Tyre effect.

Now then. Yuo have to be patient here this might be just my imagination.

I had the tyres replaced today. Same size but Colway ATs. Originally I was just going to get two but saw the price (£37) and had the front ones replaced as well.
Before replacement I had two reasonable tyres on the front and two near bald ones on the back also different manufacturers front to back. The car ,boomed, loudly when turning on near full lock at low speeds and at 30mph in 4th it did the same seeming to struggle to accelerate. Now, with the new tyres, it doesn't seem to boom in either circumstance and will even pull from 25mph in 4th. The revs are the same so the tyres aren't smaller. If anything they are taller.
The theory is that the tyre diameter difference, front to back, was increasing the drive ratio difference, front to back, and causing a more pronounced drag through the VCU. Early days yet but hopefully I will confirm after a 170 mile trip tomorrow. If it is I'll be rotating tyres on a monthly basis from now on.

I think the key here is "also different manufacturers front to back". find out from your local tyre depot the rolling diameter of the two diff manufacturers - bet yu they are different!
I had the same prob - same nominal size tyres - but diff diameter from diff manufs!

Thanks for that Hat Man.

Did you find the same improvements, cause I was getting a bit ****ed off with this particular 'quirk'. Still, at £37 quid i won't bother changing tyres except as sets in future. The back ones really were bald.

i had the problem ACROSS an axle - and i got violent - and i mean DANGEROUS torque steer on acceleration and near impossible braking. Swapped wheels across axle - problem transferred - new tyres - problem solved.

The Mad Hat Man said:

i had the problem - and i got violent -

Click to expand...

very much

evening Mondeo

eveni...zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz!

nutting new there - wot is it wiv yu and Marcus - yu aint got a baby too - have yu?

must be me hectic social life !

evnin flops. . .zzzzzzzzzzzzzzzzzzzzzzzzzzslorry musta dozed orft. . .

OK. Just done a 170 mile round trip. Its a different car it pulls upto 70+ and stays there with a lot less throttle. Only slight booming on really tight turns.
It coasts better on the old reverse on full lock. I can't belive it. So simple.

Makes me wonder how many VCUs have been replaced before their time because of tyres?

wot size is your wheels, I've got similar booming at 70, initial had pirrelli scorpions on had to change 2 and fitted kumho kh 11's started on front but booming that bad put em on the back now only get it at 70 and it's not as bad tyre size is 225 55 17" so am really limited in tyres available. wish i'd bought another 2 pirrellis and kept to silent running.
Sheriff

As Hat Man says Different manufacturers can cause a problems. Mine is quieter at 70 and the new ones are ATs not road tyres. I think they are
215/55?R16 but its dark and I can't remember.

Sheriff
Just read your bit again Sounds like the kumoh may be bigger than the pirrellis so putting them on the back should help the situation. Get the tape measure out.

measure the circumference of each wheel

In your owners manual and Haynes manual it states that new tyres should be fitted to all wheels or just to the rear.

If you fit old tyres to the rear and new tyres to the front your VCU wont be able to 'freewheel' and will scrub the rear tyres.

The previous owner of my vehicle had indeed done the above and the rear tyres were worn badly on the inside edge. I swapped the newest to the rear and the worn to the front, finished the tyres off (as fronts wear quicker) and then had a pair of new tyres fitted to the rear and the rears moved to the front.

The car handles well, I have no odd noises and my new tyres after 5K are showing no signs of strange wear.

Just thought this might be useful to others.

Regards,

Steve

it is

Hi Mad hat man,
"It is" what? Smartarsey, true or both?
Cheers
Ian Hughes
Tassie

true - but possibly smartarsey - but who am I to say