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Author Topic: Tire sizes  (Read 946 times)

Offline Martin Michaels

  • Posts: 311
  • Thank you Mr. Earl
  • CLC Number: 26833
  • Name: Marty Michaels
Tire sizes
« on: July 13, 2014, 10:04:44 PM »
Hello all, what is the width difference between L78-15 and 7.00-15. My '47 came with a brand new set of L78-15,I tried to install my wheel shields and they would not fit. Thanks
Marty  CLC#26833
1947 6269  Cavern Green
1980 CDV D Elegance  White

Offline Bill Ingler #7799

  • Posts: 1651
Re: Tire sizes
« Reply #1 on: July 14, 2014, 12:33:58 AM »
Marty: If you have the correct 47 wheels on your car, measure 5 1/2 inches wide at this point on the rim( See picture below) and the correct 47 sombrero cap which is one year only. Identified by looking at the retainer on the back of the 47 cap. If it has one drain hole, it is the correct 47 cap. Two drain holes is a 48-52 cap and is a wider cap than the 47. The 48-52 wheel is a wider wheel for the 820x15 tire introduced for the new 1948 Cadillac. Please look at the second picture below which shows the clearance at the center of the cap with the fender shield using the correct 47 wheel and correct 47 cap. Also notice the clearance with the tire and the fender shield. You might have a 48 cap and 48 wheel on the car or a 48 wheel with a 47 cap to cause interference with the cap and fender skirt. In the case of a L-78 tire, that tire is about 1 3/8 inches wider at the cross section than the 700x15 tire but if you don`t have a problem with tire clearance and the shield using the L-78 tire then I would say look at your wheel and cap width.  Bill

« Last Edit: July 14, 2014, 09:42:28 AM by Bill Ingler #7799 »

Offline Martin Michaels

  • Posts: 311
  • Thank you Mr. Earl
  • CLC Number: 26833
  • Name: Marty Michaels
Re: Tire sizes
« Reply #2 on: July 14, 2014, 09:53:35 AM »
Bill, I know I have the right wheel because I have the latter sombrero it sticks out about a 1/4".The rubber is to wide 9 1/2" approx. The L78-15s that are on the car make it very hard to get the rear tire off had to pull on the fender.My question is I guess is that 1 3/8 less give me the clearance I need. Right now I can't take measurements I have the car apart for paint.
« Last Edit: July 14, 2014, 09:57:47 AM by Martin Michaels »
Marty  CLC#26833
1947 6269  Cavern Green
1980 CDV D Elegance  White

Offline Bill Ingler #7799

  • Posts: 1651
Re: Tire sizes
« Reply #3 on: July 14, 2014, 10:59:03 AM »
Marty; The increased cross section width of the L78-15 tire is why you need to pull out the fender to get the top of the wheel past the bottom lip of the fender. The second picture I posted above shows little clearance with the shirt even using the right size tire. So when you have the car jacked up, lug nuts off, pull the tire straight out to clear the studs and try to drop the tire straight down and away from the fender, the width of that L78-15 tire is getting caught between the drum and the lip of the fender. Been there and done that so I know where you are coming from. My advice would be to sell those new L78-15 tires and get 700x15 tires which are the correct tires for the car.

Consider what might happen if you keep those L78-15 tires on the car and are out driving the car and get a rear flat. Using that suicide jack supplied by Cadillac for the 47, you manage to get the car jacked up to what you think is high enough to drop the wheel, but you find that is not high enough the get the wheel to clear the fender even with your pulling out the fender, plus now the jack won`t get the car any higher. You have the tire stuck between the drum and the fender. Need I continue the story?     Bill

Offline Martin Michaels

  • Posts: 311
  • Thank you Mr. Earl
  • CLC Number: 26833
  • Name: Marty Michaels
Re: Tire sizes
« Reply #4 on: July 14, 2014, 09:37:14 PM »
Thanks Bill, I'll be ordering up some new rubber when I get her back from paint. I found out this problem last year coming home from a show and had a blow out on the thru way that was fun but when I tried to start it back up at 90 out side and left the hood down, the vapor lock gods got me that was a fun day.
Marty  CLC#26833
1947 6269  Cavern Green
1980 CDV D Elegance  White

Offline Raymond919

  • Posts: 191
  • CLC Number: 26141
  • Name: Ray Schuman
Re: Tire sizes
« Reply #5 on: July 15, 2014, 09:08:56 AM »
Gentlemen, sometimes what's apparent is not obvious. When I first got my car I brought it to a repair shop to have all my L78 tires balanced. The technician raised the car by placing a lift under the rear axle. He was unable to remove the tire due to the tight clearance between the drum and the lip of the fender. He was momentarily confused until I suggested he lift the car by the frame instead so the rear axle will 'hang' giving him more room. It was a 'duh' moment for him. I doubt this is your problem but just thought I'd mention it. By the way, I didn't return to that shop.
Ray Schuman
#26141

Offline Bill Ingler #7799

  • Posts: 1651
Re: Tire sizes
« Reply #6 on: July 15, 2014, 10:37:25 AM »
Ray: After that story it brought to mind an incident changing a tire coming back from a show in California. Five of us in 40s Cadillacs had just finished climbing a long grade east bound out of Blyth, CA when at the top of the grade my right front tire blew. Since I was leading our convoy I pulled onto the berm and the other 4 cars parked behind me. Before I could even get out of the car, someone had the trunk open, someone had the jack and someone had the spare. In a matter of a couple of minutes the tire was changed and we are putting the jack and tire in the trunk when a state trooper pulls up and wants to know why five old cars are parked beside the road. I said I had a flat tire and he said that it doesn`t take five people to change a tire and you are causing a problem because all the traffic is slowing to look at the cars. After his lecture to all of us on not having all cars to stop to fix one tire, I said to him to think of it this way. Without any help I would have been here 5 times as long which would have slowed traffic 5 times longer than it did. That is one of those times when you look back and say why did I not keep my mouth shut. His mouth opened and I thought I just earned a ticket of some kind when he then smiled and said  "Have a good day" and left. Old cars are sure fun     Bill 

Offline 59-in-pieces

  • Posts: 1472
  • CLC Number: 17326
  • Name: S. Butcher
Re: Tire sizes
« Reply #7 on: July 16, 2014, 11:44:03 AM »
Bill & All,
If I might apologize for all Cali. folks - assuming you were on our side of the boarder on your way home - meeting one of our finest, Highway Patrol officers sounds like the DUH moment.  No offense to the cop (probably drives a Lincoln), just making light of the circumstances.
By the way, you know I'm doing my first 47 Cad rebuild, and I'm starting to hear more stories about "BLOW OUTS" not just flats on 47 cars.  These cars are not known for traveling a warp speeds.
Anything to worry about or just bad luck.
Have fun,
Steve B.
S. Butcher

Offline Bill Ingler #7799

  • Posts: 1651
Re: Tire sizes
« Reply #8 on: July 16, 2014, 12:49:21 PM »
Steve: East bound and at the top of the grade past Blythe, I think puts me in Arizona so it must have been our state trooper. My problem was not the tire but the valve stem which let loose from the tube. A freak happening and those bias tires and tubes are long gone since I now have Diamondback radials on the car. Properly restored, and I know yours will done correctly, the 47 is a very reliable car. That is not to say that if you go on some car tours you should have some spare parts in the trunk. It is the wise 40s Cadillac owner, regardless of your thoughts of touring or not touring, that puts spares on the shelf like, water pump, fuel pump, regulator and coil. Of all the tours we have been on since the mid 80s, I have not needed any of the parts I mentioned above, it has been the small items like turn signal flashers, light bulbs and the item that has failed the most, the brake light switch. If you buy some spare brake light switches try to find some NOS Delco or Ecklin or some other old NOS make brake switch. I never have had much luck with those shinny new brake light switches you see on ebay.  Bill   

 

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