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[tunnie]

Need some rear tyres for project A, ones on the back at the moment are: 225,55 R15

I could not find any the same at the scrap yard, but there are plenty tyres of bmw 5 series, but they are all: 225,60 R15

Am i right in thinking the 225 is the width of the tyre, the 60 is the wall height, the R15 is the radius.

If so it means the bmw rubber is 5mm higher than my current ones?

Will they be ok to fit on the back of a pre-facelift megga?

Hope so cause I can get each tyre with loads of tread... and a BMW alloy for a tenner each!  [smiley=laugh.gif]

[MadOnVaux]

225 is the width in mm's...the side profile number is a percentage measurement of the tyre width...so '60' in this instance is 60% of 225mm.

 Be OK to fit them id say...wont do any harm i shouldnt have thought, not something id do though.

[tunnie]

the scrap year near here had loads of tyres all in good condition, had pressure and loads of tread. But none the same size....

was hoping i could get away with 225, 60, 15's as they are dirt cheap.

Basically it will just fill the wheel arch more?

[TheBoy]

Its not the size specified by manufacturer.  Additionally, it will knock the speedo out. A savvy buyer may use it as an excuse to drop the price...

[Salty]

The larger size tyre will put the speedo out by 3.6% so with speedo showing 60 you will be doing 62.1

Bearing in mind most speedos are out by up to 5mph at 60 (usually slow) I would say it won't make too much difference.

[TheBoy]

The larger size tyre will put the speedo out by 3.6% so with speedo showing 60 you will be doing 62.1

Bearing in mind most speedos are out by up to 5mph at 60 (usually slow) I would say it won't make too much difference.

Most speedos in my experience are fairly accurate (within a couple of mph at 60ish) - the design requirement is that speedo must not be more than 7% out across its range.

[tunnie]

Grrr damn. Means I cannot get dirt cheap tyres. Ah well thanks anyway!

[Salty]

The larger size tyre will put the speedo out by 3.6% so with speedo showing 60 you will be doing 62.1

Bearing in mind most speedos are out by up to 5mph at 60 (usually slow) I would say it won't make too much difference.

Most speedos in my experience are fairly accurate (within a couple of mph at 60ish) - the design requirement is that speedo must not be more than 7% out across its range.

In my experience most are out by up to 5mph out a 60mph the speedo on my senny was out by 10mph. My Omega is out by 2 to 3 mph and my wifes car is out by 5mph.

i still think you will be ok with the other tyres as they only make 2mph difference your still within spec! potentially more accurate

[TheBoy]

i still think you will be ok with the other tyres as they only make 2mph difference your still within spec! potentially more accurate

Remember that at 60mph, your speedo should be no more than 4.2mph out....

[Salty]

i still think you will be ok with the other tyres as they only make 2mph difference your still within spec! potentially more accurate

Remember that at 60mph, your speedo should be no more than 4.2mph out....

Yep, never seen one read fast as standard so the increase of 2 mph is well within requirements.  The thing to remember is same axle same size and tread pattern

[Big Rod]

As far as I am concerned, the car's speedo is never accurate.

The best mine gets is when I've got brand new tyres on the back. It reads almost exactly the same as my GPS speedo. Although when they're worn, the speedo can be as much as 10% out!!  

Remember tho', it's not just the percieved rolling radius of the tyre that's a variable!! Things like the pressure that your tyre's inflated to and air and tyre  temperature play quite a significant part in altering the rolling radius of your wheel/tyre combo.

I have an ongoing argument with a bloke on another forum who won't accept that because his car's quite new, the speedo's likely to be as much as 10% out.

I say buy the tyres and just be aware of the potential difference. My tyres fit under the rear arches, (just!), and they're 265's.

[TheBoy]

Its all these variables that needs the speedo to be accurate to start with. 2mph for wrong size tyres, 1 mph for pressures/heat, can all bring it up to read high.  Speedo inaccuracies are not an excuse for breaking limit, and zero tolerance is becoming more common.

[Auto Addict]

My speedo on my 2.2 reads 62 @ 60.

[Taxi_Driver]

Its all these variables that needs the speedo to be accurate to start with. 2mph for wrong size tyres, 1 mph for pressures/heat, can all bring it up to read high.  Speedo inaccuracies are not an excuse for breaking limit, and zero tolerance is becoming more common.

I agree and do not condone speeding....in the older days.....in a 30 limit you had to be doing 42 or more to get a ticket...now with zero tolerance you will get a ticket for 34 or more....anything upto and including 10% over seems to be allowed.