Hints and Tips - Motorcycle Tyres on Vintage Cars

From: TATERRY
Date: Tue, 23 Feb 1999
To: British-Cars-Pre-War
Subject Re: 18 Inch Wheels

While on this tire subject, a friend with an MG F3 and I have been have a lot of discussion of late on the advisability of using motorcycle tires on a prewar car. The principal reason to do so is to approximate the thread pattern that was present in the early '30's....very Luggy, if that's a word.

Whats the list wisdom on this....I've heard that cycle tires should NOT be used on automobiles for safety reasons.....any thoughts?

TATerry
(NA fourseater that needs tires too)


Date: Tue, 23 Feb 1999
To: TATERRY
From: Mike Rambour
Subject Re: 18 Inch Wheels

>prewar car. The principal reason to do so is to approximate the tread
>pattern that was present in the early '30's....very Luggy, if thats a word.
>

The motorcycle tires I am considering putting on my toy do have a closer to original profile and get more rubber on the road than a current tire. I do know of 2 people who run their pre-war Singer's on Avon sidecar tires and they are very happy with them. I thought about it since I need 6 tires and they are less expensive and had not thought of the safety factor. These tires may leave more rubber contacting the road which theoretically should make them safer but bike tires probably were not designed to handle the weight and potentially the side loads of a bike tire.

Mike (who is glad he didn't order the tires yet)


Date: Tue, 24 Feb 1998
To: TATERRY
From: Leckstein
Subject Re: 18 Inch Wheels

Terry, I have bought Avon's for my PA. I called Avon in England to get the right "luggy" look like the factory photos of the 30s. , and they advised that 400 19 were available as a motorcycle tire that was rated higher than the original car tire. Was I given bad advise? They look great, but the car isn't on the road yet.

Mike


From: David Laver
To: Leckstein
Subject Re: 18 Inch Wheels

Mike,

Plenty of VSCC cars here in the UK use Avon motorcycle tyres. They seem to work really well on a light car like an Austin 7 in the 17, 18, and 19in sizes. Sidecar tyres are not sufficiently popular for me to have even seen them. People use them to trial, hillclimb, sprint, race and on the road.

David


From: Hugh Barnes
To: David Laver
Date: Wed, 24 Feb 1999
Subject Re: 18 Inch Wheels

David,

I thought most people using the Avons did use the sidecar tyres. They give a square section tread as opposed to normal motorcycle tyres that have a rounded section to the tread. As you say, the Avons are popular, being 2/3rd's the price of an equivalent Dunlop. The sidecar version is certainly v. popular in the A7 world.

Hugh


Date: Wed, 24 Feb 1999
From: Dr G W Owen
To: David Laver
Subject Using motorcycle tyres

Given the discussion that has been going on I thought I would add my two penny worth.

In terms of Avon tyres there are 3 options

The SM's when introduced were considered a reasonable step forward in tyres for bikes as they were reasonably soft sticky rubber - in comparison to other things available in the period (mid 60s?). They are both a round section tyre although they scrub square pretty quickly

The SM 1 is quite a knobbly tyre and I have used a pair for trialling on the Morris/JAP for years. As trials tyres they are great, a bit wider than a Dunlop K70 350x19. They were also good on the road when new. BUT after a few trials at 5psi pressure, the side walls are completely knackered and they are now not really safe for fast motoring (over 45 mph).

The SM II's are a less knobbly tyre and I use them for sprints and racing. They have a great handling characteristics, loads of grip but at quite high slip angles, go the car does drift about !!!!!!!!!!!!

The Avon sidecar tyre is just that, they are surprisingly narrow. They tend to look OK on standard Austin 7 saloons but are not known to be a great tyre, and are perhaps best avoided

NOW THE IMPORTANT BIT
Two points
1. Don't even think about using modern bike tyres for anything other than trials
2. There is some debate as to the safety of using bike tyres on Austin 7s.

It seems that if you spin then the chances are you will invert on the way back round. From a racers point of view I think you must make a judgement and drive accordingly

One final point.

Years ago when I bought the Avon SM1 400x19s, they were the same price as Dunlop 400x19 B5 pattern. If you want a period looking tyre for road use on an MG, it has to be the Dunlops

Geraint


From: Scotty
To: TATERRY
Subject Re: 18 Inch Wheels-Reply
Date: Wed, 24 Feb 1999

>Whats the list wisdom on this....I've heard that cycle tires should NOT be
>used on automobiles for safety reasons.....any thoughts?
>

Terry,

some years ago, one of the MMM cars at the MG National Meeting here in S.A. had motor cycle tyres [ tires ] fitted. We published a photo taken of the car at the point of no return during the Motorkhana [ Driving test ] there is just too much grip on the side walls and not enough slip, consequently this wee beastie rolled. The driver was OK although with a bruised ego, the M type was the worse for wear after rolling. I think A.P. might have the photo in his collection, if he has I'll scan it and frighten you out of the Motor Cycle Tires idea. Wouldn't want to damage the 'N' would we !!! 8^)

Regards,

Scotty,
Adelaide,Australia.


From: David Cochrane
Date: Wed, 24 Feb 1999
Subject Re: Motorcycle tyres

Terry,

> Whats the list wisdom on this....I've heard that cycle tires should
> NOT be used on automobiles for safety reasons.....any thoughts?

The tread pattern on motorcycle tyres tends not to be flat in cross-section to cater for the bike leaning over on corners; this obviously is not so suitable for cars. However, there are hundreds of Austin Sevens running around on sidecar tyres, which do have a flat cross-section as those machines don't lean over.

Regards,

David


Date: Wed, 24 Feb 1999
From: Barry Lovelock
To: David Cochrane
Subject Re: Motorcycle tyres

Dear All,

Just to add my twopennyworth to the debate,

I use 3.50/19 Avons on my highly supercharged (15 psig) Ulster and it wanders all over the place, it has a dual-shocker front end and is pretty low. Putting on small wheels with wide tyres spoils the looks and as I only use it on the road at the moment (shame) I'll stick with them, even if they don't! The Australian "Raid" cars of the 80's, used Dunlop Racing triangulars, with virtually zero contact patch, I think they were ok and they did 100mph.

Comments please?

Barry Lovelock.


From: David Cochrane
Date: Thu, 25 Feb 1999
Subject Pre-War tyres

Dear All,

Barry Lovelock has a very good point:

> .... Putting it on small wheels with wide tyres spoils the
> looks ....

The quickest way to ruin the appearance of a pre-war car is to fit smaller, fatter tyres. There is an argument (which Barry has touched on) to the effect that you can't go so fast round corners with original size tyres. Well, no you probably can't, so you might as well fit smaller fatter tyres, and then you'd better lower the suspension and fit hydraulic shockers, and then fit a 5-speed synchro gearbox and then a Ford CVH engine .... Why not put the thing out its misery and buy a Mazda MR2?

Circularly yours,

David

P.S. Did you see that piece in the latest 750 Bulletin about the A7 Special that tipped over at Loton Park (hillclimb) because it was wearing motorcycle tyres? Bears out Geraint's argument about not using them.


Date: Thu, 25 Feb 1999
From: Dr G W Owen
To: david Cochrane
Subject Re: Pre-War tyres

>
> P.S. Did you see that piece in the latest 750 Bulletin about the A7
> Special that tipped over at Loton Park (hillclimb) because it was
> wearing motorcycle tyres? Bears out Geraint's argument about not
> using them.
>

There has been much made of this accident and that of an Ulster at Mallory Park. By using these examples, it is claimed that 15 and 16" tyres are the only safe way to go with A7s.

It is absolute nonsense. The Mallory accident was a result of inexperience (quoted from the driver). And the Loton Park incident you describe had nothing to do with the tyres (despite the fact they were 20 year old 325x19s!). By all accounts, had the diver had modern slicks he would still have had an accident as he left the braking far far to late.

James Diffy has been going as fast as anyone in an A7 of late in the VSCC, he claims that the 400x18 Avons are fine provided you realise you are driving an A7. I find on the MOrris Jap that they are excellent. People need to realise that if you spin an Austin it falls on its side

Small fat tyres are NOT the answer

Geraint


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