Radial / Crossply Tyres
Discussion
Hi Chaps/Chapesses,
Whilst waiting for my son at school earlier, I was reading a Classic Car magazine & an article mentioned replacing the crossply tyres for radial tyres as a safety precaution. I've seen this mentioned for years & always wondered why but accepted it.
Well I've had enough & now is the time for me to understand. I'm 40 next year with a 5 year old son & I want to be able to sit him down one day & tell him about these things & what his Uncle Pistonheads has to say about it.
Thanks for your understanding,
Dave
Whilst waiting for my son at school earlier, I was reading a Classic Car magazine & an article mentioned replacing the crossply tyres for radial tyres as a safety precaution. I've seen this mentioned for years & always wondered why but accepted it.
Well I've had enough & now is the time for me to understand. I'm 40 next year with a 5 year old son & I want to be able to sit him down one day & tell him about these things & what his Uncle Pistonheads has to say about it.
Thanks for your understanding,
Dave
You only need to drive a car with crossply tyres to answer the question - why? - try going round a corner with a 80' section skinny crossply as you would in a modern car with radials! - the screams of protest from the crossplys will give you a clue. Having said that - my first car with radials was a Mk2 Zephyr with Michelin 'X's - fantastic tyre, never wore out - but on the concrete surfaced roads of the 1960's was so noisy! and I do miss the relative peace of crossply tyres - soooooooo quiet (but no grip!)
I'm not sure that is always the case. I thought quite a lot of race tyres were still cross plies. Cross plies tend to give you a better transition from grip to slide, so they are considered easier to drift.
Not all cross plies are quiet. The noise is often down to the tread pattern. My XK150 has Blockley cross plies, these have constant sized rubber blocks which are aligned right across the tyre, so all the rubber blocks hit the road surface at the same time, at very regular intervals. So they sing. My previous tyres were Avon Turbo Speeds, they were much quieter than the cross plies.
The big difference I notice between driving on cross plies and radials is that the cross plies like to follow the road, they tramline. So you are constantly needing to work with the steering. Mind you modern super stupid low profile rubber bands seem to be just as bad. I drove a new MB E-Class estate with large wheels and dumb tyres recently and I swear it tramlined worse than my 150.
There is a discussion here you might like.
http://www.f1technical.net/forum/viewtopic.php?f=3...
Not all cross plies are quiet. The noise is often down to the tread pattern. My XK150 has Blockley cross plies, these have constant sized rubber blocks which are aligned right across the tyre, so all the rubber blocks hit the road surface at the same time, at very regular intervals. So they sing. My previous tyres were Avon Turbo Speeds, they were much quieter than the cross plies.
The big difference I notice between driving on cross plies and radials is that the cross plies like to follow the road, they tramline. So you are constantly needing to work with the steering. Mind you modern super stupid low profile rubber bands seem to be just as bad. I drove a new MB E-Class estate with large wheels and dumb tyres recently and I swear it tramlined worse than my 150.
There is a discussion here you might like.
http://www.f1technical.net/forum/viewtopic.php?f=3...
a8hex said:
I'm not sure that is always the case. I thought quite a lot of race tyres were still cross plies. Cross plies tend to give you a better transition from grip to slide, so they are considered easier to drift.
Not all cross plies are quiet. The noise is often down to the tread pattern. My XK150 has Blockley cross plies, these have constant sized rubber blocks which are aligned right across the tyre, so all the rubber blocks hit the road surface at the same time, at very regular intervals. So they sing. My previous tyres were Avon Turbo Speeds, they were much quieter than the cross plies.
The big difference I notice between driving on cross plies and radials is that the cross plies like to follow the road, they tramline. So you are constantly needing to work with the steering. Mind you modern super stupid low profile rubber bands seem to be just as bad. I drove a new MB E-Class estate with large wheels and dumb tyres recently and I swear it tramlined worse than my 150.
There is a discussion here you might like.
http://www.f1technical.net/forum/viewtopic.php?f=3...
In general fitting radials does make the steering heavier too. Not all cross plies are quiet. The noise is often down to the tread pattern. My XK150 has Blockley cross plies, these have constant sized rubber blocks which are aligned right across the tyre, so all the rubber blocks hit the road surface at the same time, at very regular intervals. So they sing. My previous tyres were Avon Turbo Speeds, they were much quieter than the cross plies.
The big difference I notice between driving on cross plies and radials is that the cross plies like to follow the road, they tramline. So you are constantly needing to work with the steering. Mind you modern super stupid low profile rubber bands seem to be just as bad. I drove a new MB E-Class estate with large wheels and dumb tyres recently and I swear it tramlined worse than my 150.
There is a discussion here you might like.
http://www.f1technical.net/forum/viewtopic.php?f=3...
The drifting element seems to depend on the make of tyre as much as the type. My current tyres are radials and drift beautifully.
Blockleys are very noisy and also tend to be a bit edgy in the wet. Do you find that on yours ? A friend has an XK140 fhc and changed them after a run to Lemans when he found he couldn't bear the noise levels at higher speeds.
I've changed to Michelin pilote X - different league altogether and well worth the extra cost. They've transformed the car from the previous Vredesteins.
I guess it is a driving style/type of car thing then. For comfort I have the E-type on radials - which will last a long time - but the D-type/XKSS is on cross-plies. Yes, she darts here and there with the truck ruts but somehow it is part of the experience of owning an old car. I agree that the Blockleys are noisy but they last a hell of a lot longer than the R5 Dunlops! And mph - so sad to see your car on the market. She is such a lovely thing and I dug out the original classic Car test and re-read it. A pure work of art.
a8hex said:
I'm not sure that is always the case. I thought quite a lot of race tyres were still cross plies. Cross plies tend to give you a better transition from grip to slide, so they are considered easier to drift.
Not all cross plies are quiet. The noise is often down to the tread pattern. My XK150 has Blockley cross plies, these have constant sized rubber blocks which are aligned right across the tyre, so all the rubber blocks hit the road surface at the same time, at very regular intervals. So they sing. My previous tyres were Avon Turbo Speeds, they were much quieter than the cross plies.
The big difference I notice between driving on cross plies and radials is that the cross plies like to follow the road, they tramline. So you are constantly needing to work with the steering. Mind you modern super stupid low profile rubber bands seem to be just as bad. I drove a new MB E-Class estate with large wheels and dumb tyres recently and I swear it tramlined worse than my 150.
There is a discussion here you might like.
http://www.f1technical.net/forum/viewtopic.php?f=3...
This reminds me of an old ad from the 20s for the Rolls Royce Silver Ghost.Not all cross plies are quiet. The noise is often down to the tread pattern. My XK150 has Blockley cross plies, these have constant sized rubber blocks which are aligned right across the tyre, so all the rubber blocks hit the road surface at the same time, at very regular intervals. So they sing. My previous tyres were Avon Turbo Speeds, they were much quieter than the cross plies.
The big difference I notice between driving on cross plies and radials is that the cross plies like to follow the road, they tramline. So you are constantly needing to work with the steering. Mind you modern super stupid low profile rubber bands seem to be just as bad. I drove a new MB E-Class estate with large wheels and dumb tyres recently and I swear it tramlined worse than my 150.
There is a discussion here you might like.
http://www.f1technical.net/forum/viewtopic.php?f=3...
It read, "As the Silver Ghost whispers past in the road all that can be heard is the hiss of the tyres.
Rolls Royce don't make tyres."
Absolutely priceless!
J
I remember as a poor student driving a VW Beetle. It had radials on the rear but cross-ply on the front. On the M1 minding my own business in the inside lane I was suddenly thrust into the third lane as the front tyres wandered about in the lorry grooves. Luckily the motorways were quieter then.
Many years later I ran a Land Rover hybrid on Firestone Super All Tractions. A great 7.50 x 16 tyre for off-road and a great tyre for sliding about on tarmac. They would slide earlier than a radial but in a very predictable way without snapping away suddenly as you increase the slippage.
Many years later I ran a Land Rover hybrid on Firestone Super All Tractions. A great 7.50 x 16 tyre for off-road and a great tyre for sliding about on tarmac. They would slide earlier than a radial but in a very predictable way without snapping away suddenly as you increase the slippage.
Roy C said:
Quite. I remember a mate telling me of a drive out the Carbeth Road out of Glasgow in a mini which had radials on the front and crossplies on the back (why, I don't know)The handing was apparently "interesting"
matchmaker said:
Roy C said:
Quite. I remember a mate telling me of a drive out the Carbeth Road out of Glasgow in a mini which had radials on the front and crossplies on the back (why, I don't know)The handing was apparently "interesting"
(At very low speeds I might add)
lowdrag said:
And mph - so sad to see your car on the market. She is such a lovely thing and I dug out the original classic Car test and re-read it. A pure work of art.
Thanks for that, I hope I'm doing the right thing. When I look back at the build pictures I have a lot of doubts.Unfortunately I have to face reality and I simply can't afford to keep everything I've got and I find my needs are more towards touring these days.
If it doesn't sell I won't be too sad and maybe I'll just fit a boot rack and buy a set of earplugs ! I know you must have had similar "dilemas" with your own fleet.
Apologies to OP for the mini thread hijack.
mph said:
Apologies to OP for the mini thread hijack.
Not a problem & thanks to all for answering!Just to make sure I've got this right - basically a crossply has a too stiff side wall so when cornering, the tyre doesn't sit flat? And they overheat.
I can see where the "don't mix tyres on the same axle" comes from now!
Thanks again,
Dave
mph said:
Blockleys are very noisy and also tend to be a bit edgy in the wet. Do you find that on yours ?
I made the mistake of taking my Blockley's onto the track when they had less that 100miles on them. It was also mildly moist to start with and they were HORRID. Jerky, Snatchy none of the nice drifting characteristic you'd expect from a cross ply. later in the day though they were fine. They just needed to wear in a little.I've never found the Blockleys to be a problem on the road.
On the a wet and greasy Goodwood track I found I just couldn't drive them at all to start with, it just went where it wanted and nothing I could do would seem to make much of a difference at times I felt I was understeering and oversteering at the same time. Fortunately the guy next to me in the paddock had done much of the development driving for Blockley and when I came in he came over to talk to me. He'd heard me loosing traction on the straights. By dropping the tyre pressures much lower I could make it nearly drivable.
Generally though it put me off trackdays that are likely to be wet.
Most people make this error with Blockley's Ken. Their recommended pressures for an XK are 22psi whereas the R5's I used nearer 28psi on the track. But, going back to the original post, it is the harder sidewalls with no give in them that allow the tyre and the car to break away smoothly and proportionately. The problem with a radial is that the tyre walls flex to the limit of their adhesion and then - bang! - they let go quickly and the car snaps. Before anyone replies that "it ain't so" this is a generalisation, not intended to specific makes of tyre.
As well as the cross plies making the sidewalls stiffer, I suspect that the radial steel carcase makes the road surface of the tyre stiffer. So it is held in contact with the road for longer. Further increasing early grip.
Years ago (by my young standards) I had a discussion with an engineer working of the development of ABS braking systems. He said the maximum coefficient of grip of a tyre is actually when it is just sliding, but only just.
I suspect that with most radial tyres it isn't possible for mere mortals to hold the car of at the point of maximum grip, but if you look at that graph I posted a link too earlier I suspect that the reason the cross ply tyre can give as much grip is that it is easier for many drivers to keep at or close to the maximum grip point.
Years ago (by my young standards) I had a discussion with an engineer working of the development of ABS braking systems. He said the maximum coefficient of grip of a tyre is actually when it is just sliding, but only just.
I suspect that with most radial tyres it isn't possible for mere mortals to hold the car of at the point of maximum grip, but if you look at that graph I posted a link too earlier I suspect that the reason the cross ply tyre can give as much grip is that it is easier for many drivers to keep at or close to the maximum grip point.
lowdrag said:
Most people make this error with Blockley's Ken. Their recommended pressures for an XK are 22psi whereas the R5's I used nearer 28psi on the track.
I've had all sorts of recommendations for tyre pressures on the Blockleys, from 22 -> 35. On the dry track, higher pressures seem to work well. I know it is normal to run lower pressures in the wet, but I hadn't reduced them far enough. On the track I've normally run about 30PSI in the dry.Dear nm,
and another thing
If the car is left standing for long periods radials tend to remain round. Crossplies become permanently distorted.
I don't know if this is generic, vehicle or tyre brand specific but was observed on a Princess 4lR and confirmed as common by a specialist fettler of them.
Finding radials of sufficiently high profile to preserve rolling radius can be difficult these days. Indeed for the Princess I went up an inch (in wheel diameter) to get the rolling radius to match with a readily available tyre,
regards,
Jet
and another thing
If the car is left standing for long periods radials tend to remain round. Crossplies become permanently distorted.
I don't know if this is generic, vehicle or tyre brand specific but was observed on a Princess 4lR and confirmed as common by a specialist fettler of them.
Finding radials of sufficiently high profile to preserve rolling radius can be difficult these days. Indeed for the Princess I went up an inch (in wheel diameter) to get the rolling radius to match with a readily available tyre,
regards,
Jet
lowdrag said:
But if you put the pressures up to around 40psi for the winter they will not deform. I had this with a Mk VIII where they went "square" after the winter, but some judicious high pressure and a bit of road use sorted the problem in a very short while.
I never new there was so much about tyres I didn't know!My Uncle used to have a really old MG of some sorts (don't remember a lot about it apart from it had no roof & a tiny little windscreen - I loved it as a 7-year old!) and he used to put it on what I assume must have been some sort of wooden blocks for winter. I'm guessing stopping the tyres from deforming is the reason?
Roy C said:
Nice one Roy, I remember that red 1300 ad well.Gassing Station | Classic Cars and Yesterday's Heroes | Top of Page | What's New | My Stuff