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Author Topic: Tyre size question..18"  (Read 1938 times)

Offline Gmac

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Tyre size question..18"
« on: April 21, 2016, 03:13:15 pm »
Quick question...

I'm planning new putting H&R lowering springs on and also putting a set of 18" wheels on which are 8j wide..

They come with 235/40/18 tyres... I know normally we'd be looking for 225, but will the 235 cause any rubbing issues????

TIA

Offline pudding

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Re: Tyre size question..18"
« Reply #1 on: April 21, 2016, 03:39:35 pm »
It might throw the speedo out a little as the sidewall height is a percentage of the width.


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Offline jayha11

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Re: Tyre size question..18"
« Reply #2 on: April 21, 2016, 03:58:59 pm »
Few things that will help:

Whats the offset of the wheels?
Are the springs 30mm drop?
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Offline Gmac

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Re: Tyre size question..18"
« Reply #3 on: April 21, 2016, 07:10:37 pm »
Few things that will help:

Whats the offset of the wheels?
Are the springs 30mm drop?

The offset is et43, and the drop is indeed 30mm...

Offline jaffa

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Re: Tyre size question..18"
« Reply #4 on: April 21, 2016, 10:21:18 pm »
Probably rub with the 235's
Doing the screw mod will give you a few mm's clearance but you should get some 225's


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Offline sub39h

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Re: Tyre size question..18"
« Reply #5 on: April 21, 2016, 10:37:33 pm »
It might throw the speedo out a little as the sidewall height is a percentage of the width.

I do agree that you should run the right size tyre, but the difference is negligible - 4mm radius or less than 1mph difference at 70mph

http://www.brspecialtuning.co.uk/Tyre%20size%20calculator.htm
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Offline jayha11

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Re: Tyre size question..18"
« Reply #6 on: April 22, 2016, 10:44:15 am »
Few things that will help:

Whats the offset of the wheels?
Are the springs 30mm drop?

The offset is et43, and the drop is indeed 30mm...

Just to give you some perspective I am running the following...

18x8j ET35 (stick out 8mm further than yours)
lowered approx 65mm front & back
Tyre's are 215x40x18 to aid with tucking at the rear

Is there a specific reason you want to run 235 tyre's?
 
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Offline Gmac

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Re: Tyre size question..18"
« Reply #7 on: April 22, 2016, 11:27:12 am »
Yeh, the wheels that are for sale come with 235's.  I've currently got 17" wheels and tyres.

Offline Gmac

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Re: Tyre size question..18"
« Reply #8 on: April 22, 2016, 11:27:59 am »
Probably rub with the 235's
Doing the screw mod will give you a few mm's clearance but you should get some 225's


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Will do a search for the 'screw mod'.  :happy2:

Offline pudding

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Re: Tyre size question..18"
« Reply #9 on: April 22, 2016, 11:59:43 am »
It might throw the speedo out a little as the sidewall height is a percentage of the width.

I do agree that you should run the right size tyre, but the difference is negligible - 4mm radius or less than 1mph difference at 70mph

http://www.brspecialtuning.co.uk/Tyre%20size%20calculator.htm

Yeah it's very minor usually, but sometimes one tyre maker's '235' is a bit different to another's.   I usually find taller tyres than standard affect the gearing and unsprung mass more than anything else though!


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