Quick Tyre Question

[mandalman]

My car is fitted with the old Avon CR500 tyres. There is still a loft of tread on them although obviously they are probably at least six years old now. I'm off for a week driving around Wales next week and it may well be wet after our short hot spell this week  so I am considering replacing them with a new set of Avon ZZS's. I know the ZZS is meant to be a good all purpose tyre for wet roads but is it any better than what I have or am I just wasting money? Also my second question: I currently have 175/55/13 on the front. If I did go the ZZS route  I'd haver to go for 185/55/13. Is that going to be OK?

[Toughie]

Just seen your thread Mandalman.

I'd suggest giving Avon a call and asking their view.  They have a new set up there, and when sorting out our arrangement with them I found them very helpful, producing this special guide for the Club.

https://www.lotus7.club/guides/avon-tyre-information

You can find the number for their Motorsport Division (which they don't usually make available), which is the part that does all Avon's tyres for Sevens, here:-

https://www.lotus7.club/membership/special-offers-members/avon-tyres

While they are there to sell you some new tyres, I've always found them very ready to help, and they've been terrifically switched on about our cars, the last two of their Motosport division bosses being Seven owners.

 

[Golf Juliet Tango]

I get rid of tyres after five years, irrespective of the tread. 

I really miss AO21s which I could wear out within a year or 18 months.

[Geoff Brown]

mandalman - I am still running CR500s - they were a bulk purchase of two sets before going out of production.

The sole remaining rear pair just put on are on the cusp of five years old which technically is the life but having been stored correctly will be OK. 

The 5-6 year life of a tyre is generally viewed as on the rim but with a few checks this can be extended.

Obviously keep your CR500s at the correct pressures monitor for crazing on the outer & inner walls. Check for cracking or crazing between tread blocks & adjacent to the wheel rim.

Carrying out those checks will keep the tyres in service until illegal.

With fitting front ZZS it is a matter of the tyre wall clearing the wing stays.

When I come to upgrade to ZZS my current 175/55 R13 will have to be swopped for 185/55 R13 & my rears for 215/55R13.

As for speed ratings there is the quandry. CR 500 in 13" form were 79v front & for 8Jx13" rears 85v.

The nearest on the Avon ZZS chart is 83w & 88w respectively - speed rating of 168 mph which Caterham fit as standard.

But to add to the confusion Avon do offer ZZS in 69H & 78H form which is a speed rating of 130mph.  But what ever Caterham fit as OE is correct.

ZZS size/rating: Avon ZZS - Avon Tyres

[Richard Price]

"But to add to the confusion Avon do offer ZZS in 69H & 78H form which is a speed rating of 130mph. but what ever Caterham fit as OE is correct."

Geoff,

The tyres with the 69H & 78H rating also have labels that state:-

"For Regulation EC1222/2009 purposes only - This tyre is designed to be fitted only to vehicles intended exclusively for racing."

They are specifically designed as a wet weather racing tyre.

[MattB]

There are 2 items included in those codes - the load rating (83, 88) and the speed rating (V, H).

As I understand it the speed rating is the highest speed that the tyre is capable of maintaining, mile after mile, not the top speed it can achieve momentarily.  An H rating should therefore be fine for a 7 on the road.

The load rating is the maximum load that the tyre can carry at any speed (although the impact is highest at higher speeds, so the load and speed ratings are inevitably linked).  Given that a fully loaded 7 is unlikely to get above 800kg, each tyre needs to be able to carry around 200kg. A tyre with a load rating of 62 can carry 265kg, so shouldn't be stressed carrying a 7.

Tyres with higher load ratings are heavier, with additional material in the carcass to take the extra load (and often higher pressures) especially if they're marked XL (eXtra Load).

I'm new to the 7 world, but can't help but think that the lighter, lower load rating tyres would be better for a 7 on the road.

MattB

[Geoff Brown]

I do not continually drive around at the published top speed of an R400D - 136mph - but to err on the safe side personally I will fit ZZS with 83w & 88w speed ratings which CC fit as standard to the road cars.

There are issues that one could find fault with CC but not this particular issue.

 

[MattB]

Just noticed that Avon state, in the guidance document they put together for the club, that the lighter RT7 compound ZZS tyres are "not suitable for the road". 
 

MattB