Tyre Pressure, I know that again!!!

[television]

Sorry to see the bickering going on. No matter what one thinks that they know, there is often a better solution to what you have been doing all your life. There is nothing wrong with learning more and getting new idea's, if I had not read all the technical books that I could get hold of I would have been out of business years ago. Another example is to watch someone else doing a job that you have done, and often one can pick up invaluable tips, or ideas that you had never thought of no matter how experienced you may be. The situation is worst when you are working on your own, and the mind is set on a one way track to do the job. this is often shown up in the building trade, where a guy does it the same way as his father did it, and that it often very wrong as most small builders do not keep up to date, there is a huge difference in fixing something, or curing a fault for good with modern fast changing technology.

Back to the tyre pressures. Yes the label in the fuel lid gives both unladen and fully laden figures.

These figures are not gospel but a good guide as to where to start from, these days we have rims that are larger, and the sidewalls smaller, it is often hard to just run at the recommended pressures, as on pot hole can wreck the wheel and tyre. Slightly over inflated will stop this from happening, under inflation will cause excessive heat to the side walls, over inflating will not, but can give cause to difficult handling in the wet. I think that by juggling a little on the over inflated is the better way to go.
Tyre pressures are dictated by the weight of the car. I run my SL500 with a pressure in between the two as an all round compromise, the ride is not too hard, my wheels are safe against possible damage, if there is signs of more wear say in the center of the tyre, then I may lower the pressure a touch towards the end of the tyre life.

To test a wheel for possible pot hole damage, one has only to roll the car head on to a kerb and check how far the tyre has deformed

 

[Number_Cruncher]

>>under inflation will cause excessive heat to the side walls

Yes, absolutely. Followed soon after by catastrophic tyre failure. Most of the tyre debris found at the side of motorways is caused by this mechanism.

If you are going to fiddle about with tyre pressure, don't go below the manufacturer's recommendations - reducing pressure is a step towards the cliff edge in the dark.

 

[Number_Cruncher]

>>the mechanics course when i did mine (1992-1995) was day release with 4 days on the job. now you can qualify in a year as its a full time course with no practical experience.

Although, like you, I did day release, the full time equivalent course has been running for many years. Admittedly, the practical experience is in the college's workshops, which owing to a lack of commercial and customer pressure isn't anything like the same! One of my best ever apprentices did the full time before coming to work at the Vauxhall garage where I worked to do his part 3 on day release.

Having said that, he was an excellent apprentice because he was keen to learn and listen - he was keen enough to read about the subject in his own time, and he would have made a good mechanic with no course at all. Now, he is the mechanic to whom the troublesome Vauxhalls in the county are sent by the other Vauxhall garages, because he's the one with the knowledge to fix them.

 

[turbopete]

Sorry to see the bickering going on. No matter what one thinks that they know, there is often a better solution to what you have been doing all your life. There is nothing wrong with learning more and getting new idea's, if I had not read all the technical books that I could get hold of I would have been out of business years ago. Another example is to watch someone else doing a job that you have done, and often one can pick up invaluable tips, or ideas that you had never thought of no matter how experienced you may be. The situation is worst when you are working on your own, and the mind is set on a one way track to do the job. this is often shown up in the building trade, where a guy does it the same way as his father did it, and that it often very wrong as most small builders do not keep up to date, there is a huge difference in fixing something, or curing a fault for good with modern fast changing technology.

Back to the tyre pressures. Yes the label in the fuel lid gives both unladen and fully laden figures.

These figures are not gospel but a good guide as to where to start from, these days we have rims that are larger, and the sidewalls smaller, it is often hard to just run at the recommended pressures, as on pot hole can wreck the wheel and tyre. Slightly over inflated will stop this from happening, under inflation will cause excessive heat to the side walls, over inflating will not, but can give cause to difficult handling in the wet. I think that by juggling a little on the over inflated is the better way to go.
Tyre pressures are dictated by the weight of the car. I run my SL500 with a pressure in between the two as an all round compromise, the ride is not too hard, my wheels are safe against possible damage, if there is signs of more wear say in the center of the tyre, then I may lower the pressure a touch towards the end of the tyre life.

To test a wheel for possible pot hole damage, one has only to roll the car head on to a kerb and check how far the tyre has deformed

bickering? here? i think id call it more a heated debate myself!

 

[turbopete]

>>the mechanics course when i did mine (1992-1995) was day release with 4 days on the job. now you can qualify in a year as its a full time course with no practical experience.

Although, like you, I did day release, the full time equivalent course has been running for many years. Admittedly, the practical experience is in the college's workshops, which owing to a lack of commercial and customer pressure isn't anything like the same! One of my best ever apprentices did the full time before coming to work at the Vauxhall garage where I worked to do his part 3 on day release.

Having said that, he was an excellent apprentice because he was keen to learn and listen - he was keen enough to read about the subject in his own time, and he would have made a good mechanic with no course at all. Now, he is the mechanic to whom the troublesome Vauxhalls in the county are sent by the other Vauxhall garages, because he's the one with the knowledge to fix them.

i dont doubt there are some excellent people doing the full time course. it came in a year or so after i started my course. at that time there was no requirement at all for practical experience. IMHO its the practical side of things that helps you make sense of the classroom side of things as much as the other way around.

 

[Number_Cruncher]

>>IMHO its the practical side of things that helps you make sense of the classroom side of things as much as the other way around.

I tend to agree.

I have been lucky in that regard, as a youth, I had to spend my spare time helping in my father's garage (independent garage, MOT station, and haulage yard). When I started my apprenticeship elsewhere, I already had quite a bit of good experience of a wide variety of vehicle types under my belt.

Therefore, I find some of the jibes I've been getting today quite telling and quite laughable.

I do tend to work from the manufacturer's spec. Not because I'm technically naive, or because I don't know any other ways, but, because I have seen and been involved in the engineering design and development of complex parts, and I can see the dangers of making it up as you go along or applying rules of thumb which are actually inapplicable.

 

[turbopete]

i can see your point. at the end of the day though, all we can do is advise. its up to the people reading the advice how much, or how little of it they choose to use/ignore and their choice if they do it correctly or use a "rule of thumb". all we can do is advise on the options available and offer opinions to the pro's and con's of each

 

[television]

i can see your point. at the end of the day though, all we can do is advise. its up to the people reading the advice how much, or how little of it they choose to use/ignore and their choice if they do it correctly or use a "rule of thumb". all we can do is advise on the options available and offer opinions to the pro's and con's of each

Very true, and we can only assume that the ones doing any work does have some knowledge or experience of basic engineering when it come to replacing basics like ball joints and brake components, as you say its nice to have the correct limits posted up.

 

[Juddian]

NC must be quite amused at some comments about his lack of mechanical knowledge/qulaification.

Back to the OP, those pressures do sound too high, and unless you read the label correctly (yes i know it's missing on the OP's car) it's too easy to assume the high speed/fully laden pressure is the normal lightly laden pressure.

Just looked at my own tyre label W124 coupe originally fitted with 195/65 x 15 tyres.

up to 3 people 35 fr 36 rr.
BUT in small notice below for speeds up to 130mph subtract 4psi, and at 31 fr 32 rr the car feels spot on.

To be fair it's not really clear, you do have to read the tyre pressure notice quite carefully or you will be at maximum pressure which incidentally is 36fr 46rr for my car at full load running above 130mph...not something i do normally.

 

[television]

Appologies, just seems that every time you reply to a post, you quote books and readings, joe bloggs can do the same. I am stuck with what I have learned and what I practically do.

Books, probably ignorent. Hands on, consider myself acceptable, others think that I am A1.

Stroll on.

I used to think the same, but NC has kept me on my toes, and I have improved my answers accordingly, there is a trade off balance for those of us that have a fair engineering practice and skills

 

[Number_Cruncher]

Appologies, just seems that every time you reply to a post, you quote books and readings, joe bloggs can do the same. I am stuck with what I have learned and what I practically do.

Books, probably ignorent. Hands on, consider myself acceptable, others think that I am A1.

Stroll on.

Thanks Jet Tech - I appreciate that can't have been an easy post to write.

I try to quote a source whenever possible to help people check about what I say - otherwise it could just be me ranting on!

In this case, the dynamics book by Gillespie happens to be a very well written book, and is well worth an hour or two to have a look at it. Although considering its price, it's definitely one to get from the local library!

The lucky break I had was after working in a garage for a while, my mother said that she would be supportive of me going back to college. She stopped taking board and lodging money off me, and I got some part time and agency work (as an agency HGV driver - the kind Juddian definitely looks down upon!). This cheap living and part time income enabled me to go on, and do some more study.

I've been out of the motor trade for a while now, and only look after cars for friends and family. However, my contract runs out in December, and, if the job outlook for engineers looks bleak then (who knows what the Brown menace will do!), I may end up dusting my spanners off!

 

[Juddian]

Thanks Jet Tech - I appreciate that can't have been an easy post to write.

(as an agency HGV driver - the kind Juddian definitely looks down upon!).

Oh no he doesn't, he's done it himself at times, and like you in your field there's precious little security in any jobs at the moment...many of us may well be doing things we don't want to in the forseeable future.

 

[Number_Cruncher]

i can see your point. at the end of the day though, all we can do is advise. its up to the people reading the advice how much, or how little of it they choose to use/ignore and their choice if they do it correctly or use a "rule of thumb". all we can do is advise on the options available and offer opinions to the pro's and con's of each

Yes, short of doing the job yourself, or being the person's boss, there's no element of compunction. However, I think it's fair to say that all of the advice on the site is worth far more than people are paying for it!

In some respects, I think we who have a background in the trade do need to be careful about what we tell to DIYers who most probably do not have the same background and experience that we might enjoy.

As an obvious example, most experienced mechanics can look at a bolted joint and decide how to tighten it, and, working by experience and feel assemble the joint adequately. You can't trust a DIYer to do the same, and they should generally be using a torque wrench. Remember back to Ford pinto engines with mangled cam covers peeing oil everywhere caused by ham-fisted DIYers over-tightening the bolts.

 

[television]

As an obvious example, most experienced mechanics can look at a bolted joint and decide how to tighten it, and, working by experience and feel assemble the joint adequately. You can't trust a DIYer to do the same, and they should generally be using a torque wrench. Remember back to Ford pinto engines with mangled cam covers peeing oil everywhere caused by ham-fisted DIYers over-tightening the bolts.

An example of this is when many years ago my younger brother had to replace the inlet manifold on his transit van.

He drove it round to me and I told him what to do, sometime later he called me and said that all of the studs had broken off, when he was doing them up. it was of coarse the fact that he had no feel for the alli inlet manifold, or the size of the studs he was dealing with.

So what is the answer on these forums when we do not know anything about the skills of the guys doing the repairs

 

[Number_Cruncher]

>>So what is the answer on these forums when we do not know anything about the skills of the guys doing the repairs

I'm very supportive of the route you tend to favour, which is to forward offical information where possible. The only downside is that only the OP to whom the papers are sent learns the answer.

I'm not a legalistic type, but, what would be the situation if, after reading advice on this forum someone came to serious grief?

 

[television]

I'm very supportive of the route you tend to favour, which is to forward offical information where possible. The only downside is that only the OP to whom the papers are sent learns the answer.

I'm not a legalistic type, but, what would be the situation if, after reading advice on this forum someone came to serious grief?

Through copyright reasons the details that I send out cannot be put up here, well that is for the time being as some of the info may be more freely available soon.

Yes something could go wrong, and the OP could come back and say that I did not point XYZ out to him, maybe I should put a line in my signature on this subject that any member is doing the job on his own risk.

Funny thing is that when I used to belong to trade forums for electronics, I would not answer a post from the public for the very same reasons, and that was on the grounds of safety

 

[Number_Cruncher]

In another place, I asked a similar question of one of the moderators, and this was the result;

http://www.honestjohn.co.uk/forum/post/index.htm?f=4&t=33875

 

[television]

In another place, I asked a similar question of one of the moderators, and this was the result;

http://www.honestjohn.co.uk/forum/post/index.htm?f=4&t=33875

Thanks, this is in keeping with the forum owners here too. I still may put something up, or I may ask one of the mods

 

[brianbrian]

I've got a bronze medal in ballroom dancing!!!!!!!!!!
Mrs B

 

[television]

I've got a bronze medal in ballroom dancing!!!!!!!!!!
Mrs B

Was that for the last waltz