What radial fits a 6.7x15

[DutchEdwin]

 My 1955 plymouth plaza suburban has 205/75R15 tires on it. My problem is, the speedo meter is giving to low speed.

So I want to change to a larger size.

Doing my home work: the shop manual says the tire on the car is 6.70 x 15 bias ply (or 7.10x15 (spec. Equip.).

When I bought the car 205/75R15 radials were on it. So I do not know which of the two is the correct one. Can anyone tell whatr car had the 7.1x15?

 

I want to have wide white walls about 2.5 in. Comming from the 6.7x15 tire:

When I calculate the diameter of the bias ply tire, (in metric) it is : 15x25.4 + (2x6.7x25.4) = 721.3mm

When I calculate the radial tire: 205/75R15 : 15*25.4 + (2x 205 x 75%) = 688.5mm. So yes, is giving me the to low speed because of the smaller diameter.

 

The closest to mach the diameter is 225/75R15. : 715mm diameter.

My question is: does this tire fit my 4,5 rim and does it fit in the rear and front fender.

What else to considder?

 

. That gives the Coker (€262), American Classic (€302) or BF Goodrich (€350)   each tire. (the bias ply from Coker costs €212)

Please advise.

 

Thanks, Edwin.

[Dave72dt]

Speedometer measures driveshaft revolutions.so I would think with the smaller tires it would be reading higher than what you are going.  With the shorter tires it will take more revolutions to go and actual mile or km.  Someone at some time may have changed the differential gear ratio or the transmission was swapped from a car set up for a different ratio.  Bigger tires will mean it takes even less revolutions to go that same distance.  That's my reasoning, anyway.  and I could be all wrong.

[busycoupe]

Smaller tire diameter should make the speedo read higher compared to the speed measured by a GPS. However, your problem may be with the speedometer. I believe that many of the speedometers in our cars read low, perhaps from dried oil and/or dirt in them. You might try a couple of drops of light oil in the oil cup on the back of the speedometer.

[DLK]

215/75/15 is a close match to your tires in diameter and doesn't present the width issue on the rears that wider tires do.  I have 225's on my 50 Dodge and they slightly rub around corners. That isn't to say your car will have that issue.  Any of the sizes including 225's will fit your rims just fine.

[greg g]

I would think the up model cars got the wider tire, the skinnier one for the savoy and lightly optioned Plazas. Would surely think that v8 cars got the larger tire. I am running 225 75 15 on 5 inch wide aftermarket wheels. My speedo still reads 3/4 mph faster than road speed according to GPS. I did get some tire/fender rub with a loaded trunk on sharp turns, but recent new spring bushings, and rear shocks have addressed that. I do not know if 235s would fit but my fenders are different than your 55.

[ChrisRice]

I run 225 75 15 on my '55 Plaza with no clearence issues at all.

[50desotocoupe]

also, check with Diamondback Tires as well.  I have heard very good things about them.  I bought a set of wide whites from them in August, 225 75 15 and shipped to my house they were $876. 

[DutchEdwin]

Sorry, I mixed up the speed. My bad. The speedo give to high miles for the speed. At 50km it should be 31 miles, reads 35+ miles. Sorry, my bad. Must have been the late hour.

I called a tires shop for classic tires. They told me two things: 225/75R15 would give me very hard steering. My Plaza does not have power steering. 

Also there is a new tire on the market from Coker: bias ply sized radial tires, http://www.cokertire.com/brands/american-classic-tires/american-classic-bias-profile-radials.html

Expensive although, €310 each. In the US "only" $247 = €200.

What they told me is that Coker bought the old tire moulds from Firestone etc. and is now producing radial tires with bias ply looks. It solves the speed issue.

Chris, thanks for sharing. How is the steering at low speed and parking?

[Dave72dt]

Turning the steering wheel while the car is dead still is something we've become accustomed to doing with modern power steering. Little old ladies that looked through the steering wheel instead of over it could drive these old cars. They did it by having the car moving when turning the wheel. Even creeping along will reduce the steering effort tremendously. Just a matter of relearning an old driving technique.

[greg g]

Leave your 205s on the front, put the larger ones on the rear,save a bunch of euros.

[DutchEdwin]

Greg, I thought of that, but I'm not shure about the looks. I do not want it to look like a bad try of a hot rod.

[ChrisRice]

Mine is the 4 door wagon and steering is surprisingly easy. Mine also does not have power steering but drives almost as easily as one that does.

[greg g]

I run the set up on mine it is hardly noticeable with blackwalls. Probably less so with wide whites. You could always order up another pair if you didn't like it.