Mixing tyres

[ndevans]

I have 155x14 tyres on the front of my '69 Traveller & 145x14's on the rear. Is this
A) Safe
B) Legal ?
Also, I think the steering is a bit "floaty", ie seems to wander a little. Is that related to the 155's?

Regards,
Neil

[JimK]

A) I would say it is, though others may disagree. Mixing tyres on one axle is definitely not a good idea.
B) Yes.

As regards the floatiness, I think you're right. Fitting a wider tyre to the same rim pulls the tyre beads together and will allow the wider tyre to move side-to-side a bit more. Consider that the original tyres would have been closer to 135...

[Kevin]

At the very least swap them around the wider section should be on the rear also check the pressures they should be around 26 all round

[chickenjohn]

The best steering to be had from a Minor is from 135 tyres, which are sadly not available new .

I would agree with Kevin put the wider tyres at the back and the 145's at the front.

[Chris Morley]

I also agree -the 145s should be on the front.

[Rob_Jennings]

I'd suggest that the pressure to use is 26 for the 145 and 28 for the 155 to reduce the sideways roll by keeping them more ridgid.

[Willie]

As above, the 145s on the front will lighten up the steering.

[bmcecosse]

Agree - wider tyres on the back for now. I use 30 psi all round on 155 tyres.

[ndevans]

OK, thanks for all those replies. I have now swapped the front & rear wheels around and adjusted all to 26psi. I've only been about 10miles in it since, the steering does seem a bit more positive but difficult to be sure on a short run. Might be psyhcological, but the vibration at about 50mph which I thought was propshaft u/j's seems a bit more muted now.
On the subject of pressure, and I know everyone has their own idea about what's right, I looked in the 1989 edition of the MMOC Tech Tips manual and it suggest 20 & 23 psi for radials...???...
cheers, Neil.

[Rob_Jennings]

A complex topic.

There will be a lower safe limit to keep the tyre on the rim but the upper limit is really down to the tyre size and type and how you like the feel of the ride.

The original pressures may relate to 135 tyres with considerably less rubber than a 155, so I think most will agree that to stop the tyre rolling from side to side a higher pressure helps. As to how high, thats up to you. I increased from 26 to 28 (155's) and like the more positive feel on the car, less like riding a space hopper! I may trying going up a little more to see it that helps.

The other thing pressure will effect is the patch in contact with the road thus the overall grip and wear, too much will mean less surface contact or uneven wear, but that will depend again on the type of tyres you use. I've seen some with a very good level width profile which could be use at quite high pressure (like a modern car) and some that are very rounded on which that might not be advised (poor ground contact). Poor wear will only show over a long period of time.

[Willie]

Even 145 section radials are wider than the factory fitted tyres on the
WIDE van wheels. Since the LP917 van wheels are 4 1/2J and the standard wheels are only 3 1/2J the fitting of 155s is bound to produce
a rather ballooned side wall.

[Chris Morley]

Agree - wider tyres on the back for now. I use 30 psi all round on 155 tyres.

I've tried that before - the steering is nice & light but I found the car's a bit skittish. I tend to use 26-28 psi on my 155s.

[8009STEVE]

the vibration at about 50mph

If the vibration clears above this speed, then get the front wheels balanced.

[Willie]

If the vibration never diappears once you have exceeded the starting
speed then the propshaft may need balancing(the UJs do not have to be worn to cause this) or the pinion flange on the diff may be out of true.
Unlikely unless the vibration only appeared after a diff change.