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MG MGB Technical - Tyre sizes

Could anyone tell me the correct size of tyre my mgb roadster, 1971 GHN5-239xxx. It has 155/14 at the moment, but the local garage reconds it should have 165/14.

The technical specs I've seen give both sizes and just say 'depending on model' without clarifying which model has which.

Thanks in advance.

Steven

Steven

I may be wrong, but I think it was the rostyle wheels that came with the 165's and the wire wheels that came with the 155's... That's only a guess, because I know that my 75 came stock with rostyles and 165's (I still have the original spare) and the wire wheel rim is a bit narrower than the rostyle rim. So it might come down to what type of wheel you use
Dave

I believe Dave is right. Wires came with 155/70R14, Rostyle with 165/70R14 and GT cars always had 165/70R14 with either style of wheel. Someone correct me if I'm wrong.
Steve Simmons

The roadster came with 155 and the GT with 165 - that's what they mean by "model"
Chris Betson

Ohh - and they were never 70 ratio - always 82.
Chris Betson

In fact, a 71 car probably had 5.60 / 14 crossplys....
Chris Betson

Sorry Steve, your tyre sizes aren't quite right, not according to Clausager in "Original MGB". According to him, the earliest cars were not fitted with radial tyres, but when they became more common, 155 x 14 was fitted to roadsters and 165 x 14 to GTs. This was not standardised to 165 x 14 for all cars until the rubber bumper cars. A low profile 70 section tyre was never fitted to standard wheels. The cast alloy wheel of 1979-80 had 185/70 x 14. Clausager makes no mention of any difference between wires or steel wheels.

So in answer to your question Steven, your 1971 roadster should have been delivered with 155 x 14 radials when new, but I would recommend you use a 165 x 14, or if you want a wider tyre, the 185/70 x 14 fits OK and doesn't alter the speedo reading.

Mike
Mike Howlett

When TRYING to buy new tires for my '79 MGB, I found that the 165/SR/14 is pretty much like Beta Max video here in the US. I couldn't find anyone who still carried that size.
I did some research and found that Wal-Mart carries a Douglas tire (made by Kelly Springfield) in 175/70/14 that is pretty close to the 165/14. And they're around $45 a piece. Toyo's and Kumho's would have been around $65 per tire. I also found a good price on some 175/70/14 Cooper tires for around $50/tire, but they had to be ordered.
The 175 Douglas tires have a good tread and fit fine. I'll probably go with something a little wider next time, though. ;).

R.A. Wade

The last time I bought tires (1997), Wal-Mart was selling Michelin 'X-metric' in 185/70 x 14. Don't know if they still carry them but I am quite happy with them. They are French made (a rarity in the U.S.) and have worn extremely well.

Try the 185/70's. As was said before, they don't mess up the speedo and they improve the car's handlng. One of the nice benefits I noted was the reduction of the tendency for the rear breaks to lock up under heavy braking. Probably due to more contact patch.

Only other caveat was a slight increase in understeer with a bit more body roll (tire contact patch again?). Mine could probably benefit from a SLIGHTLY larger front roll bar than original but it really hasn't been that big of a deal.
Richard Smith

Hi folks,
If you want to check what the effect of a change in tyres (or tires) might be on speedo readings, you might like to try the following web site
www.csgrework.com/tireinfo4calc.html.

This will calculate the revs/mile (and other info) for any tyre you care to choose.

Good luck

Peter
Peter Hills

Many thank for everyones help. I'm glad to see the the tyre I already have is what would be expected. I stll have much tread left, so I'll keep on with these for now and perhaps change to the 165/14 at the next tyre change.

Mind you, perhaps a spin around Silverstone is in order...

Regards,
Steven
Steven

This thread was discussed between 20/07/2002 and 26/07/2002

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