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Tyre Advice


davebr63

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Hi there,

First post so forgive me if this is not in the right place or if the topic has been covered before - I have looked and can't find what I'm looking for. 

Hope someone can help - Roadsport 1.6 K Series 2005 - I've just had to replace the rear tyres, I had Yokohama A021R's (185/60 R13) all round but I believe the new A021R's are track tyres and not for road use - is this true? Anyway, I replaced the rears with Yokohama A539. The old A021R's were great tyres and the car handled like a dream but with the new A539's, the car is very twitchy over 45 mph and feels like it's jumping all over the place - I've been playing with tyre pressures (very time consuming) and have got it about as good as I think I can get it with 18psi on the front and 16psi on the back but still the car is twitchy and doesn't feel as sure footed going into bends. I'm not sure what to do -  Are the A539's just the wrong choice of tyre? (they do seem to have a different profile to the A021R's). Is there a recommended replacement for the A021R's on the road? Should I swap the front and rear so the A021R's on are on the rear? Should I just get 4 new modern tyres all round.

The car rarely gets driven in the rain and I don't track the car (yet). Any advice/answers to questions gratefully received.

Thanks

Dave

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I think the issue is a significant grip and/or tyre construction mismatch between the A539 which is only in the "High Performance Summer" tyre class and the classes above that (Ultra High Performance, Max Performance and Extreme Performance - I think the class that the A021R was in). Often you will get handling issues when using tyres from different tyre classes on the same vehicle. Swapping the higher grip tyre to the back would help stability, but likely reduce cornering confidence due to increased understeer.

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The 21r was a great all round tyre for a road Seven.

I am sure it is unwise to mix them with normal tyres as the car will be unbalanced, swapping them to the rear will be safer for braking but you'll understeer.

So a set of four tyres would be good, but what to choose? I do drive in the rain, have 14 inch wheels and have chosen Rain Expert Uniroyals, I am happy ,but it's hard to know if you would be driving my car.

As you already have two new tyres, and they are generally well regarded, I think I would buy another two. The car will have less grip than before, but much better balanced than it is now.

Alternatively, you can buy a set of four high performance semi slick tyres to get even more grip than the old ones.

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Also, new tyres take a bit of wearing in as they are covered in silicon mold release.

I'd be inclined to have 4 matching tyres so they all behave in the same manner.

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I definitely agree with the others re matching tread patterns

I run A539 185/60 R13 all round in late autumn/winter and found them OK at circa 18PSI all round once  they were scrubbed in

In summer though I run Toyo R888R's with 205/60 R13 on the rear and 185/60 R13 on the front - again at 18 PSI. The R888R's are great summer tyres especially with the slightly fatter ones on the rear and give spot on neutral handling (Mines a 1400 Supersport) - only caveat is you need to be careful in a downpour though as they are prone to aquaplane a bit in standing water (must admit that doesn't  really affect me - I run with Brookland screens and you'll find me stopped under a tree  first sight of heavy rain as I can't see an pigging thing !!) 

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Not so much tread pattern, more compound.

I have happily run the older standard Avons that Caterhams come with - even bought them from other owners who were upgrading to stickeir rubber.  When they ran out, I fitted the latest Avon - bit more slidey, but okay.  A year later, I fitted two Uniroyal Rain Expert to the rear - and next commute to work, promptly understeered across the road on a corner I had negotiated without any trouble for the previous 12 yrs in all weathers - grip came back just in time before I ended up on the grass (and thence into the dry stone wall).  If anything had been coming towards me . . .

New rear grip was so much stronger than the old front grip that had been okay with the previous Avons.

Promptly ordered two more Uniroyals and the balance came back - and they have more grip in all weathers than the Avons ever had.

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On a car such as a Seven with such a short wheel base & low weight not having the same tyres on all four corners will cause an out of balance effect. Differing side wall compliance, tread pattern & compound all go to creating different levels of grip between front & back. Hence the 'twitchy feeling'.

18psi is the recommended pressure for 13" tyres but experimenting anywhere within 18-20 brings acceptable results. 16psi on the back may in due course cause the tyre to unseat.

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I had A539's on my car some years ago, the grip was poor IMO compared to the A021 and have stuck with A021 since, but will need to get 4 x new ones soon. If you want good grip, I think you need to go semi-slick/trackday road legal tyres not a standard road tyre but the downside can be wet weather performance.

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Hi All,

I've just spent a fair few hours over the weekend trawling the forums, reviews and reading them all! I've been looking at Rain Expert 3's Toyo R888R's, A539's and A048's and i thought i'd share my findings. Need to bear in mind this was done for me for my car and my driving but just wanted to share what I'd found. 

My Reference links were the ones around on the forum plus some others:

Original Post: https://www.lotus7.club/forum/techtalk/tyre-advice-3#comment-2336301

A539 Link: https://www.lotus7.club/forum/techtalk/a539s-or-similar?page=2

A021r demise link: https://www.lotus7.club/forum/techtalk/a021r-be-discontinued

Tyre Reviews - these are not just Caterham reviews

ToyoR888R - https://www.tyrereviews.co.uk/Tyre/Toyo/R888-R.htm

Uniroyal Rain Expert 3 - https://www.tyrereviews.co.uk/Tyre/Uniroyal/RainExpert-3.htm

Yokohama A539 - https://www.tyrereviews.co.uk/Tyre/Yokohama/A539.htm

Summarised as follows:

Tyre Dry Grip Wet Grip Feedback Handling Wear Comfort
RainExpert3 84 92 77 74 65 84
R888R 96 72 88 90 75 67
A539 81 74 86 85 78 81
A048 96 53 96 81 51 56

The UniRoyal Rain Expert 3 appears to be a good tyre for all weather. It would be a great touring tyre – I’d have to go for 185/70 R13 as they don’t do 185/60 R13.  The grip in the dry (when the car is mainly driven) is not as good as the A021.

The A539’s are well regarded, good in the wet but not as grippy as semi-slick tyres in the dry. 

A048’s have been replaced by A052 and not much is said about them that I can see - don't fancy being a guinea pig.

Toyo R888R’s seem to have Caterham drivers pleasantly surprised by the grip they give in the wet and the dry grip seems to be phenomenal. 

I know there are other tyres out there and I also appreciate that the tyrereview.co.uk website is also not just for Caterham drivers and that the reviews I've been reading are all subjective but you have to start somewhere. Who knows what each of the tyres will be like on my car with me driving. 

You’ve probably guessed, it’s the Toyo’s for me given when my car gets driven – I’ll keep you posted how I get on!

Thanks again for all your help and guidance.

Cheers

Dave :-)

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Hi Dave

Help & guidance is one of the many things the Club and its members offer. I glad it was helpful.

Many of us are desperately sad that AO21s are no longer E marked.

Thank you for your interesting summary. Curiously, recently I was looking for 185/70 R13 RainExperts and drew a blank, being offered only 60 profile.

I'd also say that as a road driver, I have never run out of dry grip; I have run out of wet grip so value this attribute very highly.

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Why are you not considering the Avon ZZS for a road tyre in your thoughts? By all accounts these are very good, albeit extensive. I love CR500, but am on my last set before replacing them next spring, probably with the ZZS.

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Hi guys, I am new to the group. Hi.

so I am looking at new tyres for my k series supersport 14" wheels. You have'nt mention Avon zT7 which seems to be the current factory default and what about toyo CF2. Anyway thanks for now , good to hear about choices other than semi slicks

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For a 14 inch rim, you can get the Uniroyal RainSport, which on the spec look a 'better tyre' than the RainExpert. For me the problem is I have 13 inch rims, so they were a non-starter. I'm happy with the RainExpert.

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