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Welcome, and where are you from Eve - large country the U.K.

There are various sites you can use to correctly compare the "rolling circumference" of different wheel/tyre combinations. The obvious reason is to get the answers as close as possible to reduce any effects on speedo/abs etc etc.. An example Tire Size Comparison If the wheel tyre combination is listed on the fuel flap then 100% it will be OK One certain advantage of dropping the wheels size is comfort! The A6 Allroad I purchased had 20" wheels (255/40/20 tyres) ... very quickly changed to 18" (235/55/18 tyres) just for the improvement to ride ! Put simply the total radius is the wheel + the tyre.. if the wheel is large the tyre is skinny, if the wheel is smaller the tyre is taller. The taller the tyre the more flexible and capable of absorbing impacts it becomes. The fact that 18" tyres are, generally, cheaper than 20" tyres was a secondary consideration for me ...... I just wanted to keep my teeth in when driving UK potholed roads !!

Hi its KNaCKERED, with age the rubber both sides shrinks and deteriorates, they are fairly cheap to buy and fairly easy to fit and a word to the wise do both sides as I can guarantee the other side is not far behind. Steve.

Hi if you measure the wheels including tyres from top to bottom and they are the same within five millimetres they should be fine, the only thing I would say is a must is have the car four wheel aligned on a Hunter machine as it will most probably have changed the camber/castor angles, please let us know how you get on. Steve.

I’m away at the moment but my A3 was fine up until I came away on Thursday. I have no reason to suspect the issues will return after the car has been idle for a few days. A suggestion would be to ask your contacts at Southend Audi to give Callum at Northampton Audi a call. He carried out the fix for me. Don’t know whether there are differences between the A3 and Q3 MMi. It might be he is doing something different? Surely a call is worth a try?

Thanks Gareth I will do some searching.

Hi @cliffcoggin its a chain driven twin piston cp4.2 (Fig 1.) so dual cam that gives 4 compressions per rotation, can produce up to 2700 bar or zero 😒🤣 At 150,000 if it had worn I would expect to see a lot more failures of these on vehicles up round the 130K+ mile mark that were non catastrophic and it seems very rare. They are fitted to earlier 3.0 BiTDI Audi's, Ford Power strokes (6.7 V8 Diesel) and Jeeps and RAM's some BMW high performance diesels. They seem to either grenade themselves-the roller underneath the pistons rotates 90° and then the rotating cam lobe gets a nice U carved into it (See Fig 2.) The shrapnel goes through to HP side, to the injectors so they're fubar, and back through the LP to the fuel tank, them through the LP pump to the filter, or fuel starvation/water or misfuelling=zero lubrication and a similar ending just a bit less aggressive. Fig 1. Orange is HP fuel out, and as you say, no reason why (and I believe from research it happens), that something cant stick shut and stop the HP fuel from exiting. I've tried using a Birmingham screwdriver with a soft drift while cranking to shock the top (recommended method from a diesel specialist) to see if I get any pressure but nothing and I'm not prepared to hit any harder. Fig 2. I'm looking for someone to say "ah yeah I had one of these fail, it wasn't catastrophic it was the..." I've found a guy in the States who had one fail on a Ford with very similar to my symptoms, was running but had some issues (mine was throwing P0087 at full throttle but could make 2700 Bar), came back to it and it wouldn't start... He had a new HPFP that wouldn't make pressure right out the box! Eventually managed to get them to replace that one under warranty, got one with a test certificate and that sorted it. I've got a final couple of things to double check and its surgery time... I will update anon.

Sorry hit the the box. My bad

Hi Cliff, Yes I will start to have a good look through that, just wanted to introduce myself in the first instance with a bit of background info…..I’m sure there will be lots to read and learn from. Thanks very much for your reply.

Michael. Have you looked at the Q2 forum? It might give you some opinions there.

Very useful guide from Confused.com Original article and more information at https://www.confused.com/car-insurance/driving-in-europe