at 30psi.

Kento

They're doing that to cover their ***; that way, if you have a blowout for whatever reason on the highway and you come blaming them, they have an out. No drama, just deflate them to your own specs after you drive off; it's really your responsibility anyway to ensure that your tires' inflation pressures are correct.

FDNewbie

iTrader: (10)

Whadda ya know...LOL. It was right underneath my nose... It's stuff like THIS that makes me keep my username what it is hehe

Kento, am I getting the impression that you are more likely to have a blowout by underinflating the tires? Cuz I thought the more pressure, the more likely it is to burst, esp. when ppl overinflate them when it's cold out, and go for a hard drive, temps get up, pressure rises, and kaboom... So I don't see why a shop would have a prob w/ you UNDERinflating them

Kento

A tire has a number of various belts running through its "carcass" (the tire's overall structure) made from steel wire and extremely strong textile fabrics, so it's extremely difficult to cause it to fail due to excessive air pressure. What causes "blowouts" (which actually is kind of a misnomer) is the carcass' temperature rising to a high enough level to cause a delamination (separation) of the rubber belt layers, which results in a complete collapse of the tire carcass' structural integrity, usually allowing air pressure to escape. How do you get the tire carcass temps to rise? By constant flexing of the carcass, which underinflation allows to happen due to the lack of internal support from the air pressure.

BlueRex

Do what everyone else does and keep a good set of rims and tires for the track, auto x, etc. and a set for the street. That way you can have the good tires readilly available when you need them and it won't cost you a fortune driving on them around town.

DaveW

You often see tire failures where the entire tread area (belts and tread) separates as a unit from the sidewalls at the shoulder. This is caused by SEVERE underinflation (less than 10 psi) causing so much flex and heat buildup in the shoulder that the polyester body plies actually melt and the tire comes apart.

This can happen quite easily, since, with stiff carcass constructions, it is extremely difficult to feel when a tire is underinflated. We see this sort of thing happen very often in professional racing series where the tire constructions are extremely stiff.

Overinflation, unless the tire is overinflated by a huge amount, will not increase the likelyhood of a failure unless you hit something that punctures the tire or breaks cords.

dpankros

Seems like the point is both overinflating and underinflating are bad (duh) . There is a pressure range the tires are designed to operate within. Get slightly outside of it and your handling will suffer. Get further outside of that range and you're taking your chances. Just know the range and stick to it.

Kento

Actually, even running tires that are underinflated by as little as 20% can be dangerous to the tire carcass, especially if they see extended high speeds or loads. And not to get overly technical regarding tire failures, but the tread can separate and come apart long before the heat is high enough to melt the polyester strands in the tire shoulder. It's the actual delamination of the layers that's the killer, because once that structural integrity is lost, any number of catastrophic failures to the tire can occur. I've seen tire failures where the fabric plies were literally torn apart, with no indication that they were close to melting.

I just don't want people to think by your post that they'll run into problems only if they run their tires at less than 10 psi.

DaveW

Delete - double post.

DaveW

Kento, Thanks. I did not mean to imply that, either.

I know all about "BLB" (belt-leaving-belt) tread seps. The Ford Explorer/Firestone fiasco...

FDNewbie

iTrader: (10)

I thought about that, but I was under the impression that you should have an alignment check every time you switch tires/rims. Or is that not the case?

mad_7tist

i think it was car and driver had an article where they underinflated a tire and drove it over a plexiglass screen with a camers under it and compared the tire's footprint with a properly inflated tire. pretty scary as you could see the middle of the tire was loosing contact with the road. dont remember the exact psi below recomended but it was not alot.

Kento

If they are not the exact same brand (even though two manufacturers may list their tires as "225/55-17", that won't guarantee that they will have the exact same overall height and profile), offset, and size, then yes, you would need to get the alignment set properly if you wanted maximum performance and optimum tire wear. It's not that difficult or time consuming to have done, however.

mad_7tist

how would changing rims change the toe, camber or caster

Kento

I've been to one of Pirelli's test tracks in Italy where they have a similar setup. They have high-speed cameras setup in the ground below a clear lexan screen, then spread a thin layer of-- get this-- milk, and drive the car over it at varying speeds. I was told that milk has just the right properties and contrast so that they can see not only the footprint, but also its water evacuation properties for wet weather use.

FDNewbie

iTrader: (10)

Are you implying that you can do an alignment test yourself? Cuz over here, alignment runs about $100 on my FD

BlueRex

Hook-ups are your friend. Seriously though I'd get to know some people who can get you discounts it really adds up.

I guess whether or not it's worth it to you depends on a few factors:

1. How often do you track (or other automotive competition)?
2. How many miles do you drive around town?
3. What type of tire do you want for each type of driving?

I'm not sure what types of regulations the road courses have in your area, but I know when the car club at my college goes to Streets of Willow, they have a full inspection done. They often replace brake components, get alignments and what not (at a discounted price due both to it being a large group and the club president having a previous relationship with the owner).

Maybe you and some fellow forum members can go get alignments, and other maintenance together and try to negotiate a group price. There are deals to be had if you're patient and know the right people.

FDNewbie

iTrader: (10)

Yea that's really the part I'm lacking at. All the FD guys I know (ie really know, have hung out w/ etc) are not exactly in my area (100 miles away). The local guys I know don't track their cars, so for now, I'm kinda outta luck. I'm workin on it tho