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I think the offset is OK, they're just a bit narrow.
..Rosssco wrote:235/45/17 would fit better on that rim width, but as above, not ideal.
Plenty 225/45/17's available.
(ie. by increasing the profile those tyres are now 37mm too large and introduce a 6% speedo underread)) Besides, increasing the profile won't change the fact that the 235 will bulge a little on a 7J rim - it'll just reduce the visual appearance of the budge a little.(perfect fit on 8J wheels) and their rolling radius is almost exactly the same as the stock wheels - I certainly didn't notice a loss of handling compared to the stock setup I'd been driving for a couple of years previous.shinny wrote:Rosssco wrote:235/45/17 would fit better on that rim width, but as above, not ideal.
Plenty 225/45/17's available.
Why are you suggesting using oversize tyres?
.. I was just offering an option that may fit the rim better, as the higher the profile, generally the narrower the rim it will fit. Dropping down to a 225 tyre still offers limited choice - 225/40/17 aren't really available, and 225/35/17 may not even got on that rim size.Rosssco wrote:I'm not, the OP did.
Rosssco wrote:Dropping down to a 225 tyre still offers limited choice
kingsley wrote:would prefer to put a 235 on the back instead of the daft 215/40 ones it has on there at the moment.
(better than a 235 tyre, for sure!) while still matching the rolling radius pretty closely. I'd suggest a 215/40/17 is a better tyre to fit than going for a visible bulge AND an oversized profile. BTW, width does not automatically equal grip...+ 215/40/17 looks like when fitting to 17x7J wheels:
I don't think the car suits the same all round and I don't want to put really skinny ones on the front just because the rears aren't big enough. If they're wrong for the car but right for the rims, then the rims are wrong too. That is a size I had considered, if I manage to change the rims for 8" or 8.5" at the rear at some point.- I've spent hours looking on various sites for options but so far there hasn't been a happy ending 
kingsley wrote:The reason I want to put wider ones on the rear is because the car is too tail happy as it is.
Parallel or toe-out at the rear will certainly make the car more tail happy, and new tyres will not sort that!(checking and reducing pressure is free!).shinny wrote:kingsley wrote:The reason I want to put wider ones on the rear is because the car is too tail happy as it is.
As I said, tyre width is not the same as grip!
(eg slick tyres in racing) so I'd just accepted it. I admit I haven't tried dropping the pressures in the rears - how will that help? I'd never buy these again (Yokohama Paradas). They're OK in the dry but I think they're lethal in the wet.kingsley wrote:I have to admit, I've never really understood the width=grip thing because the greater contact patch would have less pressure against the tarmac by the same proportion which would reduce grip per unit area and I would have thought cancelled out the extra contact area, but getting more rubber onto the ground does seem to be a commonly strived for thing
It may not be that simple in real life, but simply widening the tyre and keeping the same pressure will give you very little. are as much to do about tyre compound than anything else. Also the bigger the tread blocks (as you'll see on your Paradas) are good for dry grip.kingsley wrote:Besides that, the car has had a 4 wheel alignment done already.
Lower pressure allows the tyre to deform more, allowing a greater contact patch on the road.kingsley wrote:The tyres are the same type all round.
- they are truly awful tyres! One of the biggest moments I've had was on Paradas in the wet when the car suddenly broke away around a corner and I had to catch a tank slapper before oncoming traffic hit me. The Nissan Micra I was following drove round the same corner at the same speed in the same manner and was absolutely fine! 
kingsley wrote:Aside from the arguments for and against, I had assumed that Toyota changed the tyre widths to a staggered setup for a good reason and this is why I was striving to do the same.
Do a lot of MR2 owners not bother with the staggered setup?
I wasn't aware you also had 215s up front too - I was suggesting a smaller stagger (205 F 215 R) given the lack of stagger on your alloys. (I don't exactly know what this will do to the handling and ride, but it clearly must have an affect as you'll be asking the sidewalls to take forces in directions hey're not designed to do)(215/40/17 Parada 2s all round) to a mildly staggered setup (205/40/17 F 215/40/17 R UniRoyal Rainsports) and found the wet weather handling was vastly improved and otherwise it was a match for the standard 15" setup I had been used to. I admit I've never had 235/40/17s on a 7J, but it looks so wrong, visually, that I didn't want to spend my money on it!(ie a tractor tyre at 8psi would probably support the car quite well, but a bicycle tyre at 8psi would be squashed flat).(therefore potentially more grip). However, as there is less tyre deformation, I presume there would be less scrubbing as the tyre rolls (not sure whether that's the right term here). This would reduce tyre wear and result in less heating of the tyre, which would then allow a softer compound to be used, thus providing more grip. Is that right?(which are easily replaced) and not the car! I'm amazed that tyres that behave in this way are still on sale these days, especially sold as a premium tyre.kingsley wrote:I suppose what a wider tyre does give you is the ability to lower the pressure a bit without as much deformation of the tyre under the car's weight
This in turn would be what would give a larger contact patch
So, from the above, having wider tyres allows for more grip, but perhaps not for the reasons that most people think.
I run below standard pressures on my road tyres, which are all 20mm wider than stock. Although lower pressure means low fuel economy, so it becomes a trade-off. Also, the car will feel sharper with high pressures, but have less grip.kingsley wrote:Your story about following the Micra is shocking but I'm glad to hear it in that I know I can blame the tyres
(which wat not fast), so to 'blame' the tyres would be incorrect. I get the blame because in that exact circumstance, 5 years ago, as I exceeded the car's performance envelope. The reason why that envelope turned out to be significantly smaller than a Micra's (and much smaller than I had anticipated) is because the car had thoroughly inappropriate tyres on.'C' classification in wet braking, however tyre reviews seem full of people warning about their wet performance.I wanted SO BAD to believe they are not a disaster on wet as i had red about, BUT THEY ARE! I bought them and i regret it! If it rains even a little, fun is over! I have a 250hp Bertone Turbo but even a 130hp car with proper tyres would beat me on wet asphalt! They are dangerous on wet and i regret so much i've bought them, i was foolished by the design.
kingsley wrote:Thanks for all of that info, very useful and well presented.
- I hope it helps