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Discussion Starter · #1 ·
Can anyone help please? I have just had two new Toyo Proxes Comfort tyres (205/55/R16 91V) fitted to the front of my Astra H Design estate 1.6-litre and it's now like driving through treacle with how sluggish the car has become. Does anyone use this brand/size of tyre on their Astra and have had any issues or change in the mpg-rate as my economy is down about 5 mpg? Any opinions, thoughts, etc would be appreciated. Cheers.
 

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Sounds like tracking and maybe tyre pressure or binding brakes, used Toyos on many cars and always great in the wet and never a problem, thats what I would look at first.
 

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Discussion Starter · #3 ·
Sounds like tracking and maybe tyre pressure or binding brakes, used Toyos on many cars and always great in the wet and never a problem, thats what I would look at first.
Cheers boggsy. I had the tracking checked @ the same time and it's fine. One thing that is a bit unusual is that the Toyos are inflated to 36psi whereas the original Avons are to 33psi. Could that have made a difference do you think? Curious, though, as to why the same size tyre (but from a different manufacturer) would need a different pressure? Any thoughts?
 

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Cheers boggsy. I had the tracking checked @ the same time and it's fine. One thing that is a bit unusual is that the Toyos are inflated to 36psi whereas the original Avons are to 33psi. Could that have made a difference do you think? Curious, though, as to why the same size tyre (but from a different manufacturer) would need a different pressure? Any thoughts?
Different sidewall thicknesses and deferring tyre sidewall designs can result in a more or less flexible sidewall than the ones you had fitted previously (think eco tyres vs sportier tyres). Although they are the same size, they could require a little more pressure to achieve the same level of performance.

Also the rolling resistance will change from tyre to tyre, but it doesn't normally make a big difference to economy, so if you have noticed a 5 mpg loss and the tyres are all 100% correctly inflated, there is an issue elsewhere.
 

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As Ayresyy says tyres really don't make a notable difference unless under inflated badly, take my BiTurbo book says you can run them at 34psi for a softer ride, or at 39psi for that sportier ride, but I run them at 40psi in the summer and 38psi in the winter, I notice a drag at 34psi and don't like it.


I would lift each corner of the car and spin the wheels, if they don't spin free then the brakes are sticking, I done all my guide pins with hi temp silicone grease and they now spin 2-3 times easily, before they would just spin about half a turn and stop, the J's are well known for this, but my H was like it too but not as bad.

What does your manual say to inflate the tyres to? This is what they should be.

The only things that will cause a drag,
Tyre pressure.
Tracking,
Brakes sticking
Handbrake sticking
I'm eliminating other things as you have only had the tyres changed and trying to keep it simple for now, could be coincidence that something under the bonnet is the problem.
 

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Discussion Starter · #6 ·
Thanks for the suggestions. She's booked in on Tuesday to have the exhaust mid-section replaced so I'll get then to check the brakes checked for binding too. I'll enquire, too, if the garage has any diagnostic equipment that they hook my car up to for a static test (I'm using a local garage rather than taking it to a main dealer) and compare my own car's stats to the Vauxhall original stats to see if there's any marked difference between the two: it might confirm where the problem lies hopefully
 
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