Welcome to our Site for MG, Triumph and Austin-Healey Car Information.
MG MGB Technical - Tyres?
|165 - 70 X 14 or 165 - 80 x 14?|
Any thoughts on the best to go for? Standard profile or low?
165/70/14 compared to 165/80/14 will give a shorter tyre (less sidewall height, minus 13.5%), the speedo will read less, you'll get marginally more acceleration but less mpg and possibly, as a generalisation, a slightly harder feel to the ride.
Back in the day the low-profile tyre to 165/80/14 would have been 185/70/14 (subject to it fitting OK on the car).
Do you know the rim width of your wheels, is your B a roadster or GT, earlier, middle or "rubber-bumper" model?
(70s chrome Roadsters wore 155/80/14 on Rostlyes.)
You could have a play and learn here - https://tiresize.com/calculator/
|Thanks Nigel, car is 71 roadster on wires.|
I have 2 sets of tyres, both new, so was just interested what anyone thought.
|I found that there was very little choice in 165/80x14, so opted for 175/70x14.|
How new are your new tyres?
|Dave O'Neill 2|
|Roadster with wires, 155 width tyres would probably give a nimble feel (if they're available) as 155 were fitted to the 5" width Rostyle roadster wheels and wires are 1/2" narrower (4.5") rim width.
Other than width 155/80/14 is a similar size to 175/70/14 but the same make and model of tyre in those sizes would feel different when used on the wheels and car.
I suppose it would depend on your driving style and the construction and materials of the particular tyre as to which between 165/70 or 165/80 but you do need to compare like with like to get a more accurate answer as even the same make and model of tyre can vary with its size.
But I expect I'm overthinking this and you just want a generalisation, straw poll. :)
And sorry I don't know as I don't have current experience.
|The GT used 165/80s which made the speedo under-read relatively by 2.6% compared to 155/80s on the roadster. However that should still be within the 0% under-read to 10% over-read of a typical speedo.
165/70s will over-read by 2.7%, i.e. make the speedo even more optimistic, and grannies on shopping trips will be overtaking you. Plus the other comments on hardness, acceleration and MPG.
175/70s are the closest at just +0.3% i.e. very similar in all aspects to the original roadster tyres. However the wider you go the more you risk rubbing the tyres on the arches. Even with a pukka wire wheel axle my 175s still rub slightly when touring fully laden. 165s didn't at all with this axle so I'll be going back to them next time. But even they rubbed badly when I first fitted wire wheels using the special conversion hubs to a stud-wheel axle.
All anyone can give you is facts, the rest is down to personal perception.
|My 79 MGB replacement tires are Good Year 185/75x14. The speedometer now registers correct mph and close odometer readings as well. The car also sits higher.
I do have two of the old rostyle mounted tires in the loft. They are Kumho tires 185/65x14. Speedomter readings were approx 5 mph higher than actual speed as well as the odometer being incorrect.
The 185/75x14s give more of a "Boulevard" ride and cornering is feels more "surefooted". Steering is feels a slightly "heavier"
|Colin you say that you have wire wheels, are they tubed or tubeless wheels, depending on which you have the choice is limited (not on size) but make of tyre.|
|This has cropped up before. Wire wheels with tubes can be used perfectly safely with standard tubeless tyres. I've had those for 30 years, multiple tyres, only one tube has failed in that time and that was due to a thorn through the sidewall.|
|Andy they are tubed.|
|Wire wheels with tubes can be used perfectly safely with standard tubeless tyres, I think if you leave out the words perfectly safely, I would agree,|
"Tubeless tyres fitted to appropriate rims and operated correctly do not need inner tubes; however, there are some applications where users may choose to install a tube, SUCH AS WITH A SPOKED RIM or when using a tube type tyre."
Given matching sizes of tube and tyre, no problem.
|Scaremongering. No safety, how many major manufacturer state it is completely safe to run with tubes in a tubeless tyre, I knew someone who smoked 40 cigarettes a day and got run over by a bus at the age of 95, but that doesn't mean smoking is safe.|
|I heard that if you have radial tires and mount them on wire wheels, the tubes need to be radial rated. Is there any substance to that statement??|
|Gary, in my younger, poorer and totally ignorant days I replaced the worn out Michelin ZX radials on my '65 TR-4A with a set of less expensive bias ply tires in anticipation of driving the car from Maine to South Carolina (I was stationed in Maine and was being sent abroad so I was taking the car home for storage). To save a few bucks I used the "radial" tubes from the Michelins in the bias ply tires. First blow out and shredded tire on the Maryland turnpike. Second one just south of Richmond on I-95. Third blowout on I-85 just north of home in Greenville, SC. Needless to say I got all new tires and tubes when I returned from overseas.
Don't mix - it doesn't pay.
|J. K. Chapin|
I believe that is so.
I run radial tyres with radial rated tubes without any issues at all - 18 years in all.
My tyre supplier has told me that radial rated tubes are now only available from a couple of suppliers - Michelin still being one of those. (They don't have sufficient demand for these tubes and need to order them in when required. A sign of the changing times I suppose).
I suspect that has to do with aggregation of former separate tyre suppliers, the move to world-region focused tyre products and lesser demand for the tubes.
I agree with Jud and would not mix bias ply with radial tubes. Then again, I would not fit those tyres to my car as I am not that interested in originality. Fully understanding of those that might be.
|Jud & Roger, thanks for your personal testimony on radial and non-radial tubes. Obviously it matters that tubes and tires must match.
The other myth is tire plug. You pick up a nail in the tread area of your tire. You "plug" the tire with a plug strip threaded though a split "T-handle" and push it into the nail puncture (after removing the nail) apprx. 2/3 the length of the plug strip, then withdraw the "T-handle". After which you trim off the excess plug material and check the tire pressure.
The myth is, the plug will disturb the radial plies and make the plies delaminate thus causing a tire failure.
I worked with at friend's garage for years and we plugged tires every day without a single failure. Further, I had a tire plug in my MGB for 4 years prior to replacing the entire set.
Any thoughts on the tire plugs??
|How about this for a 'plug'? Made for a bit of a bumpy ride.|
But are you just being mischievous, hoping to start another war? Repairing tread punctures with a rubber plug, usually mushroom-headed in the UK, and with adhesive, has been going on for decades. But like most things I'm sure someone will come along and say it is dangerous.
I've has two plugs done - both in relatively recent driving years. Both on our family cars - not the wire wheeled 'B', so not really driven to extremes though both of reasonably high k's. The second is currently on our Mazda Tribute. Never had any issue with either. The first lasted through to eventual tyre replacement caused by normal wear.
I had not heard of the myth re delamination. There are, though, strict rules here re where plugs may/may not be inserted in the tyre structure. Essentially limited to contact patch with a safety margin clear from the side wall.
|Ditto here - the central 3/4 of the tread.|
|I have Dunlop SP 20 FE tubeless tires - P185 70R14 on my 1970 MGB GT. Very pleased with them and they look good.|
The "T" handle type plugs that you push in from the outside don't cop it with the insurance companies in Australia and anyone doing them leave themselves wide open if there 's a failure
Any plugging has to be done from the inside using a mushroom patch, with the stalk pulled through from the outside till the patch flattens out inside, then cut the stalk off level with the tread
Illegal to patch Z rated tyres
|Roger, yes the T-handle plug can only be used on the tread area. If the sidewall is punctured, the tire is discarded regardless of existing tread life.
Willie, in Florida, some auto stores and shops were telling me using the T-handle with the red strip plug will compromise the steel belting, resulting in a tire failure. As in my previous post, we've been "plugging" radial tires for at least 15 years and never had a report of a single failure.
Not to start a firestorm here, but there are a myths about to get you to buy tires that you do not need.
|I am a big supporter for the use of the gooey string repairs using the T handle and split end. Been using them myself for years in treaded areas of the tyres. To date never had one fail. Used them on my tubeless motorbike tyres too but only until I could get a new tyre. A local garage introduced me to that type of repair many years ago when I had a puncture at the start of a fishing trip. I was suspiscious at first but the repair held so bought the kit and used it many times since.|
This thread was discussed between 15/01/2019 and 20/01/2019
MG MGB Technical index
This thread is from the archives. Join the live MG MGB Technical BBS now