machin Posted March 18, 2003 Share Posted March 18, 2003 I'm thinking about joining the Speed Series next season.....and spending this year changing my Westy from a touring spec to more of a "race" spec. I was wondering what wheel and tyre sizes people use? I only have a 120bhp crossflow (though the power will probably be upped slightly over the course of the year). Currently I have 13"x6" wheels......do people use 13" or do you generally go for 15"? As I am going to change from swept to cycle mud guards it makes a difference...... Yokohama's 32r's are only available in 195 width...therefore necessitating wider mud guards than the 185 tyres...... And why go to 15" tyres? Well I was thinking if I was going to eventually get bigger brakes (is this recommended -seeing as sprints are so short is a bigger brake good, -bearing in mind they're heavier?) then they wouldn't fit behind my current 13" wheels. And of course there is side-wall deflection on 13" with 70 section....... Your thoughts would be appreciated. Machin Quote Link to comment Share on other sites More sharing options...
Blatman Posted March 18, 2003 Share Posted March 18, 2003 Stick with 13's. Less unsprung weight than the 15's, and cheaper tyres. You won't need more than 185's until you get beyond 180ish bhp, IMO, and you'll never get that out of a crossflow........ I use 13's on a 240bhp atmo Cossie car...... Quote Link to comment Share on other sites More sharing options...
Mark Stanton Posted March 18, 2003 Share Posted March 18, 2003 Tyre spec will depend on what class you enter Quote Link to comment Share on other sites More sharing options...
Rob Navin Posted March 18, 2003 Share Posted March 18, 2003 Quote "You'll never get that out of a crossflow....." I hate to disagree with you Blatman but if you are talking about fly wheel power output, mine was doing more than that last year. However getting the power is not a cheap option. Rob Quote Link to comment Share on other sites More sharing options...
Blatman Posted March 19, 2003 Share Posted March 19, 2003 Never say never..........I kind've had "never 'cos it'll cost a fortune" in my head, but didn't type it......... Quote Link to comment Share on other sites More sharing options...
guy g Posted March 19, 2003 Share Posted March 19, 2003 The answer is very simple: If you're on List 1As ( ie roadgoing classes) there is no decent rubber in 13". So if you want to be competitive you'll need 15". No-one ever wins on 13" List 1A tyres anymore. It's not about handling it's about GRIP. If you're in modified on List 1B or slicks the answer is 13". Quote Link to comment Share on other sites More sharing options...
Blatman Posted March 19, 2003 Share Posted March 19, 2003 Why would a 13" tyre with a wear rating number of, say, 200 have less grip than a 15" tyre with the same wear rating? I'm assuming similar widths, but not necessarilly similar profiles, ie a "real world" scenario where 15's are probably a 50 aspect ratio, and 13's would almost certainly be 60 or even 70. I'm deliberately ignoring the fact that different manufacturers calculate the wear rate slightly differently, but for the sake of this discussion, can you answer the above question? For the uninitated (not guy), the wear rating is a number on the side of every tyre that relates to how soft the compound is. The lower the wear rating number, the softer the compound. In theory, any tyre with a wear rating of 200 will have a comparable compound to any other tyre with the same wear rating number, so why would a 13" tyre have less grip than a 15", if the compounds are the same, and they are the same width? I agree that decent list 1A tyres are getting hard to find, but they are out there. In fact, I'm hoping I've found some........ Quote Link to comment Share on other sites More sharing options...
fordy Posted March 19, 2003 Share Posted March 19, 2003 So whats the best 15" tyre to have then ?? ive got Yoko A539's on mine - will these be OK, or should i look at changing them - and if so, what to. cheers chris Quote Link to comment Share on other sites More sharing options...
RICHARD+PHILIP Posted March 19, 2003 Share Posted March 19, 2003 MMM Now your asking Until last year I reckon the 15" tyre to have was the Bridgestone Potenza SO2 Everybody was using them! Unfortunatly Bridgestone don't make it anymore So you won't be able to have them! I've heard some good reports about Toyo Proxies, but at the momment until somebody finds a really good tyre to use It's suck it and see time. Just a suggestion Use your A539s for the first year to get a bit of practise then worry about the grip levels. Quote Link to comment Share on other sites More sharing options...
Mark Stanton Posted March 19, 2003 Share Posted March 19, 2003 Speed Series championship was won on Yoko 539's in 2002 and a few class contenders as well Where's Mr Wotbox and his 16" wheels with 539 rubber Quote Link to comment Share on other sites More sharing options...
Fat Albert Posted March 19, 2003 Share Posted March 19, 2003 This is a topic (wheel size and tyre grip) which I have never understood. I remember the 'O' level physics friction experiment using a brick. Lay one down on its largest face on a table, attach a cord and weight such that the brick only just moves across the table. Stand the brick on end, attach the cord and it will only just move at the same rate. Friction is 'INDEPENDENT OF THE SURFACE AREA OF CONTACT', it depends only on the co-efficient of friction between the two surfaces and the force (in our case gravity, in F1 cars gravity plus downforce) acting between the two surfaces. So how does that reconcile with larger wheels/wider tyres mean more grip? Can somebody with more knowledge explain? Please? Quote Link to comment Share on other sites More sharing options...
guy g Posted March 19, 2003 Share Posted March 19, 2003 When will I ever learn? I always regret responding to anything on here. Someone asks for the benefit of experience, you give it, then get innundated with misguided and simplistic theories proving that black is white. Suprisingly there is much more to tyre technology than a simple O level physics experiment. Don't believe it - ask Mr Bridgestone or Mr Goodyear, they spend $billions per year on research. But there again maybe they're wrong. All other things being equal 13" would be much better on a Westfield - I think that is generally accepted. But all other things aren't equal as far as List 1As are concerned. No-one has made performance cars with 13" wheels for what must be nearly 10 years now. Tyre technology and performance has come on in leaps and bounds since then and, suprise suprise, this hasn't been applied to 13" sizes because there is no market. It's not just about compounds (though modern compounds are not on 13" tyres), it not just about the static contact patch, there's the casing construction to consider as well, then how all these thing's change and behave under load, at temperature, and interact with and suit the car/ suspension behaviour. There is no doubt that those winning (overall not necessarily WSCC) in roadgoing classes (list 1As) were using 15" wheels with Bridgestone SO2s (which do not necessarily give more grip than one or two other 15" tyres, but are much more progressive and hence consistent). Why because they work and they consistently beat other combinations. That's the benefit of experience. Theories do not win races!! Quote Link to comment Share on other sites More sharing options...
SteveD Posted March 19, 2003 Share Posted March 19, 2003 hmmmmmmmmmmmmmmmm Quote Link to comment Share on other sites More sharing options...
Fat Albert Posted March 19, 2003 Share Posted March 19, 2003 Shame, Guy that you interpret a request for someone to explain scientifically why something is, as opposed to just accepting it, as a threat to your manhood. Alternatively, of course, perhaps you don't know. I suppose that what Ferrari, Williams, BMW, Mclaren and Mercedes spend on basic research (materials, aerodynamics, wind tunnels, electronics etc.) and the hundreds of people they employ in these fields are just there to use up the sponsors money and don't explain why they are consistently better. Now, is there somebody out there who can explain why, not just for Westfields, but in any situation, increased width = increased grip? PS Ron Dennis once said (allegedly) of Eddie Irvine that he would never employ a driver who had more between his balls than he had between his ears! Quote Link to comment Share on other sites More sharing options...
SteveD Posted March 19, 2003 Share Posted March 19, 2003 or even why an avon a 39 slick size 22 x 13 x 9 has a bigger footprint than a a 39 size 20 10 13 hmmmmmmm anwer that coz thats what BMTR told me ,sorry 20and 22= overal diam 13 = wheel size and the other is tyre width Quote Link to comment Share on other sites More sharing options...
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