Hello everyone,

I've recently purchased a new Skoda Fabia 1.6 CR TDI 90bhp with 195 55 R15 tyres. I had some fuel consumption issues and have been checking the tyre pressures a lot. On the information sticker inside the fuel filler cap, it says the pressure for normal should be 2.2bar (32psi) for the front and 2.4bar (35psi) for the rears, increasing to 2.4bar and 3.1bar respectively when loaded. However, this suggests the front tyres should be at a significantly lower pressure than the rears which is a bit unusual. I thought cars normally had the front tyres at higher pressure for normal loads as they have to carry the engine. with the rears only exceeding the fronts when loaded. Am I being a bit suspicious, or do other people find this odd? I've also checked online and the various sites suggest the reverse should be true, with the fronts at 2.4 and the rears 2.2. This seems more reasonable to me.

Thanks,

Mike

Hello Mike,

Yes, sound confusing. But actually it's normal stuff these days for most front wheel drive cars. What happens is that due to the fact the front wheels do the driving (propelling), most of the stopping and all the steering too, the tyres heat up much more than the rear tyres because of all that extra work. This being the case, the front tyre pressures will easily reach and sometimes exceed (depending on speed) the same hot driving pressure as the rear tyres within just a few miles. It's the hot pressures that are important or course and not the cold pressures (as long as they are at the manufacturers recommended cold set pressure).

You can test this for yourself by testing the pressures before lift off, and then when you have covered a good few miles check them again. It's quite surprising just how much the fronts have crept up and if you have been going fast on the motorway, they will often be higher pressure than the rears. All that energy being transfered through the tyres to the road really heats them up.

There are some other factors involved, but this is the main one.

Edited 2 November, 201015 yr by Estate Man

Hello everyone,

I've recently purchased a new Skoda Fabia 1.6 CR TDI 90bhp with 195 55 R15 tyres. I had some fuel consumption issues and have been checking the tyre pressures a lot. On the information sticker inside the fuel filler cap, it says the pressure for normal should be 2.2bar (32psi) for the front and 2.4bar (35psi) for the rears, increasing to 2.4bar and 3.1bar respectively when loaded. However, this suggests the front tyres should be at a significantly lower pressure than the rears which is a bit unusual. I thought cars normally had the front tyres at higher pressure for normal loads as they have to carry the engine. with the rears only exceeding the fronts when loaded. Am I being a bit suspicious, or do other people find this odd? I've also checked online and the various sites suggest the reverse should be true, with the fronts at 2.4 and the rears 2.2. This seems more reasonable to me.

Thanks,

Mike

My tyres are front 38 psi and rear 36 psi. They are narrower 165 tyres. This is about right for mine as I can see the wear pattern is even across the whole of the front tyres (rears havent worn hardly at all). If this were not a Greenline I have no doubt the pressures would be 4 or 5 psi less. Its a quick trick to improve mpg at the expense of road noise.

I always took my tyres over book figures on my last Fabia petrol. It gave better mpg and better handling. The down side is more road noise and a slightly firmer ride.

The max inflation pressure for my Greenline tyres I believe is 44psi (will need to check but its wet and dark outside and cant be bothered right now). This means the front are within 6-7 of max. On my old petrol Fabia the same applied as far as margin to max pressure.

Unless they are going for a greener mpg manufacturers always opt for the pressure that gives the best ride. I would not hesitate to a add a few PSI to any of my cars, especially the fronts. As far as heating up of tyres goes, having tyres at a higher pressure will reduce the heating effect anyway. Without boring you all stupid having a tyre under inflated by 20 percent will increase the heat generation by over 80 percent (Sorry thats aviation proof but tyres are tyres). Allthough you cant see it having a higher pressure can improve grip as a compressed sidewall raises the centre of the tyre. Thats why the outer edges wear faster.....its not rocket science.

If you dont mind more road noise and a firmer ride give it a try. There are those on here that will blather on at length about "oh thats dangerous, the manufacturers set the pressure for safest practice". Well let them, it works for me and many of my friends. I just turn up the stereo :p

Hello Mike,

Yes, sound confusing. But actually it's normal stuff these days for most front wheel drive cars. What happens is that due to the fact the front wheels do the driving (propelling), most of the stopping and all the steering too, the tyres heat up much more than the rear tyres because of all that extra work. This being the case, the front tyre pressures will easily reach and sometimes exceed (depending on speed) the same hot driving pressure as the rear tyres within just a few miles. It's the hot pressures that are important or course and not the cold pressures (as long as they are at the manufacturers recommended cold set pressure).

You can test this for yourself by testing the pressures before lift off, and then when you have covered a good few miles check them again. It's quite surprising just how much the fronts have crept up and if you have been going fast on the motorway, they will often be higher pressure than the rears. All that energy being transfered through the tyres to the road really heats them up.

There are some other factors involved, but this is the main one.

Hello Estate Man,

I'm really rather confused by this. From the online data, all versions of the Fabia prior to the recent facelift and new engines has the front tyres at higher pressure than the rears under normal conditions and this switched round when laden with the fronts rising only a little and the rears a lot. Unless something has changed with the new engines, I would have thought this would remain the same now. The reason I'm asking is that I set the tyre pressures to those stated on the fuel cap when I got the car home after purchase, but with the recent cold weather, adjusted them. So, I set them to 32 front and 35 rear as per the fuel filler cap. Now the temperature has increased, they're at about 35 front and 39 rear. This happened at about the same time as my mpg improved. Now, I'm sure the rears are too firm, but the fronts are at the same pressure as the fuel filler cap says for the rears. Today, I did 57.7 and 58.2mpg for my two journeys. I have a horrible suspicion the fuel filler cap is wrong and they've got the front and rears round the wrong way. This might be why my fuel economy was poor. Running 32 instead of 35psi?

Thanks,

Mike

Hello Estate Man,

I'm really rather confused by this. From the online data, all versions of the Fabia prior to the recent facelift and new engines has the front tyres at higher pressure than the rears under normal conditions and this switched round when laden with the fronts rising only a little and the rears a lot.

Mike

Hi again Mike, my 2008 Fabia 2 1422cc Estate 80bhp TDI has lower cold front pressures than the rears and these of course are upped when carrying a heavy load as per usual. Never owned a car than wasn't like that, even most of my rear wheel drive cars too. Obviously Raisbecks Greenline has the higher front pressures, but not seen any others. This may be a new thing.

There is one point to be aware of...if anyone overinflates their tyres by more than 4psi cold or lowers them by more than 4psi cold from the manufacturers specified figures (not the tyre manufacturers figs), if the car is then involved in an accident you may be prosecuted for not maintaining your car correctly. I'm talking about probably a more substantial accident when they do the full 'CSI' thing. The fact is the car might be deemed unroadworthy. No vehicle with incorrectly inflated tyres will pass an MOT if they are substantially more or less than the manufacturers figures. It can be dangerous to be over or under inflated especially on wet roads. In reality, I, like other testers would just let some air out of the tyres or put some in, and inform the owners of the situation. I don't think I ever failed a car due to over or under inflated tyres.

Note: the a figure of 4psi was the figure generally agreed by the MOT but is not actually specified as a legal actual...unless it has changed since I did testing. Therefore a vehicle would only ever fail if it was under or over by quite a bit in reality. A slightly open for debate type of situation.

Edited 3 November, 201015 yr by Estate Man

Note: the a figure of 4psi was the figure generally agreed by the MOT but is not actually specified as a legal actual...unless it has changed since I did testing. Therefore a vehicle would only ever fail if it was under or over by quite a bit in reality. A slightly open for debate type of situation.

Well adding the 4 psi gets my vote every time. The Greenline tyres aren't special in any way, Skoda just put a few extra PSI in. Same goes for any tyre. If you look up my tyre size online the recommended tyre pressures are 32 front and 29 rear. Thats 6 psi more added by Skoda to make them more efficient hence the recommended 37.6 ( 38 I like round numbers).

You only have to look at a rear tyre to see it needs less air, unless your carrying around a family and a grand piano all the time.

Edited 3 November, 201015 yr by raisbeck

Hi Raisbeck, yeah...I wouldn't disagree with much of what you say. But bear in mind, when a manufacturer does something such as up the pressures for your Greenline's tyres for example, it's only done after extensive testing and it's centred around safety. When joe blogs does it he sometimes goes to extremes and hasn't a clue about safety. Just saying... With the rear wheel pressures, the weight on them at motorway speeds can easily equal or even exceed that of the front wheels as the weight of the vehicle transfers rearwards, aided by frontal air pressure and drag of course. At a constant 70mph most vehicles have a fairly even balance of weight front to rear with just the driver in it. Put that grand piano in and it makes quite a difference with that rearward bias. And of course the faster you go the more weight over the rear wheels.

With the rear wheel pressures, the weight on them at motorway speeds can easily equal or even exceed that of the front wheels as the weight of the vehicle transfers rearwards, aided by frontal air pressure and drag of course. At a constant 70mph most vehicles have a fairly even balance of weight front to rear with just the driver in it.

In the nicest possible way.......I couldn't disagree more

Your going to have to be pretty spectacular in providing some science to back that. If you plot the cars centre of gravity against the resultant air/drag force it would be barely inches above the c of g. This would give a small increase in rear loading against a massive drag force acting parallel to the airflow...........

Car companys dont really care about tyre wear. They just want to obtain the best safety against ride comfort and handling. Harder tyres make for a harder noisier ride. Softer tyres give quieter running and smoother rides. They have to overdo the rear pressures as its possible the car will be used loaded and with passengers. If this were done on a softly inflated tyre which would otherwise be perfect for single driver use then you will get over compression of the tyre which would reduce the contact area (centre of tyre is pulled of the road) and a hugely increased temperature caused by friction heating.

No offence intended. I am an engineer by trade and that levelling up of weight distribution just doesnt sit well with my cynical brain....

In the nicest possible way.......I couldn't disagree more

No offence intended. I am an engineer by trade and that levelling up of weight distribution just doesnt sit well with my cynical brain....

Non taken...Raisbeck. Indeed this is a very polite site with everyone getting on, and that sets it apart from many other forums out there.

We actually agree on pretty much everything...not that it matters of course if we don't. I probably overstated the "At a constant 70mph most vehicles have a fairly even balance of weight front to rear" bit. I based that statement upon information I collected some years ago. It depends on so many factors, height, length, mass, suspension settings, tyres and a huge amount of other stuff, but many vehicle will have that balance at some point in the speed range, and some sooner than others even lightly loaded. Many motorcyles achieve this state very early after launching! In fact, lighter vehicles can often achieve this state sooner than heavier ones subject to the loads of other stuff being right. I too am an ex-engineer, not just a fitter. I trained as turbine engineer and later airframes (Military) and in an alternate life became, amongst other things an MT. It just means that like you I studied the laws of physics and can fumble about with spanners! But I do remember we did some testing on military vehicles which included some cars with some nifty electronic load gauges that we used, to tell us how much load was safe to carry in various vehicles. It has sensors on the springs and a bubble gauge so in use the vehicle could tell us how much load was being dealt with front to back on a per axle basis. This was a few years ago now but we found a heavy rearward bias to many of the cars when being driven at speeds above 50mph. With modern cars being more slippery and with better suspension I would guess the affects are not as dramatic now.

But I do remember we did some testing on military vehicles which included some cars with some nifty electronic load gauges that we used, to tell us how much load was safe to carry in various vehicles. It has sensors on the springs and a bubble gauge so in use the vehicle could tell us how much load was being dealt with front to back on a per axle basis. This was a few years ago now but we found a heavy rearward bias to many of the cars when being driven at speeds above 50mph.

Now they wouldnt have been rear wheel drive would they ? If so then you would get a much more significant rearward force due to the torque reaction at the axle unloading the front and transferring to the rear. We have all seen American muscle cars 'hunker down' at the rear under power. Fabia just wouldnt do that. A rear wheel drive at speed with all the associated drag from the airflow would indeed increasingly load the rear wheels as the drag/power increased.

Regardless of the physics involved I would experiment with upping the pressures a bit. Hard to see if you have an mpg improvement unless you do the same drive every day AND the car is already run in, otherwise the extra efficiency of running in will give you a false impression of fuel saved due to the tyres.

Just seen the new VRS advert............makes a change from jelly and sponge.

Now they wouldnt have been rear wheel drive would they ? If so then you would get a much more significant rearward force due to the torque reaction at the axle unloading the front and transferring to the rear. We have all seen American muscle cars 'hunker down' at the rear under power. Fabia just wouldnt do that. A rear wheel drive at speed with all the associated drag from the airflow would indeed increasingly load the rear wheels as the drag/power increased.

Austin Maxi 2200cc, and Austin Princess 2200cc both front drive, Rover SDI early shape 2000cc rear drive plus one or two others that I can't remember much about. Staff cars for our AAC senior officers (I was rotary not fixed wing engineer). You can tell how long ago it was from the cars involved. But seriously, from memory, it didn't make any difference to whether it was front or rear drive on our meter, certainly not for the purpose of our tests. Both axles being equally loaded quite early in the cruise. Front or rear drive is just another variable like high or low roof vehicle, heavy or light vehicle, wide or slim vehicle, powerful or not so powerful vehicle, if you get my drift. At one or two of our meets I've seen plenty of Fabia's 'sit down' at the rear on take off. Same laws of physics apply to front or rear drive. All will transfer their weight to the rear but to differing degrees.

PS. I know you know that!

Edited 5 November, 201015 yr by Estate Man

Interesting,

I am not completely convinced on the tyre pressure being decided on just safety. I can see it being based on road handling and ride comfort. I think if a manufacturer found a car to have good handling at 32 and 35 PSI but the 32 gave better comfort and noise the 32 would be the book figure.

I cannot seem to forget the Suzuki Vitara and the way it handled or didn't in bends - I cannot remember Suzuki doing anything about the problem of the cars falling over if driven a certain way on a bend - or maybe I am wrong?

Interesting,

I am not completely convinced on the tyre pressure being decided on just safety. I can see it being based on road handling and ride comfort. I think if a manufacturer found a car to have good handling at 32 and 35 PSI but the 32 gave better comfort and noise the 32 would be the book figure.

I cannot seem to forget the Suzuki Vitara and the way it handled or didn't in bends - I cannot remember Suzuki doing anything about the problem of the cars falling over if driven a certain way on a bend - or maybe I am wrong?

I agree with you. My tyres are nothing special. Just inflated higher to give better mpg at the sacrifice of road noise and firmer ride. Nobodys going to buy a car thats a bit noisier and firmer just to save a few mpg that cant be seen at purchase. The Greenline was pushed as efficient so they probably just biased toward efficiency over ride.

Its up to the individual of course. I always inflated mine over book pressure to give the optimum handling,mpg and wear characteristics. On the Greenline they have worked that out for me as they are inflated to where I would put them anyway.

Hi can anyone help for tyre pessures for Skoda Fabia 1.6 cr tdi 105 Estate on 205/45R16 new reg so tyre pressures websites not showing any results.

Hi can anyone help for tyre pessures for Skoda Fabia 1.6 cr tdi 105 Estate on 205/45R16 new reg so tyre pressures websites not showing any results.

31 psi

on my ContiPremiumContact2 205/45/16

but after 1 week the pressure decend to 29

Hi thanks for that

Well what you need to take into account is, that ff (front engine front wheel drive) cars usually tend to understeer. By increasing the rear and decreasing the front pressure, you make it less understeering. Why? Because when you attack a corner, your front wheels squeeze to the side and you have more contact with the road. Yes, it rolls a bit more, but it "sticks" better. It also makes the car more predictable and less prone to act up upon quirky drivers steering input.

But the rear wheels when they have higher pressure, they do not squeeze, they only have a part of their surface in contact with the road, which means that the front axle has better traction than the rear. That allows you to control the car with throttle and it keeps the car basically in the ideal line. If your front wheels had more pressure, they would not be able to handle the lateral G's, the bumps and the torque from the engine.

On the other hand, if your goal is low fuel consumption and not a smooth and best-grip ride, you may use the "heavy load" pressure setup and even add 10% of pressure to your front wheels and to your rear wheels too. The ride will be a bit bumpy, but amazingly you might save up to 10% of your precious fuel. But be careful not to drive agressively, because the car will be less stable in tight corners. Also pay close attention to your tires wear. It may increase the tire wear on the inner side (left side of your right wheel and so on). And finally, increasing your tire pressure a to higher values might result in increased bearing and suspension wear.

I hope this helped. Sorry I was so elaborate, but I have been looking into this matter for quite a while now. Cheers.

I run 40psi all round !