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CR500s


Kingsley Young

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haha! that's a good one. It's like if you need to ask, it's time for new ones.

not much or more than you might think : seems to me it all depends how fast I do the hairpins. 

In principle I always start a tour with fresh or nearly fresh tyres - or have a new set of wheels in reserve if travelling with the trailer.

To answer the question... 5,000 miles and if much cornering alacrity is involved then 3,000 miles. So between "not much" and "some". Also the rears wear out twice as fast as the fronts.

Doughnuts/wheel spins and track time mean all bets are off.

I suppose it also depends on whether the tarmac has warmed up - for example Alps versus Portugal.

I've been on CR500s since about 2003.. though not the same set and Avon (an engineer at the Donnington 60th) tell me their new design is a better tyre; better for me in the road and not the race form, though that tempts me to the softer fronts when I run out of CR500s. I suppose tyre design has moved on in the 18 years or so since the CR500 was created.

edit: my context is an R500K, maybe less power might mean more miles.

Anthony

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Technology might have moved on but the fundamentals of unsprung and rotating weight haven't - the CR500 is lighter than than new ZZS and I like the idea of keeping the weight off the wheel/ tyre assembly.  

Some comparisons here http://www.caterhamr500.co.uk/2016/07/new-cr500s-with-weights.html

"A quick check in Tech Talk has resulted in the CR500 175/55/13 weighs 6.05kg (my weight 6.3kg) and 205/55/13 weighs 7.03kg (same as my weight) compared to 7.65kg and 8.8kg for the ZZS tyres respectively. 

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I've written to Avon in these terms:

Dear Avon,

This is a begging letter.

Your "new" ZZ tyres have a massive increase in unsprung weight for my K series R500 Caterham.

EG the CR500 175/55/13 weighs 6.05kg (my weight 6.3kg) and 205/55/13 weighs 7.03kg (same as my weight) compared to 7.65kg and 8.8kg for the ZZS tyres respectively. 

PLEASE let us have some tyres (fast road) that are designed for our light weight cars like the CR500 is/was.

I know you will now  add something ideal to your line up, perhaps a ZZt (for lightweight touring). 

I've been using your CR500s since 2003 so I will FEEL a dreadful loss when I run out.

Your advice always welcome.

Anthony

Doubtless they will change their manufacturing just for me.

Be interesting if they can offer an existing solution... lighter wheels?

Anthony

 

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Kingsley, I got 8,500 miles out of a set of rears (175/55R13). I don't have a record for the fronts, but my fronts generally last twice as long as the rear. For comparison, I got 3K / 6K with Yoko 032R and 6K / 12K with 021R.

CR500 is my favourite Seven tyre by far, for the right balance of grip, wear, ride comfort, weight, and cost (once you take into account how long they last).

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my understanding of that "limited numbers" is it's to allow all old stocks to be used up, so for example they won't leave me with just two tyres I already hold and will sell me another pair.  Any mention of when they will cease production entirely?

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aha, "foreseeable". Thanks.

unsprung weight is an issue, wonder if anyone knows about sidewall properties - as in the CR500 was designed with light, i.e. not tintop, weight cars in mind.

 

edit: reminds me, istr the inboard suspension design reduces unsprung weight, or is that my imagination?

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... the inboard suspension design reduces unsprung weight, or is that my imagination?

Discussed here in a Sevenish concept, but not very clearly. Was there a particular version or comparison you had in mind?

(Moving brake assemblies inboard with otherwise unchanged suspension reduces unsprung mass. As does the whole de Dion tube design.)

Jonathan

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no, just seems very clever. Seen anything about sidewall differences CR500/ZZS?

 

edit: having read the PH thread linked above, it seems unsprung weight may NOT be reduced, but that there are all sort of positive / negative issues and my physics is no longer up to it, if it ever was.

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I have been talking to Avon about CR500s for my CSR.  They say that they intend to keep them in production, and that they only have one compound.  This is their recent quotation... and they are about to deliver four of them.  I am not keen to transition to the ZZS since is not the intended aspect ratio, and they are heavier.  But I doubt if I would notice the difference, once I had finished fooling around with the front mudguards so I could get them to fit.  And I think that they must intend to keep making them, since tires on the shelf only have a limited life before people will start complaining about the build date, but I will ask about this before I order them.  But I bet I wear them out before they time expire...  LOL.

“We currently have stock available of both sizes requested below. You can purchase them direct from us and the tyres can be despatched for a next working day delivery if ordered and paid for before 12 o'clock.

The CR500 are only available in the one standard compound.

Here are the prices again...

195/45R15 CR500 - £129.50 + VAT 

245/40R15 CR500 - £166.30 + VAT

Freight - Approx. £20 + VAT (per set)”

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  • Area Representative

David 

I tried a set of the ZZS  tyres on the same rims as mine , which are 195-45-15   They fitted under my front wings fine when I offered the top of the wheel under the mudguard first.

Kingsley

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If I remember correctly, the reason for the big difference in weight between the ZZ and the CR tyres is that the old CR500 tyres had kevlar skeletons, not steel wire. I'm not sure but I think even the latest CR500 tyres might have moved to steel too?

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Hello Kingsley,

Thanks.  I actually thought that might be the case... but I was also contemplating getting some new CF wings from CC and asking them not to drill the front mounting hole.  But, in truth, I am pretty happy with the CR500s.  I will ask Avon if they have changed from Kevlar to steel, though.

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195/45R15 CR500 - £129.50 + VAT

Ouch, that's a tad pricey.  A ZZS in the same size is £110 + VAT (at least, it was a couple of months ago).

ETA: Of course, I should have said "similar" or "replacement" rather than "same" as the ZZS is 195/50R15.

JV

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I still prefer the CR500's even though the ZZx seem to hold on for longer and break away more progressively. I find the more compliant CR500 much better over the bumpy Kent/Sussex "B" roads which is my morning blat stomping ground. On track the ZZx are great but on road ZZR temp falls off quickly after you have been "on it" and then they are [i am] all over the place.

I usually get about 6k out of a set of CR500 on road, fronts maybe slightly more than the rears but usually end up changing all at the same time. That's with c.200bhp and set up by Andy at PGM for very fast road and occasional track days.

Cheers, Julian

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here's a bit of history, page 4 the creation of the CR500, designed for the R500 Seven AD 2000

http://lowflying.lotus7.club/2000/2000_06_05_R500.pdf

Col 1 para 2

I once tried ACB10s and delaminated the rear pair simultaneously. Maybe user error, but not for me - and the tram lining was dreadful. Track tyres for sure. Happily WRS saved the day. (WRS=Wife Rescue Services).

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