[foolhandy]

I have a Cabrio that had 17" alloys with low profile tyres fitted when I bought it.

The ride I can cope with but I've been led to believe that having smaller wheels (15") and higher profile tyres will see the tyres take some of the flex that's currently going through the body and lead to improved handling.

I know it's never going to be a sports car but if it helps the handling I'll change the wheels. Not sure though whether it's worth it.

Any thoughts?

[Clawjaw]

bigger rim, smaller profile will make the handling better... so ive read

[foolhandy]

Me too...until I owned this car and now people are saying the opposite. Confused...

[E_T_V]

I wrote a bit about this a little while ago
http://www.roverdiesel.co.uk/menuwheels ... tyres.html

The 15's will be comfier and quieter and more forgiving on the limits. The 17's will have a faster turn-in and "may" ultimately provide more grip in the dry (but conversely less in the wet).

[Fatdave]

I had the standard 15" alloys on both my coupes and changed to 17" alloys. I found the cars to be a little bumpy but the handling was far better. On my last coupe i changed the 17" alloys to 16" mg hairpins and found almost no difference in handling but the overall ride was better. Maybe that would be a good compromise.

[foolhandy]

Hmmm...it has now been suggested to me that it might be the fact that my wheels are offset (correct term?) more than should be for a Rover (it doesn't have spacers) and so the steering geometry is out causing extra-understeer.

So maybe smaller, less offset wheels would help? And improve the ride?

You can see how much further stuck out they are in this pic :

[Fatdave]

they do seem to stick out a little. I remember a friend putting BMW 4 stud aftermarket alloys on his vauxhall a while ago and had the same problem as you. I think the offset is around 20 on BMW and around 40 on rover, thats what my wheels are and they fit fine. Take one off, it will usually tell you on the back somewhere. Have a look at http://www.alloyguide.com/home.php This site might help.

[Fatdave]

Did you find out what the issue was with the wheels. I see you now have them for sale, what are you replacing them with?

[RalphG]

It does look like the wheels that you have on the car have a smaller offset than standard, probably around ET35. The offset should be around ET42 to ET45 for standard wheels. This lower offset will put more strain on the suspension components, and in particular the wheel bearings. However, having a wider track will make the car handle better around corners. If the rims are wider than standard you may have to decrease the offset in order to prevent the inner edge of the tyre rubbing on the wheel arch liner.

The optimum wheel size for a car varies. For an MG ZS the optimum size is 17", and going above this adversely affects the handling. If your car has standard suspension I would suggest changing the wheels to 16" ones. I've got 16" wheels on my Rover 400 with Spax RSX suspension.

[foolhandy]

Right, I have new wheels and have been using them for just over a week so thought I'd offer some feedback.

I replaced my 17" wheels with 15" Rover alloys which, crucially I think, are offset correctly for the car. I also fitted four new Kumho Ecsta Spt tyres as a new start.

Here's a rather comical half-way shot:


and a rather unflattering final shot:


The result? Well I actually think it's improved the looks, as the wheels seem to fit the car now rather than appearing oversized. (Although I concede in these pictures they look a bit small - I think that's down to optical illusions due to being next to the old ones and then the funny camera angle - but I'll put up a better pic when I get around to taking one.)

More importantly though there has been a massive improvement in handling and ride.

Where before the steering was jittery and there was massive understeer going into corners now it's all smoothness and gradual turn in. Honestly, it's actually almost fun to drive now whereas before it was scary knowing that a bend of any sort at almost any speed would have the front wheels fighting each other and me trying to avoid the hedge.

The ride seems much improved too with the dreadful flex less obvious. I presume the higher profile tyres are soaking up more of the bumps thus putting less stress on the body.

Downsides? I think it seems to be more affected by motorway crosswinds than it was. Not badly, I just noticed it on the way home from fitting the new wheels. And that's it.

Don't get me wrong, it's not suddenly become a sports car, but the difference is remarkable and the thought of owning this car for a couple of years has suddenly become something I'm up for rather than feeling it was something I was going to have to endure.

What's more, even with the price of the tyres it cost me next to nothing to do. A great mod!