Good tire pressure for 18570R14 tires on a '74 'B?

[wkilleffer]

Hey all,

I just bought a set of four BF Goodrich Touring TA tires. It's the first set of new tires the car's had since 2002. While not the sportiest tires out there, they're supposed to have a decent amount of grip and tread life. Perfect for the amount of money I had available for the purpose.

While driving the car home, the handling seemed off. Not sure-footed at all. I was about to blame the tires and was feeling like I'd taken myself for a ride. But I checked the pressure, and all four tires were blown up to at least 34psi. Maximum pressure on those tires is 35psi.

So, what's the "correct" tire pressure for these tires on this car? Seems I've read that MGBs do best with higher pressure in the back, but really don't know. Seems that a pressure below 30psi would use more fuel and cause tire wear due to under-inflation.

Any suggestions would be appreciated.

Thank you,
-Bill

 

[19_again]

Bill,I had been running my Kumhos on 30F and 33R as a result of reading somewhere that it would be a more spirited ride, but a later thread (maybe 6-8 weeks ago) dealt with much lower pressures. I lowered mine gradually and have settled on 24F and 28R and it's a much better ride. less understeer, smoother on the bumpy roads. Manual of my year calls for very low 20's in front and 4-5 lbs more in the rear( I don't have it with me right now). I think that the difference of 4-5 pounds between F&R is as important as the actual pounds of pressure in the tires, as that is the real determining factor in under/over steer. Maybe Goodrich would have a recommendation with respect to your concern about having too low pressure.
Do a search in the archives and you'll get plenty of educated opinions, mine is based on my own experience.

 

[wkilleffer]

How do you search the archive? I tried the advanced search function and chose the MG forum. Typed "tire pressure" into the field and only got back three results, neither of which were dealing with the topic of tire pressure LOL.

Thanks for the pressure tips. I'll contact BFG and browse their website.

Do you still feel like your car and tires have enough grip? How's the handling with the tires set up like that?

What kind of fuel mileage have you seen running your tires on those lower pressures? I'm not compulsive about fuel mileage, but at the same time, my take on it is that the less money I waste on inefficiency the more money I have to actually enjoy the car.

Thank you,
-Bill

 

[tony barnhill]

I run my Kuhmo's at the max pressure stamped on the edge of the tires.

 

[19_again]

Searching the archives is always tough when some posters insist on using titles like "Look what I found" when posting about master cylinders . I just tried the same search and got the same results as you, I addressed that in a pm I sent you. Basil has put up a message regarding more accurate descriptions in the title and it helped but it is still a pet peeve of mine as I always try the archives first before asking questions that I figure have been asked 100 times already.
Anyhoo, I think i'm probably suffering a 3-4 mile a gallon drop in mileage, I don't know that but since the change in pressure, I think I'm using more gas. I don't really care how my mileage is as the car is properly tuned and runs great, and that's why I drive it. As for handling and grip the whole drill was caused by the serious understeer I was experiencing with the higher pressures, the lower pressures provide great grip and the rear end is directly behind the front end now. I don't like making a left hand turn and having the feeling that I could look over my left shoulder and see the rear end of the car sitting over there! There is the factor of how the sidewalls are rated, most of the guys here know a lot more than I ever will about the technical aspects of the tires, but sticking as close as possible to the manual while giving consideration to modern advances is always the best route with our little toys.
Mike

 

[Deleted member 8987]

Tony-
I just took the Kuhmos off my Jag.

Squirrely, squealed on crosswalks when turning, alignment dead on.

Weatherchecked so bad you could see the air inside!

Tread like new.

Got some "Arizonians" or some such, huge difference.

Yours get weatherchecked or was it just an anomaly?

Dave

 

[wkilleffer]

The reason I brought up fuel mileage is that recently my car didn't seem to be able to top 18mpg. I *think* the carbs are tuned properly, but don't really know. I don't know anyone nearby who has a twin SU MGB right now. Sometimes the tuning instructions in the books seem a little counterintuitive. I like to read but learn best through experience and having things demonstrated.

I just did some work on the front brakes, replacing the rotors and front pads followed with a complete system bleed. The fluid that came out was quite dirty looking and I wonder if my front brakes might have been a bit tight as the pads were not evenly worn. Time will tell, I suppose.

I haven't done a mileage check lately cause my efforts to fix the tank sending unit created a temporary leak. It's been eliminated, but that would make the mileage look artificially low.

 

[tony barnhill]

Tony-
I just took the Kuhmos off my Jag.

Squirrely, squealed on crosswalks when turning, alignment dead on.

Weatherchecked so bad you could see the air inside!

Tread like new.

Got some "Arizonians" or some such, huge difference.

Yours get weatherchecked or was it just an anomaly?

Dave

No, no chcking...they just wear out around 45,000 miles.

 

[19_again]

I haven't checked since the new pressure levels but prior to that I was getting 25-30 miles a gallon, 18 sure seems low to me. but if my guess that I'm getting 3-4 miles a gallon is right, I'm not doing much better than you. I will check it this weekend, now you've got thinking. I've got the HS4's and haven't touched them other than cleaning after sitting for a while.

 

[wkilleffer]

My car's a 74, but it has an 18GK engine and HS4s. They've been rebushed once, and I've replaced the jets when the tubes started coming apart. I can only assume they're properly matched and all that. The big problem seems to be having no information about the car prior to my ownership.

I've checked the mileage twice recently before the tank leak. The first time showed a reading of around 23mpg. But after that, it was back down to 18. I can't remember if I did anything differently.

 

[aeronca65t]

I'm running about 30 psi (cold) front and back in ~My '69~ .

Seems decent. Tires are Sumitomo HTR200s on wire wheels. I would raise that pressure if I was autocrossing it. To about 35 psi all around.

My mileage (done over a 300 mile trip) was almost exactly 25 mpg. My car has the Weber 2 bbl. I'm not keen on this carb but it came with the car and runs OK. I bought a pair of SUs to put on it one of these days.

 

[DrEntropy]

I'd say 28 front, 32 rear should give you the best all-around performance/wear.

The power-to-weight ratio difference between Mike's car and the '74 could account for the mileage variance, too. :wink:

 

[Bruce74B]

I run about 26 and 30 around town...a little more if I am gonna be on the highway a lot. Better ride and a little more stick at the lower pressure. I don't put enough miles on the tires before they get too old to use, so the extra wear is not a factor in my considerations.

 

[Nunyas]

I ran the pressures doc mentioned. 32 on the rears and 28 on the fronts. The MPGs I got with my '76 were 16-18MPG city driving depending on traffic and how much lead was in my right foot and I would get 25MPG highway w/ an average speed of 70MPH.

 

[DrEntropy]

Nunny!!!

'bout TIME ya show'd yer cute li'l mug!

 

[Nunyas]

I'll pretend you didn't just say that! LoL

 

[DrEntropy]

Just show up a bit more often, mmmkay?

 

[Stewart]

the 73 with 30/32r gets 17 to 19 around town upper 20's low 30's highway with overdrive. I've always run my 75 at 28/30 and it was getting low 20's in town mid to high 20's highway prior no overdrive. Now with overdrive it's getting low 20's but the engine only has 400 miles on it since I just did a mild rebuild rings and all new bearings so I'm sure thats the cause. Runs great otherwise.

If your worried about wear get some chalk and make a line across the tread and drive in a strait line for a bit and check it for wear. If the center is gone your over inflated if the edges are gone your under inflated if the wear is even your gold.

 

[Nunyas]

now THAT is a good idea I haven't heard before....

 

[sultanoswing]

I run 32 front / 34 rear. Drives just fine, haven't gas-miled it, easier steering at lower speed.

The tyre shop I went to pumped 'em up to 40psi all around - WTF?!

In terms of over / under inflation, wear on the centre of the tread moreso than the edge means pressures too high, wear at the edges rather than the centre, too low.