Help, running 205/40/17 on front and 205/50/17 on rear

[rossforest]

I drive a VW Golf mk4,
Just got these tyres free with my wheels and they are all brand new, however the rear ones look at least an inch larger than the fronts, The handling on the car has changed but I used to run 15's on it so Im not too sure how much of that is due to the odd tyres. Apart from looking a bit silly are there any negative things about this setup I should really look out for, apart from friend's constant commentaries about me driving a top fuel funny car replica haha? Matching all the tyres will cost me at least an extra £100 with fitting so is it something that needs to be changed asap? Ive been told that surely its a good thing as the front tyres will have more grip as its a fwd car? Any gurus out there?

Thanks,

Ross!

[shorod]

What year is the mk4? Does your car have ABS or some type of stability control? If so, the difference in tire diameters could cause issues with the ABS and stability control and potentially the speedometer (due more to the potential difference in overall height from the original wheel/tire conbination). Also, it will look really funny if you were to attempt to rotate the tires to keep the wear matched. Compared with the OEM tire and wheel combination, the 17 inch wheels will be a bit harder on the suspension and may make the braking slightly less effective (unsprung weight). This, along with the likely reduction in sidewall height, will contribute to the handling differences.

Did you buy the wheels and tires from a mail order place, and did you order two different sizes? If not, why didn't you contact the supplier and not install them? The supplier should have replaced the two of the incorrect size at their expense, shipping and all. That is unless you ordered them incorrectly.

I don't understand the comment about having more grip with a lower profile tire on the front. The tire footprint will be essentially the same since the tire width is the same for both tires. The aspect ratio (sidewall height) is the difference, which is based on the width.

-Rod

[MagicRat]

Originally Posted by shorod

I don't understand the comment about having more grip with a lower profile tire on the front. The tire footprint will be essentially the same since the tire width is the same for both tires. The aspect ratio (sidewall height) is the difference, which is based on the width.

I agree, the grip will be the same. What will be different is the responsiveness.

The taller 50-series tire will 'sway' a bit more, so that when the car changes direction the rear will feel just a bit more loose.

IMO this may be a bit hazardous because it will make the car feel like its about to 'oversteer' when going into a sharp corner, etc.

IMO this makes for somewhat unpredictable handling. I think the taller tires should be on the front, so the car will feel like its going to understeer a bit. IMO this change would make the car feel more predictable and controllable.

Or, sell 2 of the tires and buy 2 new ones so you have a matched set.

[rossforest]

Its a 1998. What I have been told at the garage is that with the larger tyres at the back will place the car at a forward angle therefore putting more weight at the front of the car improving the handling, but I dont know how much of that was just crap they fed me to get the job over and done with! I have been told the opposite by some garages and to actually put the big tyres on the front. The handling is horrible at the moment, the car is going all over the place! Which tyres would you guys go with, 40 or 50 aspect ratio? 40s will be closer to the original size meaning that the speedo will only be 3mph over at 60mph, whereas on the 50's it will be more like 8mph, however, the larger tyres at the back seem to fill out the arches better. Also, I am putting the car on coilovers and lowering it around 100mm in a week and the ride already feels somewhat harsh with the 40's on the front end. Do you think 50s would be a better idea just for that reason?

[Moppie]

VW Saved millions of dollars to ruin the Golfs handling by fitting it with a beam rear axle, then you have come a long and altered its weight distribution by adding taller tyres to the back than the front.

Of course it will drive funny. If your really lucky it might even swap ends under hard braking.

[shorod]

You're going to drop the car nearly 4 inches! You'll be lucky if there is clearance for even the 40 series tire at that rate!

Sounds like you need to consult with a professional suspension and tire shop before spending any more money on this car and make sure what you want is physically possible and practical. There's a point where appearance of the car should not be considered more important than safety.

And for what it's worth, I wouldn't suggest the shop that sold you the two different sized tires along with the story.

-Rod