The age old tyre question

[Black Magic]

I have to replace the rears on my C5. I have been able to find 3 run flats to choose from, but I was wondering if anyone here can decipher some of the jargon on the tyre wall. The tyres are 275 40ZR 18's,

Bridgestone REO50A RFT 99W, £238.53 each

Bridgestone REO40SZ RFT 99W and £238.53 each

Goodyear F1 EMT 94Y £277.30 each

all fitted and balanced at home and includes disposing of old carcase

My question is, for the Bridgestone's what is the difference between the two and
what is the difference between the 99W of the B/stones and the 94Y of the Goodyear

[seefive]

The hieroglyphics on the wall of the tyre (sp?) are as follows

275mm width of tyre, 40 profile (height of wall) ususally expressed as a percentage of the tyre's width - i.e, 40% of 275mm.

The ZR rating - Z denotes safe speed for that particular tyre, R denotes radial ply construction - in your case, ZR means that the tyre is certified for vehicles with a speed capability over 240 Km/h.

Lasty bit... fitting on an 18 inch diameter wheel.

edit... oops... missed the last bit of your mail. the last bit on the selection of tyres you list (99y) is the load index of the tyre. Basically, the higher the number the the greater load the tyre can take (in kg).

>> Edited by seefive on Friday 2nd June 09:21

[anonymous-user]

I was half tempted by the Bridgestones but avoided in the end for 2 reasons. First they're not in the full C5 speed rating (but how often do you drive at 150 mph?) and second the BMW forums are full of people complaining about the ride on their runflats. Bridgestone are one of the BMW suppliers.
Goodyear EMT - expensive, correct rating, original equipment tyre.
Michelin Pilot Sport - expensive, correct rating, non-runflat for better ride and handling. Need a can of foam.
Falken - a lot cheaper, correct rating (I think), non-runflat as per Michelins.

[adetuono]

seefive said:

275mm width of tyre, 40 profile (height of wall) ususally expressed as a percentage of the tyre's width - i.e, 40% of 275mm.

That's something that's always puzzled me. I've got 295/35's on the back of my car, therefore, the sidewall should be 103mm tall, but the total 'height' of the sidewall is 80mm, and that measures from the bead to the top of the tread. In the example quoted above, a 275/40 tyre would have a sidewall of 123mm, or nearly 5" (for us old gits). Hardly low-profile, so what gives?

[seefive]

Absolutely Ade.... I checked the web first to confirm my thoughts on what the definition actually was rather than my interpretation. The web stated that the profile was "usually" expressed as a percentage.

[Y50 VET]

Probably the speed rating from what I can remember the Goodyear is higher, talk to John Pettifer at Northants Tyres (shoebags brother ask for Corvette Discount)
01252 318 666
01252 613 261
[e-mail]

www.northhantstyre.co.uk/

Not wanting to advertise but I found them very helpful and they will have the Tyres in stock

Sam

[Black Magic]

Thanks for the replies all.
I have since found out that the difference between the 2 Bridgestones is just down to an uprated tread pattern. The 98W and 94Y does indeed relate to a speed rating. I am reliably informed that the Bridgestones are good for 176 mph and the Goodyears for 186 mph.
I was also told that there are currently none available in the UK or Holland. A quick call to our good friend Ian Goss and he believes that he can get me a pair of Goodyears in 4 to 5 weeks and at a substantial saving from my quoted price so far.
He now has my order and I am a happy bunny

[eurovettes]

I can supply US based Run flats and NON runflats - shipments monthly

But be aware that fitting / balancing and disposal of old ones will be extra - my local 'corvette freindly' tyre place changes over 4 with balancing etc - for £50

Typically I have found that runflats can be a bit hard/harsh on the ride due to the harder sidwalls - many people are switching to the cheaper non runflats (and keeping a tyre inflator bomb in the car). Khumo Ecsta SPT W rate twi 320 are very popular - cost of the c5 set (17/18) coming over is £580 delivered
Be aware a nail in a runflat can render the tyre u/s.

If you need more on the deciphering let me know

just realised that since joining PH's some may think I am always selling - but I want to pass on honest advice based on my experience - of course the choice is yours where to buy from - and I hope you will consider my service too
Keith