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RE: What size tyres for my Jubilee??

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I was looking at the original size tyre of 175 SR14 but really any thing other than the 165 on there now. Lets not re-callabrate and will fit the tyre that works best

Did you know that the Jubilee was supplied with 165's not 175's otherwise the factory would have to have supplied different speedo's and not the 1000TPM. (the V8, which has 175 x 14 tyres, is 960TPM). If 175's are fitted then the gearing is taller and your speedo will under read (70MPH would in fact be nearer 72MPH). I don't know about Norway but most countries are okay with a speedo that over reads but not the other way around.

185/70's are virtually the same rolling circumference as 165/80's (being only 6mm less in diameter or approx 0.5 MPH slower on the speedo reading)

Here is a list of tyre available tyre sizes available but note that anything 195 or above may require xtra clearance on the rear wheel arches

Tyre code Diameter Circumference Difference
---------- -------- ------------- ----------
165/80 R14 620 mm 1947 mm 0.00 %
195/65 R14 609 mm 1913 mm -1.69 %*
175/70 R14 601 mm 1888 mm -3.07 %
185/70 R14 615 mm 1932 mm -0.81 %
195/70 R14 629 mm 1976 mm 1.45 %*
175/75 R14 618 mm 1942 mm -0.31 %

185/75 R14 633 mm 1989 mm 2.18 %
175/80 R14 636 mm 1998 mm 2.58 %

*these may cause fouling to the bodywork and if so the bodywork would require modifying to suit

If it ain't broken don't try to fix it as if you do it will definitely break

Just discovered this useful note on tyre sizes for a Jubilee in the archive. Most useful thank you for all the sums and thinking.:)

Do you know whether this will copy across to a Roadster? Or are they meant for smaller tyres, are the wheel arches not able to take say 185/70R14's?
My roadster has 165R14 84T's fitted dated back into the last milenium and 2 are seriously crazed and cracked, but this size is now quite hard to find and when I did find some and I turned up to have them fitted they were date stamped early 2009 so were already 4 years old and not what I was looking for.... 😉

This may come in useful if messing around with widths and aspect ratios.

Not my find, that credit goes to an american B owner on a different forum.


Hmm thanks, 😀 but a 185 tyre must be some 20mm wider than a 165 tyre so will it fit under the wheel arch on a roadster without fouling? I am aware that Colin's 2009 note suggests that this is ok for a GT.

It seems also a fact that the old 165x14 tyres had actually a height of 82, not 80 as with what the "miata" system gives as a max. height.
I also use the "miata" calcutor, beause it's simple to use.
I have - I believe 185/65x14 - tyres on my 1978 (us) MGB roadter on the ex factory wire wheels, will check tomorrow, car is not next to my house.
My UK-LE runs currently on 15" Dayton wire wheels with 175/70x15 Vredestein "classic".
Both cars are on standard riding height.

Firstly there is no dimensional difference between the roadster and GT shells with regards to track width etc-the only difference is that the wire wheel axle is narrower to accommodate the difference in the wire wheel design.

Interestingly I'm looking at the same for my roadster but the only difference is that I'm going up to 15" 72 spoke MGC wires.

The options with all the tyre sizes stated above are the same but there are two problems with widening the tyre sizes much over a 175 on wires.

These are the rim width & the fact that all original wires need inner tubes.

The standard rim width for the B & infact C wires is 5J (5inches). This, without the concerns of possible fouling of the bodywork, limits the increased tyre widths considerably as there is a real life risk the the an over width tyre could peel itself from the rim :o:o

The second issue that a lower profile tyre should have a lower profile tube to suit otherwise it is liable to get pinched and you've guessed it go bang :o:(

In theory a 185/70 14 should be okay with a 5J wheel and I am pretty sure that it is possible to get tubes to suit (if you want me to check let me know?) and these will fit the arches as the same size as your GTLE or an LE with alloys.

If you don't fancy going with 185 section you could go for 175/75 (there seems to be a reasonable selection of tyres) and this is almost exactly the same as the original 165 tyres- only -0.31% difference / speedo reads 69.78 mph rather than 70...basically nothing.

Hope this helps but if not give me a shout.

Incidentally in my case I have a nice friendly tyre guy who is fitting a pair of worn 195/60 x 15 to try ;);)

If it ain't broken don't try to fix it as if you do it will definitely break

sid has 195s on the back but he has the deeper dish scimitar wheels,weve never had any problems and if anyone has seen the poor car when he does a show his totally loaded up and steve is not exactly a slow driver but never scrapes wheelarches.:D

Guys & Gals

Thank you all for your help & advice. 🙂
Most interesting too as my desire to run the same tyres on my LE roadster as I have on my GT will have to end!
'Skaliwag' will therefore stay on 165/80/14/85T tyres except that this time they will be an almost unknown make 'Barum Brillantis' which should get fitted on Friday to get me away from some well cracked up & fairly scary 1997 dated tyres. 😮

Glad your sorted but you can fit thee same size as your GT/better handling as i have found inner tubes ;);)

If it ain't broken don't try to fix it as if you do it will definitely break

According "Original MGB" the Jube's had 175HR-14 tyres fitted,
the US-LE had 185/70SR14 fitted also the UK-LE with those wheels.
The USLE's have even a sticker confirmed that with tyre pressure in the dashglove box, regretfully I was unable to look today at the tyresize on on the wirewheels of my 1978 MGB.

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