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Model specific boards => Golf mk5 => Topic started by: rugbymad on 06 November 2008, 19:33

Title: what difference will this size of wheels affect spedeo
Post by: rugbymad on 06 November 2008, 19:33
http://cgi.ebay.co.uk/18-ALLOY-WHEELS-VOLKSWAGEN-GOLF-MK5-225-40-18-TYRES_W0QQitemZ350119098166QQcmdZViewItem?hash=item350119098166&_trksid=p3286.c0.m14&_trkparms=66%3A4%7C65%3A1%7C39%3A1%7C240%3A1318 (http://cgi.ebay.co.uk/18-ALLOY-WHEELS-VOLKSWAGEN-GOLF-MK5-225-40-18-TYRES_W0QQitemZ350119098166QQcmdZViewItem?hash=item350119098166&_trksid=p3286.c0.m14&_trkparms=66%3A4%7C65%3A1%7C39%3A1%7C240%3A1318)
HI folks

i'm intresten in these wheels for a golf gt sport 07, these are 1 inch bigger than my standard wheels, will this make a difference to my spedo reading and mileage.  i.e the wheel size.i am away from home at the moment and unable to check my standard size of tyre i know they are 17 wheels.

YOU ARE BUYING A BRAND NEW SET OF 18" CRUIZE 258 ALLOY WHEEL AND 225/40/18 PERFORMANCE EXTRA LOAD TYRES FULLY FITTED AND BALANCED

the size of tyres given will be
thanks
i can upgrade to 235/40/18 as an option
Title: Re: what difference will this size of wheels affect spedeo
Post by: bacillus on 06 November 2008, 19:50
Using the 225/40/18 tyres will keep your speedo readings unaltered from at present.

The 235/40/18 tyres will make your speedo under read.
Title: Re: what difference will this size of wheels affect spedeo
Post by: markymark on 06 November 2008, 19:51
I think your 17's will be 225/45/17, my wheels are 18's and the tyres are 40 profile so they wont make a difference to your speedo as the rolling radius will remain unchanged! :smiley:
Title: Re: what difference will this size of wheels affect spedeo
Post by: Greenouse on 06 November 2008, 19:51
As 18's are an option on both the GT Sport and the GTI I cannot forsee a problem. I have recently upgraded to 19's and the GPS readout on my Tom Tom is the same as it was on the 18's!  :wink: HTH
Title: Re: what difference will this size of wheels affect spedeo
Post by: markymark on 06 November 2008, 19:53
Using the 225/40/18 tyres will keep your speedo readings unaltered from at present.

The 235/40/18 tyres will make your speedo under read.

But the 235 only relates to the tyres width, I cant see how this will change speedo readings.
Title: Re: what difference will this size of wheels affect spedeo
Post by: mortygt140 on 06 November 2008, 19:53
Off the top of my head at about 70mph the gps reads 63mph, if Im going through a 40mph gatso gps reads 35mph.

Im on 225/40/18 dont go for the 235 tyres cos you'll just get more tram lining than you need, and also if the offset is lower than std then you may get some rubbing on the back arches?

Darren
Title: Re: what difference will this size of wheels affect spedeo
Post by: JC on 06 November 2008, 19:54
http://www.tyresave.co.uk/tyresize.html

stick them in there, will tell you expected % you will be out
Title: Re: what difference will this size of wheels affect spedeo
Post by: mortygt140 on 06 November 2008, 19:56
Sorry should have said im running a GT diesel so std rims would have been 16",  by the way is there anyway of changing this with my vagcom?

Darren
Title: Re: what difference will this size of wheels affect spedeo
Post by: Hurdy on 06 November 2008, 20:11
There will be no noticeable difference between using the standard 16" wheels and tyres you have now, to using the 225/40/18's in the advert. If you want to go to 235/40/18 then there will be a small difference in rolling circumference, but nothing to worry about. I thought about this too, for the slightly extra grip you would get. I don't think you would get any rubbing issues either as long as you went with the correct offset.

225/40 will give you a sidewall that is 40% of 225mm width = 90mm

235/35 will give you a sidewall that is 40% of 235mm width = 94mm

so the difference in sidewall is 4mm = 8mm smaller diameter with 235/40 section tyres.

Rolling circumference is 2002mm stock and 2010mm with 235/ section tyres which means an error of less than 1% :nerd:

Title: Re: what difference will this size of wheels affect spedeo
Post by: bacillus on 06 November 2008, 20:13

But the 235 only relates to the tyres width, I cant see how this will change speedo readings.
The profile of the tyre (in this case 40) is a ratio of the tyre width and it's height.
The 235/40/18 tyre height will be greater will be greater than the 225/40/18 one. This in turn will mean that rolling circumference is greater hence the speedo will under read.
Title: Re: what difference will this size of wheels affect spedeo
Post by: pw motorsport on 06 November 2008, 20:14
Ask the seller what the wheel weight is?
If they are a lot heavier than the oe wheel your performance and fuel economy will suffer.

Title: Re: what difference will this size of wheels affect spedeo
Post by: markymark on 06 November 2008, 22:15
Cheers for the correction Hurdy and bacillus I never knew that!  :wink:
Title: Re: what difference will this size of wheels affect spedeo
Post by: rugbymad on 07 November 2008, 16:32
Thanks everybody, it's cleared it up for me.. think i'm gonna have to buy these wheels.  yuipeee!!!!!!!!!!!!!