Rich Posted March 15, 2012 Report Share Posted March 15, 2012 If I was to run 215/45/17 on the rear and 205/40/17 on the front, just so I can get some more wear out of them before replacing (the fronts), is this going to cause any problems? Quote Link to comment Share on other sites More sharing options...
ChannelZ Posted March 15, 2012 Report Share Posted March 15, 2012 If I was to run 215/45/17 on the rear and 205/40/17 on the front, just so I can get some more wear out of them before replacing (the fronts), is this going to cause any problems? If you've ESP, bad things will happen. Otherwise, should be OK, there's not a huge difference. Quote Link to comment Share on other sites More sharing options...
Tony Posted March 16, 2012 Report Share Posted March 16, 2012 Tyre width and contact patch are very misunderstood globally.... Maybe this should be another topic but here goes..... Lets assume the rubber compound/ aspect ratio and grip coefficient levels are met. Next question is what makes you think the entire, tyre is involved with grip? Keeping things simple you should now there is a geometric focus point, more so for the front but nevertheless a focal point. The front steering geometry aims at a contact patch not a width, the contact patch is were all the steering functions take place. The same can be said for the thrust patch, braking, suspension deflection and inertia fields..... Oh dear now things have become complicated? If we look back an additional 20mm width does not assume an additional 20mm contact patch, in fact it's around 2mm within the working arena., and if we want to get anal about it the actual additional contact patch is distorted. Problem we have is there's no absolute law on the coefficient saturation limits albeit born from design or lack of design since there's one criminal. The EU includes minimal requirements but so does the people that make my socks. When it comes to tyres size does not matter, efficient limits do but this is be design...... Think about it? Quote Link to comment Share on other sites More sharing options...
Rich Posted March 19, 2012 Author Report Share Posted March 19, 2012 I take it that means yes it will be ok Tony? It would only be for a few months anyway. I know some RWD cars have larger tyres on the rear but I wasn't sure if it's ok on FWD. If I was to run 215/45/17 on the rear and 205/40/17 on the front, just so I can get some more wear out of them before replacing (the fronts), is this going to cause any problems? If you've ESP, bad things will happen. Otherwise, should be OK, there's not a huge difference. I have VSC and TRC....what would happen then, they'd keep kicking in? Quote Link to comment Share on other sites More sharing options...
liner33 Posted March 19, 2012 Report Share Posted March 19, 2012 I take it that means yes it will be ok Tony? It would only be for a few months anyway. I know some RWD cars have larger tyres on the rear but I wasn't sure if it's ok on FWD. If I was to run 215/45/17 on the rear and 205/40/17 on the front, just so I can get some more wear out of them before replacing (the fronts), is this going to cause any problems? If you've ESP, bad things will happen. Otherwise, should be OK, there's not a huge difference. I have VSC and TRC....what would happen then, they'd keep kicking in? Yes the ecu will see the wheels running at different speeds so may interpret that as wheelspinng but i doubt it Big no-no on 4wd's as well Quote Link to comment Share on other sites More sharing options...
Rich Posted March 19, 2012 Author Report Share Posted March 19, 2012 I'll give it a go then, if it causes problems I'll have to replace all 4 unless I get the same size tyre, which I don't really want to do. Quote Link to comment Share on other sites More sharing options...
adam_r Posted March 19, 2012 Report Share Posted March 19, 2012 Tony. you may need to explain in more (dumb ass) terms for me. Im looking at buying some new tyres for my summer wheels. My current wheels are 7JJ 17" rims. current tyres are 225/45/17 and my biggest issue is there is no rim protection... If i where to step up to a 235/45/17 this would give me a little more width to protect the rim. I also know my speedo would read slower due to the increased size in rim diameter. Wha issues would i see tying to run a 235/45/17 on a 7JJ rim ? im really sorry for the stupid question but one thing i dont get much is your explination above about contact patch etc Quote Link to comment Share on other sites More sharing options...
liner33 Posted March 19, 2012 Report Share Posted March 19, 2012 Wouldn't a 235/40/17 be the logical choice? Quote Link to comment Share on other sites More sharing options...
adam_r Posted March 20, 2012 Report Share Posted March 20, 2012 Wouldn't a 235/40/17 be the logical choice? yes it would be, but the 40 profile adds an extra 30 or so quid to each tyre and i have alot less choice. Quote Link to comment Share on other sites More sharing options...
Rich Posted March 20, 2012 Author Report Share Posted March 20, 2012 Tony. you may need to explain in more (dumb ass) terms for me. Im looking at buying some new tyres for my summer wheels. My current wheels are 7JJ 17" rims. current tyres are 225/45/17 and my biggest issue is there is no rim protection... If i where to step up to a 235/45/17 this would give me a little more width to protect the rim. I also know my speedo would read slower due to the increased size in rim diameter. Wha issues would i see tying to run a 235/45/17 on a 7JJ rim ? im really sorry for the stupid question but one thing i dont get much is your explination above about contact patch etc I think what Tony is saying, is the extra 20mm of tyre going from 205 to 215 won't mean all of that extra rubber is being used on the road at the same time. So really it doesn't matter if I use 215 or 205 on the rear...I hope I got that right anyway! If you want to go wider and still keep the height at 45 will you get any issues with rubbing on full lock? Quote Link to comment Share on other sites More sharing options...
parthiban Posted March 20, 2012 Report Share Posted March 20, 2012 I've read on the merc forums before where even a very slight difference in tyre size caused problems with the ESP but never heard of it on a Toyota........ Quote Link to comment Share on other sites More sharing options...
Tony Posted March 20, 2012 Report Share Posted March 20, 2012 Aspect radio ( height of the wall ) will do that. Quote Link to comment Share on other sites More sharing options...
Rich Posted March 21, 2012 Author Report Share Posted March 21, 2012 I'll try it and see what happens, hopefully nothing! Quote Link to comment Share on other sites More sharing options...
SteveOC Posted June 30, 2012 Report Share Posted June 30, 2012 I'll try it and see what happens, hopefully nothing! Did you try it and what was the outcome? I am in a similar situation - I want to fit new rears for the MOT and am having trouble getting the size that I want, which are original fitment, however the US original fitment are available. For some reason, the US fit 235 45 R17 and the UK fit 225 45 R17 to the same wheels on the same car. Forogt about possible issues with DSTC fitted to the car (or perhaps not) until I read your posts. Steve O. Quote Link to comment Share on other sites More sharing options...
Rich Posted June 30, 2012 Author Report Share Posted June 30, 2012 No not yet Steve as I haven't even sprayed the wheels yet. It was always raining whenever I had the time to do them! I think I will end up spraying them indoors just to get them done and then getting the larger tyres fitted. I'm hoping that will be ok and I don't get any issues with traction control. Quote Link to comment Share on other sites More sharing options...
Tony Posted July 1, 2012 Report Share Posted July 1, 2012 TC would be fine, it's the rolling radius -V- millimetre you should be concerned with. Quote Link to comment Share on other sites More sharing options...
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