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Author Topic: Tyre fitment to standard 18" Monzas  (Read 4581 times)

Offline AnilS

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Tyre fitment to standard 18" Monzas
« on: February 27, 2010, 07:53:37 am »
Can anyone advise.

Just bought a Golf GTI for my wife (will post up pics soon) and the front std tyres need replacing soon but the rears still have plenty of life. They are 225/40/18s. I have a nearly new pair of Conti Sportcontact 3s in 245/40/18.

Would actually fit on the rim? If so I can get another pair and sell the current rear tyres. Not sure if it would rub or affect the ESP, but the tyre size calculator has it fairly colse to OEM for speedo readings.

Thanks. :innocent:

Offline gazbutS3

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Re: Tyre fitment to standard 18" Monzas
« Reply #1 on: February 27, 2010, 09:56:16 am »
245 is to wide for a 7.5" rim, which is what the std Monza's are :smiley:

Offline nc35

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Re: Tyre fitment to standard 18" Monzas
« Reply #2 on: February 27, 2010, 10:38:49 am »
Getting confused myself now.

Thought Monza II were 225 40 18 standard fitment on an 8 1/2" rim?  245 will be too wide for the rim.  May be talking out of my  :booty:

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Offline gazbutS3

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Re: Tyre fitment to standard 18" Monzas
« Reply #3 on: February 27, 2010, 10:48:07 am »
std monza's are 7.5x18 ET51 :happy2:

Offline nc35

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Re: Tyre fitment to standard 18" Monzas
« Reply #4 on: February 27, 2010, 10:50:53 am »
Thank you...

How does the 225 245 size work please?

Think I may have to look it up on a wiki
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Offline gazbutS3

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Re: Tyre fitment to standard 18" Monzas
« Reply #5 on: February 27, 2010, 11:32:04 am »
225 or 245 is the width of the tyre in mm, the 40 is the sidewall measurement which is % of the width(so 40% of 225mm) and the 18 is the diameter in inches, hope this helps :happy2:

Offline AnilS

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Re: Tyre fitment to standard 18" Monzas
« Reply #6 on: February 27, 2010, 03:44:57 pm »
Many thanks Gaz. :happy2:

I'll have to keep them for the 530i then :wink:

I'm not one for mixing brands. There are Contis allround on it and the front are low. The rears have about 5mm (CSC2) which I could switch up front but I'm not a big fan of CSC2s. Had them on my BM and replaced them with Goodyear F1s Assymmetrics, which are very good.

If I switched the CSC2s to the front, would Falken 452s on the rear be OK? Its the cheapest option at the mo.

Regards

Offline nc35

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Re: Tyre fitment to standard 18" Monzas
« Reply #7 on: February 27, 2010, 10:06:52 pm »
Thank you.

How does the 225mm relate to 7.5". Really confused now.
Being a muppet. What do some users mean by streach re tyres?
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Offline Teutonic_Tamer

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Re: Tyre fitment to standard 18" Monzas
« Reply #8 on: May 06, 2010, 09:14:10 pm »
245s will fit perfectly OK on a 7.5" rim.
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline gazbutS3

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Re: Tyre fitment to standard 18" Monzas
« Reply #9 on: May 06, 2010, 09:38:06 pm »
245s will fit perfectly OK on a 7.5" rim.

the OP was quoting 40 profiles for both sizes

yes they will fit, but everything I've read recommends a 8" rim for a 245 tyre, it may give a comfier ride but would lose some sharpness to the handling and would affect the speedo readings too

Offline Teutonic_Tamer

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Re: Tyre fitment to standard 18" Monzas
« Reply #10 on: May 07, 2010, 09:43:13 am »
245s will fit perfectly OK on a 7.5" rim.

the OP was quoting 40 profiles for both sizes

yes they will fit, but everything I've read recommends a 8" rim for a 245 tyre,

Gaz, you need to look a little deeper at this - yes, 245 is recommended for an 8" rim width.  However, it is also permissible to fit it on a rim as narrow as 7.5", or as wide as 9".  So whilst 8" is the ideal width, there is clearly a wider scope for narrower or wider rims for the 245.



it may give a comfier ride but would lose some sharpness to the handling

Huh, disagree with both.  If you are going from a 225/40 to a 245/40, then all other things being equal (tyre make/type, load index, etc), then there would be no change in comfort.  And there would be no loss in 'sharpness' to the handling either, in fact, wider tyres will improve handling stability during hard cornering.

and would affect the speedo readings too

Agreed - but rather than speculating, the maths need to be done.  Don't fo rget that on the standard sized boots, the GTIs speedo over-reads (just like all cars).  So, as an example, at 5,000 rpm in 4th gear (DSG), on the OEM 225/40 size, the speedo reads 90mph, but the genuine actual speed is 83 (speedo over-reads by 7mph) - but at the same revs and gear with 235/40 boots, the speedo reads 89mph, but now the genuine actual speed is 84 (speedo over-reads by 5mph).  So, if anything, 245/40 will make the speedo even more accurate.
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Richn83

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Re: Tyre fitment to standard 18" Monzas
« Reply #11 on: May 07, 2010, 10:33:36 am »
Thank you.

How does the 225mm relate to 7.5". Really confused now.
Being a muppet. What do some users mean by streach re tyres?

Its just the confusion between wheel size in imperial, and tyre size in metric, 7.5 inch is the width of the rim, 245 is the width of the tyre, if you fit a tyre that is not of a compatible width for the alloy rim you wont have a vertical side-wall to your tyre, if you want to see this in action go into halfords, they always fit a cheaper not wide enough tyre to there wheels and you get left with an ugly looking side wall. (thats IMHO so please dont shoot me) as mentioned there is an ideal size or range of tyre widths for a specific rim width.

I would also assume but may be wrong that a stretched tyre could have a slight impact on cornering ability due to the tyre wall be stressed (down-ward cornering force) being applied at a different angle than intended through the side wall.


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Offline Teutonic_Tamer

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Re: Tyre fitment to standard 18" Monzas
« Reply #12 on: May 07, 2010, 11:49:36 am »
Thank you.

How does the 225mm relate to 7.5". Really confused now.
Being a muppet. What do some users mean by streach re tyres?

Its just the confusion between wheel size in imperial, and tyre size in metric, 7.5 inch is the width of the rim, 245 is the width of the tyre, if you fit a tyre that is not of a compatible width for the alloy rim you wont have a vertical side-wall to your tyre, if you want to see this in action go into halfords, they always fit a cheaper not wide enough tyre to there wheels and you get left with an ugly looking side wall. (thats IMHO so please dont shoot me) as mentioned there is an ideal size or range of tyre widths for a specific rim width.
Exactly.


I would also assume but may be wrong that a stretched tyre could have a slight impact on cornering ability due to the tyre wall be stressed (down-ward cornering force) being applied at a different angle than intended through the side wall.

I agree.  Whilst streched tyres seem to be all the rage, there are two very distinct disadvantages.  Firstly, your wheel rim is considerably more prone to kerbing and general damage, and secondly, stretched tyres not only loose grip very quickly when cornering (ie, with little or no feedback), but it can also place massive stress on the tread-to-sidewall join inside the carcass during hard cornering.  NOT good.
Sean - Independant Automotive Engineering Technician (ret'd)
------
07 Golf5 GTI 5dr (BWA), DSG, colour coded, Revo, WALK, WL ARBs, 235 PS2s, seat drawers, OEM tints, custom/hybrid engine mounts, Audi-esque soundproofing

~~ free official Golf V factory workshop manuals ~~