Tire shelf life

[Lars Kanter]

We have two unused sets of Goodyear 20x6.5-13 R065s that we were intending to use this past year, but the damn things wouldn't seat on our BBS wheels. I was wondering if there is an issue with storing them until the spring to use on our next car; that is, does the compound degrade over time? I imagine the rubber is a damn stable material, but who knows what else goes into the compound.

[Buckingham]

Just as long as you don't "leave em out back behind the tool shed", they should be fine.

I don't know if I would run them at competition, but they will perform fine for testing/practice.

I've run on tires a few years old before without any problems.

[Didier Beaudoin]

Make sure they are well wrapped in plastic film because the compound can dry if it stays exposed to the air for a long time.

[Charlie]

It's all relative, and I'm not saying rubber and air are like vinegar and baking soda http://fsae.com/groupee_common/emoticons/icon_wink.gif but rubber is not stable and will break down, components will evaporate and the compound will change.

Keep the tires in a cool, dark dry place. Sunlight's a killer and so is heat and moisture. Wrap them in plastic wrap. They should be good for several months that way. They'll still end up harder than new tires but usable.

[fsae racer]

and store them on their side in order to prevent the carcass from going out of round.

[Tommo]

They will seat
they just might require a shit load of pressure
probably not ideal for competition as mentioned above

[Jreyenga]

make sure to keep them away from ozone or sunlight.

Most plastic bags still breathe a little bit. The best idea for storage is something totally air-tight. At the least, don't keep them in the shop around the welding machine. Though it might be worthwhile to get new tires for competition.

Formula V or HotLap ought to also help bring them back to new.

There are lots of fancy oils and stuff in the rubber that helps maintain their visco-elasticity, which is one of the big effects for generating grip.

Is vacuum bagging tires overkill? Perhaps, but tires are the most important part of the car.

Also, make sure they aren't sitting at elevated temperatures. I'd imaging anything over 100 degrees ought to heat cycle the tire some. (no tin shed in the Florida sun)

[Lars Kanter]

Thanks for the input everyone.

Jreyenga,

I don't think vacuum bagging is overkill; not only are they one of the most important parts of the car, they're one of the most expensive!

Tommo,

I assume you have experience with the BBS/Goodyear combo. How did you get them to seat? We took them to a few different shops and they cranked up the pressure to 120psi or so and lubed up the rims and they still wouldn't seat. Any higher (and even that high), you're risking catastrophic failure and possible serious injury if the thing explodes.

This brings up an interesting question: if the tire doesn't seat, who's fault is it? The Goodyears seat on other wheels, but they could be manufactured slightly smaller than spec and thus not quite fit on the BBS wheels. Alternatively, the wheels might be slightly larger than spec. The Hoosiers seat on the BBS wheels with no problem, so something went right there. I can't imagine it being our fault - a 13" tire should fit on a 13" wheel of the correct width and that's all the info a designer should have to deal with... Bottom line is we have two sets of expensive tires that we won't be able to use in competition, and whose properties will probably change noticably before we finish our next car, thus not giving us accurate representation of our competition tires should we choose to use them for suspension set-up and tuning. In my opinion, whoever's responsible should pay for our somewhat wasted tires.

What do you all think?

[Jarrod]

Having fitted a lot of different tyres to FSAE cars over the last couple of years, (dunlop, avon, hoosier, goodyear, formula ford) to a few different rims (mostly spun aluminium)I can tell you that some tyres will go on very easily, (avon and hoosier), while the others are typically a lot tighter. The wire around the bead of the tyre is very stiff, so it won't take much difference to make them hard to seat. Measure your rims, if you have different sets you may find a bit of difference (we have seen over 1mm on diameter, apparently the tolerances are quite large.) So a small tyre bead and a large rim bead will hard to seat. Be very careful about overpressurising tyres, Dunlop recommends never going above 65psi ever, and 40psi is the general limit. I imagine other manufacturers have similar limits. Spun aluminium sheet rims can be very dangerous at high pressures. Make sure you have safety cage if you really want to crank up the pressures, it can be really messy.

[james17]

To all attempting to mount tires, I don't know if this is an approxed method of seating beads but it is an old one and it does work. Mount the tire on the rim, then take either a leather belt (preferable) or a ratchet strap and wrap it around the circumfrence of the tire. When you inflate the tire the pressure in the middle of it's cirumfrence will cause it to seat. Has'nt ever not worked for me.