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Re: Running 18's
[Re: Broombeastie]
#1250215
17/08/2011 17:25
17/08/2011 17:25
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Joined: Dec 2005
Posts: 2,168 London
EDz
Competition Level
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Competition Level
Joined: Dec 2005
Posts: 2,168
London
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I run 225 35 18s They are virtually the same height at the stock wheels and tyres Not noticed any performance difference But ride quality is the issue - had my 16`s on last year for Stanford hall - Auto italia - felt lovely But 18s do look cool
e46 M3 330D Sport
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Re: Running 18's
[Re: Broombeastie]
#1250237
17/08/2011 18:19
17/08/2011 18:19
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Biggenz
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Biggenz
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I wonder if there really is a massive difference betweeen 17's and 18's? My ride is pretty good with 17's, and I'm thinking about trying out some 18's.
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Re: Running 18's
[Re: Broombeastie]
#1250240
17/08/2011 18:21
17/08/2011 18:21
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h2ypr
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h2ypr
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Bear in mind that 18's are usually heavier as well, which will impact on ride quality and handling.
So as regards a performance increase, unless the weight is the same as a standard wheel or less, your unlikely to benefit from any other changes.
Ross
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Re: Running 18's
[Re: Broombeastie]
#1250242
17/08/2011 18:24
17/08/2011 18:24
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DidCoop
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DidCoop
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Rolling radius wise with a low profile tyre you shouldn't notice a great deal of difference performance wise! Only thing you will find is they're heavier and the ride will be firmer due to the lack of tyre lol!
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Re: Running 18's
[Re: Broombeastie]
#1250391
18/08/2011 01:34
18/08/2011 01:34
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Per
Unregistered
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Per
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The 225/35-18 tire has the exact std Fiat radius so no change at all there. Better grip/reactions and worse comfort is the actual result.
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Re: Running 18's
[Re: Broombeastie]
#1250601
18/08/2011 18:14
18/08/2011 18:14
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Biggenz
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Biggenz
Unregistered
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Does anyone know if you can run 7.5J 18" rims without any problems?
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Re: Running 18's
[Re: ]
#1250612
18/08/2011 18:52
18/08/2011 18:52
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Joined: Sep 2009
Posts: 5,063 ation
szkom
Club member 2000
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Club member 2000
Forum is my life
Joined: Sep 2009
Posts: 5,063
ation
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The 225/35-18 tire has the exact std Fiat radius so no change at all there. Actual or effective rolling radius? The two are very different.
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Re: Running 18's
[Re: ]
#1250673
18/08/2011 20:49
18/08/2011 20:49
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Joined: Mar 2006
Posts: 223 Billericay, Essex
Broombeastie
OP
Making a profit
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OP
Making a profit
Joined: Mar 2006
Posts: 223
Billericay, Essex
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Does anyone know if you can run 7.5J 18" rims without any problems? I believe if you run 35 profiles you'll have no probs, not sure about 40's though.
Back into retirement, for now at least . . . Broomy will come out to play next year
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Re: Running 18's
[Re: Broombeastie]
#1250677
18/08/2011 20:52
18/08/2011 20:52
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Joined: Feb 2007
Posts: 3,486 London Tan
technics
I need some sleep
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I need some sleep
Joined: Feb 2007
Posts: 3,486
London Tan
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Biggenz, I think mine are 8.5 j, 18"
Now in the 400+ bhp club!
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Re: Running 18's
[Re: Broombeastie]
#1250678
18/08/2011 20:53
18/08/2011 20:53
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Biggenz
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Biggenz
Unregistered
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Cheers, but I'm more after the max width of the rim you can run.
I've got 17x7 on at the moment, and the rims I want only come in 18x7.5 or wider.
What's the widest rim you can put on the coupe, does anyone know?
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Re: Running 18's
[Re: Broombeastie]
#1250682
18/08/2011 20:56
18/08/2011 20:56
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Joined: Feb 2007
Posts: 3,486 London Tan
technics
I need some sleep
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I need some sleep
Joined: Feb 2007
Posts: 3,486
London Tan
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Look above mate, lol. Mine are 8.5.
Now in the 400+ bhp club!
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Re: Running 18's
[Re: Broombeastie]
#1250683
18/08/2011 20:59
18/08/2011 20:59
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nismo
Unregistered
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nismo
Unregistered
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mine are 8.5j with a 215 tyre on , lowered 30mm and i get no rubbing but i wouldn't go any wider .
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Re: Running 18's
[Re: Broombeastie]
#1250688
18/08/2011 21:01
18/08/2011 21:01
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Biggenz
Unregistered
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Biggenz
Unregistered
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Oops!
How do you fit a 215 tyre on an 8.5J rim?? Surely the tyre is way too narrow?
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Re: Running 18's
[Re: Broombeastie]
#1250766
18/08/2011 22:20
18/08/2011 22:20
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nismo
Unregistered
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nismo
Unregistered
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it has the drift look but the rolling radius is the same as the 20vt standard wheel , when i need to change the tyres i will be going for a 225/40 or 35 .
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Re: Running 18's
[Re: Broombeastie]
#1250837
19/08/2011 00:08
19/08/2011 00:08
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Joined: Feb 2007
Posts: 3,486 London Tan
technics
I need some sleep
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I need some sleep
Joined: Feb 2007
Posts: 3,486
London Tan
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I think 225/40 might just rub here and there. I have 225/35, no problem!
Now in the 400+ bhp club!
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Re: Running 18's
[Re: technics]
#1250938
19/08/2011 10:16
19/08/2011 10:16
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roly
Unregistered
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roly
Unregistered
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Re: Running 18's
[Re: Broombeastie]
#1251008
19/08/2011 13:51
19/08/2011 13:51
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nismo
Unregistered
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nismo
Unregistered
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35's it is then and i'v replyed to you pm roly .
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Re: Running 18's
[Re: Jimbo]
#1251016
19/08/2011 14:09
19/08/2011 14:09
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h2ypr
Unregistered
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h2ypr
Unregistered
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225/40 will rub on full lock. I have 215/40/18 on mine and I had to remove the first 5mm of the vents in the front wheel arch to stop the rubbing. I had 18's on my old coupe and had no rubbing. I ran 215/35/18's with 20mm spacers. Bk racing wheels. Ross
Last edited by h2ypr; 19/08/2011 14:21. Reason: ah you mentioned 225's
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Re: Running 18's
[Re: Jimbo]
#1251142
19/08/2011 18:29
19/08/2011 18:29
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h2ypr
Unregistered
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h2ypr
Unregistered
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225/40/18 will rub Ross, it's a wider tyre and has a higher side wall so the combination will cause rubbing. Spacers don't solve rubbing issues, they just give the correct offset or clearance from the caliper. Yeah edit note was to explain noticed 225/40. Only mentioned spacers to show setup when fitted. Makes sense now. Ross
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Re: Running 18's
[Re: Broombeastie]
#1251718
21/08/2011 14:29
21/08/2011 14:29
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Joined: Dec 2005
Posts: 2,168 London
EDz
Competition Level
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Competition Level
Joined: Dec 2005
Posts: 2,168
London
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I was talking about 225 so should be 35s and there still very slightly taller than stock But what ever work for everyone -
e46 M3 330D Sport
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Re: Running 18's
[Re: Broombeastie]
#1251732
21/08/2011 15:27
21/08/2011 15:27
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nismo
Unregistered
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nismo
Unregistered
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215/35/18 is a correct rolling radius for the standard wheel on a coupe with 205/50/16 or 225/45/16 check for yourself - http://www.rtecshop.com/?p=calculatorwith 215/40/18 your Speedo will be 3.3% too slow and When your speedo reads 60 mph, your actual speed will be 62.0 mph with 225/35/18 your Speedo will be 0.8% too slow and When your speedo reads 60 mph, your actual speed will be 60.5 mph
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Re: Running 18's
[Re: Jimbo]
#1252040
22/08/2011 03:34
22/08/2011 03:34
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Joined: Dec 2005
Posts: 2,168 London
EDz
Competition Level
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Competition Level
Joined: Dec 2005
Posts: 2,168
London
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215/40 is a correct rolling radius EDz. The 40 just gives you that extra side wall to make the ride slightly more bearable. Looks like your wrong I can live with 225 35s
e46 M3 330D Sport
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Re: Running 18's
[Re: EDz]
#1252063
22/08/2011 09:45
22/08/2011 09:45
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roly
Unregistered
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roly
Unregistered
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Re: Running 18's
[Re: ]
#1252521
23/08/2011 15:21
23/08/2011 15:21
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Joined: Dec 2005
Posts: 2,168 London
EDz
Competition Level
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Competition Level
Joined: Dec 2005
Posts: 2,168
London
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215/35/18 is a correct rolling radius for the standard wheel on a coupe with 205/50/16 or 225/45/16 check for yourself - http://www.rtecshop.com/?p=calculatorwith 215/40/18 your Speedo will be 3.3% too slow and When your speedo reads 60 mph, your actual speed will be 62.0 mph with 225/35/18 your Speedo will be 0.8% too slow and When your speedo reads 60 mph, your actual speed will be 60.5 mph Actually with a Fiat speedo might be spot on
e46 M3 330D Sport
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Re: Running 18's
[Re: Broombeastie]
#1252530
23/08/2011 15:41
23/08/2011 15:41
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Joined: Dec 2005
Posts: 8,485 Lightwater, Surrey
DaveG
Club Treasurer Member 311
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Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,485
Lightwater, Surrey
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Precisely. I run larger diameter tyres on 17" wheels and the speedo is accurate (vs. @GPS) to 1-2mph up to 90. OE wheel/tyre makes speedo read too high, at least on early Coops, maybe later speedos were changed?
1996 Portofino 20vt & 2000 Pearl White Plus 2008 Ferrari F430 & 2017 Fiat 124 Spider
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Re: Running 18's
[Re: Broombeastie]
#1252543
23/08/2011 16:13
23/08/2011 16:13
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Per
Unregistered
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Per
Unregistered
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All speedos are set slightly too high, on all cars of all brands. Don't remember exactly why but that's how it is. 215/35/18 is a correct rolling radius for the standard wheel on a coupe with 205/50/16 or 225/45/16 No, it's 225/35-18. These are 0.5% bigger diameter than the original 20VT 205/50-16, which is the closest you get with 18".
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Re: Running 18's
[Re: ]
#1252574
23/08/2011 18:09
23/08/2011 18:09
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nismo
Unregistered
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nismo
Unregistered
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no 215/35/18 is the same rolling radius as a 205/50/16 or 225/45/16 standard coupe wheel and tyre - check for yourself - http://www.rtecshop.com/?p=calculatorStock Tyre: 205/50x16 New Tyre: 215/35x18 Sidewall: 4.0 in .... Sidewall: 3.0 in Radius: 12.0 in .... Radius: 12.0 in Diameter: 24.0 in .... Diameter: 24.0 in Circumference: 75.4 in .... Circumference: 75.4 in Revs/mile: 840.3 .... Revs/mile: 840.3 -------------------------------------------------------------------------------- Your speedo will be 100% accurate! no its 225/35-18.These are 0.5% bigger diameter than the original 20VT 205/50-16, which is the closest you get with 18". as you say yourself its 0.5% bigger so it must be wrong
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Re: Running 18's
[Re: ]
#1252712
23/08/2011 22:12
23/08/2011 22:12
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Joined: Sep 2009
Posts: 5,063 ation
szkom
Club member 2000
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Club member 2000
Forum is my life
Joined: Sep 2009
Posts: 5,063
ation
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no 215/35/18 is the same rolling radius as a 205/50/16 or 225/45/16 standard coupe wheel and tyre - check for yourself - http://www.rtecshop.com/?p=calculatorStock Tyre: 205/50x16 New Tyre: 215/35x18 Sidewall: 4.0 in .... Sidewall: 3.0 in Radius: 12.0 in .... Radius: 12.0 in Diameter: 24.0 in .... Diameter: 24.0 in Circumference: 75.4 in .... Circumference: 75.4 in Revs/mile: 840.3 .... Revs/mile: 840.3 -------------------------------------------------------------------------------- Your speedo will be 100% accurate! no its 225/35-18.These are 0.5% bigger diameter than the original 20VT 205/50-16, which is the closest you get with 18". as you say yourself its 0.5% bigger so it must be wrong Calculating the circumference will not give you a figure of the percentage difference. It's all about the amount the tyre deforms when it contacts the ground. Measure from the ground to the wheel centre and note the measurement. Try it again with different tyre pressures and you will get different figures. These are the numbers you need to use for calculating your effective rolling radius so you can compare. In short it's suck it and see. These tyre calculators are nonsense. There are far too many variables to get anything more than a guess at the percentage difference.
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Re: Running 18's
[Re: Broombeastie]
#1252808
24/08/2011 08:41
24/08/2011 08:41
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nismo
Unregistered
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nismo
Unregistered
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so maths is wrong then i'v seen and read it all now
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Re: Running 18's
[Re: ]
#1252904
24/08/2011 14:11
24/08/2011 14:11
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Per
Unregistered
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Per
Unregistered
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as you say yourself its 0.5% bigger so it must be wrong Well the 215/35-18 is 0.6% smaller than 205/50-16 so it must be more wrong then..? Check for yourself: http://www.algonet.se/~leffmans/dack/dack.htm Also, most 18" rims are 7.5-8.5" wide which makes a 215mm wide tire a little narrow. Also #2, on your 18" wheels you'd better off with a little more tirewall/comfort than less... Also #3, 225mm looks better, offers more grip and is what 20VT Plus has.
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Re: Running 18's
[Re: Broombeastie]
#1253018
24/08/2011 19:36
24/08/2011 19:36
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THE_G
Unregistered
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THE_G
Unregistered
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what about 19 inch rims
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Re: Running 18's
[Re: Broombeastie]
#1253022
24/08/2011 19:39
24/08/2011 19:39
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Joined: Dec 2005
Posts: 2,168 London
EDz
Competition Level
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Competition Level
Joined: Dec 2005
Posts: 2,168
London
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I think the 225 35s are best option My Speedo matches gps pretty close (maybe a mile out) So they must help make it more Accurate
e46 M3 330D Sport
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Re: Running 18's
[Re: Broombeastie]
#1253272
25/08/2011 11:04
25/08/2011 11:04
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Per
Unregistered
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Per
Unregistered
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If it affected acceleration it must be due to different gearing (bigger wheels). The extra weight wont be noticable that way.
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Re: Running 18's
[Re: ]
#1253328
25/08/2011 12:41
25/08/2011 12:41
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Joined: Dec 2005
Posts: 17,370 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,370
Staffordshire
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If it affected acceleration it must be due to different gearing (bigger wheels). The extra weight wont be noticable that way. You're kidding... Heavier wheels are a brilliant way to slow down a car - rotational inertia is a huge drain on acceleration Increasing the wheel diameter almost always ends up with a corresponding increase in weight, which has an immediate adverse effect on acceleration. Think of your wheels as a pair of extra flywheels - we all know that a lightened flywheel helps throttle response and acceleration, so it follows that heavier rotational items in the drivetrain will have the opposite effect. Why do you think F1 cars have such small wheels? I know that they use tyre deflection as part of the suspension, but if 20" wheels and ultra-low profile tyres gave more grip, they would use them (and then find a way of making the mechanical suspension work around it). Ultimately, a small wheel and tall tyre is easier to accelerate and brake The primary reason for me having 17" wheels on my car is that they are lighter than the stock wheel and thus aid performance. The secondary reason is better handling due to a lower sidewall and less unsprung weight and the final reason was aesthetics.
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Re: Running 18's
[Re: Broombeastie]
#1253823
26/08/2011 14:58
26/08/2011 14:58
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Per
Unregistered
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Per
Unregistered
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Yeah, my 18" wheels are MUCH heavier than the std 16" wheels but when I swap over I can't say I feel any difference in acceleration. What I do feel is the nimbler feel and better handling.. Which also could be down to the Toyo R888 on the std wheels!
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Re: Running 18's
[Re: szkom]
#1254140
27/08/2011 13:15
27/08/2011 13:15
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NineOneSix
Unregistered
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NineOneSix
Unregistered
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Your maths is fine. I think you misunderstand. If you have a calculated radius of 12 inches ,when the tyre is unloaded, it will change as soon as you put the load of a car on it. Like I said measure it. Measure from the top of the tyre to the wheel centre and then measure from the ground to the wheel centre. You will produce two different radius measurements. The later of the two is the one you use to calculate the effective rolling radius.
Remember the above mentioned phenomena varies based on tyre, pressure, relative conditions and rotational speed. It is also more pronounced on a higher aspect ratio tyre, like the stock wheels. So once again tyre calculators are nonsense.
Doesn't matter how much the tyre deforms, the circumference does change. Rolling radius will change but the RPM of the wheel does not.
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Re: Running 18's
[Re: ]
#1254254
27/08/2011 20:14
27/08/2011 20:14
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Joined: Sep 2009
Posts: 5,063 ation
szkom
Club member 2000
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Club member 2000
Forum is my life
Joined: Sep 2009
Posts: 5,063
ation
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Your maths is fine. I think you misunderstand. If you have a calculated radius of 12 inches ,when the tyre is unloaded, it will change as soon as you put the load of a car on it. Like I said measure it. Measure from the top of the tyre to the wheel centre and then measure from the ground to the wheel centre. You will produce two different radius measurements. The later of the two is the one you use to calculate the effective rolling radius.
Remember the above mentioned phenomena varies based on tyre, pressure, relative conditions and rotational speed. It is also more pronounced on a higher aspect ratio tyre, like the stock wheels. So once again tyre calculators are nonsense.
Doesn't matter how much the tyre deforms, the circumference does change. Rolling radius will change but the RPM of the wheel does not. Not quite. The circumference of the tyre remains constant. What I'm saying is the deformed tyre will produce a smaller radius (effectively) and therefore produces a smaller effective rolling radius and thus cover less distance per rpm . I think I may produce a how to guide with some diagrams to help explain this.
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