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Discussion Starter #1
Good Morning All,

I recently had 2 new front tyres on my 159 2.4 ti ? the tyres that were on the front were 235/35/19 so when I took it to the garage they replaced it with the same size, replaced upper and lower arms on drivers side front and did a 4 wheel alignment.

Since picking up the car I realised the rears are 235/40/19 and now understand that it should be 40 all round. I spoke the garage and they can?t accept the front tyres back now because they have been used for a few days ? and they informed me that I shouldn?t have a problem as long as the 2 front tyres are the same.

However, since having the front tyres replaced I have notice that sometimes when I accelerate while turning the traction light flashes on the dash and power is cut temporarily, it may be coincidence but this has only started happening since I had the work done. Tyre pressures are all even 40psi on the front and 36psi on the rear.

My questions are:

1.) How vital is it for me to have 40?s all round ? is it worth me selling these 35?s while they are only a week old, and putting 40?s on the front to match the back?
2.) Could the fact that ive got the wrong profile on the front be causing my traction issue?
3.) Is there anything that could have been disturbed during the work eg. ABS sensor or similar that could be causing an issue?
4.) Does anyone have any other suggestions?


Thanks in advance

Otis
 

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The traction control will be constantly seeing the front tyres rotating faster than the rears, so will think you have permanent wheelspin.
The 235/35 will also be underrated for the 159 (the load index will be too low).
So yes you should replace the fronts with the correct size.


There will also now be cries from people saying that the new tyres should go on the rear.
 

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Hi Otis,

I have the exact same issue. Local tyre supplier who know their Alfas very well recommended a new tyre for the front of my 159, a Zeta tyre with 35 profile. Like yours, my rears are still a 40 profile. They explained that some additional width in the Zetas would afford more kerb protection (which I was almost insulted by, given that I avoid being within anything less than a country mile of any kerb, or kerb-looking solid item!!).

Like yourself, whilst turning and accelerating simultaneously, I experience the same traction issues - so thank you to David above for the explanation as to what is going on!

I think I'll be raising this with my tyre provider when the time comes for some replacements. They assured me that the different profiles would be fine on the car as the two fronts matched and the two rears matched - seems the car doesnt like it and I think David has hit the nail on the head as to why!

Glad to know I'm not the only one, and thank you David for the explanation!

Phil.
 

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Discussion Starter #4
Thanks for the replies guys - this explanation makes sense, but what confuses me is my car had 235/35/19 on the front up until they were changed week and it never had this traction problem.
 

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It's amazing how tyre dealers always reckon they know what's best for your car.
As always, RTFM.
 

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New tyres tend to be a bit slippy compared to old, worn in, tyres, until they themselves are worn in a touch - ie all mould release agent worn off etc.

You might simply have a less grippy new tyre than the old ones.
 

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My car has different size tyres front and back, and that how Lexus want it, so it's not uncommon, as can be seen on a lot of super cars.

I'd live with it unless you've got money to burn.

But bear in mind what David said, they may be underrated for your car, and not what Alfa Romeo recommend, or your insurance would be happy with.
 

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Good Morning All,

I recently had 2 new front tyres on my 159 2.4 ti ? the tyres that were on the front were 235/35/19 so when I took it to the garage they replaced it with the same size, replaced upper and lower arms on drivers side front and did a 4 wheel alignment.

Since picking up the car I realised the rears are 235/40/19 and now understand that it should be 40 all round. I spoke the garage and they can?t accept the front tyres back now because they have been used for a few days ? and they informed me that I shouldn?t have a problem as long as the 2 front tyres are the same.

However, since having the front tyres replaced I have notice that sometimes when I accelerate while turning the traction light flashes on the dash and power is cut temporarily, it may be coincidence but this has only started happening since I had the work done. Tyre pressures are all even 40psi on the front and 36psi on the rear.

My questions are:

1.) How vital is it for me to have 40?s all round ? is it worth me selling these 35?s while they are only a week old, and putting 40?s on the front to match the back?
2.) Could the fact that ive got the wrong profile on the front be causing my traction issue?
3.) Is there anything that could have been disturbed during the work eg. ABS sensor or similar that could be causing an issue?
4.) Does anyone have any other suggestions?


Thanks in advance

Otis
You don't say which tyres you had on before, and which after? swapping Goodyears or Contis for cheap Ling Long remoulds would also give poor traction.....

Further, is it just the light coming on and the traction control cutting in, or with the traction control switched off, do you feel when driving there is an actual reduction in traction from your previous tyres? bear in mind they will need to be run in a little bit before giving their optimal performance...

also see below Re: tyre profile. 235/40/19 and changing to 235/35/19 will impact on rolling circumference and speedo reading...but changing to 245/35/19 may not if they have put on a wider tyre to compensate for the lower profile....

Hi Otis,

I have the exact same issue. Local tyre supplier who know their Alfas very well recommended a new tyre for the front of my 159, a Zeta tyre with 35 profile. Like yours, my rears are still a 40 profile. They explained that some additional width in the Zetas would afford more kerb protection (which I was almost insulted by, given that I avoid being within anything less than a country mile of any kerb, or kerb-looking solid item!!).

Like yourself, whilst turning and accelerating simultaneously, I experience the same traction issues - so thank you to David above for the explanation as to what is going on!

I think I'll be raising this with my tyre provider when the time comes for some replacements. They assured me that the different profiles would be fine on the car as the two fronts matched and the two rears matched - seems the car doesnt like it and I think David has hit the nail on the head as to why!

Glad to know I'm not the only one, and thank you David for the explanation!

Phil.
Having a lower profile doesn't necessarily matter so long as the outside rolling circumference is the same/similar.

wider tyre and lower profile would still give a similar/same tyre wall thickness and therefore outside rolling circumference. Further to consider is that if you start a tyre with 8mm tread, you can loose 6mm and still be legal but that's 12mm off your diameter and therefore smaller rolling circumference...so the traction control can't be too fine tuned or it'd mess up as your tyres wear and you replace them out of sync front to back.

you can find outside diameter calculator things in 'tinterweb so use that to compare and if its with 2-3% I think is the guideline figure, then you are ok. (also impacts on your speedo reading having non standard tyre size).

worth also noting that non-standard tyres are a modification and ought to be declared to insurer or it is technically void....
 

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The traction control will be constantly seeing the front tyres rotating faster than the rears, so will think you have permanent wheelspin.
The 235/35 will also be underrated for the 159 (the load index will be too low).
So yes you should replace the fronts with the correct size.


There will also now be cries from people saying that the new tyres should go on the rear.
Interesting that. I always (wrongly) assumed the traction control only checked rotation on the same 'axle' only. :beer:
 

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I would suggest that as you replaced the fronts with the same size the issue is more likely to be the quality of the tyres you put on rather than the rolling circumference.

It could well be a combination of both the size and new tyres being less 'grippy' than the old ones.

I have read on other (motorbike) forums that even good quality tyres have a slippage of upto 10% when used hard, (which means even in a straight line when pushed hard tyres will be covering 10% more distance than actually travelled, I don't know if I believe/understand this but the quote was from a guy who works in the tyre industry)

'If' thats true, and traction control does monitor all 4 wheels even in a 2wd car, you would probably have seen the traction control kick in less as the tyres bedded in.

Axe.
 

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Keep in mind, its more likely to be the ESP or VDC? Stability control that's doing this as that would be 4 wheel linked and would impact on the power if it thinks the car is sliding in some kind of way.
 
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