Tyres "perishing"

goonarmy

facade wrote: »

That isn't the reason.

Most likely the nitrogen is a safe cheap dry inert gas to have knocking around in high pressure cylinders, rather than compressed air which needs driers and a creaky clanky old compressor.

Oxgen molecules are usually said to be about 3% smaller than nitrogen molecules, and over a year, you may see a very very very slight difference in pressure loss over an 80% nitrogen, 20% oxygen (air) tyre vs a 100% nitrogen filled tyre, but certainly not over the duration of a race.

The reason Kwikfit try to sell you nitrogen at a huge price is because some people will actually buy it, then it is extra bubbly at the shareholders meeting

Er, no.the nitrogen is more stable (less expansive) at race temp and less likely to migrate through the rubber(yes an issue in one race) and nothing to do with health and safety. A risk assessment that goes along the lines of "we have something safer so we will offer that in addition to the original thing" is more risky than leaving things alone as now you have two things to manage. But yeah, not much use in a standard nissan micra used on the school run.

facade

goonarmy wrote: »

Er, no.the nitrogen is more stable (less expansive) at race temp and less likely to migrate through the rubber(yes an issue in one race)

I'm no expert, but I would have thought that at the sort of temperatures & pressures used, both pure nitrogen and the mixed gases in air behave as ideal gases, and therefore would expand the same.
However, if there was water in the air mix there would be some effect as it evaporated and put more gas into the tyre.

The migration through the rubber issue, I really don't know.

Elf & Safety: I do know that passenger aircraft tyres use pure nitrogen as there is a low limit on the amount of oxygen they can contain in case the tyre catches fire, I've no idea about race regs.

But the conclusion is the same: A pure nitrogen fill on a road car tyre is a waste of money if they charge extra.

Ultrasonic

50Twuncle wrote: »

UPDATE:
New tyres being fitted today - paid for by the dealers who I bought the car from 2 years ago.

Good to see you got the right result in the end. This was what should have happened when you first went back to the dealer IMHO.

colino

Nitrogen, the next profit line for KF! If the tyre is mounted to the new wheel and attached to a vacuum pump to strip the air out and then filled from a 100% N tank, how much more beneficial is that to the garage airline, which will pump in fresh air, made up of around 79% Nitrogen?
They'll start charging for putting the cars on the lifts next.

red_eye

facade wrote: »

That isn't the reason.

Most likely the nitrogen is a safe cheap dry inert gas to have knocking around in high pressure cylinders, rather than compressed air which needs driers and a creaky clanky old compressor.

Oxgen molecules are usually said to be about 3% smaller than nitrogen molecules, and over a year, you may see a very very very slight difference in pressure loss over an 80% nitrogen, 20% oxygen (air) tyre vs a 100% nitrogen filled tyre, but certainly not over the duration of a race.

The reason Kwikfit try to sell you nitrogen at a huge price is because some people will actually buy it, then it is extra bubbly at the shareholders meeting

nitrogen is not brought in, next time have a look inside the workshop, there will be a big blue uniflate box. This is hooked up to the air compressor and filters out the N7 from the o2.

Ok moving on,

slicks generate alot of heat during a race, this heat causes the o2 to expand increasing the tyre pressure.

for a car to be competitive it need its chassis tuned for the track, there are a load of adjustments that effect the handling, tyre pressures is one of them adjusting the tyre pressures can affect how quick the tyres heat up, how the chassis feels also is used counteract over and under steer, so it is a good idea to have a gas that is not sensitive to temp.

red_eye

colino wrote: »

Nitrogen, the next profit line for KF! If the tyre is mounted to the new wheel and attached to a vacuum pump to strip the air out and then filled from a 100% N tank, how much more beneficial is that to the garage airline, which will pump in fresh air, made up of around 79% Nitrogen?
They'll start charging for putting the cars on the lifts next.

the air is not stripped out filtered N7 is pumped in along with the o2 contaminated air that would be present outside of a vaccum.

on a plus side as this is is stripped of 02 and moisture wheels are less likely to corrode :j

colino

So if the newly fitted tyre already has most of its volume filled with good old fresh air (79% N) when you increase the pressure with this stripped air, there really isn't a whole lot of difference in percentage terms of the amount of nitrogen in the fully inflated tyre.

Ultrasonic

red_eye wrote: »

nitrogen is not brought in, next time have a look inside the workshop, there will be a big blue uniflate box. This is hooked up to the air compressor and filters out the N7 from the o2.

N7? A nitrogen molecule consists of two nitrogen atoms, so it would be N2 in the same way that oxygen molecules are O2. (7 is the atomic number of nitrogen, which I guess is where the confusion arose.)

slicks generate alot of heat during a race, this heat causes the o2 to expand increasing the tyre pressure.

for a car to be competitive it need its chassis tuned for the track, there are a load of adjustments that effect the handling, tyre pressures is one of them adjusting the tyre pressures can affect how quick the tyres heat up, how the chassis feels also is used counteract over and under steer, so it is a good idea to have a gas that is not sensitive to temp.

If you had two tyres, one filled with 100% nitrogen and the other filled with 100% oxygen they would both show pressure variations with temperature that are near as makes no difference identical. The potential gain from a motorsport point of view arrises from the lack of moisture in nitrogen filled tyres compared with those that are air filled.

Ultrasonic

As a side note, I always top up the pressures in my tyres with a manual pump. Am I potentially doing long term damage to my wheels due to the moisture content of the air, compared to fuel station forecourt compressors that I guess dry the air?

mattyprice4004

Ultrasonic wrote: »

As a side note, I always top up the pressures in my tyres with a manual pump. Am I potentially doing long term damage to my wheels due to the moisture content of the air, compared to fuel station forecourt compressors that I guess dry the air?

You guess wrong - they don't.