Is Honest John correct?

[opsmajor]

Happy New Year

In nearly all his 'advice' in the DT Honest John advises ignoring manufacturer's recommended tyre pressures, e.g. 35/38 psi, and, unless we are doing 100 mph all the time, run on 30/30 (he says all his cars are on that). What do you say?

Krs

Mike

Edited January 7, 2017 by opsmajor
misspelling

[PCM]

Does he? I've never seen that...

I say follow the manufacturer...

 

[Verbout]

Doesn't it give that sort of information on the door pillar of all Lexus cars?

Pressures relating to car type, tyre size, front/rear tyres and speed.

[floggit]

Honest john or the manufacturer that designed the car and spent ages testing it to make it safe, easy choice .

How can he say 30/30 without knowing size/width/speed rating, load of tyre. Total rubbish.

[Britprius]

There is a law in the UK that states running a vehicle on under or over inflated tyres is an offence. Now I would imagine there is a reasonable percentage figure allowance on the manufactures figures of perhaps 10% or more, but down to 30 from 38 is a 27% drop would surely be outside of any reasonable figure.

Also remember the manufacturers figures are cold pressures so a cold pressure of 38 could be a warm figure of 40+.

John

[Haylands]

There is a way to work out the tyre pressure for any size/type of tyre...

You start off with a cold pressure of say 30psi, then drive the car at motorway speed for 30mins to get them up to temp, then take another reading, the tyre should be 4psi higher than it was when cold, if it is more or less you wait for it to cool and try again. it's a recognised way to work out the pressure when changing tyre sizes..

I'm with PCM and others though, never had any problems when running at what the manufacturer states...

 

 

[Rabbers]

He might be Honest but he can also be Wrong.

[Verbout]

11 minutes ago, Rabbers said:

He might be Honest but he can also be Wrong.

Or could it be just his opinion ?

[Silversalmon]

I generally think his advice is spot on. I would reduce pressure by 4psi (measured cold)  as they will run at the correct pressure when heated up.On my RX450h FWIW I think setting them cold at 32psi would be a reasonable solution. 

 

[Verbout]

7 minutes ago, Silversalmon said:

I generally think his advice is spot on. I would reduce pressure by 4psi (measured cold)  as they will run at the correct pressure when heated up.On my RX450h FWIW I think setting them cold at 32psi would be a reasonable solution. 

 

Interesting, and why would you trust Honest Johns' advice over the manufacturers?

[Zotto]

In a forum I write about hybrids where most people are concerned on hypermiling the suggestion in to overinflate to gain mpg. I prefer full load suggested pressure.

[PCM]

5 hours ago, opsmajor said:

Happy New Year

In nearly all his 'advice' in the DT Honest John advises ignoring manufacturer's recommended tyre pressures, e.g. 35/38 psi, and, unless we are doing 100 mph all the time, run on 30/30 (he says all his cars are on that). What do you say?

Krs

Mike

Where does he say it, Mike?

[sorcerer]

There seems to be a lot of talk on these forums about increasing/decreasing tyre pressures to achieve better MPG or this or that. I've said it before but it's worth stating again. It doesn't matter what you want to run your tyres at or what some guy in a newspaper says, it's what the manufacturer says.

I once worked with a guy who was involved in an accident and on investigation his tyres were found to have incorrect pressures. I (still) can't remember if his insurance company paid out a reduced sum or rejected the claim completely but they certainly did one or the other, as they deemed him to be partly to blame for the accident due to not running his tyres at the recommended pressures.

Does anyone really want to risk that for the sake of a few more MPG or a smoother ride or whatever?

[Silversalmon]

1 hour ago, Verbout said:

Interesting, and why would you trust Honest Johns' advice over the manufacturers?

I've read his info over the years, often followed his advice and never been let down. He is independent, though he does seem to be on an anti VAG crusade at the moment and doesn't appear to have an axe to grind. 

Why would you slavishly follow the manufacturers handbook?, it is healthy to question things you know. Do you do everything you're told?

[royoftherovers]

2 hours ago, Silversalmon said:

I generally think his advice is spot on. I would reduce pressure by 4psi (measured cold)  as they will run at the correct pressure when heated up.On my RX450h FWIW I think setting them cold at 32psi would be a reasonable solution. 

 

I too think that his advice is spot on  and generally full of commonsense.He has no axe to grind when reporting on problems and "tells it as it is "

Although I must admit that I cannot bring myself to brake with my left foot (one of his pet recommendations), when driving an automatic !

I think that my relcutance to do so stems from an incident perhaps 40 years ago when I foolishly attempted to brake with my left foot when driving a manual car and almost broke my nose on the steering wheel !!

 

Regards

John

[Britprius]

Tyre ware is directly affected by tyre pressures as is the grip of the tyres on the road. Under inflating tyres causes accelerated ware on the shoulders, more heat to be generated by the flexing of the tread, increases rolling resistance, and fuel used ultimately increasing pollution. Things are made even worse when you load the car with passengers that are not normally carried unless you adjust the pressures. Lets be honest do we alter tyre pressures unless we are going on a long prearranged run with 4 or 5 people in the car or do we carry on driving with the same pressures.

Over inflation causes the centre of the tyres to ware, road grip to be lost, and extra shock loads to be transmitted to the suspension, and car body, and a greater risk of punctures and blowouts. There is a reduction in the amount of fuel used so less pollution.

John

[Verbout]

1 hour ago, Silversalmon said:

I've read his info over the years, often followed his advice and never been let down. He is independent, though he does seem to be on an anti VAG crusade at the moment and doesn't appear to have an axe to grind. 

Why would you slavishly follow the manufacturers handbook?, it is healthy to question things you know. Do you do everything you're told?

I don't recall nailing my colours to the mast about the manufacturer's handbook. 

It is healthy to question things, that's why I question your reason for taking the advice of HJ.

[The-Acre]

I wonder if an insurance company may find a way out of paying up after a serious accident if the tyre pressures were below manufacturers recommendations.  On the subject of braking with the left foot, I've always done it with an auto, it feels completely natural.

[opsmajor]

Wow! What an eclectic range of views but that's what Forums are for. So we have Honest John with 30 psi, (a quick search on Google gives), Pure Tyre.com with 33 and Tyre Pressures.com with 35 - still lower than my door post 38. The-Acre's comment is interesting/worrying - that might be worth exploring further.

Thanks for all the replies chaps

Mike

[doog442]

My wifes Mini wants 40 PSI in her run flats when fully loaded. 

Just make sure you wear your specs and dont confuse 2.7 Bar with 27 PSI and wonder why the hell those tyre warning lights wont go out  

[sorcerer]

On 07/01/2017 at 8:05 PM, The-Acre said:

I wonder if an insurance company may find a way out of paying up after a serious accident if the tyre pressures were below manufacturers recommendations.  On the subject of braking with the left foot, I've always done it with an auto, it feels completely natural.

I guess you didn't read my reply above that I posted on Saturday at 3.26pm - have a look at post No. 13

[royoftherovers]

1 hour ago, sorcerer said:

I guess you didn't read my reply above that I posted on Saturday at 3.26pm - have a look at post No. 13

I do wish that the MODS would arrange for each contribution to each thread to be numbered sequentially !!

This is not the first time of asking.

[The-Acre]

1 hour ago, sorcerer said:

I guess you didn't read my reply above that I posted on Saturday at 3.26pm - have a look at post No. 13

Whoops, sorry I missed that.  However, it would seem that we both have great minds as we clearly think alike!

[NemesisUK]

As I posted in this thread ....

The manufacturer's recommended pressures take the heat expansion into account. It would be impossible for Joe Public to inflate their tyres to the operational temperature.

It's well known under inflation is the more dangerous scenario as tyre sidewall flexes excessively and overheats the tyre with possible disastrous consequences. 

Over inflated tyres will simply wear prematurely and give a hard ride. Because they are harder the tyre wall won't flex so much so overheating isn't a problem.

Tyre pressure is a function of axle weight so it is recommended to maintain the front to rear differential or handling could be compromised.

Bottom line, I'll stick with the pressure recommended by the manufacturer and listed in the handbook. It's stood me in good stead this last 40+ years....

[Verbout]

That ^^^^^.

Common sense, why would you trust an arbitrary man, who you don't know and don't know his qualifications, because he's given you advice that you deem to be good advice in the past.

Is it good advice because you agree with it?