Tire Sizes

[LAS VEGAS DAVE]

I've decided that I want a bigger tire on my car then the size it has. The stock size in 1938 was a 650/16 tire, of course they didn't have radials back then. When I bought my car in June it still had the original tires on it which were 77 years old with only 18000 miles on them. Since I wanted to drive the car on a regular basis I bought new tires. I was told that Coker made a radial tire with a wide white wall that looked like a bias and so a set was purchased with new tubes and had the dealer that sold me the car install them before he shipped the car to me. Now I wish that I would have bought 750/16 instead of 650/16 even though it would mean that the car would lose points if it were in a AACA show. I don't care about that since I mainly just like driving the car. In any case the tires were 280.00 each and new tubes and taxes put each tire at about 325 dollars. I ordered a set of the 750//16 wide white wall tires today and they were even more, over 1600 dollars. If someone on the Pre War Buick site would like to buy the 650/16 tires I will sell all four of them with the new tubes for 600 dollars and ship them to you at cost. I paid eighty dollars to have my new ones shipped to me. The tires still are like brand new and still have the titties sticking out of them. The white walls are still flawless. I like the way the larger tires look as they will fill in the fender well better and give a slightly higher overall rear axle ratio. 

Edited October 20, 2015 by LAS VEGAS DAVE (see edit history)

[Dwight Romberger]

Good move Dave.

When something like that bothers me, the only solution is to change it.

Every time I would look at the car, it would be all I would see.  Even if no one else even notices it.

Be sure to let us see some pics!!!

Dwight

[LAS VEGAS DAVE]

Good move Dave.

When something like that bothers me, the only solution is to change it.

Every time I would look at the car, it would be all I would see.  Even if no one else even notices it.

Be sure to let us see some pics!!!

Dwight

 

You and I are the same. I would just keep saying to myself that I wish I had the bigger tires so instead of that I'll just get them and deal with the finances. I'll take some pictures after I get the new ones on the car. 

[suchan]

I had a 38-41 that came with a set of 215-85/16 radials, the rough equivalent of 7.00-16's. They looked and worked great, the only problem being the tires would rub on the front fenders in sharp turns. 7.50's would be about an inch taller, so you may experience the same.

[LAS VEGAS DAVE]

I had a 38-41 that came with a set of 215-85/16 radials, the rough equivalent of 7.00-16's. They looked and worked great, the only problem being the tires would rub on the front fenders in sharp turns. 7.50's would be about an inch taller, so you may experience the same.

I think there is clearance but I will know for sure next week. Maybe I'll put the new tire on the front before I put it on the back and if it rubs I will trade the 750R16 front tires for a 700R16 or keep two of my present 650R16 tires on the front, hopefully the 750R16 tires will not rub, I'll post the final results. Even though they are a little over an inch taller than what I have it will only affect the clearance by one half an of that since the radius not the diameter is the measurement thats critical.

[Dwight Romberger]

a 1/2" lift kit should not be too hard to come up with.

Of course the judges would take points off.

[LAS VEGAS DAVE]

I turned my wheels to the spot where I would have the least possible clearance and as far as I can tell it looks like there won't be any problem. As far as judges go they will deduct points anyway because the tires are the wrong size. Most likely I'll never enter this car in a show to be judge. It did win an archiveal award in 1990 at a national BCA meet. As far as I can tell its the only 38 Special to have ever done it and it wears the badge on the grille. It was out of the Lewis Jenkins collection and he put it in that show. He owned the car over 32 years until his death when I got it. He probably wouldn't like the overdrive or the new tires as he still had the original tires on it when I got it. The problem is that Lewis was a collector with a museum and I am a driver with only one old car so I'm glad it got the award but now its getting the miles.

[jenz38]

For me its important to have in front a low center of gravity. In curves the car will push to outside about the front tires, because of the heavy front and the (softy) bias 6.50-16 tires.

I cant imagine to drive the car with yet higher 7.50-16 in front in curves without slowing down the car ahead of a curve.

For better drivabilaty (and because of this exploding costs ) i will switch over to radials in 215/85R16 in rear and 205/80R16 in front.

Then of course without WW, but this is OK for me.

[C Carl]

Hi Jenz ! The problem you speak of has nothing to do with high center of gravity. The miniscule difference in C.G. height caused by a slightly taller tire is undetectable in the real world of handling. With cornering considerations , slip angle is of great importance. Radial tires have a very low slip angle. In general , a high pressure radial has even less slip angle . Directional high pressure radials , better yet. Because I am late for something , I will elaborate later. Feast your eyes on this Michelin LTX 235/75 R15. It is on a '76 Cadillac Eldo Conv. I believe it is the fastest such Cad in the world. I'll tell you why later. - CC

[LAS VEGAS DAVE]

Unless I somehow enter a road race I don't think the cornering will be a problem.

[jenz38]

Your absolutly right carl,

what i mean is to keep the car low with 6.50 or 205/80 in front...;-)

and im courios about your cadillac experience

Dave,on our small twisty country roads its not unimportant to have good directional stability

tires while passing other cars fast

[LAS VEGAS DAVE]

Jenz, I realize that its important but with the car less than 1 inch higher than a stock car and with even a little wider tire than a stock tire I doubt there will be any difference in the way the car handles with a 750 verses a 650. Both of these are radial tires which should also improve the cornering characteristics slightly over a bias tire anyway.

[C Carl]

Dave , Jenz , Dwight , Suchan and all : You just can't have handling that is too good ! Not only for the pleasure of feeling a car doing what it should , but also the increased safety in an emergency. I have been using radial tires for quite a large range of applications for over 50 years. Radial tires have a very wide range of operating inflation pressures. This allows you to tune them , and by extension your suspension , to road ( or off-road) , conditions and velocities. I used to drive all over this country , but am lucky to have done most of my driving in the West , where wide open spaces have roads which are seldom used or patrolled. My driving specialty was covering long distances at sustained high speed. I particularly enjoyed the challenge of high speed driving on and off road in Mexico and Central and South America. I have established long distance elapsed times considered impossible by the professional high speed V8 Ford collectivo drivers in The Andes. I was also the driver of choice by U.S. and British embassy personnel for various weekend mountain climbing expeditions. This required my full-time 4-WD Blazer with automatic trans and rear locker to get trough difficult traction situations , both up and down the access routes. High speed to get to our mountain , and off-road as far as could be driven. Such experience helped me design a '71 Eldo convertible Cadillac off road Baja cruiser. I believe I have covered certain technical aspects of this car elsewhere , but for our discussion here today , let me just say it stands tall on a modified suspension , 17.6% greater cross section torsion bars , taller coils in the rear , 17% greater cross section with air bags to tune for proper F/R spring rate ratio and load. Wears 33" BF Goodrich All Terrain Radial TAs. Loaded for adventure , she tips the scales at 6200-6400 lbs ! Lots of tools , parts , extraction eq'p't , survival and camping gear , toys , and dual spares mounted on the trunk lid chained through a 5 gal. Jerry can locked to the rear bumper. The monster is very carefully loaded , some heavy compact stuff like 200' of 3/8 galvanized cable and associated chains and snatch blocks locked to the R.F. seat mechanism lie on the rear floor. Heavy tool box also chained to the pass seat , tucked close in the well. Heavy stuff securely lashed in the engine compartment. Fore/aft balance is very important. High/low polar moment of inertia considerations will have implications. I suppose we could cover aerodynamic factors at speed , like the need for maintaining center of gravity ahead of center of pressure ( model rocket guys know that one). But for now l am here to tell you that the design was a success. Credit must be given to Bill Monague of the old Off Road Chassis Engineering in So. Cal. Those old Cadillacs are much tougher than their freeway flyer status would lead you to believe. It would almost be easier for me to tell you where that thing has not been in Mexico than where it has. It has traversed a rock garden that high clearance trucks feared to crawl. It saved us when I entered a sweeping left hander and encountered a bus coming at me partially in my lane. With woman and child aboard , I firewalled it and let the 514 cubes ( .050 over) , pull me through a safe line. The top was down as we barely missed , and I still remember those chrome lug nuts on his Alcoas whirling past so close to my head. The thing could roll down the line at over 100, hour after hour to get through the North Mexican deserts. All this on the big radial 33" BFGs. Yeah , a real success. Ask me about it sometime !

Well , that abbreviated intro was a set up to tell you about the slightly larger tire you see in the earlier posted pic. From what I learned from the "Off Roader" , I gave the '76 a light touch. Gas shocks at the corners , air bags in the coils , urethane bushings for the sway bar , and above all , the tires. About the same oversize as 'Vegas is mounting up. But , what gives my mods on this car the high speed handling advantage is the huge operating pressure range allowing me to pump up the fronts for a low slip angle. These light truck tires carry a max load rating at 50 psi. For high speed and handling I ran the fronts at 45-47 psi. The rears don't do anything other than follow on these front wheel drive cars , and can carry 30-35 psi at speed , depending on load. Around town these pressures come down to say 36 psi front , and low to mid 20s rear , depending on load. Now looka here. I reckon that in my prime I could drive one of these FWD stockers as fast as anyone. I was still pretty good when I did this to the '76. ( Was it 20 years,ago ?). The cars handling at that point then exceeded my abilities ! The faster you drove it , the better it behaved ! I did something I hadn't done in years. I scared myself ! I backed off , and never again tried to test its limits. Now THAT is why I call it the worlds fastest !

All right , my treasured cyber friends. So I did the same above light touch to my '76 Fleetwood. The tires were 44 psi radials. Huge difference. My '95 Fleetwood simply rides on 44 psi Hankooks. I pump 'em up just a bit for the road. It feels a little like it is standing on its toes for a while, but once you "get it" , you really appreciate it. These are cars that enjoyed sustained 100 or just a bit more. Late 20th century Cad sedans merely need to be fitted with the very most expensive highest pressure directional tires you can find for the front. Forget the rear. I have driven my thusly equipped '93 so hard through a corner that I flung the rear end out with my go foot on the firewall ! Like Speed Channel footage of FWD rally cars ! Always wanted to do that on a Cadillac ! Check that one off the bucket list. Stabilitrac and Stabilitrac 2 equipped STS and DTS Cadillacs are superb handling cars , with or without the very best directional radials. 21st century cars generally handle so well that they really do not need anything. If you feel they are a bit mushy in any way , you know what tires to give 'em. If you want the advantage of increased handling and safety on your old cars , consider the appropriate high pressure light truck radials. They might look somewhat different for a while. By and by , you will come to love them. They look like they mean buisiness , and identify you as a cruiser. Not for everyone , I will be the first to admit.

Seems I am forgetting something , but I have been on this longer than I intended. I have enjoyed tapping this out , and I hope all who read it enjoy it. For those who don't , who may be appalled , or law enforcement officers , E.M.T. personnel or others who have had to deal with the tragic results of automobile accidents , I merely offer : When I drove fast , it was in remote areas in daylight , never driving beyond my visibility. My eyesight was 20/15. Always on roads that were not going through animal or bird habitat . The only little animals or birds I have hit were at or under the speed limit. I hit one deer who jumped right in front of my car at dusk. I had just slowed down to under the speed limit. In Washington State , you can not keep road kill , so I very reluctantly left it. I slow WAY down in areas where deer or other animals are a known hazard at night. Like Key Deer on Big Pine Key , or on 299 west of Austin , Tx. I have never had a ticket , accident , or incident at very high speed , say 90+. Lots of people drive steadily at 85 or so around these parts. These days they generally pass me at 10 mph or more than I am doing. I think my youthful years of fast driving has made me a better driver , now that I am old. I have suddenly driven through at least 4 high speed multi vehicle accidents on the freeway. I have got through them safely because it all just looks like slow motion to me.

I do have a couple of fairly fast Mercedes Benz cars. A 2007 E550 , and a 1998 V12 SL600. I do run them up a bit from time to time in remote safe locations. 2 weeks ago I went out to the racetrack. I completed a Mercedes Benz Club Safe Drivers - Safe Families program. Take such a course. Go sharpen your skills. I leave you precious people with a tip I learned that particularly older drivers may well not know : Some people do and do not know how to adjust their rear view mirrors. I thought I knew. I was wrong! We all know to adjust the inside rear view mirror until the reflection of the rear window is centered in the mirror. Correct ! But many of us adjust the outside mirrors so we can just barely see a bit down the side of the car. No ! Not quite ! What you must do for the drivers side outside mirror is lean left until your face is almost touching the window glass. It is from THAT point which you adjust to barely see down the side ! And for the opposite side wide angle mirror you must adjust it from the middle of the car ! Put your head in a line with the inside rear view mirror. At that point , if you just barely see down the side of your car in the right side mirror , your mirrors will now be adjusted properly. You will have complete overlapping coverage . It will eliminate blind spots ! It takes just a bit to get used to. Check it at night on the freeway. You will see an overtaking car in the lane next to you in the inside mirror. It will move to the left. Just as it leaves the mirror , you will see the lights picked up on the inside of the left hand mirror. As it passes out of the field of the mirror , you now will see it in your direct vision. As you pass a car on your right , it will also smoothly transition , always visible. Try it. I have had visibility difficulties because of blind spot . I might have caused an accident. Maybe you too? Other people I have told this to have said they have almost caused an accident because of blind spot issues.

And there you have it . Something for everyone. And radials. Some better than others for handling. Try the best high pressure tires. Experiment a little. Try 80% - 90% of the max load bearing pressure. You may see most of that mush disappear. Let the car be all it can be. A bit like putting higher compression pistons in your old '30s OHV car. Or sticking an overdrive in it. - Carl

[LAS VEGAS DAVE]

Today was a good day. The new tires arrived and are now mounted. There is no problem with clearance at the front fender which I was little worried about. The back tires have to be slid in at an angle and once under the fender they then can be turned slightly and go right on the drum. These are 750R16 with a 4 inch white wall. The tires are 8 inches wide and have a 31.14 inch diameter. They feel great driving the car and they don't have as much of a flat spot where the tire touches the ground as the 650R16 tires did. I like the way they look as they fill the fender wells better. I drove it on the freeway at 65 mph and it was perfect in my opinion. The engine is turning a lazy 2174 rpms at that speed which is exactly where I like it. I drove the uphill route on the freeway at 65 for ten miles and the engine loved it, on the return it was downhill so it was nothing to go 70 mph, but it likes 65 so thats where I drive it. Around town I don't use the overdrive but the larger tires also help the stock gearing do a better job when not in overdrive. I'm going to add some pictures so you can see how they look. Another good part about today is that I sold the tires that I took off for 600 dollars, the guy got a great deal and it helped a little with the cost of the new ones.

Edited October 27, 2015 by LAS VEGAS DAVE (see edit history)

[Dwight Romberger]

[SBRMD]

Dave, your car looks excellent with the new tires, enjoy!

 

Carl:  Very much enjoyed reading your post.  This is going a little off-topic, but here goes: given your background and opinions on radials for old cars, how do you stand on mounting state-of-the-art radials on the old cars' "original" wheels?  This is a topic that has been touched on from time to time with differing opinions.  I have the Goodyear wide-white radials, 235/75-15, on my '49 Roadmaster's original wheels.  They feel great, but I sometimes wonder about the safety angle as has been discussed by others.  Interested in  your opinion.

 

Thanks in advance,

Steve in Mpls.

[C Carl]

Thank you , Steve , glad you could get through all my yapping. I hope Jenz is able to work through it considering the possibility of some idiomatic dropout. I do not know the safety vulnerabilities you refer to , could you please give me a link to the threads which have debated this safety aspect ? Also , precisely what might be the potential danger in your particular application ? I have mounted radials which have been a significant mismatch to mounting recommendations , but you have some concerns I would like to know more about. I will be happy to give you some examples of the indecent liberties I have taken , and the discussions that preceded doing so. Also , the benign results of having done so , in spite of the wide range of inflation pressures over radically different conditions. Your extremely important safety concerns seem right on topic to me. I am curious. By the way , 'Vegas Daves application looks perfect to me , and definitely indicates he is a real cruiser. Thousands of miles of great roads through nearby wide open spaces await ! Just in time for the cool weather !

ALSO : ALL OF YOU WHO DO NOT NEED OR WANT TO READ MY PREVIOUS LONG POSTING , PLEASE DO READ MY COMMENTS ABOUT REAR VIEW MIRROR ADJUSTMENT TOWARDS THE END. IT WAS A REMARKABLE NEW TRICK FOR THIS HIGH-MILEAGE OLD DOG ! SEEMS THAT SHOULD BE POSTED WHERE EVERYONE WILL READ IT. THE LIVES IT MAY SAVE WAS OBVIOUSLY WORTH THE DAY AND $80 I SPENT LEARNING UP AT THE TRACK. Woof , woof , old dog , Carl

[LAS VEGAS DAVE]

Dave, your car looks excellent with the new tires, enjoy!

 

Carl:  Very much enjoyed reading your post.  This is going a little off-topic, but here goes: given your background and opinions on radials for old cars, how do you stand on mounting state-of-the-art radials on the old cars' "original" wheels?  This is a topic that has been touched on from time to time with differing opinions.  I have the Goodyear wide-white radials, 235/75-15, on my '49 Roadmaster's original wheels.  They feel great, but I sometimes wonder about the safety angle as has been discussed by others.  Interested in  your opinion.

 

Thanks in advance,

Steve in Mpls.

 

Steve, I think you might be referring to something I read somewhere that our old wheels might crack if radials are mounted on them. That may be a possibility but going by my own previous experience over the last 50 years I think its unlikely. I'm 73 and started owning and driving hot rods at 16 in southern California. All the guys I knew were into hot rods. Over the years we all put radial tires on our old car rims after radials hit the market and drove the hot rods much faster and crazier then I do now. I never cracked a wheel or heard of anyone else that did either. I think if the old wheels aren't rusty or damaged they will be just fine. The old Buick wheels were made when there was terrible roads with many being not much better than dirt if they were even paved. There are many people that would argue that these old cars are not  safe even if the wheels were kryptonite, after all there don't have impact bodies or impact bumpers or seat belts or safety glass and on and on and on. I still ride motorcycles and feel fine on them so radial tires on my old wheels don't make me lose any sleep. By the way Carl I'm going to adjust my mirrors the way you described on my pick up truck today and see how it works out. The old Buick doesn't have any side view mirrors and I have to turn my head sometimes because of that, oh well, no turn signals either and I don't know if people even know what my hand signals mean any more, even if they do when I drive at night I don't think they even see them. I have to look carefully at the car behind me when turning or stopping to try to determine if they also see that I am stopping or turning. 

[SBRMD]

Carl, Dave's last post succinctly states the concern that's out there, namely that the higher laterally-oriented forces generated by radials can cause older wheels, which presumably weren't engineered to withstand such forces, to crack or separate under stress.  I tend to think of this issue as sort-of an "urban legend", but it has been debated on the forum here and there.  I will try to find the threads and post them when I do.

 

Dave, I think your point that original Buick wheels were built beefily enough to handle the rough roads of the times is a well taken one.  Also, it could be that the so-called radial tire induced wheel separations have happened in the setting of original wheels from other makes which didn't specify as stout of a wheel as Buick did (just speculating).  Similar to the valve seat-recession issue with unleaded gas in old cars, which upon further examination seems to not be an issue for Buick, with it's higher-nickel content valve seats.

[LAS VEGAS DAVE]

Carl, Dave's last post succinctly states the concern that's out there, namely that the higher laterally-oriented forces generated by radials can cause older wheels, which presumably weren't engineered to withstand such forces, to crack or separate under stress.  I tend to think of this issue as sort-of an "urban legend", but it has been debated on the forum here and there.  I will try to find the threads and post them when I do.

 

Dave, I think your point that original Buick wheels were built beefily enough to handle the rough roads of the times is a well taken one.  Also, it could be that the so-called radial tire induced wheel separations have happened in the setting of original wheels from other makes which didn't specify as stout of a wheel as Buick did (just speculating).  Similar to the valve seat-recession issue with unleaded gas in old cars, which upon further examination seems to not be an issue for Buick, with it's higher-nickel content valve seats.

I think there's lots of things that we hear about that are blown out of perportion in the automtive world today. Types and kinds of oil, leaded gasoline, tires and tire pressures, how hot or cool should the water temps be, how much zinc is enough in oil, what weight oil is best, these are some of the subjects that comes to mind. They're all interesting subjects that many of us have an opinion about but in the long run it seems that no matter what oil, what tire, what gasoline etc the cars seem to run just fine and unless we crash them they'll most likely outlast us.

[C Carl]

After giving this some thought (I might also have heard this a long time ago , if I did I did not take it seriously) , I lean towards discounting it. Wouldn't mind reading debate , though. Anecdotal evidence might reveal weakness in an improperly designed brand X wheel which had fatigue issues. Although engineers knew something about unsprung weight implications , you can see from the mass of components under your old vehicles that skimping on materials generally did not happen. Many old cars look almost like some agricultural machine down below. In fact , as 'Vegas says , to some degree they had to be ! So in general , it is unlikely that the wheels would be under designed , or to have been the sacrificial weak link to what end ? Reduce unsprung weight ? Lacking whatever modern engineering tools like Nastran or finite point analysis , or you engineers tell me what , could some mistake have been made ? Maybe , but those vulnerable wheels would have a recognizable fragility resulting at best in a limited service life. I so , could the slightly higher lateral , and potentially , braking loads (in general braking puts greatest loads on wheels) , accelerate fatigue in a poorly designed wheel? Would that mean that running radials for 90,000 miles would risk failure on a wheel by mistake designed to last only 100,000 miles ? Maybe. The wheels I run last WAY more than that , unless they hit something pretty hard. Modern larger diameter wheels with modern hard, low-meat "rubber band" tires have less protection from road hazards than older generation wheels and tires. Ride harsher too. Look a bit too modern (a bit goofy) to an old guy named - Carl

[Ben Bruce aka First Born]

  I am 79, [almost], . My first contact with a Buick was in 1948, helping Dad on a 1932 that had a broken axle. Most of my growing up years, Dad drove Buicks. Anything else was 2nd best, at most. I have owned several Buicks. In the time period radials came out, I worked in repair/tire shops a lot. NEVER have I seen a broken Buick wheel. NEVER have I seen any wheel broken by a radial. I now have a 1950 with the original wheels with radials mounted. Seven thousand miles and counting.

 

  Ben

[LAS VEGAS DAVE]

  I am 79, [almost], . My first contact with a Buick was in 1948, helping Dad on a 1932 that had a broken axle. Most of my growing up years, Dad drove Buicks. Anything else was 2nd best, at most. I have owned several Buicks. In the time period radials came out, I worked in repair/tire shops a lot. NEVER have I seen a broken Buick wheel. NEVER have I seen any wheel broken by a radial. I now have a 1950 with the original wheels with radials mounted. Seven thousand miles and counting.

 

  Ben

 

I have never seen ANY wheel break by radial tires either Ben, I doubt anyone you or I know has seen that happen either. Guys been mounting radials on their old cars stock wheels since radials first came out with no problems and that was the days when most of the old cars were just transportation, not really collectable.