Punctures.

[Burnerman]

A grand post, and thank you very much for that
Yes, I ride a Blackbird (41 psi front and rear) I can't really say if 2 psi makes any difference - its a much better bike than I am a rider
Of course I see the theory of having the better tyres on the rear of a FWD car, but just in reality I find the best ones on the front are better! If the car is understeering, say in the wet or snow, just lifting off the gas puts everything right again in the majority of cases.
For all I know, if my car steering wheel doesn't oscillate at any time, then the balancing must be ok, surely? Thats all I judge it on.....
Regarding my 500 mile puncture, the car was actually brand new (Fabia vRS) so I do think they were taking a lend.
No matter - unlike some, who never check pressures (and some cars come to me as low as 10 psi) I have no problem in splashing the cash.
John

 

[FriedFreddy]

I'm puzzled by the notion that "nitrogen maintains its pressure better than air"? For a start, "air" is about 70% nitrogen anyway! (and that's before you take into account whatever was in the empty tyre prior to inflation)! Secondly, Nitrogen is a gas, and like any other gas, is subject to the gas laws. If you heat it up, it will expand. If that takes place in a closed chamber, the pressure will increase. Whether it does so less than other gases, I'm not sure, but given that 70% of what's in any tyre is already nitrogen, I'm surprised at any differences claimed.

I think the main benefit of using nitrogen is that
(a) as has been said, it's quite a big molecule, so won't leak through the rubber as readily as the smaller molecules in the remaining 30% of the air;
(b) its pretty inert, so is less likely to react with the rubber of the tyre, improving its life very slightly
(c) because its an industrial gas from a bottle, as has been said, it's likely to be drier than air straight from a compressor.

What I want to know is whether people who have had their tyres filled with nitrogen always go back to a nitrogen-vending outlet to get their pressures checked - and if not, how do they top their tyres up?

As for valves, I have re-used ordinary valves in the past and lived to tell the tale, but I do a fair few miles and get through tyres relativey quickly, in terms of time. Whether they hit the rim or not depends, as much as anything, on the design of the rim. I've known various very quick cars to have been fitted with conventional valves with no ill effects. I prefer them to bolt-in valves as they will usually get replaced every time the tyre is changed (thereby also changing the valve core - another potential source of leakage) and it gives a chance to clean the valve seat on the rim. I've seen alloy rims damaged (corroded) and leaking as a result of bolt-in valves being fitted.

Nitrogen does expand, but a let less then regular air (providing as much air is swapped out with charging/re-charging with nitro,) hence F1 cars ONLY use nitro !

You are spot on, most people just check/adjust with reguar air thereby diluting the nitro every check, though most nitro used to come in bottles from BOC a lot of tyre shops now make it on the fly in-house with a neat gizmo that takes if from the regular air in the workshop via ozmosis.

Again spot on with the core being changed and the rim-rot on bolt in valves, bolt-in valves ALWAYS have either a rubber washer or an O-ring to seal to the wheel and these do perish, these days we actually see more valve leaks due to to dodgy seals on bolt-in valves then snap-in rubber valves though this is mostly due to the rubber valves being changed at every tyre change/repair and people (even skilled tyre fitters) thinking a bolt-in is good for the life of the vehicle !

 

[FriedFreddy]

A grand post, and thank you very much for that
Yes, I ride a Blackbird (41 psi front and rear) I can't really say if 2 psi makes any difference - its a much better bike than I am a rider
Of course I see the theory of having the better tyres on the rear of a FWD car, but just in reality I find the best ones on the front are better! If the car is understeering, say in the wet or snow, just lifting off the gas puts everything right again in the majority of cases.
For all I know, if my car steering wheel doesn't oscillate at any time, then the balancing must be ok, surely? Thats all I judge it on.....
Regarding my 500 mile puncture, the car was actually brand new (Fabia vRS) so I do think they were taking a lend.
No matter - unlike some, who never check pressures (and some cars come to me as low as 10 psi) I have no problem in splashing the cash.
John

You are spot on with the Bird pressuers (2.9bar at both ends)

On the Bird tyres, if you have BT020's do you have the correct fitments ? (BT020-W front and BT020-L rear) as they are reinforced versions specifically for the Bird.

With the balancing, modern cars can take quite a big inbalance before the steering wheel starts to shake, however the balljoints and steering rack knuckles will wear quicker even if the steering wheel does not shake.

Check my ride out :-

http://www.rumblebee.org/album_pic.php?pic_id=25416

315/35ZR24 Coopers on 11.5" x 24" 5-spokes, when I originally got the rims from California (and the tyres from Avon (happily FOC as we sell £5m pa of Avon bike & car tyres) I had to fit the tyres by hand with levers as our machines only go up to 22", also I couldn't balance them for the same reason, when I replaced the balancer with a new one that could handle them they averaged 30 - 40g a wheel, I drove her for a week before the new machine was installed and no vibration at all (though didn't go over 120mph at the time) and she had less then 10k miles on her so all joints were still nice & tight, though with the original factory fitted 20" rims I did get vibration when she 1st arrived in the UK bran-spanky with 5 miles on the clock (buggers bust have driven her round the docks in LA) and all because a 20g stick-on weight had fallen off !!

 

[Burnerman]

Regarding the Bridgestones for the Blackbird, I can only assume that they are correct as I go back to the supplying dealer for new rubber - but I will check!
Whats your comment concerning snow tyres for FWD then? Obviously we need the traction they give, if they were on the back they would be useless, but isn't this the same as having new rubber on the front, to some degree?
I'd also welcome your comments on the BMW Mini rubber - (replacements, that is) run flat, Finilec or conventional tyre?
John

 

[PJF220]

Choosing where to place tyres is not always that cut and dry. My BMW has directional tyres and staggered wheels so the rears are wider than the fronts.

 

[FriedFreddy]

Regarding the Bridgestones for the Blackbird, I can only assume that they are correct as I go back to the supplying dealer for new rubber - but I will check!
Whats your comment concerning snow tyres for FWD then? Obviously we need the traction they give, if they were on the back they would be useless, but isn't this the same as having new rubber on the front, to some degree?
I'd also welcome your comments on the BMW Mini rubber - (replacements, that is) run flat, Finilec or conventional tyre?
John

Winter tyres are an exeption to the general rule, you obviously need the best grip on the driven axle, though not much good having the front end planted and the rear end coming round to meet it on every corner - hence it's recommended to fit a full set of 4 (IF you can ever find any in the UK when required !)

Run-Flats are a whole new can of worms (the term run-flat is actually incorrect) - Goodyears are called ROF (Run On Flat) - Dunlops are SST (Self Supporting Tyre), Conti's are SSR's (Self Supporting Radials) and Michelins are ZP's (Zero Pressure) - ALL are oficially NON-REPAIRABLE and are designed to take the weight of the vehicle at a much reduced speed to get you to a garage to have the tyre replaced, they do not go flat and wobble about on the rim like a regular tyre, due to their nature (they have a VERY strong and VERY thick sidewall) there is no way to check for internal damage after being used un-inflated as they dont crumb up like regular tyres so internal damage is not visable, hence the replace over repair rule.

 

[FriedFreddy]

Choosing where to place tyres is not always that cut and dry. My BMW has directional tyres and staggered wheels so the rears are wider than the fronts.

You are not alone on your beemer, the worst are some Porsche & Ferrari's with 4 distinctly different tyres, each corner having a completely different tyre (handed / directional & different sizes from & rear)

And several 4 wheel drive models also require all 4 tyres to be within 2mm of each other, get a flat-un @ 6mm and you need FOUR new tyres ! - skimp on these and suffer a new transfer box or in some cases the ABS will pack up !

 

[Avocet]

Yes, we might be in that very situation this coming year. My wife has a little 4x4 and we've been trying to wear all 4 tyres down at about the same rate to give the centre diff an easier time. It does, however, mean forking out for four newies at the same time - which I'm sure is going to hurt!

 

[gblades]

When I have a BMW with 225/50/16 tyres I certenly noticed the tyre pressures changing with temperature. If I pumped them up when it was cold and then checked a month or so later when the temperature was 15C higher I could see the pressures were anything up to 2psi higher and that was with cold tyres and using the same digital pressure gauge.
Nitrogen is mostly used on racing cars which makes sense as they can be expected to generate the most heat in the tyres and given how much they cost to run the cost of the nitrogen is practically insignificant.

 

[jetex]

This has all made for some very interesting reading, from some very knowledgeable people. I'm a car mechanic myself, and I asked at ATS about their nitrogen machine. I thought that it had a nitrogen cylinder inside, but the guy said that the machine just removed the other gasses from the air, leaving only the nitrogen.

Sorry, just noticed earlier post saying that this machine uses osmosis to separate the nitrogen from the other gasses in the air.

 

[FriedFreddy]

I'm afraid when it comes to tyres I do have the Anarak, the hood, the gloves and the string that goes up the sleeves

 

[Burnerman]

I do hope the hood has fur around it.....
I've got a very slight dent in one of my Fabia's alloys (inner rim) - however, tyre fitter man managed to balance it out.
Seriously, is this a sensible move, or should I replace it? There's no steering wheel wobble, but you can sort of sense it, if that doesn't sound too daft.
Think is, looking at the state of our roads, there's more buckled rims to come....
John

 

[jetex]

Freddy, I hope your anorak never wears out !. Tremendous info on the tyres, always welcome to get advice from an expert. Liked your truck by the way. I used to go to Liverpool docks to get all the Jaguars and Triumph TR6's going when I worked for a main dealer. They went to America on the Atlantic Conveyor, which was later sunk in the Falklands war.

 

[birkee]

I would guess not, as no hint has come up elsewhere, but when I started reading this post, a thought crossed my mind.

Would they put Nitrogen in a repaired tyre, as some sort of reactive ingredient to cure the adhesive on the puncture repair plug?
From my experience, so many things get done these days, "because we do", that quite often the reason for doing so is forgotten.

 

[wotan]

Nitrogen is a none reactive gas, it would not aid curing, it's used for pressure stability, pressure does not increase with temp like air does.

Wotan