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Help me with tyres MV2 18'

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Hi guys,

 

Looking to buy some new tyres, I have had my car on 240/40/18 on front and 245/40/18 on the rear.  Not sure if these are the correct ones but this is what the car has come with since I baught it so always changed them to the same size.

 

Have been using branded Alphine Pilot PA3 for two year (changed once a year) and they last me a whole year!  Can't really fault them apart from being hardcore winter tyres.

 

I need to know whether the size is correct for my MV2 or it should be something else? Also this time I am looking for all year around tyres instead so that I do not loose performance throughout year and a long lasting quality brand.

 

Any information welcome!

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I'm assuming MV2s are Style 135.  

 

These are 8J x 18 rims with no option of staggered set up so the correct tyre front and rear is 245/40R18 93Y  240 width on a 40 profile will give you too small a rolling radius.  So you will have the fronts spinning slightly faster than the rear which may upset anything that uses the input from the wheel sensors to control it, shift patterns on an autobox being one.

 

The rolling radius should not differ front to rear which it would with 240/40 front and 245/40 rear.  

 

A staggered set up with a wider rim then uses a lower aspect ratio to bring the rolling radios of the wheel down to the same as the front. Rear 9J rims on 18s use a 275 width tyre but with a 35 aspect to match the front which is 245/40.

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There is an E60 520d that I park next to at my local station, he is running MV2s with Michelin winters on it since I first saw it and that was last winter so he's been running winters during the summer months, not that where we are there has been anything remotely summery.

 

At 245/40 on 18 rims you will have a good choice of winters. Going wider at that size, the availability of winters dissapears. I couldn't see 275/35 winters for my 18" on my E60 so never went for winters.

 

Why are they called MV2 s then?  I've always been puzzled by that, no one ever refers to them by their style number.

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1 hour ago, Chris Wong said:

I use 245/40/18 front 255/40/18 rear

 

Any issues caused by the difference in wheel rolling radius?  That you are aware of?

 

Mibbies  that explains your slowness off the line, the bigger wheels at the back will not help your 0-60 times but only by milliseconds. :D It will improve your top speed by a teeny tiny amount tho!

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15 minutes ago, 535iAR said:

 

Any issues caused by the difference in wheel rolling radius?  That you are aware of?

 

Mibbies  that explains your slowness off the line, the bigger wheels at the back will not help your 0-60 times but only by milliseconds. :D It will improve your top speed by a teeny tiny amount tho!

Only wider the radius is the same 

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3 hours ago, Chris Wong said:

Only wider the radius is the same 

 

Sorry but that's not correct.

 

The height of your sidewall thus radius of the tyre, is based on a percentage of the width which is the second figure of the tyre size.

 

The second figure (after the /) of a tyre size is the height of the sidewall expressed as a percentage of the width.  Otherwise known as the aspect ratio.

A 245/40 tyre has a sidewall height of 40% of the width of 245 mm = 98mm

A 255/40 tyre has a sidewall height of 40% of the width of 255 mm = 102mm

 

Yes it's only a few millimetres..... But at those numbers every revelation of the rears, the front tyres have travelled a distance of an inch further.

 

Explanation of tyre size.

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10 hours ago, 535iAR said:

 

Sorry but that's not correct.

 

The height of your sidewall thus radius of the tyre, is based on a percentage of the width which is the second figure of the tyre size.

 

The second figure (after the /) of a tyre size is the height of the sidewall expressed as a percentage of the width.  Otherwise known as the aspect ratio.

A 245/40 tyre has a sidewall height of 40% of the width of 245 mm = 98mm

A 255/40 tyre has a sidewall height of 40% of the width of 255 mm = 102mm

 

Yes it's only a few millimetres..... But at those numbers every revelation of the rears, the front tyres have travelled a distance of an inch further.

 

Explanation of tyre size.

Interesting.. So your saying every car that is manufactured with a staggered setup is wrong? 

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4 hours ago, Chris Wong said:

Interesting.. So your saying every car that is manufactured with a staggered setup is wrong? 

 

No because the staggered sizes specified by BMW are done so the rolling radius is nearer than the example Based on your sizes.

 

Wider tyres like 275 (rear) are specified with a 35 sidewall aspect and the fronts 245 are specified with a higher 40 or 45 similar sidewall aspect to get the rolling radius nearer each other than the example you are running with.

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2 hours ago, 535iAR said:

 

No because the staggered sizes specified by BMW are done so the rolling radius is nearer than the example Based on your sizes.

 

Wider tyres like 275 (rear) are specified with a 35 sidewall aspect and the fronts 245 are specified with a higher 40 or 45 similar sidewall aspect to get the rolling radius nearer each other than the example you are running with.

Yep I totally understand now thanks so in truth i should be running 255/35/18

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Sorry bud, I don't have knowledge of what the staggered set up would be for MV2s. The tyre pressure/data plate on the drivers door slam panel will give you an indication of what should be fitted to your car.

 

Generally you only stagger when the rim sizes are different front to rear.  If you have 4 No. 8" wide rims you tend not to stagger tyre sizes front to rear. On the E60 I had, the fronts were 8" rims with 245/40 and rears were 9" rims with 275/35.

 

For increasing the rim width by an inch you drop 5 from the aspect ratio, the size you quote would be a nearer match but check that you can get tyres in that size as some width/aspect ratios are non standard sizes. 

 

Having differing rolling radius of wheels front to back on a car like E60s may upset anything that uses input from the wheel sensors as it will get confused in the different speeds of each axle. 

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For a staggered setup with 245/40s on the front you would be looking at 275 on the rear with a 35 aspect ratio to keep the closest circumference but putting anything wider than 245 on an 8" rim would likely result in worse handling due to the tyre being overstretched which results in more tyre roll when pushed. I'm not sure what the standard width is on the stock MV2s but 8" seems to be whats quoted, perhaps you could get away with a 8.5" rear from an E46 MV2?

 

As for changing the circumference, you may not have noticeable changes but I suspect some of the electrical systems wont work quite as well as they should (minimal change though), like ABS/TCS not kicking in soon enough or too soon ect but its likely marginal for daily duties but I would worry about them potentially throwing toys out of the pram. Having said that, with the variations were talking about here, its not that different to having a slight puncture on the front wheels and that doesn't make the car have a fit (apart from the TPMS obviously).

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I am using spacers 20mm at the back and if I remember correctly 15mm in the front. I have put 245/40 on my MV2s in the front and 245/45 at the back to give a car a stance it should have when it came from factory. I don't care about the rolling radius BCS I DRIVE A MANUAL..so don't do this if your's is automatic as it may upset some sensors, but I have no issues to report only good looks :P and handling :D.

IMG_20190616_204724.jpg

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