Tyre pressure

[charliechalk]

Just a quick question that might seem obvious to some but I'm not so sure about. If you change your tyre size and wheels size would a different tyre pressure ensue? Or does it not matter? The size change in question is from 14x6 195/60/r14 to 16x7 205/45/r16.

Hoepfully someone on here knows, because I forgot to ask about this at the tyre shop.

Thanks

[merc-blue]

dont need to change pressures, abotu 32pound for road use is a good starting point
specialy for road use, if were talking about track time depends on the car driver length of the race and tyres in question

[Bahnugget]

most people run slightly higher pressures in low profile tyres but its not essential. just use a pressure around whats written on the tyre wall

[DTrain]

if you look on the tyre itself there will be a max psi - that will give you an idea on what can physically go in before bad things happen. my 205/45/r16 falkens say max of 40 or 42psi i think - i usually go 36psi. its always better to put a little bit more in than to not put enough in as if your running on 26 for example more tread will be on the road and they will wear quicker.

[TRAV-KE55]

Just a quick question that might seem obvious to some but I'm not so sure about. If you change your tyre size and wheels size would a different tyre pressure ensue? Or does it not matter? The size change in question is from 14x6 195/60/r14 to 16x7 205/45/r16.

Hoepfully someone on here knows, because I forgot to ask about this at the tyre shop.

Thanks

When ever ive ran low profile tyres i have always used slighty less pressure, there side walls are much stiffer and have much less give in them, a slightly lower pressure will give you back a bit if ride quality as well as the tyre conforming to the road better.
Trav

[kingmick]

pardon, less flex?

For genral driving to save fuel etc you can take them up atleast to 36psi and more depending on the tyre compound and width.
For performance you have to play around with 1psi diffrences to get it just right for your setup.For lap dash and full field you will have diffrent tyre pressures front to rear as one end of the car always works harder.
Just buy a good pressure gauge and try a few diffrent pressure setting {same all road for the road} and find the compromise you like best.

[TRAV-KE55]

Kingmick,
not undermining your experience, but what you will use on the road is vastly diffirent to circuit (yes i do both), for circuit yes you can up the pressures due to much better surfaces and predictability, as for general road driving with shit roads we have, you will need to have run less pressure because a low profile tyre isnt as forgiving as a high aspect ratio tyre, i imaging he has mags that have bugger all spokes and are all positioned to the outside of thewhell, these style wheels while look nice are inherintly weak on the inner side of the wheel and will suffer from a out of round wheel after a few rough roads/ potholes etc etc. Evenm on the circuit there is a balance of what works for your car and driving style/preferences. If we all wanted less flex in our tyres wi would all run light truck tyres!!!lol
Agreed for better economy and tyre response you can up the pressures like you said and you will notice a diffirence and sharper responce, but more than likley his suspension isnt setup like a race car, and bump & rebound rates are incorrect and as a result his car will tend so skip over bumps mid corner (on public roads) however with a slightly less pressure the tyre will tend to conform to bumps in the road and absorb more road shock, the low aspect ratio tyre itself will be a more responsive tyre due to less side wall flex & better design constructiopn etc etc. Also seen alot of low profile tyres on lighter cars that witha drop of a couple psi tends more often than not to improve the general feel of the tyre & be less tram tracky for general road driving.
Just my two cents worth from experience.
Trav

[kingmick]

With any tire you run lower pressure to make the sidewall flex which creates heat
A tire with less air works harder and generates more heat.

[kingmick]

They tram track less because they work more{flex}. The tyre has give with lower pressure so the Tyre Carcass will move more with the surface and not force the whole car to move like it does with a higher pressure tyrer. It is the same Affect as diffrent tyre ratio's.

[TRAV-KE55]

With any tire you run lower pressure to make the sidewall flex which creates heat
A tire with less air works harder and generates more heat.

Exactly, that works great on the track or if your pushing hard in the hills and the tyres need more heat, but the extra heat generated on a everyday road car isnt going to make diddly diffirence.
This just from my experience from competing for many years in all combinations of cars with diffirent tyre combinations from time to time.
Ultimatly he will just have to arm himself with a good tyre gauge and try what he feels is best. my Preference is a car that is a little forgiving on the road! However my last car i always ran 42psi due to them being a cheap ass tyre that had zero sidewall strentgh and needed the extra pressure just to keep the bastard on the road in a cross wind!! oh they where high aspect ratio 14' tyres to!!!

[TRAV-KE55]

They tram track less because they work more{flex}. The tyre has give with lower pressure so the Tyre Carcass will move more with the surface and not force the whole car to move like it does with a higher pressure tyrer. It is the same Affect as diffrent tyre ratio's.

Kingmick,
I think we argueing the same point here.
*trav puts his pistols back in there holsters and walks away*
Trav

[kingmick]

If you got a non "Run Flat" tire{everyday street tire and halved its normal press to exadurate the flexing, i think you would be very surprised what happens even every day driving. This is why with Run Flat tyres you have a 60km/h speed limit with them, besides the fact it will hammer the rims.

[TRAV-KE55]

kingmick
im not talking bout running them at 15psi, no doubt that will make the hot as buggery, but thats exagerating what we are on about here, why dont you pump them up to 120psi and see what happens......... Get my point.
What im saying say if he was happy running 32psi before with old high aspect ratio tyres, i would probally end up running somewhere around 28-30psi. At those pressures and even a few pound lower you will have less chance of the rims going out of round from hammering. At 28 or even 25psi if your rim hits gets hammered as you call it its because you have belted a gutter or jumped the car dukes of hazzard style onto the freeway not from normal every day driving unless your name is Bo Duke!!! He is a medium weight car ST165 Celica not a V8 falcon or commodore that wieghs plenty more.
Trav

[kingmick]

We where talking of your "less side wall flex from lower pressure" comment

[TRAV-KE55]

huh, i never said that, what i said is that with less pressure the tyre will conform to the road better... ie: the sidewall will flex more.
Trav