Race tyres? Crossply or Radial?

[graham blackwell]

Afternoon all.
Need to get my first set of slicks, and its a tad confusing to say the least. Avon sells Crossply or Radial's? WTF? Whats the difference?

TIA

[graham bahr]

the difference is in the construction just like road tyres, road tyres are all radials now but were crossplies once, i dont think it really matters which you use as long as they are suitable for your car, once choosen just stick to the same type or your never get your suspension sorted to suit, as slicks require very different spring rates and possably geometry , in same way the different constructions require different geometry, i and all my close friends that race use radials on our saloon cars as the choice seems to be better and radials seem to suit saloons better which is probably born out by the fact that car manufactures fit them
as std,

lots of single seaters seem to use crossplies but then they weigh next to nothing and have very wide wheels to support the tyres.

you dont say what sort of car you have, but i'd start by seeing what the majority of compeititors in your class run.

dont forget that the tyre has to suit the car, putting a 900kg car on a tyre designed for a 400kg single seater is down right dangerous as the tyre wasn't designed for that sort of loading.

[Goran Malmberg]

Originally posted by graham blackwel
Afternoon all.
Need to get my first set of slicks, and its a tad confusing to say the least. Avon sells Crossply or Radial's? WTF? Whats the difference?

TIA

I have been using Avon cross ply slicks for a coupple of years.
23,5x9,5x15 and 25x13x15.
The cross ply tires is more forgiving concerning camber setting. They also has a larger slipp angle and tells you earlier when you are close to traction limit.
So we could say they make the car easier to set up and drive. So if one not have the experience or time to testdrive and set up the car properly each race, one might benefit from bais ply tires.
The price is not beeing as fast as a properly set up car with radials.
Goran Malmberg

[Mackmot]

Radials are better, they are always the same everytime you get a set. With Crossply you have to check the sizes in every set and stretch or shrink to make sure they are a similar size. So in terms of practicability Radials are easier to set up than crossply.

[james_williams]

What car is it for and what catagory? Is it a hillclimb or sprint car?

One of the most helpful people I have come across for this type of thing is Dave Wooten at BMTR.

Send him an email or give him a call. He will be able to answer all your queries or concerns.

[graham blackwell]

Thanks for the replies. I'm in Sports Libre in the Midland Speed Championship (Came 1st last year!) and I run a Mk1 2.0 Zetec Fiesta (Heavily modified). I sprint and hillclimb at tracks like Loton, MIRA, Harewood, Aintree, Silverstone Stowe, Curborough etc etc.

I've run a set of Yoko A032R (S) in 205/50R15 for two years, and the fronts are now decidely worn, and I'm just sorting myself out a set of super-lite Ultralite 3 piece rims, and I need a set of slicks to go with them. I can run slicks in my class (must) but haven't been able to afford the additional set of wheels and tyres until now.

The car has totally new suspension fitted (just completed) which comprises of tubular steel arms with rod ends and spherical bearings throughout, so I have caster and camber. The rear axle has been altered to allow adjustable camber too, and I now have 1.5 degree on each rear wheel. She's on 450lb springs at the rear now, with 270's at the front. New Piper Cams just installed which should hike the power up to around 185 BHP.

You may have seen the car before, its on my website www.zetecinside.com and was in CCC last October (Last ever edition, sniff) and made the front cover of Retro Cars last year too.

Here's a pic (at Loton Park last year)


I've emailed BMTR (last night) for guidance, though it sounds like you guys have got it covered. I think I need 7.5/23 tyres in Cross Ply, and whatever the equiv is in Radial. Aren't the markings complicated when you first start looking in to them 8)

[zefarelly]

I have to run cross ply tyres for the historic saloon series, theyre Dunlop CR65 (classic 60's race tyrres) they're pretty soft and seem ok and predictable in the dry . . .but theyre absolutely hopeless in the wet, even in an old Cortina GT you can wheelspin, steering is vague and front end grip is predictable but appalling . . . . I do need to learn a heel of a lot more about suspension set up as well, thats just first impressions !

[Chucky]

Crossplys for historics, radials for anyone who actually wants to go fast.

[1200Datto27]

Sorry to go off topic, but has CCC magazine really gone? We don't always get it in OZ, so it's hard to keep a track of.

Oh, my Datsun 1200 sports sedan went 3 seconds (3.2k track)quicker on the same size radials than cross plies, and was also more consistent during runs.

[Goran Malmberg]

In my opinion I should not make a to definite statement about what is best, radials or bais ply. Radials are faster, but even so the bais ply have their field of use.

To compare the two we must know if both tires is working under the right temperatur. On the skidpad I have been going as fast on bais ply as on radials. The same goes for braking power. I can se bigger differences between rubber blends.


Goran Malmberg

[zefarelly]

chucky . . . .I dont know what you drive but people go fast on Crossplies . . . . . .60's F1 was as fast as any and that was mainly on crossplies.

might explain why everyones dead or sh*t themselves to death going round corners though !!!

[Bob Riebe]

Radials greatest advantage is longer tread life.
A cross ply can and often did corner on the side wall, the heavier flexing wears the tire quicker.
If a radial is stressed, too much weight for the tire, that it folds over on the side-wall, tire failure will result. This is one reason that stiff sidewalls, which help tire life, are an absolute necessity in radials.

Cross ply tires are not getting the developement tht radials are getting. Only Hoosier in the US is doing it as far as I know. Before NASCAR banned them, they were working on a Bias-belted tire for racing that incorporated some of the strengths of radials with a bias (cross) ply tire.

This is obviously an abstract and it is far more complex than that this but each tire has its good and bad points.

[graham blackwell]

Yep, CCC died last October 2003. Shame, it had been running for nearly 40 years apparently.

Thanks for the info on tyres. Sounds like Radials are the way to go. Need to rob a bank to buy a set though (~£160 each)

Maybe I'll keep going with the A032R's until they resemble slicks

[graham blackwell]

AVON 190/570 R15 radial slicks (A15 compound) just been quoted £171 each + VAT from BMTR. Will see how much the equiv from Micheline/Yoko/Dunlop/Hoosie (if any!) compare before parting with cash.

Does anyone have any preferences? Or are AVON considered the best for hillclimb/sprint?

[RWC]

Maybe others may find this interesting..

I allways assumed that crossplies had diagonal plies while radials actually did use threads alligned parallel to the circumference of the tyre
This is just not the case apparently!*
When one sees cuttaway diagrams they don't look a whole lot different
Weird


*No doubt there are exceptions such as the radially wound motorcycle tyres and such
If anyone knows much about these kind of things i'd find it interesting

[Goran Malmberg]

Originally posted by RWC
Maybe others may find this interesting..

I allways assumed that crossplies had diagonal plies while radials actually did use threads alligned parallel to the circumference of the tyre
This is just not the case apparently!*
When one sees cuttaway diagrams they don't look a whole lot different
Weird


*No doubt there are exceptions such as the radially wound motorcycle tyres and such
If anyone knows much about these kind of things i'd find it interesting

I may recomend the book "The Racing & High Performance Tire" by Paul Haney. It explains a lot of theese construction matters. Even if called "radial" there is an angle involved.

Goran Malmberg

[listernoble]

Originally posted by graham blackwell
AVON 190/570 R15 radial slicks (A15 compound) just been quoted £171 each + VAT from BMTR. Will see how much the equiv from Micheline/Yoko/Dunlop/Hoosie (if any!) compare before parting with cash.

Does anyone have any preferences? Or are AVON considered the best for hillclimb/sprint?

Most of us use cross ply,but some of the top boys use radials although some of the best times are on cross plies,makes are 90% Avon,the rest Hoosier,and a few Dunlop.
I beleive Hoosier make the softest compound available,but BMTR-(Avon) give excellent service and know what they are talking about.
I run a 1969 Ginetta G17 Formula 4 in historic/classic so must use cut slicks,21x7.5x13 A45 compound Front and 22x9.2x13 A40 Rear
Lister

[Eric Falce]

Thanks Guys,I have been thinkingof putting my Mk1 Escort onto slicks,the disscusion has realy cleard the problem for me.I think I will run a Dunlop radial on my n/s/r,Yokohama on my o/s/f,Avon crossply on o/s/r and a Hossier on the n/s/f.Try it and see which one works the best and make a choice,should make the Escort a lot more fun!

[graham blackwell]

I hear that the Dunlop Clio Cup tyres are the same size as the ones I need, but I'm unsure as to their compound. EARS in Macclesfield can supply them, but can someone tell me if they're available in differing compounds?

Does anyone have any part worn ones they'd sell me?

[graham blackwell]

The Clio Cup tyres are exactly the right size, but they may be a bit too hard a compound. I've located the championship control tyre supplier and he's going to try to locate a set of 2nd hand tyres so I can try them on the Fiesta to see if there's any improvement over my worn out A032R's.

Better to start with a medium compound, than splash out for a set of new softer compound tyres, and find that the mediums would have given me the improvements I was after. My car is 200Kg lighter than the Clio's so it'll be interesting to how she performs.

[cannardd]

You will find that most control tyres have quite a hard compound (everyone has the same so no point going softer).
Dunlop's compounds are also quite hard (even their softest).
Your car being lighter than the Clio will emphasise that even more.
A hard race slick can take a couple of laps before it really starts working, by which time your sprint has already finished.
Avon/BMTR's main business is to sprint/hillclimb and short club races so they have a very good range of soft compounds and for a sprint in a light car you will need a soft compound tyre (miles away from a Dunlop control tyre slick).

[graham blackwell]

These are Michelins though, not Dunlops as I previously thought.

[Kid Prozac]

Originally posted by Goran Malmberg
I may recomend the book "The Racing & High Performance Tire" by Paul Haney. It explains a lot of theese construction matters. Even if called "radial" there is an angle involved.

Goran Malmberg

Agreed, this book is an excellent read for anyone looking to learn the basics of race tyres. It is not too technical, and as ever with all of his work, he weaves some excellent stories into the text.

For slightly more understanding, read the obligatory Milliken, and for anyone wishing to learn about tyre models and their basis, Pacejka's book is the one, although this is very heavy mathematics, although provides the basis for some excellent simulation.

I say it a million times to people designing their own suspension, your suspension is only as good as your tyre data/model..................

[graham blackwell]

Bought some Michelin N00 moulded slicks on 19/57R15 for this weekends Shelsley Walsh hillclimb. First time at Shelsley + first time on slick = loads of fun methinks.

[listernoble]

Graham,
Are you sure your car is set up to run radials?
Because I understand that they need totally different camber angles compared with crossply.
Are you running ultra soft compounds selected according on the car loading?
Why didn't you take the advice to use BMTR and Avon?
Lister