Tyre sizes

[jaguar68]

I've not had any trouble with the Bridgestone 145's run at 28 psi and have covered approximately 8000 miles on them, and I don't drive like a vicar!!

Regards

John

[Kevin]

I've not had any trouble with the Bridgestone 145's run at 28 psi and have covered approximately 8000 miles on them, and I don't drive like a vicar!!

Regards

John

I should hope not our local Vicar drives like he on a Rally course

[charlie_morris_minor]

I've not had any trouble with the Bridgestone 145's run at 28 psi and have covered approximately 8000 miles on them, and I don't drive like a vicar!!

Regards

John

more like the bishop that looked after the parish in ravenshead where i lived in the 70s who rebuilt and drove one of these?[frame][/frame]

[Peetee]

I've been through this tyre choice thing before with another vehicle and have come to the same conclusion on both occasions. That is that the stated width is a nominal measurement. The visual difference in width between a 145 and 155 tyre (or any other sequential 'pair') can be very slight indeed when two brands are compared because some tyres have a square or flat tread section whilst others have very rounded shoulders. The rim they have been fitted to has just as much effect on the perceived width too as it dictates to a large degree the curvature of the tyre carcus between rim and tread.

[C6Dave]

Original spec was 5.00x14 crossplys which is why the handbook states 22/24psi. Radials need to run at higher pressures because the sidewalls are weaker. Nearest modern equivalent to 5.00x14 is 135/80 R14 but these are no longer manufactured unless special runs are made of them (and very expensive). Nearest sensible modern size is 145/80 R14. Tyre pressure is dependant on your level of comfort and load carried so start at 28 psi all round and increase slightly if it feels too squashy. But dont go more than 32psi.......

I have a 1959 edition owners handbook and it says 5.0 - 14 tyres and a pressure of 22-24 psi and shows the car with tubeless tyres.

The car is a 59 convertible however it came with 155X80X14 Nankang (from Taiwan) radials fitted. The spare was flat when I got the car and the tyre walls are as soft as a bicycle tyre.

At 22 psi the steering when parking is ultra heavy so went up to 30 psi which improved that (Max on the side-wall says 32 psi) but I'm not sure on the handling at 30 psi as the car felt 'twitchy' (though I need to get more miles under my belt to get to know it better) but am probably going to gradually reduce the pressure to see if I can find a happy medium

[robbiesmith]

30 psi does sound a little high and I know what you mean about twitchy.

When I bought my MGB four years ago the vendor had filled the tyres to 32psi all round. I attempted to take a wide roundabout at 40ish on the way home and the rear did its best to overtake the front.

With the pressures reduced to 22 front and 24 rear it handles beautifully and tyre wear is nicely even. I run on 26 front and 28 rear on the Traveller but I have 145s front and 155s rear (inherited) so I'm not sure if that would work so well on yours.

Robbie

[C6Dave]

It's interesting that 135X80X14 are no longer available as when you look at the differences in rolling radius to 155X80X14 as there is a large difference of 32mm which will alter speedo readings

The difference between a 145X80 and 155X80 is + 1mph at 30 mph so the speedo is reading lower than the actual speed. You can check Here

The only way to be really sure is by sticking a sat nav on the windscreen and doing a comparison to what the GPS speed is and what the speedo reads

It's worth doing to be sure what the car is actually saying in case your ever clocked by someone with a speed gun

[mike.perry]

145/80/14 = 872 revs/mile
155/80/14 = 849 revs/mile
175/80/13 = 840 revs/mile
Cross plies are 88% and a 5.20/14 has a slightly larger diameter than a 155/14 radial
Presumably these figures are calculated on new tyres with a tread depth of 7mm? What would be the difference on minimmum tread depth of 1.6mm?
The 1408 speedo appears to be very optimistic on standard 155 x 14 tyres and 4.22 diff. Has anyone checked their speedo with a sat nav on standard setup?
My Traveller is fitted with 175/80/13 tyres and a 3.9 diff and the 1408 speedo is within 1mph

[melanddoug]

Hi Mike,

What's the handling like on 13" 80 profile tyres ? I'd imagined that 80 profile tyres would be like having a baloon attached to each wheel - but never tried it.

Also, presumably there's increased un-sprung mass, so I was wondering whether you notice bumps more than with standard wheels ?

I ask cos I have a set of 13" rims whcih I've come to like, but the tyres are 65 profile (I think) - better handling, lousy top speed and a very rattly ride as the tyres feel 'kard' (even at 26 PSI)

Cheers,

Doug

[bmcecosse]

65 profile is FAR too low profile for a Minor.......The tyre contact patch must be WAY outside the design point. The wheels must look completely lost in the arches. Why on earth would 13" wheels cause 'increased' unsprung weight???????

[melanddoug]

Only just seen this .. 13" wheels seem heavier to pick up than standard ones I think because they are quite a lot wider, so there's a lot more rubber. Also they're quite thick metal. Either way, they just seem heavier. Maybe because they're cheapo and crap haha

I don't tend to use them now anyway- but they do improve the handling, no doubt. And yes they look lost in the wheel arches !

D