new tyres and traction control

[just_william]

Hiya
Put two new front tyres on my old Mondeo last night. Due to complications I couldn't put the 195/60/R15 on that were the original fit and had to settle for 195/45/R15. Now driving down the main road the traction control seems to come way too often at approx 40MPH + and kills the drive. Fine when I turn it off. Is this because of the lower profile tyres?
Cheers

[Munter]

Well every time the rear wheel go's around once. The front will go around about 1.095 times.

So the car thinks you have wheel spin is my guess. Plus at 40 on your speedo your probably not doing 40 but something around 10% less.

[just_william]

does sound like a theory. DO you think it will improve if I put the same tyres on the rear as are on the front. Trouble was I had to put new rubber on it last night and couldn't wait till this morning

[Munter]

I have absolutely no idea what that would do. But I can imagine it throwing some errors in the traction control system....all guess work.

Shirly you are currently arranging for a mobile tyre fitter to come and fit the correct tyres today/tomorrow wherever you are and therefore it's not really a long term issue just drive with TC off for a few days.

[just_william]

Well trouble is I then have £80 worth of front tyre which are perfectly good but i'm kind of stuck with and of course having to buy another two new ones. Will leave them on if I can although talking to the garage at mo to see what they say as they said it would be fine to put them on in the first place.

[phumy]

just_william said:

Well trouble is I then have £80 worth of front tyre which are perfectly good but i'm kind of stuck with and of course having to buy another two new ones. Will leave them on if I can although talking to the garage at mo to see what they say as they said it would be fine to put them on in the first place.

Then the garage lied to you as its clearly not ok is it.. I would be getting the correct tyres on there asap, otherwise youre going to have this TC problem or your speedos going to be way out, either way you need to be doing something, or not as the case may be.....

[Number 7]

As already stated, the big reduction in profile has changed the gearing by almost 10%, which is throwing the speedo reading out by that much. Plus you have now lowered the front of the car by about 30mm. Who were these cowboys?

I'd get them to put the correct tyres on asap - there may also be insurance implications if the wrong tyres are fitted.

7.

[tristancliffe]

Go back to the garage and reject the tyres as being unfit for the application. Tell them to get the equivalent tyres in the correct size for you, and to swap them over (plus balancing) for free.

Don't accept anything else.

Don't bother fitting the wrong tyres at the back - two wrongs don't make a right. Your speedo and odometer will be out, and clever things like ABS/ESP/TC might have difficulty coping (of course they might not, but why take that risk?).

Then don't use that tyre fitting place ever again. They are numpties.

[just_william]

tristancliffe said:

Then don't use that tyre fitting place ever again. They are numpties.

This is starting to make perfect sense

[cyberface]

just_william said:

tristancliffe said:

Then don't use that tyre fitting place ever again. They are numpties.

This is starting to make perfect sense

One section wider is OK (e.g. 225/50 to 235/45) if you alter the profile commensurately.

But 195/60 to 195/45 is fking crazy, any tyre fitter that did that shouldn't be doing his job, he's a bloody fool and is putting you at risk. If the drive was cut by the ECU when you went for an overtake you'd be in trouble.

Because of this obvious risk, I reckon you should go back to the fitter and ask them politely to take back the 195/45s free of charge and fit some correct rubber. The only reason this shouldn't work is if they *did* warn you of the dangers and you pressed on and forced them to fit the incorrect tyres.

If you didn't do this, then you've got legal standing to sue them for putting you at risk - obviously you don't have to get lawyers involved, because a friendly word with the boss will get it straightened out immediately. My local tyre fitter knows width/profile ratios in his head and will refuse to sell the wrong tyre to a customer, whatever the customer says... next time find someone like that

In the meantime, swapping fronts for backs may get you out of the problem, if the TC works on the front wheels only. However the 4-wheel ABS will be confused by the different rotation speeds of the rear wheels relative to the fronts, and in a braking situation could cut in unnecessarily, etc. It's not really safe - get the tyre guys to supply you with the right rubber.

[leorest]

As suggested, swapping the fronts for the rears might give you a work around for the problem, but if you start swapping tyres around you risk complicating the dispute. First course of action is to return the tyres based on the fact that they are not fit for purpose, dangerous and invalidating your insurance. Confirm with a main dealer that such a change in profile is unacceptable. If they say so then your insurance will be invalid! Take this information back to the tyre centre and stick it up someone's nose. Best of luck.

[stevieturbo]

all 4 tyres must have the same rolling circumference.

End of story.

The tyre place needs a good slap.

[mat205125]

just_william said:

does sound like a theory. DO you think it will improve if I put the same tyres on the rear as are on the front. Trouble was I had to put new rubber on it last night and couldn't wait till this morning

Your TC problems will be solved, however your speedo accuracy will still be out by the increased percentage from standard.

[paintman]

That's a massive difference!
Have a look & use the calculator on this link to see. Scroll about 1/4 of the way down the page to the heading 'a tyre size calculator' & enter the details of then tyres into the boxes. http://www.carbibles.com/tyre_bible_pg2.html
Get the correct tyres for the car fitted before you damage something.
Your speedo will also be out so you will also have fun deciding what you are doing when you go past cameras!

Edited by paintman on Friday 15th January 09:39

[just_william]

booked in tomorrow morning for the day and I have asked as you have all suggested that they put the original size back on and I am now armed with some responses should they try and charge me for it. Will let you know what the outcome is as the ABS is playing up as well now!! But hey no real surprises there. Just can't believe they said it would be ok to put them on????? I really should have known better and thought about it a bit longer myself. DOH

[just_william]

Tyre shop changed tyres for correct spec without fuss, however I might have slipped in some comments that you have all suggested. Did have to pay for one of the tyres unfortunately as the wife hit one of those pothole things that seem to have appeared everywhere and it took the tyre and wheel out so no arguments there. Driving home last night all warning and alarms cleared and even with the dodgy suspension (that is being fixed today elswhere) the car dorve fine.
Many thanks to you all for your help on this. Invaluable as always chaps
cheers jim

[Munter]