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MG MGB Technical - tyers

ive just purchased some lovely american style wheels.now i want to choose the tyers ,ive looked on the tyer calculater and found the closest wheels in rolling circumference are 195*60*15 i would rather go slightly smaller than bigger. can any one tell me iff they will rub on the inside of the arches,ive got 185*70*14 on at the moment and there ok thanks daren
darenparker

I run 195SR65-15" on my MGC with Minilyte replicas. I rub on the inner fender well on the right hand side during hard right turns or with a passenger and a full tank of fuel.

FWIW

rick
1978 MGB
1969 MGC
1974.5 MGB/GT V8 conversion
rick ingram

I got 195/60/15 Continental tyres on my 76 mgb with no problems at all !!!

hope this helps

Cheers
David
David Watters

Daren, just measure the tread width and compare to the fender clearance you have now. It's that easy. Assume all the difference in width is to the outside.
Jeff Schlemmer

Jeff..you have to take into consideration any shifting of the differential during turns, etc...that's where I run into trouble with the MGC. A panhard rod would help, as would rolling the inner lip or flaring....FWIW...rick
rick

OTOH my '67 rubs not at all with 205/55R-14 tires on minilite replica knock-on wheels.

mike!
mike!

thanks for that, i think iff you have a j of 7 thats when you have problems .the max wheel size 6 j daren
daren parker

Daren, I might be interested in the old 185/70s if they are half good and you are getting rid. Email me if want to discuss. Cheers,
Steve
Steve Postins

hello steve i only purchased the tyers last year there budget tyers only done a thousand miles,the wheels are rostyle but have been beed blasted and powder coated in alloy silver.i think 15 inch look much better.iff you look on the tyer calculater the185 are a little smaller than the standard 165*80*14,and as a result the speedo is a bit out.its difficult to choose the correct tyer for the 15inch wheel 185*65*15 is larger than the standard tyer and the 185*60*15 is far to small ,the best tyer for height is 195*60*15but ive got to be carefull it dont catch .any one out there with that size thanks daren
darenparker

Daren,

An important point is wheel offset. I do not know what american wheels are but in tehe past american muscle car mag wheels were positive offset configuration. With a MGB a positive offset will definitely rub wheel arches. Concerning tyres selection, I suggest a speed rating 'H' as a good choice.

Cheers,

JGC
JGCatford

I have fitted to my car Compomotive ML wheels 6x15" ET6 shoed whith Yokohama 032R 195/55x15. No rub in rear wheel archs, but I have Panhard rod.
Regards.
http://membres.lycos.fr/mgcontact/fileupload/uploads/1105892563_tyres.jpg
michel

I run 195 55 15 tires on 6" wide wheels with fiberglass springs on a 67 GT.

I have not modified the lip on the inside of the rear fenders. I had a little inside rubbing on one side on hard cornering so I installed a 1/4" wheel spacer. Now I have a little outside rubbing on hard cornering.

The solution from all sources I've read is a Panhard bar to solidly locate the rear axle laterally. When the rear axle mooves sideways under hard cornering the 1/2" clearance is inadequate. The new wide sticky tires make the problem worse, not only because they are wider, but also because of the higher cornering traction. - g forces -.
Barry
Barry Parkinson

barry hello ive just been on the tyer calculater the origanal size made for the car is 165*80*14 which as a rolling circumference of 76.62inches.your wheels 195*55*15 have a circ of 73.63 this means that it is a danger to fit these wheels even iff they dont rub, your brakes could fail.also your speedo will show 62.5 mph when your doing sixty iff you can fit 195 tyers fit 195*60*15 which are 4mm smaller in diameter. i have gone down this road before and the best tyer to go for on a 15 inch wheel is a(185*65*15)this tyer is perfect only 1mm higher than the origanal tyer and will fit with out rubing thanks daren
daren

I'm running Dunlop 15x5.5" 72-spoke wheels with Mihcelin Pilot 195/60 tires. No rubbing at all unless cornering hard with a really heavy load in the car (don't ask how I know). Without overloading the car with cargo there is no chance of rubbing. I do have poly bushings installed which probably helps.
Steve Simmons

hello steve i think it makes a difference when you have a 6 j,the tyer must squash in a little with the 5.5 j thanks
daren parker

Daren
The 195 55 15 tires are a little smaller diameter than stock. The 80 profile is larger than the 5.60x14 stock tire. The difference from stock is actually a little over an inch. The car is lowered by about 5/8". There is much more clearance around the brake disk and better brake cooling with a 15" wheel. The tires are rated for more than a 3000 lbs car. The smaller diameter tire makes it easier for the brakes to slow the car. The combo improves the handling and the go and the stopping. What more can you ask for?
With the late model overdrive, 1967 odometer (1040 turns per mile) and the small tires the speedo is pretty close to accurate.
Barry
Barry Parkinson

barry im a little confused i thought the stock tyer was a 165*80*14,i have beem baseing all tyer sizes against that size.i invesregated this and it does not tell you the size on the tyer and the tyer calculater does not reconise that size .please tell me the correct size then i can start again thanks daren
daren parker

barry .ive contacted longstone tyers (classic tyer specialists).they confirmed that the stock tyer is 165*80*14 diameter of 24.39inches .your wheels are 195*55*15 which have a dia of 23.44inches ,this means your tyers are 3.9 % difference .each revalution you are loosing over3 inches in travel . check tyer calculter on google forth down thanks daren
daren parker

Daren
The 560 14 tire which came with the 67 GT is 24.6". The roadster used a smaller tire. The tire I'm using is 23.4".
The difference between the two tires in height is 1.2". This lowers the car by .6" I was using a late model overdrive trans. I'm now installing a 1981 280z trans. 5th gear has a much bigger stepup (.745) than the MGB overdrive (.82) resulting in low cruising rpm.
With the 5% tire diameter reduction that results in an equivalent top gear of .78.
The car corners like it is on railroad tracks. And with the fiberglass rear springs rides quite nicely. The tires are rated for over 1200 lb load per tire. My car is down to almost exactly 2000 pounds. I think that these tires are more than adequate given the total 4800+ tire rating.

The late model mgb trans turns the odometer 1000 times per mile. The '67 odometer requires 1040 per mile. My speedo is within 1% of its rating with a late model transmission.
Barry
Barry Parkinson

hello barry you learn something every day , ive had my roadster for two years so its all new to me. so what would you go for on a 15 inch rim, the choices are 185*65*15 these tyers are sold as standard for the 15 inch rim 195*60*15 or 195*55*15. my car as been droped 1 1/2 inch the same as the chrome bumper roadster thanks im just worried that the 195 may rub thanks daren
daren parker

Daren
I think, from recollection, that the closest modern 15" size to the stock diameter would be a a 195 60 15. I was unable at the time (2 years ago) to find a hi performance sticky tire for street use that size and went to the 195 55 15 instead.

The total width of the tire (not just the tread width) is critical. In my experience with a 67 gt the 195 profile is as wide as you can get without too much tire rubbing in the corners. The rear is the problem, not the front. A taller 80 profile tire may be wider overall even with less tread width. Dunlop used to have a web catalog site that gave all this data for their tires.

The new hi performance road tires really stick - wet & dry - dramatically better than a "touring tire". The few extra $ to get a sticky tire is really worth it. The Potenza Pole Position SO 03 or 02 are a great compromise for handling and ride, wet and dry (not snow) in my opinion. Check out the ratings and testing and feed back at the Tire Rack web site.

I found a set of aftermarket alloy wheels 6" wide for a Datsun 200z as I recall, which had the right offset.

Good luck.

Barry
Barry Parkinson

barry thanks for that , iff you have any pictures of your car i would like to have a look thanks daren
daren

Am I missing something guys, why does anyone want, or need, to put oversize low profile wheels or tyres on a road going MGB?
Is it because they -
1)cost more.
2)possibly rub the bodywork (safety hazard).
3)make the car look like a boy racers car.
4)make a bigger skid mark on heavy braking.
5)give the most uncomfortable ride possible.

We do some modest rallying in our 67B, shod with 175/70/14's and we throw the car around as much as anyone, without any braking, or road holding problems at all.
(I didn't mention going into the ditch in France, but that was just driver error).

I also have a friend who does track days in his 67BGT. If you saw him drive, I could well see you saying, "he must have some big low profile sticky glue specials on the car", wrong, 175/70/14 Colways £22 each fitted and balanced.

Sorry, I just couldn't resist
Graham
Graham Cherry

graham iff you want origanal wheels you need 165*80*14 which are even more narrow,the 175 tyers are alot smaller in diam.i am running orig rosstyle wheels at the moment with 185*70*14 a much better all round size .the cost for a budget tyer little as 20pounds the budget tyers are softer compasite which would make it perfect for you .go to any tyer spec they will recomend 185*70*14 thanks daren
daren

try driving a car with some good wet and dry hi performance tires. Then give me your comments. I used to throw my car around too in the '60's and the '70's with street tires at .6 g , if I was doing good. Now I go around faster with no muss or fuss. If I want to go way faster it is still very predictable.
If you want to be on the edge of control at .5 g be my guest. If you want to push to .8+ g and still be on the edge of control - join the club.
If you want a comfortable sedan challenged by the local roundabout to drive to work each day why mess with an antique obsolete sports car that is unreliable, slow and can't keep up with the neighbor's sedan between the hedgerows?
The B isn't even collectible. The only reason to fix it is to drive it and enjoy it.
Modern tires and wheels bring the handling into this century.
Barry
Barry Parkinson

Darren
can't go to 185, the max allowed is 175.

Barry
I think your'e missing the point, firstly we're not using 60s,70s tyres, we're using modern tyres with the same compounds as the current low profile tyres, so the amount of grip is comparable. My point was that the average MGB (or any other antique obsolete sports car)driver, driving on the nations roads, will not see a gain big enough to warrent the cost and problems encountered on fitting oversize wheels and tyres to cars not designed for them.
My other car is few months old Jaguar with modern all singing, all dancing, low profile tyres, very quick and predictable and BORING. I much prefer to drive and rally the antique, obsolete, can't say unreliable, since it has not let us down in 38,000 miles so far, MGB with it's narrow 5J wheels, much more fun and CHALLENGING.
Good luck with your mundane comfortable sedan, join the rest of the rat race.





Graham Cherry

Graham
you missed or ignored my point. The tire manufacturers now make tires in the low profile sizes that have very hi performance rubber compounds for dry, or wet & dry conditions that are way more fun to drive with than the standard compounds used in more standard size tires. The low profile tires with wider tread width and lower profile, better rubber compounds, provide quicker response, much more traction and much more fun.
If you just want a car to be unstable for fun try frozen lake driving. My antique 67 gt has given some modern hi performance cars a lesson in a twisty mountain pass that I frequently drive. I wouldn't think about going over that hill, at any speed, without superior wheels and tires.

Three years ago I installed some used Police interceptor tires on a pickup. They were low profile and high speed rated. They drove like the road was greased. In wet conditions they were downright scary. I changed them for another brand -same size and speed rating but different rubber compound and wear ratings -and it was like I was glued to the road.

In the US, hi performance tires are marginal that come with new cars. The manufactures can pick up gas mileage rating credits with low rolling resistance tires. The after market tires will lower gas mileage in my experience 1/2 to 1 mile per gallon. Some super hi performance models are now being sold new with true sticky tires, such as the Saturn red line, WSX Subaru, and the like.

Your Jag with after market hi perf tires would be noticeably improved in handling with aftermarket tires, here in the US.

Barry


Barry Parkinson

Dunno where everybody is getting this "original was 185/70-14" stuff from. Stock was 5.00x14 for roadster with wires and 5.60x14 for rostyles with "uprated" tires for both wheels on roadsters of 155R-14.
GT had 165R-14.

I put 185/70-14 tires on my roadster with wires once and it looked SILLY. Like having a doughnut on there.

OTOH, I purchased 6x14 minilite replicas in a knock-on style and wrapped them in Kumho Victoracers in 205/55R-14 and "lo! it is a RACECAR. Good-bye screeching tires and bad times (also have a quaife and gnarly front sway-bar). The spectators were disappointed but my adrenaline level went up ten notches!
I have nylatron shackle bushes (and new stock front-eye "silentblock" bushes) and axle-pads but no panhard bar (want one).

Went back out to look and yup, I rub on occasion but certainly only on hard cornering.



Why do it? Why not?!?!

In the real world, 185R-14 tires are the smallest easily found anymore so it is a matter of economy to be able to fit them.

Mike!
mike!

Barry, no disrespect, but I couldn't disagree with your statement "Modern tires and wheels bring the handling into this century" strongly enough. I absolutely, in the strongest terms, refute that statement.

The MGB is forty years old, and you can do whatever you like with it, but you will never bring the MGB into the 21st century. Which is why I like them.

I've driven a friends RV8, which is the most modern incarnation, possibly, of the B. Competely different front cross-member, composite back springs, tele shockers, a lovely engine, and very wide tyres. What's it like down the lanes? Pure MGB! IMO.

Sure its different in other respects, but I don't think it would go down the lanes any better than my car. It'd kill me on a fast road, but I don't think it handles any better. (Incidentally, here in the uk the RV8 was voted as the second worst sports car of all time, in a magazine. Thats how much you can bring the MGB into the 21st century. I'd still like to own though, I see it a realistic alternative to a Morgan)

I have to say, I also feel strongly about this. I know you guys fitting wide low profile tyres to your cars won't be persuaded, but I worry about newcomers reading this stuff and wasting their money.

This is what I think. Wide low profile tyres will make NO improvements WHATSOEVER to these cars. They weren't designed for them. They can't make use of them. But you CAN ruin your cars very easily. You fit the wrong offset, or wheels that are too heavy, and you'll ruin everything.

I absolutely challenge anyone to prove me wrong. I would make myself available at any track day in the uk anyone wants to be at, and I will make myself available to be shown to be wrong. I'll be at any test that anyone wants to be at, provided they're realistic tests that have some connection with everyday roads. We could have a slalom in a car park, or whatever. We could swap wheels on our cars - anything you like.

I run 175/70x14 tyres, and I think that changing to wider won't achieve anything at all WHATSOEVER! I think lower profile tyres will only make the ride quality worse than it is, for absolutely no gain.

I'll give you an example: I also own a Mazda MX5 1.8. (Miata). It came with 195/55x15 tyres on aftermarket alloy wheels, fitted by the UK importer. Correct offset and everything. I knew that my car did not ride as well as the 1.6 cars that I had driven. I acquired a set of wheels with the 185/60x14 (both sets of wheel/tyre combos have the same rolling radius) that the car was originally designed to have. Its been transformed. The crashy/bangy ride quality has gone. The tramlining has gone. The bigger wheels were 7kgs heavier than the smaller ones, multiplied by 4 means I now have 28kgs less unsprung weight than I had before.

Other than the bigger wheels looked nicer, I cannot see any benefit to those bigger wheels. I think my car has benifited in every way, to no detriment.

My MGB GT was transformed by changing the front anti-roll bar to the next size up. I would be willing to change back to the old bar, and challenge anyone to fit a wheel/tyre combo that would provide the same improvement. I say its not possible.

Personally, I would love to try a modern tyre in 165/80x14. Its only the lack of wheels that stops me from doing so.

Just a final word. On the track days I've done I've overtaken or stayed pace with: Lotus Elans. A Mk2 Ford Escort RS1800 in the wet. Austin Healeys. TR6's. (Jeez, they don't half lean) Alfa Romeo GTV, both 60's and 70's incarnation. On the one speed test on a road rally, involving a thrash up and down a quarry lane, I beat the Porsche 911 that started ahead of me by 9 seconds. The stage prepared 911 monster that was behind us went off the track, damaging itself. The first time I ever drove a B on a race track, thanks to the succesful amateur racing driver sat in the passenger seat, we were the fastest car on track in our session. The car was totally bog standard, probably on 165 tyres.

I STRONGLY believe, unless you've got 140bhp or more, you'll ruin a B by fitting modern tyres.
Michael Watkins

I've driven my B and others with various tires and wheels. I've had numerous high performance cars over the last 40+ years. I've driven my current B before and after change of wheels and tires.

I agree a good driver in a bad car can do better than a bad driver in a good car in the proper circumstances.

To argue that modern wheels and tires don't help performance??

Last time I checked they called those folks Luddites.

Barry

Barry Parkinson

hello mike i did not say that 185*70*14 is the stock tyer . all the 14*165 tyers have a 80 wall(80 percent of the 165)i just wanted something bit wider ,and they fit ok from a 5 j wheel. is perfect for a rostyle wheel or a 6 j alloy. iff you go on the tyer calculater i think the 185 tyers make the overall diameter 4mm smaller the only method of fitting low profile tyers is to go to a 15 inch rim thanks daren
daren

>>To argue that modern wheels and tires don't help performance??<<

Well, don't forget you can't buy 'old' tyres, all tyres you buy nowadays will be modern. Even if you buy a brand thats been around for years, the compound will have changed. A tyre of today, in the same size, will be vastly superior to one that you would have bought in the sixties.


I say that wide low profile tyres won't do anything to improve an MGB. I say the chances are much more likely that the car will be spoiled, ruined even, by a poor choice of tyre. I think the ride will be too harsh, I think the steering will become heavier, and you'll lose the 'feel' of the steering. Wide tyres coupled with a small steering wheel could be absolute purgatory, IMO. The wheel/tyre combo will be heavier. That'll make the acceleration worse and the braking worse. Marginally, I'll admit, but its the fact nevertheless. The suspension will have to cope with controlling the heavier wheels. You just can't turn an old car into a new one, it can't be done and I can't understand why anyone would want to. If you want an old car, buy one. If you want modern performance, buy a modern car. But just about any attempt to combine old with new usually means you get the best of neither.

As an aside, I wonder what the quality of roads are like in the US? Here in the UK, round where I live, the roads are pretty bad. A B can be uncomfortable enough, without fitting low profile tyres.



Michael Watkins

Michael
I converted my 67 gt from wires to 15x6 wheels with 195 55 15 hi perf street tires. The weight of the new tire wheel combo was almost the same as the stock wire wheel and tire.

I'm using glass rear leaf springs and stock shocks and sway bar. The car rides much better than stock. The only complaint is in a sharp hi speed corner it takes some muscle. Parking, around town, ordinary driving, etc the steering is not noticeably more dificult than stock.

The difference in traction and handling between a cheap 195 55 15 vs one that has hi traction rubber compounds is dramatic. Yes, the cheap is better than the OEM 1967 tire, but the few extra $ for the hi performance tire makes all the difference in the world.

The MGB handles well notwithstanding your reference to the GT V8 being rated poorly. The light rear end with hi friction multi leaf rear suspension was a weakness. With the low friction fiberglass springs(or single leaf steel springs)the ride is much better and the axle traction control is also. With a panhard bar the rear axle stays in it's place and makes for very predictable handling. With a v8, traction bars are also needed to keep the rear springs from winding up, resulting in rear axle hop off the line. An irs rear suspension is heavier than the live axle system although the sprung weight per wheel is less. But it is not that much less per wheel when you are using glass springs. (5 lbs per side vs 20 lbs per side with the stock leaf spring) A bump on one wheel is not lifting the entire axle. As a result the unsprung weight is not that much different than an irs. A bump that impacts both rear wheels at once does bring the entire live axle into motion, and there is more unsprung weight than a comparable irs suspension in those circumstances.

The front suspension is modern in geometry but not in greased bushings etc. There is no need to apologize for the front suspension. The car is narrow by modern standards which results in hi weight shift on cornering. The larger/stiffer sway bar will help with transient handling but will also cause a greater tendency to understeer.

The GT with some upgrading is well balanced car that will handle right with modern cars.

It's a lot of fun to have an antique that can show a modern car the way down the hill through the twistys. When you figure a new performance compact costs $20,000 ++, its a lot cheaper too.
Barry
Barry Parkinson

This thread was discussed between 09/01/2005 and 23/01/2005

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