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Is it ok to use cross ply on front with radials on rear?

Started by _v8slrtorana_ , Mar 17 2009 09:29 PM

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19 replies to this topic

#1 _v8slrtorana_

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Posted 17 March 2009 - 09:29 PM

As the title says.
Is it safe to use street legal cross plys on the front and radials on the back.
(and around all week for that matter

)

I'm starting to get lazy, and are no longer wanting to change 4 tyres over at 11:30pm after the drags to drive home.

I do know for sure, its dangerous to drive with radials on the front and cross plys on the rear. Trust me

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#2 GML-31

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Posted 17 March 2009 - 09:34 PM

I would be more concerned about your insurance if you do have a crash, they will wipe you as quick as

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#3 _bathurst-racer_

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Posted 17 March 2009 - 09:47 PM

Nope don't do it. Way too risky to yourself and other people on the road.

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#4 ls2lxhatch

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Posted 17 March 2009 - 09:52 PM

Tyre construction and size must be the same on each axle. Therefore a pair of cross-ply front and a pair of radial rears or visa versa are legal however mixing a cross-ply and a radial on the front or back is not legal.

See page 14 of this document.

It would be worth confirming in your state are rules vary. The tyres also have to have the appropriate load and speed ratings. There are also rules regarding profile and width.

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#5 _v8slrtorana_

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Posted 17 March 2009 - 11:05 PM

NT rules state the same.
However i can't find the definition of axle, unless the document is relating to heavy vehicles or trailers.
I'm now arguing with my brother, he seems to think a torana has 4 axles. I don't.

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#6 ls2lxhatch

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Posted 17 March 2009 - 11:21 PM

I think the term axle in this case is used to describe tyres that are mounted directly opposite each other. They talk about a vehicle that has a front axle and a rear axle, even if there are actually four axles making up the front and rear axle. The reason behind the rule is that mismatched tyres on the same theoretical axle with cause the vehicle to turn when braking.

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#7 _Squarepants_

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Posted 18 March 2009 - 09:50 PM

Ha ha ha ha ha! I can't believe you're even contemplating doing this.
Man, stay away from the cross plys, ESPECIALLY on the front.
If you've got some to use, put 'em on the back and enter a burnout comp! That's all they're good for, I reckon.

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#8 _Herne_

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Posted 18 March 2009 - 09:53 PM

Cant wait till you drive it set up with radials and crossplys lol Don't reckon you would drive it too far for too long

As per the video below its worse having crossplys on the rear

But still not nice on the front.

Herne

Edited by Herne, 18 March 2009 - 10:02 PM.

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#9 _why-psi_

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Posted 18 March 2009 - 09:59 PM

heres why....

mixing cross ply and radial tyres

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#10 _v8slrtorana_

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Posted 18 March 2009 - 10:02 PM

Ha ha ha ha ha! I can't believe you're even contemplating doing this.
Man, stay away from the cross plys, ESPECIALLY on the front.
If you've got some to use, put 'em on the back and enter a burnout comp! That's all they're good for, I reckon.

OK, but why?

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#11 _v8slrtorana_

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Posted 18 March 2009 - 10:09 PM

heres why....

mixing cross ply and radial tyres

Thank you

I know its dangerous to put radials on the front and plys on the rear.
Its actually a ANDRA drag racing rule not to run do so.

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#12 _v8slrtorana_

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Posted 18 March 2009 - 10:32 PM

As the title says "Is it ok to use cross ply on front with radials on rear"

I got answer today from my local Bridgestone dealer.
He said "Rags b4 radials, and u will be fine"
He also did comment on how the car would drive if i fitted them opposite to im asking. He words describe that youtube video perfectly.

Has anybody got the lastest SM mag? i haven't got it yet, but there is a article on Street Machine Streetcar Superstars event at wisid. I know they ran radials on the back, but does anyone know wats on the front?

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#13 _Herne_

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Posted 18 March 2009 - 10:58 PM

Drag strip applications are far different from street.

If you are talking about street runners then go ahead but if you can drive you wont like them. If you cant drive a pig to market then it wont matter at all.

Herne

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#14 _rorym_

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Posted 18 March 2009 - 11:01 PM

Basically...
The radial ply tyre is designed to flex in the side wall...this "plants" the tread ..suppsoedly on a flat plane on the road...hence giving flat contact..hence more contact and road holding. the cross ply was never designed for this...more designed with stiffer sidewalls for a slower vehicle in older days that did not travel at such high speeds...the theory was a wider bias ply face woud compensate for lateral forces....as we know today...codswolop.....
so...what you have..is 2 tyres flexing to keep the whole tread face planted on the road surface...and 2 tyres rolling up and standing on their shoulders due to no flex in the side walls and sitting on about 1 inch of their tread face....pretty simple actually....where ever you fit them...that end will break away and slide first...watch out for that tree!!!!Probably a 30 year tyre type laymans description of what happens but hope it is what I'm trying to deliver
R

Edited by rorym, 18 March 2009 - 11:06 PM.

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#15 Struggler

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Posted 19 March 2009 - 07:27 AM

I drove around with crossplys on the front and radials on the back for years, it is actually legal in the A.C.T.

Its fine in a straight line but you really have to slow down for corners.

Would I do it now ? No way, but to get home from the drag strip I can't see why not if you drive accordingly.

JMHO

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#16 _Herne_

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Posted 19 March 2009 - 08:18 AM

I think many of us older forum members have been there and done that at some stage Struggler but it seems to me this one chappy wants to learn for himself

I remember the fun?? we had as youths when we tried mixing radials and crossplys due to financial circumstances, remembering radials were very new then. We soon learned what not to do after a couple of close shaves

Cheers
Herne

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#17 _OtG_

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Posted 19 March 2009 - 08:19 AM

I have actually raced at the drags with slicks on the back and standard street radials on the front, in my old ute.

It was not fun!! Crossing the line at 111mph or so while tank slapping all over the place!!!!

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#18 _torbirdie_

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Posted 19 March 2009 - 11:52 AM

just thinking out loud here: Aren't you better off with radials one set of axles than cross plies on both? Im not claiming that it will be as good as a set of radials.
I realise that when one end brakes traction and the other doesnt the result can be a spin if the car was in a turn, but the cross plies arent any more likely to break traction just because there are radials on the other end of the car, it would still need driver error to occur. The car would still be going off the road if it was in a four wheel drift on crossplies. Given that the biggest problem of crossplies was massive sidewall deflection that induced massive understeer in all early holdens, putting some radials on the front might be a good thing?

Edited by torbirdie, 19 March 2009 - 11:54 AM.

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#19 _rorym_

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Posted 22 March 2009 - 03:08 PM

but the cross plies arent any more likely to break traction just because there are radials on the other end of the car,

Wrong...Radials flex and plant the tread..their breakaway point is about 3 times higher than any cross ply...the CPs will be long gone before a radial breaks away.
R

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#20 _torbirdie_

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Posted 22 March 2009 - 09:30 PM

Wrong...Radials flex and plant the tread..their breakaway point is about 3 times higher than any cross ply...the CPs will be long gone before a radial breaks away.
R

Yes, I dont have any problem with your idea of how a radial outperforms a crossply(three times as much grip?), perhaps if you read my whole post again you'll see Ive made a similar remark about understeer. Regardless, perhaps you can explain how Im wrong, how does putting radials on the other end of the car reduce the performance of the crossplys?

Edited by torbirdie, 22 March 2009 - 09:33 PM.