MGB MGB Tire and Wheel Sizes

[glemon]

I have an MGB and an club autocross coming up and had a wickedly delicious thought, the car came to me with rather wimpy Goodyear 165/70-14 rubber. The cars has bolt on wheels I have some panasport type 15 X 7" wheels with 205/65s on them ready to go for another car that is far from being ready.

I know a "C" uses 15" wheels, is the bolt pattern the same for a B as a Triumph? the TR wheels have a 4 X 4.5" bolt pattern, I think a B does too but not sure.

And will the tires fit a stock B?

 

[RJA]

No, too wide and to tall. May run in a streight line but will be hard to corner.

RJA

 

[glemon]

Thanks, oh well...

 

[Steve_S]

With poly bushings and a well aligned body / suspension, it may fit. On most MGBs you would have rubbing issues in the rear but some people are lucky in this regard. I run 15x5.5" wheels with 195/60R15 tires on my '65 B with no problems. Good luck!

 

[WA1KWA]

What rule set are you running under? Been a few years for me, but, under SCCA Solo stock class rules you will only be allowed the stock 14" size. Anything more & you're out of stock class. You can squeeze a 195/60 x 14 on there, the rears should JUST clear the quater panels. That's what I used when I ran my B.

Colin

 

[glemon]

Colin--Just our local club, no SCCA rules, run whatever want, classes are based on engine size, then we breake those up into stock and modified.

I realize the size is prbably too big and not ideal, but I may put them on to see if they fit, I have a later bumper B with the raised ride height, which I assume may give a little more room for wheels.

This is not a real serious effort, I just happen to have the new wheel tire combo and thought it might be fun to raise a few eyebrows we started doing club autocrosses 5 years ago or so, and some guys have gotten pretty serious about it.

 

[swift6]

If the rest of your car is still stock, pump up those wimpy tires to something like 40psi and go for it. Those bigger tires and wheels will only slow you down.

 

[WA1KWA]

Good advice from Shawn. Remember to keep the fronts 4 psi more than the rears. Get a big piece of that sidewalk chalk they sell for kids & use it to mark your sidewalls onto the treads. That way you can see if you are cornering on your sidewalls & adjust the pressure accordingly. Unless you have a supply of air wher you are running, think like you dress when you go out on a spring or fall day: you can always take off, but you can't put on what you don't have. Same with your tires. Pump them up high; if there is no air there, you won't be able to add any, you can always bleed off, but do it spairingly.

Most important: Have Fun!

Colin

 

[glemon]

Thanks guys--I will have fun--Greg

 

[Steve_S]

That's the first time I've heard of someone running more air in the front than in the rear on an MGB. With more weight in the rear, the typical setup is to run 2 PSI more in the rear! Of course everyone's setup is different after 40 years of fiddling and driving style will make even more of a difference.

FWIW, I run 195/60R14 on one of my Bs and there is ample clearance. The ride height is unchanged from stock but with those little tires is could stand to come down at least 1/2", which would reduce clearance slightly.

 

[glemon]

I am certainly not an expert on MGB handling, but in general I run the fronts higher than the rears in solid axle front engine british cars including Sprites, TRs, etc.

Although I don't have empirical data to back it up (haven't tested it) the theory is: 1) Front end is heavier, so needs more pressure 2) Reduces understeer 3) the rear ends tend to be stiff and have limited travel, so a little more cushion at the rear than the front to prevent rear end bounce and slide on rough surfaces.

 

[CurtisJ]

The original post seemed to ask about putting aftermarket (oversize) wheels from a TR6 onto an MGB.

The two suspensions were designed to accept wheels with different "offset" measurements. Offset is the dimension from the mounting surface (hub) to the plane that goes through the center of the wheel perpendicular to its axis. For oversize MGB wheels, offset of 22mm (or more) is normally used. For oversize Triumph TR6 wheels, offset of 6mm or less is normally used. In other words, even if the tires would fit, the TR6 wheels would mount them in the wrong plane.

For what it's worth, there are a few MGB V8 and V6 conversions driving around on 15 x 7 tires. It can be made to work quite well...

This MGB is running on 15x7 wheels and 225/50 tires:

 

[glemon]

Thanks Curtis, best answer yet, didn't know the offset was different, my 15 X 7s are zero offset.

P.S. the B looks nice with those wheels.

 

[Steve_S]

TR6 wheels will fit on MGB but as Curtis said the offset is different. I've seen a B driving around on them with no issues but I would be surprised if the steering didn't suffer a bit from the change in geometry. The other option is to remove the rims from the TR^ wheels and have them re-centered. New rims would most likely have to be used. Many older wheel shops can perform this service.

Regarding tire pressures, remember there is more to it than simple weight balance. The front tires are steering the car and the rears are subject to power being transmitted through them to propel the car forward. Every setup is a bit different, but typically more pressure is used in the rear than in the front.

 

[glemon]

Well, I was just thinking of popping them on for our club autocross since they were just sitting there with nothing to do. I know they were really not the ideal size, sounds like the "might work" but the autocross was today, and my brother offered the use of his 911 so I took that route.

It is just a very hard life I lead....