Tyre Pressure?
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  1. #1
    1000+ Posts Shobbz's Avatar
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    Tyre Pressure?

    What tire pressure does everyone use?

    I usually have mine at around 35-38psi.

    I noticed that the tires have a max psi of 40 with a load of 1530kg.

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    The manual recomends a 24-26psi pressure for similar tires?

    THis is just for normal city driving, comfort orientated. Will the lower pressure affect the wear considerably?

    any thoughts

    thanks

    James
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  2. #2
    1000+ Posts Rod Hagen's Avatar
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    Shobbz:
    What tire pressure does everyone use?

    I usually have mine at around 35-38psi.

    I noticed that the tires have a max psi of 40 with a load of 1530kg.

    The manual recomends a 24-26psi pressure for similar tires?

    THis is just for normal city driving, comfort orientated. Will the lower pressure affect the wear considerably?

    any thoughts

    thanks

    James
    35-38ps is a lot of pressure for regular profile tyres on a 504, james. You need pressures like this in very low profile tyres at speed or under load, but not on a 504 with regular rims and tyres. In fact you are likely to suffer premature tyre wear running them at this pressure. If I were you I'd be trying around 30psi around town, front and rear, on the 504 and boosting it to 32psi for country trips or heavy loads.

    These pressures are for cold tyres, of course.

    Cheers

    Rod
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  3. #3
    1000+ Posts Shobbz's Avatar
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    Cold Tires?

    Heard this mentioned, thought it only applied to motor racing.

    U mean tires that have been road warmed I assume?

    thanks

    James
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  4. #4
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    Shobbz that's right. If you inflate tyres when they're warm (eg when you stop at a servo) you'll get incorrect ratings.

    Out of interest, I run my 306 tyres at 36psi (but then they're lowish profile - 195/55R15 - I last pumped the tyres up to 36 before leaving home for a recent drive for several hours. When I stopped later on I checked the pressures - it was up to 42 psi.

    Make sure you check the tyre pressure at home before you drive anywhere. Also, do not trust a guage at a servo - buy your own one to keep in the glove box.

    We run our 504 at 30 around the town and a bit more in the rear when there's lots of weight on a country trip. I do know that even putting up to 40psi in them doesn't make the steering any less heavy, so we just keep it at 30.

    Derek.

  5. #5
    Fellow Frogger! frogs4ever's Avatar
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    I've experimented with several different pressure combinations for my 504.

    At first I used to run the fronts, which were Continental EcoContact 175/80's, at around 31 psi, but found that the sides scrubbed out too early. (My rather spirited driving style probably didn't help though). Finnished up running them at 34 psi which gives a sharper steering response, easier low speed steering, and should even up the wear profile. Thanks to a recent tire-destroying puncture, the front Conti's have since been replaced with Michelin XH1 175/80's which I also run at 34 psi. The Michelins actually ride confortably even at this relatively high pressure.

    The rear is a different story. It's shod with a couple big, hard, Chinese 185/80's which refuse to wear out. Someone in the tyre business chuckled at them and said they are actually light truck tires! They certainly feel like it - hard riding, noisy, very loud over ripple strips etc. As a consequence, I run them at just 27 psi, in an effort to improve the ride at little, and to encourage them to wear out a bit faster so I've got an excuse to replace them with some proper (French) tires.

    In any case, the 504 tends to be a bit understeery in most conditions, so lower rear inflation helps to balance this out a little, introducing a welcome touch of rear end give.

    Furthermore, most cars, including the 504, are heavier at the front than than back, so I can't understand the logic of inflating the rears harder than the fronts, except when carrying very heavy loads in the boot or trailer.

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  6. #6
    Moderator Alan S's Avatar
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    James,

    If your car is a 504, chances are that originally they may have even been fitted with crossply tyres. In this case 24 - 26 psi was about right.
    I have 185X75X14 on the CX and usually run 32 front to 28 rear & find that's about spot on for one of those particulatly as it has an east-west engine & transmission sitting almost directly above the front cross member assembly & is a front wheel drive.
    As a rule of thumb, scrubbing the outer edges is usually a sign of too low a pressure and scrubbing out the centre of the tread indicates too high. Also, too low a pressure tends to giva almost an audible scrubbing noise on a hard corner and over pressure causes the car to skip a little sideways particularly on corners with a bit of corrugation in them.

    Alan S
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  7. #7
    1000+ Posts Shobbz's Avatar
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    Well atm I am running Michelin XZX's on the front Which I am pretty sure are light Truck tires Hard as anything but last for ever.

    They have wear around the edges, the alignment is a bit out, that will be fixed when i replace the other tire rod end.

    The rear's are Michelin MX's prolly another sort of truck tire.

    I ask all of this because even after replacing the crossmember rubbers, the rear still sounds rather loud when hitting anything at speed ie 60km/h, especially those gas line cuts in the road.

    thanks

    James
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  8. #8
    1000+ Posts Rod Hagen's Avatar
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    XZX's are almost certainly just regular passenger car tyres, James, not light truck. They were the "standard" tyre after the ZX (and before that, the X), and before the MX- which agian is a car tyre). Check the ply rating to be sure. Yes, they were a long lasting tyre, but I'd be suspecting that they have probably "hardened up" a fair bit over the years.

    With the pressure you say you are running I'm not surprised they make a noise when hitting things!

    Drop them all down to 30 psi and see what difference it makes.

    Cheers

    Rod
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  9. #9
    1000+ Posts Rod Hagen's Avatar
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    XZX's are almost certainly just regular passenger car tyres, James, not light truck. They were the "standard" tyre after the ZX (and before that, the X), and before the MX- which agian is a car tyre). Check the ply rating to be sure. Yes, they were a long lasting tyre, but I'd be suspecting that they have probably "hardened up" a fair bit over the years.

    With the pressure you say you are running I'm not surprised they make a noise when hitting things!

    Drop them all down to 30 psi and see what difference it makes. Don't forget that over-inflation adds to stress on a host of other componments in a car too.

    Alan, 504's were definitely equipt with radials from new. So were 404s from memory, although many people (sadly) changed them over to 590/15 crossplies when they wore out.

    Peugeot used to actually recommend something like 22psi in the 403 handbook for cars fitted with Michelin X! Again, 30psi worked best with them though.

    Cheers

    Rod
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  10. #10
    1000+ Posts Shobbz's Avatar
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    Thanks Rod, well they are certainly very hard tyres atm

    they are at 30 psi atm, I shall report on the ride difference after my next trip in car, hopefully tommorrow

    James
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  11. #11
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    404s were fitted with cross plies (in 1969 these were Goodrich Silvertown, a shocking tyre) as supplied from the Australian factory. I am always amused to see the road testers of the time praise the handling of the car on cross plies, knowing how much better it is on good radials.
    I have never seen a 504 fitted with cross plies, the early ones were fitted with Dunlop SP41s, later Aquajets, the first half decent tyre to be fitted from the factory was the Uniroyal 180 "Steelcat"

    Graham Wallis

  12. #12
    nJm
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    I've been experimenting with pressures in my 505's 185x75x14 Michelin Certis (yeah I know, budget tyre and all). I've been running them around the 28-30psi mark as I really do appreciate my comfort. However, the other day I was just thinking how flat it felt, and when cornering it just felt sloppy - quite obviously srubbing the sidewalls. For a little experiment I popped them up to 36psi and what a difference! Sure, the ride is a little more jittery over corrugations, but the increased cornering grip is marvelous! It also has really light steering and seems to bound over speed humps a little better.
    Nick
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    Budding Architect ???? pugrambo's Avatar
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    i used to run 215/65/14's on my 504 and 604 and used to run 34 front and 36 rear
    the 306 running 195/55/15's i run 36 all round
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  14. #14
    Fellow Frogger! Jez 405's Avatar
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    Nick, aren't yours filled with N2?
    Have you got a nitrogen gas tank and compressor at home, or are you blending it with Melbourne air?

    nJm:
    I've been experimenting with pressures in my 505's 185x75x14 Michelin Certis (yeah I know, budget tyre and all). I've been running them around the 28-30psi mark as I really do appreciate my comfort. However, the other day I was just thinking how flat it felt, and when cornering it just felt sloppy - quite obviously srubbing the sidewalls. For a little experiment I popped them up to 36psi and what a difference! Sure, the ride is a little more jittery over corrugations, but the increased cornering grip is marvelous! It also has really light steering and seems to bound over speed humps a little better.
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  15. #15
    nJm
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    I had to blend it with air.

    When Bob Jane filled them up with Nitrogen they obviously didn't do a very good job. For weeks the car had really unpredictable handling. Then I found out why - 3 tyres had 30psi and one rear tyre had 40psi!

    Since then I've just been adjusting them as per normal with air frown
    Nick
    1983 Peugeot 505 GR


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  16. #16
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    My 505 which has around 0.5 degrees of negative cambre at the front and a degree or so of negative at the rear seems to handle ALOT better with about 36psi in the tyres.

    On my 504, however,which had approximately zero camber, I didn't notice so much difference in handling between high and low pressures. In fact I found I had to run the rear tyres a couple of psi BELOW the sticker recommended figures, otherwise it would wear out the centre of the tyre very quickly (this was with the same 195/65 MXF michelins which I have on the back of my 505).

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  17. #17
    Gone Fishin' Ray Bell's Avatar
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    Graham... I think you might find that radials were an option on 404s, and that most people got them when buying the new car, certainly by 1967 or so. After all, Holdens came with a radial option those days too!

    You're right, of course, about 504s not coming on crossplies at all... but this is another pointer to the late 404s not having crossplies fitted at all, after all there was some overlap in production.

    And I wouldn't be at all surprised that crossplies were never seen on any road test cars. Do the road tests you have mention the tyres at all, other than in the specs?

    No motoring journalists I knew at that time wouldn't have said something like "the car will be better on radials" if crossplies had been fitted.

    And I knew quite a few...

  18. #18
    Gone Fishin' Ray Bell's Avatar
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    Whoops... forgot to mention...

    I always run 32psi front, 30psi rear on 504 sedans. Balances out the understeer a bit, not harsh, not soft.

    And French tyre pressures are often set very low. Check the pressures recommended for Michelin X and ZX on Renault 8s and 10s for instance... like 16 in the front or something!

    And even with those pressures and thin sidewalls, they still storm up gutters to park their cars!

  19. #19
    Budding Architect ???? pugrambo's Avatar
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    rule of thumb is that the manufacturer advises tyre pressures for cars for a comfort level not a performance level
    generally the run of the mill cars that we all drive have a suggested tyres pressure way below what you would run if you were after higher grip levels
    i even used to run 34psi in a 404 and it handled a lot better than what the book suggested
    same went for the 403's
    mind you i didn't run standard wheels on any of my cars though
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  20. #20
    2000+ Brad's Avatar
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    I was running 36 front 34 rear on my S16 with 195/50/15 Falkens. I went to the track and went to 40/38 cold, which ended up being 48/44 warm. These give much better lateral response, though are obviously quite firm in ride, though nothing too bad, and in my mind worth it for the better feel on the road.
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  21. #21
    1000+ Posts Rod Hagen's Avatar
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    mmm

    Like I said, higher pressures are desirable, even necessary, on the low profile tyres mentioned by many people here, but I have pretty serious reservations about them on standard wheels and tyres on a 504, especially as the Michelin XZX tyres on the particular car in question are pretty old too.

    I've used 504's with up to 34 psi all round on long fast trips with heavy loads, but even this is pretty close to the useable limit in them I reckon. For the sort of driving that James is suggesting (suburban / round town.etc) I think 30 psi remains the best bet. Apart from potential tyre wear issues the extra hardness will putting more stress on just about everything else, from suspension components to exhaust and engine mounts, none of which will be exactly "new" anyway given the age of the car.

    Cheers

    Rod
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  22. #22
    1000+ Posts Shobbz's Avatar
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    Well all the rubbers are new. Crossmembers were not fun to do. Are there any other rubbers at the back apart from the ones at the top of the shocks?

    If driving at 30psi means I don't have to all that again. 30 Psi it is. Maybe even 32 at the front, 30 is a little sloppy for me

    Its mainly the rear that is the issue. It just jumps up on any bump. That was the initial reason for the lower pressures.

    Does the lower pressure lessen the tire life span? I guess if it saves the suspension then its a good thing.

    thanks

    James
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  23. #23
    1000+ Posts Rod Hagen's Avatar
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    Shobbz:


    Does the lower pressure lessen the tire life span? I guess if it saves the suspension then its a good thing.

    thanks

    James
    Low tyre pressures can reduce tyre life, James, but 30 psi isn't "low" in the present context. I suspect they will last longer (in terms of tread wear) at 30 psi than they would at 36. You risk wearing out the centre tread line with these sorts of tyres at that sort of pressure in a reasonably light vehicle.

    Cheers

    Rod
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  24. #24
    1000+ Posts Shobbz's Avatar
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    Will See how 30psi goes after a week or so.

    testing cannot hurt

    James
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  25. #25
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    Alan S:
    As a rule of thumb, scrubbing the outer edges is usually a sign of too low a pressure and scrubbing out the centre of the tread indicates too high.
    Alan S
    I understand that too-low pressure causes the tyre to sit curved with the centre not touching the road (exegerating a bit), thus wearing out the outer edges only. While too-high pressure causes the tire to expand and thus sits with only centre touching the road, so wears out the centre only.

    But does frequent fast/hard cornering causes the tyre to wear out the outer edges faster as well? (assuming the tyre is always at right pressure)

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