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Discussion Starter · #1 ·
Hi

I recently changed all 4 of my tyres from run flats to standards; and also had an alignment done, on my 2.2D auto…..

Not sure if linked or purely a coincidence, but since then the car doesn’t seem as good of a drive as it was previously, now seems a bit sluggish, gear changes are lagging a bit but were pretty smooth before; and I’m fairly sure my fuel consumption has reduced.

I’m being advised to reset the auto gearbox so it learns new driving styles, but I’m worried this may make matters worse.

Anyone had similar experiences?

Cheers
 

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Tyre pressures correct? Sure they are but just a thought.... 🤔
 

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Load index? The RFT feel like a 110 I guess. XL 99? and STD are 95 I think.
Did you fit STD 95s? They would feel really different I guess?
 

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Discussion Starter · #5 ·
Load index? The RFT feel like a 110 I guess. XL 99? and STD are 95 I think.
Did you fit STD 95s? They would feel really different I guess?
The run flats were the Goodyear EfficientGrip
235/45 R19 95V and I changed them to standard non run flat Goodyear Eagle F1 Asymmetric 5 235/45 R19 99H (Reinforced, Asymmetrical)
Not sure if this helps?
Thanks
 

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You describe an unusual outcome? I would gave guessed with the new tyres the ride should be more compliant over pot holes and if anything smoother and similar MPG and I would have done exactly the same thing you have and fitted XL 99H. I am a bit stumped now 🙃. Tyre circumference, rolling radius and weight and road resistance should all be pretty identical 🤔.
I would reset the gearbox, put some fuel cleaner in the tank and use a top garages standard fuel. Maybe disconnect the main battery for a couple of hours as this may reset the fuel trims to relearn them. I am clutching at straws a bit here.
The alignment along with the tyres now seems the most logical change, this will give you a different steering feel and driving characteristics which makes sense. I would monitor your fuel consumption on your normal routes over a thousand miles and draw a conclusion then?

🖐
 

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Discussion Starter · #7 ·
You describe an unusual outcome? I would gave guessed with the new tyres the ride should be more compliant over pot holes and if anything smoother and similar MPG and I would have done exactly the same thing you have and fitted XL 99H. I am a bit stumped now 🙃. Tyre circumference, rolling radius and weight and road resistance should all be pretty identical 🤔.
I would reset the gearbox, put some fuel cleaner in the tank and use a top garages standard fuel. Maybe disconnect the main battery for a couple of hours as this may reset the fuel trims to relearn them. I am clutching at straws a bit here.
The alignment along with the tyres now seems the most logical change, this will give you a different steering feel and driving characteristics which makes sense. I would monitor you fuel consumption on your normal routes over a thousand miles and draw a conclusion then?
thanks for the advice Mate I’ll try all that out and see how it goes 👍
 

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Discussion Starter · #8 ·
thanks for the advice Mate I’ll try all that out and see how it goes 👍
Just to confirm Mate, when you say reset the gearbox, is this the proper way via cable/obd through the dealer ie Nissan in UK, or you mean the steps for a throttle reset?
I believe with the gearbox reset via obd there’s software updates available too?
 

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Its probably the same as the throttle reset. It might not help at all but it will not hurt either 🖐 Its the one where the gearbox memory for the last forty shifts gets set to default and it relearns again over the next forty shifts. 🙂
 

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Discussion Starter · #10 ·
Its probably the same as the throttle reset. It might not help at all but it will not hurt either 🖐 Its the one where the gearbox memory for the last forty shifts gets set to default and it relearns again over the next forty shifts. 🙂
Thanks Mate, think I have the instructions somewhere I’ll give that a try.
One last query you may have the answer to, I read on a Mercedes forum re air filters (as it’s the same part as Q30), so I replaced mine with a Bosch one last June during a service, but some Merc owners are highlighting problems with Bosch air filter; and recommend a Mann or Filtron filter specifically for Q30.
Possibly faulty air filter as the issues I’m having recently are similar, although they only started a month ago.
Should I consider changing the filter too, just to rule that side out?
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I would change the filter out too. They are not expensive less than £20 I think on the Web. You could always keep you old one if its low mileage and see if the new one makes a difference?
Thankyou for high lighting the Bosch filter issues, that's what I am running also a Bosch filter so I need to check. I change my filters every 8k miles normally.
Our bosch filters are German bosch I think, and the Americans I guess will be bosch USA I think - so hopefully not an issue with our filters. 🤓
 
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