M350ZB Posted March 10, 2009 Share Posted March 10, 2009 Bit confused with tyre sizes, e.t.c, and off-sets ....... would 20" wheels compared to 19" wheels, bring my ride height up at all ? Currently have BBS 19" wheels, which are > Front > 245/35/19 Rear>275/35/19 And im not to sure on the offset ,anyone know ? I have done the following calculation to work out the distance (mm) from centre of wheel to ground> 19" is approx 485mm, diveded that by 2 to give 245.2, then i have added the 35 mm tyre profile, giving me a total of 277.5mm, this being from the centre of the wheel to ground. Right now the confusing bit, i have seen a set of wheels i like but they have a smaller profile on the rear compared to the front, they are 20" and are as follows > Front>245/35/20" Rear>285/30/20" Is this correct ? If i do the same calculation above with the 20" wheels and 30mm profile, it works out as follows > 20" is approx 505mm, divide that by 2 = 252.5mm, then add the 30mm profile, gives you 282.5mm So then 20" = 282.5 take off 192 = 277.5 will give me a 5mm height increase, does all this make sense and can any one shed any light on this for me ?, Another thing, im thinking will the 20" wheels and them tyre sizes fit in my arch's or will there be a bigger gap, any advice, much greatfull guys and girls. Thanks Quote Link to comment Share on other sites More sharing options...
Chris`I Posted March 10, 2009 Share Posted March 10, 2009 You make my head hurt man When changing wheel sizes, it is impreitive to keep the rolling radius of the wheel the same. Google, tyre size calculator and stick the old wheels in then change it to 20" and adjust the profile until the RR is the same as you currently have. Thats the size tyre you need. Keeping the same profile will make the RR bigger and make the speedo under-read. Can also balls up the TC if you dont get the front to rear RR stagger correct. Quote Link to comment Share on other sites More sharing options...
3FIDDYZ Posted March 10, 2009 Share Posted March 10, 2009 Are you lowered or on coilovers? Quote Link to comment Share on other sites More sharing options...
Greekman Posted March 10, 2009 Share Posted March 10, 2009 you are right... although there is an easier way of calculating it.... 1inch= 2.5cm ish so 2.5cm/2 (wheel radius) - 0.5mm (profile decrease) = 0.75cm ish... so its about 0.7 cm or 7mm.... dont know if the ESP will be happy with the new dimensions... Quote Link to comment Share on other sites More sharing options...
Rob_Quads Posted March 10, 2009 Share Posted March 10, 2009 Fronts will sit 1.27mm higher Rears will sit 0.19mm higher If you change the fronts to 30 profile then you would only sit 0.045mm Play around on http://www.kouki.co.uk/utilities/visual ... calculator to see the differences Quote Link to comment Share on other sites More sharing options...
M350ZB Posted March 10, 2009 Author Share Posted March 10, 2009 Are you lowered or on coilovers? No not lowered or nothing Quote Link to comment Share on other sites More sharing options...
M350ZB Posted March 10, 2009 Author Share Posted March 10, 2009 You make my head hurt man When changing wheel sizes, it is impreitive to keep the rolling radius of the wheel the same. Google, tyre size calculator and stick the old wheels in then change it to 20" and adjust the profile until the RR is the same as you currently have. Thats the size tyre you need. Keeping the same profile will make the RR bigger and make the speedo under-read. Can also balls up the TC if you dont get the front to rear RR stagger correct. What are the stock rays bud ?, and how comes then some companies have a smaller profile at the rear Quote Link to comment Share on other sites More sharing options...
Chris`I Posted March 10, 2009 Share Posted March 10, 2009 You make my head hurt man When changing wheel sizes, it is impreitive to keep the rolling radius of the wheel the same. Google, tyre size calculator and stick the old wheels in then change it to 20" and adjust the profile until the RR is the same as you currently have. Thats the size tyre you need. Keeping the same profile will make the RR bigger and make the speedo under-read. Can also balls up the TC if you dont get the front to rear RR stagger correct. What are the stock rays bud ?, and how comes then some companies have a smaller profile at the rear Well there is a bit of room to play with, but as you'll have seen on many threads on here, you need to keep it pretty accurate. I beleive Rays are 225/45/18 and 245/45/18. Thats just the Rays though, the other std wheels may have different RR, just they keep the ratio of front to back the same. If you do a search I posted pretty comprehensive numbers before of the ratio you need to keep. If all else fails though, aim for what you have now in terms of RR Quote Link to comment Share on other sites More sharing options...
Adriank Posted March 10, 2009 Share Posted March 10, 2009 You make my head hurt man Your not the only one! What are you doing with your calculations! The profile of the tire, E.G. in your example 35, doesnt mean 35mm!!! It means 35% of the tyres width So per se on a 275/35 the sidewall is 275x0.35 = 96mm So for the 20s it would be 285x0.30 = 85.5mm Total radius therefore of each wheel is 275/35/19 = 9.5" + 96mm = 32.87cm 285/30/20 = 10" + 85.5mm = 33cm 20 slightly larger. Quote Link to comment Share on other sites More sharing options...
M350ZB Posted March 10, 2009 Author Share Posted March 10, 2009 You make my head hurt man Your not the only one! What are you doing with your calculations! The profile of the tire, E.G. in your example 35, doesnt mean 35mm!!! It means 35% of the tyres width So per se on a 275/35 the sidewall is 275x0.35 = 96mm So for the 20s it would be 285x0.30 = 85.5mm Total radius therefore of each wheel is 275/35/19 = 9.5" + 96mm = 32.87cm 285/30/20 = 10" + 85.5mm = 33cm 20 slightly larger. Now it makes sense, i think i finall get it, so on 20"s then the wheels i have seen, they have 35 on rear and 30 but this would equal the same profile in mm ? Quote Link to comment Share on other sites More sharing options...
M350ZB Posted March 12, 2009 Author Share Posted March 12, 2009 Fronts will sit 1.27mm higherRears will sit 0.19mm higher If you change the fronts to 30 profile then you would only sit 0.045mm Play around on http://www.kouki.co.uk/utilities/visual ... calculator to see the differences Would this minor difference up-set the T/C, as have heard some stories about tyre sizes and T/C ? Site pretty good, cheers bud Quote Link to comment Share on other sites More sharing options...
Stew Posted March 12, 2009 Share Posted March 12, 2009 It's all very well breaking out the calculator for this but the best thing to do is ask an experienced 350Z trader. They should be able to advise you. Then it's a case of search the site for what they tell you on offsets etc and then order up. It's far too complicated getting a lot of non expert opinions. I'm not douting anyones knowledge but it's a majot purchase and can really make or break a car. Quote Link to comment Share on other sites More sharing options...
Chris`I Posted March 12, 2009 Share Posted March 12, 2009 It's all very well breaking out the calculator for this but the best thing to do is ask an experienced 350Z trader. They should be able to advise you. Then it's a case of search the site for what they tell you on offsets etc and then order up. It's far too complicated getting a lot of non expert opinions. I'm not douting anyones knowledge but it's a majot purchase and can really make or break a car. +1 Quote Link to comment Share on other sites More sharing options...
M350ZB Posted March 12, 2009 Author Share Posted March 12, 2009 It's all very well breaking out the calculator for this but the best thing to do is ask an experienced 350Z trader. They should be able to advise you. Then it's a case of search the site for what they tell you on offsets etc and then order up. It's far too complicated getting a lot of non expert opinions. I'm not douting anyones knowledge but it's a majot purchase and can really make or break a car. Great advice Stew , looking more and more into it though, with 20" wheels i reall dont gain to much height, not that, thats what i wanted or was going for, just thinking the price of a re-furb is a lot cheaper than a decent set of 20"s....... Quote Link to comment Share on other sites More sharing options...
Adriank Posted March 12, 2009 Share Posted March 12, 2009 If i was going for 20" wheels, id want: 245/30/20 Front 275/30/20 Rear. That way you are keeping the ratio front - rear the same, and its that ratio that seems to upset the traction control. That said with heavy 20" wheels on i doubt you will be spinning the wheels much anyhow!!! Quote Link to comment Share on other sites More sharing options...
M350ZB Posted March 13, 2009 Author Share Posted March 13, 2009 That way you are keeping the ratio front - rear the same, and its that ratio that seems to upset the traction control. ,Are you saying this ratio will trigger off the T/C ? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.