wheelback Posted October 22, 2012 Report Share Posted October 22, 2012 Hi! Im looking for some new wheels and im thinking between 7.5"x 16" et 25 with 185/ 50 tyres and 7"x 15" et38 or 20 with 165/55 tyres, which is the better combo? Im running now with the 14"x6" wheels with the 185/60 tyres. The motor is screaming as hell when i drive the highway speed (100- 120km/h) so i think the tyres can be littlebit bigger than those what im runnning now?!? And im from finland so sorry about my english ....and there will be some coils and i will get it low... Quote Link to comment Share on other sites More sharing options...
ministig Posted October 22, 2012 Report Share Posted October 22, 2012 165/50 on the 15x7195/40 on the 7.5x16 Quote Link to comment Share on other sites More sharing options...
wheelback Posted October 23, 2012 Author Report Share Posted October 23, 2012 Why those sizes? Those tyres diameter what i have now on the car is bigger than those, 195/40/16 or 160/50/15. So thats why asked about those other sizes above.. bigger diameter would help the engine to calm down on the highway speeds, by lowering the rpm. Quote Link to comment Share on other sites More sharing options...
Koop Posted October 23, 2012 Report Share Posted October 23, 2012 No it won't. Well, technically it might but you won't notice it, your speedo will still read the same whatever your rolling radius is. Quote Link to comment Share on other sites More sharing options...
Silver! Posted October 23, 2012 Report Share Posted October 23, 2012 Actually yes it will. I ran 185\60\14 on my Arosa for a while. Looked crap, but it did lower the rev's a little. Speedo was out by about +2mph at 60mph or +3K at 100kph (over the standard 185\55\14)When I dropeed to 165\60\13 there was a big difference: Quote Link to comment Share on other sites More sharing options...
Koop Posted October 23, 2012 Report Share Posted October 23, 2012 This makes no sense, the speedo has no idea what your rolling radius is. You will get lower revs at the same actual speed yes but indicated speed should remain the same at x revs in y gear as a speedo measures rotational speed, not the distance traveled by the circumference of the tyre. Quote Link to comment Share on other sites More sharing options...
JoeA Posted October 23, 2012 Report Share Posted October 23, 2012 The gearing of the whole car changes with rolling radius. Smaller wheels will generally accelerate quicker. If you put 17s on a Lupo the motorway will be much more liveable. Quote Link to comment Share on other sites More sharing options...
scotty_82 Posted October 23, 2012 Report Share Posted October 23, 2012 Treat the wheels/tyres (rolling radius) as a kind of final cog/gear. The OD makes a decent difference. 1 Quote Link to comment Share on other sites More sharing options...
Koop Posted October 23, 2012 Report Share Posted October 23, 2012 I'll test this when I get my 16s back on. If I'm reading any less than 3.7K rpm at an indicated 70 mph I should just about have enough time to eat my hat before my brain implodes. 1 Quote Link to comment Share on other sites More sharing options...
ministig Posted October 24, 2012 Report Share Posted October 24, 2012 I just went on what looks the best Quote Link to comment Share on other sites More sharing options...
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