MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - How much power is safe with wire wheels?

I have a 1965 Roadster with a Rover SD1 3.5, offenhauser + holey 390 carb, free-flow manifolds.

I'm currently trawling through the archives for recommended options for power upgrades - any advice here would be much appreciated - I was considering replacing the cylinder heads with a Peter Burgess Econotune version.

Anyway, I remember reading before that at some point on the power curve it is unwise to continue to use wire wheels. I'm a big fan of these and wouldn't want to lose them - what's a safe bhp to reach?

Thanks, Chris.
Chris Holmes

If you look on the MGC BBS, there was something recently about a wire wheel specialist company, I'm sure they would help. I know there are competition grade wire wheels which have more spokes, I believe. You could go for some of those. I think wire wheels are pretty strong if they are in good condition, certainly old bugattis, ferraris etc had wire wheels, but of course the spec may be much better than the standard MGB ones!
T Green

Bugatti wire wheels were different. The wires only served to keep the rim concentric with the wheel hub and as such were not pulling in opposite directions but were radial and little more than piano wire. The drive and braking forces were taken by toothed wheels on axle hub and wheel rim.
Paul Hunt

Off the subject of wire wheels, but i can heartily recommend the Econotune heads. I fitted a set to my factory BGT V8, with excellent results. Mid range power increase is superb, a wise investment!
KD Rowson

It's torque that matters, and if you've got enough power to spin your wheels now then you've reached the (axle) torque limit of those tyres. Further engine work will just allow you to apply that same torque at higher speeds and thus no damage can be done that you can't do already.

However if you've somehow put 7" wide slicks on a normal set of wire wheels then a torquier engine may provide enough grunt to damage them.

I say stick with 'em :o)
--
Olly
Oliver Stephenson

I think you will find it has less to do with BHP ot HP and is more an issue of Ft/lbs of torque. The Maximum amount of stress on a drive-train is moving the car from sitting still to moving. With a 4cyl car, the motor does not produce much torque off idle, they are revving motors, thus they cannot put maximum stress on the drivetrain unless you rev the motor way up and dump the clutch.

On a V8 the base idle torque could well be 2X a 4cyl max torque. That is just a guess I have no actuall numbers for a 4cyl, but my motor puts out 150ft/lbs at idle. This power is right off idle, so a normal traffic lite start is producing a large amount of torque. The quiet (not revving high) smooth operation and pure excitement of a strong takeoff with little effort will mask the fact that the drivetrain is undergoing large amounts of stress. This will just eat up wire wheels.
Larry Embrey

"thus they cannot put maximum stress on the drivetrain
unless you rev the motor way up and dump the clutch."

What about emergency braking, or just plain hard braking? Decelleration happens much quicker than the car will ever accellerate.
.

Both of your scenarios woudl quickly over stress tghe tires grip on the road resuting in a skid which everyone knows produces less friction. strong take offs from a standstill can produce larger stress over a longer period which is what will tear up wheels....
Larry Embrey

If you think of the heaviest car using the same wheels it is probably the MGC, although an Aston DB5 or 6 or V8 would probably be heavier. They all have wires spec'd as standard. I would agree that a severe brake and swerve situation must be a real test for any wheel and you do not hear of wires failing, except when they are old and rusty. But surely the manufacturers would have some real data.
T. Green

MGC wheels are 15in versus 14in on the MGB, and also I believe they have more spokes, is it 72 versus 60? Theincreased size looks better, and more spokes is stronger.

Does anyone know if MGC wheels fit MGB hubs?

Another alternative for maximum strength is to use Minilite type with chrome centre and spinners . V. expensive but I like the looks, they are much easier to maintain on a regularly used car. I will be going for this on my MGC rebuild in (V.slow) progress.

I know MGC racers prefer to use disk wheel hubs.
Roger

Jaguar racers and AC Cobra drivers both discuss this issue and I think lateral G's must be considered also. Dunlop has gone as far as advertising that their vintage tires are SMALLER than almost all competitors. New tire compounds and construction have started to create failures. A properly designed wire can hold extreme forces, have you seen the U.S. fad of 24" wires on SUV's. 300hp in a 5500lb vehicle with 4 wheel disc brakes. Now there is stress! I think the best and smartest thing to do before going crazy is to call up Dunlop. They've been in the field for just a few years and they do offer variants of wire rims for more strength.
Luke Staley

This thread was discussed between 12/07/2002 and 19/07/2002

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now