jefalad

Going off topic but for information, 115bhp will get a typical modern family car to well beyond 70mph. On a level road and in still air (no headwind/tailwind) the car will need 13bhp to cruise at 50mph, 26bhp for 70mph, 47bhp for 90mph, 79bhp for 110mph, 150bhp for 140mph. An Octavia 1.0Tsi with 116bhp is quoted as having a max. speed of 126mph.

Correct. The European Tyre and Rim Technical Organisation (ETRTO) defines Extra Load (or XL) tyres as "Passenger car tyres and/or motorcycle tyres designed for loads and inflation pressures higher than the Standard version". Within the ETRTO Standards Manual there are separate tyre inflation pressure charts applying for Standard Load Tyres and Extra Load Tyres. Extra Load Tyres are capable of carrying higher loads because they can be inflated to higher pressures than Standard Load Tyres (however at "normal" loads, slightly higher pressures are specified for Extra Load Tyres compared to the Standard version). No hate mail need be directed towards the ETRTO. It is not a political organisation and was formed to establish common technical standards across the tyre/motor industry in Europe.

Yes, tyres specially manufactured for either RHD or LHD applications on certain cars do exist. The differences are in the construction of the tyre's carcass, not in the tread pattern. They are specified to assist straight line running when the car is driven on cambered roads (hence the different types for RHD and LHD cars). Most tyres supplied to car manufacturers for original equipment (OE) fitment are made to specifications which meet the requirements for a particular model of car, and tyre manufacturers are involved in the testing and development stage of a new car model to ensure these requirements are satisfied. On some cars the correct tyre fitment is considered to be particularly important and tyres manufactured to the OE specification have an identifying mark to aid selection of tyres for replacement fit (the vehicle owner's handbook will usually refer to this). Application specific tyres have been around for many years (50+) and have become progressively more complex as the demands of car manufacturers become more rigorous. I believe that RHD/LHD OE tyres were originally specified for a Japanese car model but this feature is likely to become more widespread in the future.

And to comply with legislation, ensure the wheel is labelled or clearly marked TEMPORARY USE ONLY - MAXIMUM SPEED 50MPH. If not you can mark it up yourself.

There are a number of ways of lowering tyre rolling resistance to improve fuel efficiency/emissions, and reduced tread depth is one of them. Whether this shortens tyre life depends on other features of the tyre's design and construction.

As explained in the Oponeo link, sawtooth wear is a "normal" feature of wear on tyres with block pattern treads due to the flexibility of the tread rubber. However it is a slowly developing feature and does not tend to occur on tyres which are subjected to higher wear effects due to, for example, driving and cornering forces. Hence it is most often found on the rear tyres of front wheel drive cars used mainly for motorway driving. Wheel geometry can increase the sawtooth effect by concentrating this wear phenomenon on one side of the tyre but is not the cause of it. The geometry settings specified by car manufacturers are not necessarily chosen to get the best tyre wear, stability and handling are more important to them than tyre life. As the cause is tread flexing, new tyres suffer more than worn tyres. If tyres with 4mm of tread remaining have no sawtooth wear, it will probably not occur before they are worn out wherever they are fitted. Tyre rotation is the solution and clearly this is more important early in the tyre's life. Sometimes just one rotation at 8-10,000 miles is enough to avoid significant sawtooth wear during the whole life of a tyre.

The tyre label noise rating is a measurement of the external noise emitted by a tyre and is not directly related to "tyre noise" heard inside a car (typically referred to as "road roar". A tyre with a high external noise rating can be better for road roar than a tyre with a low external noise rating. New tyres should not be compared to worn out tyres (common sense?). New tyres are generally quieter than worn tyres. You should notice an improvement when replacing worn out tyres even if the replacements are the same brand/type.

nickoll, the convention for toe settings is that toe-in is positive, toe-out negative. Two adjustments seem to have been done, front axle was toed-out and is now slightly toed-in, rear axle has had left side toe adjusted to equalise with right side and overall has increased toe-in. These new settings may explain the difference you feel but another factor is fitting a new pair of tyres to the front (presuming the rear tyres are OE). Small amounts of front axle toe-out will typically enhance turn in and make the car feel more responsive to steering inputs. Toe-in will cause the car to feel less "pointy" but add to straightline stability and perhaps feel as though there is a little more understeer. Put new tyres on the front wheels only and the front to rear tread depth disparity will cause an understeering effect due to the greater tread flex occurring at the front. Add these effects together and there is no doubt that the car will feel different. I recommend that you try swopping tyres/wheels front to rear. This alone should improve the feel if there is an appreciable amount of wear on the OE tyres. One step further would be give the front axle a little toe-out. I would leave the rear toe as it is as this will help counter the slight "oversteering" effect of putting the new tyres on the rear.

Wheelspins, I wouldn't worry about it. We have a 1999 Polo 1.4 that has a gearbox rattle exactly as you describe. Bought s/h at 25k miles, I first noticed it at around 50k miles and now at 144k miles it seems no worse. The car still has its original clutch, gearbox, and engine and they have never been disturbed.

With regard to the OE tyre fitments referred to in the OP, Huskoda's advice is perfectly correct - the 50mph/80kph speed restriction applies because the 195/55R15 spare is a different size to the 205/45R16 tyres normally fitted (regardless of the fact that the diameters of these tyre sizes are almost identical). Under the UK Road Vehicle (Construction and Use) Regulations, tyres fitted to the opposite ends of an axle on a car must have exactly the same size marking. The size markings on these tyres differ in every respect - different section width, different aspect ratio, different wheel diameter. However, if one of the tyres is defined for "temporary use only" and speed is limited to 50mph, such mixing is permitted. The sticker applied to the wheel of the 195/55R15 spare defines this for temporary use only and it therefore becomes a legal fitment (but the 50mph limit must also be obeyed to avoid prosecution, the actual speed rating of the tyre is not relevant in this circumstance). With the 195/55R15 winter tyres fitted, there is no need for the spare to be defined for temporary use only so the sticker could be removed and normal speed limits would apply. There is a potential problem. The spare will have a different tread pattern and tread rubber compound, and probably a different speed rating compared to the winter tyres. The law permits this mixing but motor insurers make up their own rules and it might lead to some difficulty in the event of a claim. The best practice would be to leave the sticker on and still treat it as a temporary spare and/or check with the insurer. We should be aware that vehicle regulations differ in other countries (even within the EU) so these rules might not apply elsewhere.

The 50mph speed limit is applied to make the fitment of a different sized wheel and tyre legal. It is against the law to fit tyres with different size markings to opposite ends of an axle unless one of them is designated for temporary use only. Although that tyre may be a "standard" tyre, in law there is no difference between it and a special "skinny" spare tyre (because they are both different in size to that fitted to the vehicle normally). The wheel to which the temporary use tyre is fitted must be different or a different colour to the other wheels on the car, and be clearly marked for temporary use only and maximum speed 50mph. Exceeding 50mph with a temporary use tyre fitted to a vehicle carries the risk of prosecution.

In the UK we need to be aware that the fitment of a tyre that is a different size in any respect (section width or aspect ratio or rim diameter) to the tyre fitted on the opposite side of the same axle is illegal unless it qualifies as a temporary spare. For a tyre to qualify as a temporary spare it must be fitted to a wheel that is visibly different to the normal wheels on the vehicle or is painted a different colour, and the wheel must be clearly marked for "temporary use only" and "50mph maximum speed". The yellow circular stickers applied by vehicle manufacturers to the steel wheels typically supplied with temporary spare wheel/tyre combinations are sufficient to conform to the regulations. It does not matter if the spare tyre is a special high pressure "skinny spare" or a "space saver" (ie. a standard tyre but with different section width/aspect ratio/rim diameter to the normal tyres but perhaps with an almost identical overall diameter). In summary, any different sized wheel/tyre combination fitted to an axle is only legal if the wheel is marked correctly as a temporary spare and the vehicle is driven at speeds not exceeding 50mph.

Our 2011 Seat Ibiza 105Tsi had an rattle which could be heard when the car was stationary with the driver's window open and the engine was accelerated gently with no load (there was no noise when idling). It appeared to me to be coming from the exhaust system and I guessed it was the wastegate "fluttering". Sure enough this was cured last year when the wastegate actuator was shimmed. Since it is not a safety related issue there was no recall, VAG dealers do this when a car is booked in for other reasons. At the same time an updated engine map was loaded which has improved the transition between no boost and boost when accelerating the car at engine speeds from 1300 - 1600 rpm, The only other engine noise I have heard is a muted "tinkling" sound which I believe to be from the high pressure direct fuel injection system. I mentioned this to the dealer and they agreed and consider it normal for these engines. I have never heard any noise that could be attributed to the timing chain.