Tyre aging and the use of Nitrogen in tyres.

[rgh0]

Tyre companies make almost no money from OE fitted tyres, they make their money from replacements as the consumer tends to replace their tyres with the same brand

Not always. My Mazda came with some really crap Bridgestones: noisy, only merely adequate in the wet, and short-lived. I did NOT want more Bridgestones after that (especially as they get consistent crap ratings in every user-review I've read) , and got some much more satisfactory Contis instead. I think Mazda just went with the cheepest USA-market tyre they could get when deciding what to put on at the factory.

You get crap tyres sometimes on new cars as the tyre companies are bidding for the work at almost no margin driven by their marketing departments. If the car company also wants the cheapest workable tyre to meet a price point and the tyre company really wants its brand on the car then you may end up with the result you got and the marketing failure you observed.

cheers
Rohan

[rgh0]

rohan
just a small point regarding brake fluid......I used silicone dot 5 in he G4 and must say i did not notice any 'soft' feel to the pedal.....replaced the fluid in the elan last year with ordinary dot 4 and can't say there is any difference in the 'feel' of the elan brakes
I suppose it could be that all seals in the G4 were new, but only some of the elan's were....
fred

The Dot 5 fluid itself is definitely more compressible. Whether you notice this in a brake system probably depends on the pressures involved. I used it in my Plus 2 for a few years and with the booster pressures I got a longer pedal travel than with Dot 3 or 4 fluids. I never tried it in my Elan but I could believe it is less noticeable in a light car without brake boosters.

Dot 5 silicone fluid is certainly a viable alternative to glycol fluids. Its major selling point is that it does not absorb moisture that lowers its which is true. This may be useful in a car that is rarely driven in the wet as it will not absorb moisture from the atmosphere. But if you drive a car in the wet, much of the moisture in the brake fluid comes from getting past the seals on the calipers as the pistons move and this is the same for all fluids. This why you find rust inside the calipers but rarely inside the master cylinder.

cheers
Rohan

[rgh0]

I think I recall a story that with nitrogen you have no moisture in the tire. Moisture can result in pressure changes in hot tires at the limit making for curiously hard behavior to diagnose.

I haven't tested the idea myself. Could also be a load of bunkum.

John

Hi John
As i said in my post above the lack of moisture in nitrogen will give greater pressure stability compared to pumping up your tyres with air when in a damp wet climate that may introduce free water into the tyre which can evaporate when the tyre is hot increasing the pressure. This is an issue with race cars where tyre pressure stability with temperature change is critical as their operating temperatures are much higher than road cars, Pressure regulating valves to blow off the excess pressure in a race tyre are common due to this. A road car may benefit from greater pressure stability but the operating temperatures are low enough and pressure operating band wide enough to mean it is not a real issue in real life most of the time.


Just checking you tyre pressures regularly will have greater benefit as "Tyre Rack" accurately says

cheers
Rohan

[prezoom]

The other problem with having most of the places that want to sell you nitrogen is, you have to evacuate all of the air out of the tire before adding the nitrogen. Usually that means filling and emptying the tire several time with nitrogen, and it is still near impossible to get all the air out. Using two points for filling the tire can help speed things up, as you are filling the tire with nitrogen, you can have the other one open to let out air and nitrogen until you think you have evacuated all the air. This take some experimentation by checking the pressures after each session. Pretty soon, you will figure out just how long you have to go through this drill to get where you want to be. As Rohan says, keeping the tire pressure stable in a race car from the start to finish is the goal. Otherwise, you have to start the car with a lower pressure than you want, and let the growing heat of the tire bring the pressure up to the desired number, or use a pressure bleed and start with higher pressures.