scottr13

I'm not sure if this is a coincidence but after changing my two rear tyres (different brand from fronts now) the traction control light flashes every time I go over a bumpy bit in the road

This only happens though for the first 1-2 miles of the journey then the car drives fine the rest of the day

It's very strange and not sure if it is related to the tyre change but that is all that is different than from the week before when there was no issues

Anyone noticed their traction control light going crazy? I hope it isn't something serious otherwise it may be time to trade in

ithinkmac

I would imagine the computer will pickup the difference in tread pattern and how the tires roll compare to your front tires, and throws error. But I bet the engineers know people change tires, mix and match. So it'll warn first, then becomes a learned behavior?

I noticed this happens to me when I put on the spare. The initial startup and drive will triggered traction control, then it goes away. So I just assume that the computer is learning and figured out I have a spare that spins differently then the rest of the car. But the next time the car starts, the computer will go through this whole process all over.


-ThinkMac-

DieselDave

more than likely it's the tread depth. Some say you need to change all four tyres at the same time, others no more than 2mm difference between old and new.

how worn are the old tyres? If they're less than 5-6mm, then this is probably the issue. have the new ones put on the front, they'll wear quicker there and will likley even out the difference quicker too.

scottr13

Thanks guys, put my mind at rest. Was thinking some crazy expensive traction control module was on its way out

The front tyres have around 5mm, the rears were right on the limit. Just noticed when I was washing the rear wheels last week and ordered two. I'll try swapping them onto the front

pchansen

Just make sure your two sets are within tolerance with respect to each other. That very small difference in rolling diameter will not do your quatro all-wheel drive system any favors and if it's out of spec, you could damage the system. If it's in your budget, I'd replace the older set as well. Otherwise you'll always have mis-matched tires.

JAHWORKS

yes my car is doing that now…and it’s frustrating as hell…last month I changed my two rear tires because they were bald *** hell…I bought two used damn near new tires from someone and I pulled out of the tire shop after they put them on and less than an hour my traction light came on…I paid it no mind because I thought I ran into grease or something from the shop that put the tires on…but then every time I get into my car every now and then it would happen..so I looked at me tires and noticed that the two tires are two different treads on them so now I have three different treads on my tires …the two front are the same but the two rear are different…I thought it was a transmission issue or something but now I’m going to change all the tires and see if that fixes the issue…cross your fingers

dreadlocks

If you buy an AWD vehicle you should be prepared to change all 4 tires together, ALWAYS, no exceptions.. If you cannot afford four tires at once, sell it and get something else.. yeh all are ****in the diffs up, if you RTFM it clearly says dont do what you are doing.

I'm surprised you guys are even finding shops to do this, they must not see AWD vehicles much.. I know there is not a tire shop within 100 miles of me that will replace anything less than 4 tires on an Audi, the'll send you home w/out tires before they just put two on.

JAHWORKS

I just can’t see how something as minor as that can cause my car to drive so messed up …I prey that’s what it is but I will keep y’all posted when I change the tires

dreadlocks

you have a front, rear, and center differential in an awd vehicle.. they allow wheels to spin at different rates when you turn and automatically compensates for wheels that are losing traction.. all the tires must be the same make/model/age and wear or else the wheels will turn at different rates when you are going in a straight line on the highway at speed w/no traction issues..

except now with different diameter wheels on your diffs are operating at 100% duty cycle and never getting a break cuz mechanically with different sized tires you are doing doughnuts at 75mph on the interstate in a straight line.. each wheel has speed sensors that are exceptionally sensitive and can detect if the air pressure in the tires is off from eachother, it uses those sensors to actuate each corner brake independently to vector power to different wheels as required, its seeing something is not making sense and it thinks your sensors or modules are faulty and throwing a fit.

If you put many tens of thousands of miles on your vehicle with mismatched tires your working your differentials at duty cycles and rates that are extremely abnormal, the wear and tear on the lubrication and gears is going to be absurd.

but hey, those Germans who made your vehicle and wrote the manual must not have the vision you have.

tigerwillow1

I didn't see where you mention what year Q7 you have. The owners manual for my 2009 says "Tires should be replaced at least in pairs and not individually (for example both front tires or both rear tires together)." It also says all tires must be the same size, construction, and tread type. I guess there's room for interpretation of what "size" means, although I don't see any mention of tread depth. Different brands I think would violate the same tread type requirement, but there's room for argument there too. I wish they'd be more specific. The manual for my '94 quattro is a bit better, saying when you replace a pair of tires the deepest tread should go on the front.