Hudster Posted October 31, 2005 Report Share Posted October 31, 2005 if you take the 16" rims off a car and whack on some juicy 19" bad boys... you're technically raising the car (since the radius is larger) so are you likely to see poorer performance around the twisties? Link to comment Share on other sites More sharing options...
Thorburn Posted October 31, 2005 Report Share Posted October 31, 2005 A larger diameter wheel will generally also be wider so the tyres will be wider too, giving more mechanical grip. The centre of gravity will be raised however, increasing bodyroll. Since you are saying the car will be raised and there will be a greater rolling radius then the gearing will also be 'longer', so the car could take longer to reach 60 (or less time if for example before 2nd gear was 59mph at the limiter and the increased radius negates the need for another gear change), and the speedo will not be accurate. Link to comment Share on other sites More sharing options...
Ritey Posted October 31, 2005 Report Share Posted October 31, 2005 Yes, chances are without serious hacking on inner arches you'll be rubbing the rubber and killing your bushes Link to comment Share on other sites More sharing options...
Chris_B Posted October 31, 2005 Report Share Posted October 31, 2005 Usually to accomodate larger wheels, you fit tyres with a sidewall lower profile so that the rolling diameter is as near as possible to the stock size, otherwise the speedo is wrong. So, with 16" wheels and say 185/60 rubber, you'd go for something like 19" wheels with 185/40 or 225/35 rubber to get near to the same rolling diameter. See http://www.miata.net/garage/tirecalc.html for a handy online size comparison tool. Link to comment Share on other sites More sharing options...
Chris_B Posted October 31, 2005 Report Share Posted October 31, 2005 [ QUOTE ] Yes, chances are without serious hacking on inner arches you'll be rubbing the rubber and killing your bushes [/ QUOTE ] Oh yeah, and the risk of rubbing if they're too wide. Link to comment Share on other sites More sharing options...
Omi Posted October 31, 2005 Report Share Posted October 31, 2005 http://www.tyresave.co.uk/tyresize.html Is easier... You can keep the outer dimensions of the tyre virtually identical with the correct offset, maybe a little rolling of the arches. Your ride will become a lot more crashy, as tyres do all the fine damping and suspension and a lower sidewall will remove most of that... That's why I'm only putting 16"s on my car, compromise between handling, ride and good looks. - I could put 19"s on if I REALLY wanted! Interestingly, BMW's Gruppe N E30 M3 racers ran on 18"s... But their suspension was rock solid with slicks and a largely smooth road surface! Link to comment Share on other sites More sharing options...
Snail Posted November 1, 2005 Report Share Posted November 1, 2005 I found when going from 15"s to 18"s on standard suspension, that my cars handling improved massively. She corners well, and can keep the power down better, before grip is lost. If your only interested in twisties, and not looks, then uprated suspension is a better choice, because you get lots less body roll, and thus the car has less weight transfer issues. As mentioned above, if you keep your car a long time, it will eat bushes, CV Boots/joints, front suspension components, if you change wheels/suspension. Link to comment Share on other sites More sharing options...
R32North Posted November 1, 2005 Report Share Posted November 1, 2005 Plus the all important fact that you NEED to keep the rolling radeius the same so the speedo is accurate. If the wheels + tyres are bigger than the orginnal sizes then you'll be travelling faster than your speedo indicates - not good in our speed camera ridden country! Link to comment Share on other sites More sharing options...
Sponge Posted November 1, 2005 Report Share Posted November 1, 2005 Wider tyres don't necessarily mean more grip, by the way. http://autospeed.drive.com.au/cms/article.html?&A=0996 Link to comment Share on other sites More sharing options...
Durrsaku Posted November 1, 2005 Report Share Posted November 1, 2005 Well i can testify for a big improvement in grip since i changed my 16" wheels/tyres for 18". I just think the car handles much better too around corners. Link to comment Share on other sites More sharing options...
Hudster Posted November 5, 2005 Author Report Share Posted November 5, 2005 hmm forgot about the speedo... is there any solution to this apart from getting a close match to the origial diameter (inc tyres)... are speedos adjustable? Link to comment Share on other sites More sharing options...
Durrsaku Posted November 5, 2005 Report Share Posted November 5, 2005 No idea but the difference for me if i was doing 70mph was only about 2mph which is fine. Link to comment Share on other sites More sharing options...
Omi Posted November 5, 2005 Report Share Posted November 5, 2005 WHY ON EARTH do you want a bigger rolling radius? 1) Raise your centre of gravity, messes with your handling. 2) Increase circumference of rolling stock, puts your speedo out. 3) "Juicy Bad Boy" alloys implies you only want them for the adoring looks of your peers... So why are you worried about going faster and giving people less chance to see them? 4) To maintain the same overall diameter jumping THREE inches in diameter you will need super-low profile tyres which will mean crashier handling, increased road noise, more stress on dampers and a large hike in tyre prices when they need replacing. 5) If you're concerned about handling, get some lightweight magnesium alloy Compomotive rims, maybe in conjunction with a rim increase of an inch or so. 6) If you're so ill-informed as to think that your car will drive better, you won't want to know about the ramifications for your dampers, wheel bearings and braking system. Really sorry dude, just had to rant at someone. - I'm fine now. Good luck with your new rims, just make sure you've covered all angles first. Link to comment Share on other sites More sharing options...
R32North Posted November 5, 2005 Report Share Posted November 5, 2005 [ QUOTE ] hmm forgot about the speedo... is there any solution to this apart from getting a close match to the origial diameter (inc tyres)... are speedos adjustable? [/ QUOTE ] The only real option is to match the overall rolling radius of current wheels/tyres with the enw ones. Link to comment Share on other sites More sharing options...
rhyds Posted November 5, 2005 Report Share Posted November 5, 2005 back in the day you could calculate the difference and have a new speedo drive sprocket installed in to the gearbox to even things out, but I'm not sure what the setup with moderen cars is Link to comment Share on other sites More sharing options...
Hudster Posted November 5, 2005 Author Report Share Posted November 5, 2005 thanks for the advice, I think I'll stick with something a little more standard ) Link to comment Share on other sites More sharing options...
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