quick tyre question please...

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OldEnglish68
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Hi there

My '93 300ges has 255/60/18s on it at the moment.

Can I change all four to 255/70/18 without complications please?

(Wheel clearance, gearing, steering etc etc??)

All advice very gratefully received as always

 

OE68

Jdring
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Re: quick tyre question please...

Theo had some real input on this about the tolerance in increased circumference 

The tyre sizes for the different G models have the same circumference:  for example 265/ 60 R18 = 265/ 70 R16. You can fit larger tyres but you have to adjust the settings both for the instrument cluster and transmission module.  The reason:  the ESP tolerates a deviance in the tyre circumference of about 2%.  The difference between 265/60R18 (2367 mm) tires and the popular upgrade 275/70R18 (2590 mm) is about 10%. Without adjustment the ESP will interfere in faster turns.  There are a number pre-programmed tyre sizes in the G-electronics (and that varies depending on model year), it has been disucssed on this forum before (and there is more if you google it).  

I promoted the thread that had that information.

I also did some calcs of my own, because I wanted to 'gear up' my 4 speed auto 460 by putting larger wheels on that.  Larger circumference wheels would mean faster for the same rpm.  But the calcs showed bugger all difference realistically, so I didn't buy the spacers and the longer wheel bolts to try it.  No ESP or DTC to worry about on the 460.

(edit: I was thinking of puttingn wider 463 wheels onto my 460, but the circumference increase was only about 5%, increasing my cruise speed from 60mph to 63mph.  not worth it)

This was the thread for that: http://www.gwoa.co.uk/content/bigger-wheels-460 

 

markhowes
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Re: quick tyre question please...

I'm definitely no expert but I don't think so.

I also have a 463 G300 SWB and according to the Owner's Manual the orginal wheels/tyres should be 225/75/16

Those you have on at the moment already have a 2.6% greater circumference which is more than the recommended - although probably not critical on a 1993 vintage model with not so many electrical sensors.

The ones you want to fit have a 9.4% greater circumference than those listed in the handbook. So, at the very least there would be a 9.4% difference in the speed you are showing compared with originals. I don't think this is an accepted excuse should you trip a speed camera wink

Useful calculator which allows you to compare 3 different sized wheel/tyre combinations here:-

https://www.tyresizecalculator.com/tyre-wheel-calculators/tire-size-calc...

No doubt someone will be along shortly to say that they've got even bigger wheels/tyres with no problems

OldEnglish68
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Re: quick tyre question please...

Thank you both.

True, I was looking for lower revs on the motorway...

Although not what I was hoping, this information is good to know and really useful.

The thought was being driven by the need for one new tyre - need one, why not five?!

Sounds like I should stick with what I have.

Best wishes to all