Wheel and tyre size question

[SteveH1960]

Hi,

I am new to MGB ownership, very new, so apologies for what could be idiot questions. I have tried searching the forum but without success and I am sure this subject has been done to death but I can't locate it.

I have a 72 Roadster with 14 inch minilites, they are a little shabby and the tyres are Goodyear NCT 185/70R14 and they look a bit balloon like.

I'd like to change to 15 inch minilites, something like the ones on MGBHive, 5.5 x 15 inch, what would be the correct size tyre?

Or do I have to stick with 14's?

Thanks in advance

Steve

[Ian F]

Steve, take a look at a tyre size calculator such as this one:

https://tiresize.com/tyre-size-calculator/

This should tell you what will fit your chosen wheels.

You need to know the "standard" wheel/tyre circumference and ideally should stay close to that - important for speedometer accuracy.

The other factor is fit under the wheel arches. The MGB often has some asymmetry of the back axle - one tyre often being closer to the wheel arch than the other side. Depends what your car is like!

Hope this helps

Ian F

[Bumpa]

On the MGB Hive website they also offer the 15" x 5.5" wheel with tyres fitted and they are using 185/65 x 15. That size should give you the same speedo readings as the standard 165/80 x 14 fitted at the factory.

Ian is right about arch clearance being assymetric side to side. Most MGBs I have seen have less clearance on the left side. Also you need to consider that the axle can actually move sideways slightly during heavy cornering.