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Shaun_E
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Avon ZZS tyre sizes

As we are likely to compete in class 5 this year, we need to buy new tyres. It seems that Avon ZZS are the tyre of choice now and I guess most people are using 185/55R13 and 215/55R13. Has anyone used 215 on the front with 245/50R13 on the rear? I know the 215 fronts can be fitted but I'm not sure if 245s will fit on the rear. We currently run 235 Kumho on the rear and they are quite close to the ARB.

I guess the other question is why ZZR are not preferred over ZZS. I know one competitor will be running ZZR but I understand most of the 2021 class 4 decided ZZS were better.

Drumster
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Sean, the only thing I can comment on is that the ZZSs have a more 'bulbous' sidewall compared to the  'flat' sidewall of the Kumhos. I found that even with 235 Kumhos the sidewall was flexing enough to rub a little on the radius arms.

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Dannyboy
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Sean.. 

how much grip do you need ? 
if you have the same as others in class why would you need more? You have the talent to drive round this. 
 

failing that, drive round the ARB by removing? Your dampers can more than compensate. 
 

ZZR ultimately have more grip, however in my opinion in anything but dry conditions the ZZS are probably the slightly better tyre overall given that ZZR from cold are dreadful and we don't often have a hill long enough to generate significant heat across the tyre with the 1B compounds . I'd go with the one that  moves more across the tread blocks thus generating heat... 

Dannyboy
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There is the argument in class 3 that 185 front and rear work best as the gearing is better and arguably the smaller width will generate hear across the tyre quicker.. 

i personally will stick with 185 front and 215 rear and work the fronts really hard at the start of a sprint 

Richard Price
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Shaun,

I'll confirm Dan's comments. They don't work that well from cold, so a smaller tyre, worked hard from the start, gets better as the run progresses. If you go too wide, you may never get them warm enough to work....

The 215's are larger diameter than Kumho 215's , so you would also need to drastically rework your front wings and stays.

They're also around 20mm larger in diameter than 215 Kumhos, so, to run at the same ride height, you'd need to use up some of your bump travel. How much bump travel do you currently have before the bump stops?

Wide, cold ZZR's on a damp track..... No thanks :-) 

Shaun_E
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Thanks for your thoughts. I've been running Kumhos in 215 fronts and 235 rears for years - heating the rears up has never been a problem which is why I was wondering if 245 ZZS might work. Sounds like they would probably rub on something though. I was worried about the wide fronts in a 1B although I know Mike Sankey runs them and is still breaking his PBs. 

I think I will try 185 front and 215 rear then. Will the 185s fit on 7.5" rims though? Avon seem to recommend 7" max.

AMBO
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Shaun, I can't help with the size questions, but suggest ordering sharpish as prices are apparently going up in the New Year. Got ZZS 185/55 and 215/55 13's direct from Avon Motorsport for £550 delivered, just before Christmas. Good luck! Nick

Hampshire West AR
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Slightly cheaper from Caterham Cars for 4 delivered.

mikes
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If only I had set some more PBs!!

Both Jeremy and I tried the ZZRs a few years ago when the requirement for !B to be road tyres came in and we agreed that they were the wrong choice for sprints and hillclimbs. Even though the ZZR was supposed to have the slightly softer compound it was not apparent in comparison to Class 3 (who were all on ZZS) in the dry and they were a nightmare in the wet. Of course it didn't help that the rake on the car was totally out but I think the ZZS is far better for what we do.

When I changed to the ZZS I did keep the 215s at the front and they do not heat up much ....... but then neither do the rears in comparison to the Kumho supersofts. I cannot compare what it is like with smaller fronts but you do have to allow for more understeer on the first few corners, and it is certainly a different technique getting off the line! Overall, I was pleasantly surprised with the grip they gave last year, it was not as dramatic change as I thought - but maybe I am just getting old! PGM did change the setup compared to the Kumhos to give more camber, front and rear though. Oh, and the other good thing is that they do not wear out so fast!

Hope that helps

Mike

Shaun_E
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Thanks Mike Smile

Guess I'd better get an order in.

Simon.Rogers
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Shaun.  245 do fit fine on 8.5" rims.

I had them on the Ecoboost car you may remember.  They were same offsets as I have now.

until you do a back to back test on the same day with different set up it's always going to be something in your mind asking that question.

I have always been one for the biggest contact patch possible but I have no evidence that I am correct.

I can supply all the Avon tyres and will hopefully get them listed on the website tomorrow.

www.meteormotorsport.com