203 tyres

Um, the problem with a 175 (even 80 series) tyre on a 4" rim is proper bead seating. The sidewall is forced to misalign the bead on the seat & it can become unseated under lateral stress. The danger is more the lower the pressure is & 175 is not the risk that 185 or 195 or 205 . . . would be but I wouldn't do it - not on legal grounds (though that is worth thought) but on technical ones.

I am no enthusiast for Michelin's X but the 165 sounds like the only sensible option.
 
The Longstone website lists the 5.50 Michelin X under 165/16 but it is a 175. There is little available in the size. They list an Avon under 5.00/16 and the dreadful Excelsiors.
 
Give up what? The range of 16 inch tyres for the 203 sedan is limited. When I bought tyres for the car some years ago Antique Tyres only offered the Excelsiors and they are poor quality tyres. The 5.25 Avon isn't available and a Dunlop made somewhere had disappeared. The wagons had a better range because London cabs and Lada Nivas shared the size. The 5.50/16 was the original tyre listed by the importer in 1949. 203's that turned up were shod with anything from 5.00 to 5.50. My experienced tyre man who I trust had no problems with fitting the 5.50's to the 4 inch rims. Fitting the 5.50 Michelin X to the 4 inch rim on the 203 is quite common now and I'm not aware of problems. Clearance at the front is tight but no worse than for the wagon.
 
Morris Minor 1000 sedans ran a 5.20 tyre on a 3" wide rim, 145 is the recommended radial replacement width.

I guess you could run tubes if you were concerned about the potentially"misaligned" 175 bead flexing enough to allow air to escape?

My Rover 9/20 had tubeless 175/75R15s on the front on 4" rims. I chucked them on by hand and they were easy as pie to fit. I even had Atlas white walls stuck in the bead as well.
Ran it like that for a few years with no problems.

I guess the legality is something the owner would need to weigh up.🤷‍♂️

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I've always run tubes in 203/403. Safety? When I put my 203 back on the road I ran it for a while on cross plies that had sat flat for 25 years. Basil did the same with his. Those old Australian made cross plies were tough.
When you fit 15" rims to an early 203 the tie rod ends can foul. Jim O'Brien adjusted his clearance with an angle grinder mildly applied to the tie rods.
 
So does anyone have a list of 5.25/16 tyres? Avon does a 5.00/16 available from Longstone, Antique Tyres has Excelsior 5.00/5.25/16.
 
Made some enquiries. As the 5.50 /16 on the 4 inch rim is the listed original fitting size by both the manufacturer and importer it is perfectly legal.
 
pugrambo said:
You need to run tubes in 203/403 wheels as they don't have a safety rim as needed by tubeless tyres
Click to expand...
No. No legal necessity & technical reasons for not using tubes.

Here's the analysis.

First, having the safety ridges (one or two) is decidedly "a good thing". When a tyre is flat, or at very low pressure, the bead will tend to "walk" across the rim & fall into the centre trough. Thus one gets a rim-on-road scenario - not good, especially if one is in a corner. The safety ridges keep the tyre's beads from migrating.

So, what if one has not got them?

First, note that the only role for such ridges is when a tyre's flat or near so. When pressures are normal they do no work as air pressure keeps the bead of the tyre in place. This is so whether one has that air enclosed in a tube or sealed within the inner envelope of a tubeless tyre.

When pressures are low enough for a bead to migrate then you'd realise that something was wrong. Say, though, that you're insensitive & don't notice; is there an advantage in such a person having a tube?

Not really. At very low pressures, there is a considerable chance of a tube rupturing (from pinching or overheating). If this happens, then sudden air loss occurs. A tubeless tyre won't do this. Mind you, without normal air pressure maintaining a seal, one can get brief episodes of near flat tubeless tyres desealing (from road or lateral load inputs) & consequent air loss as the bead seal deforms before forming again. So far, a draw perhaps in the near-flat scenario. This scenario is the only technical reason for the suggestion that rims without the ridges should have tubes fitted & it's not quite thoroughly thought through &, in any event,swamped by other considerations. Note that if the bead does migrate into the well, then each tyre type suffers rapid loss of remaining air (any tube becomes swiftly ruptured).

Say one does not have a rim with safety ridges & has the tyre pierced by something like a screw. Either it stays struck in the tread or not.

Say it does.

In the case of a tubeless tyre, one might not even notice & the likely result is a slow leak. Not dangerous & easily remedied in due course.

In the case of a tubed tyre, & assuming that full penetration has occurred, the tube is ruptured & a comparatively rapid loss of pressure occurs via the valve stem hole. Certainly more dramatic & definitely potentially dangerous depending on what one was doing at the time.

Say that the screw (or whatever) pierces but then works out.

For a tubeless tyre, it will still likely be a slow leak but even if faster, it is not going to be as fast as the rapid loss from a ruptured tube unless a 1 cm hole is punched in the tyre.

So, summary to date: safety ridges only matter the tyre is near flat & in such a scenario the tube is of no help. Moreover, having a tube makes a tyre more vulnerable to road hazards.

But: say that, despite this, one wishes to fit a tubed tyre to such a non-ridged wheel. It might be that the only tyre available or the tyre that one really, really wants (it was original fitment & just looks so right!) is tube-type. This is technically sub-optimal & a tubeless type would be better in many ways but so be it.

Suppose, though, that one wishes to fit a tubeless tyre to such a rim (for argument's sake, a tubeless 165/80-15 Hankook Eco2 to a non-ridged 404 rim). Originally tubed tyres were fitted, so should one fit a tube? No.

The inside of a tube-type tyre is smooth. The inside of a tubeless tyre is ridged. The interaction of a tube on that ridged surface has two effects: chafing of the tube & heat generation. Both are causes of potential tube failure. And, recall, tube failure results in rapid pressure loss. It might be that chafing will merely cause some tube porosity & a consequential slow leak & thus that one will get some warning of a developing problem but things might move faster. Depending on vehicle use, tyre pressures, tyre ridge prominence & tube thickness one might even "escape the bullet" & not develop a problem. Fine; but however fortunate that might be, there are other potential issues with tubes (see above) & if one is going to fit tubeless tyres, then nothing is gained & much is lost (see above) by putting tubes in them.

So, in summary, if there's a choice then fit tubeless &, although ridged wheels are best, tubeless on non- ridged wheels is better than tube-type.

cheers! Peter
 
Sometimes you have no choice but to run tubes in tubeless tyres if you want radial tyres.
My F250 has RH-5 Firestone "widowmaker" split rims with 245/65R17 tubeless tyres with tubes in them as these rims are not airtight.
My Mustang has 195/75R14 tubeless tyres with tubes in them on spoked wire wheels as these rims are not airtight.
My Studebaker has 215/75R15 tubeless tyres with tubes in them as the factory rivetted rims are not airtight.
The youngest of these combinations is over 4 years old and I've only had one tube "failure". It was a slow leak due to a perished valve stem on the F250.🤷‍♂️
 
You couldn't put tubes in the Uniroyals they used to put on 504's because they sometimes had wires poking out inside.
 
So the 203 tyre situation has not improved since I put my car back on the road in 1998. I did have a nice set of 15" wheels complete with reasonable tyres but the car just didn't look right to the eye. So I swapped them for another set of 203 wheels.
This shortage of earlier tyre sizes affects more than cars. A problem with Australian tractors and headers. Michelin seems to have kept their non current moulds and now have a good business making old car sizes in Serbia. The Olympic tractor moulds were sold to India. Given that tyre making is high energy input and energy prices are soaring in Europe their tyre prices could well follow suit in coming months.
 
I first saw that car, painted yellow then, in the Monash Uni car park in 1968. Geoff Strachan owned it for many years then Brian.
 
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