I have been working on upgrading my 9" drums on my 65 Barracuda to disc brakes from a 74 Duster parts car (and going nowhere fast). One of the things that needs to be sorted out is to upgrade the speedometer pinion to keep my odometer reading correctly.

My car came with 6.50x13 tires, 2.93 axle, and an automatic transmission and my new axle has a 2.76 axle and obviously needs 14" or larger wheels. From what I have learned so far, my OEM pinion should have 17 teeth and the transmission output shaft should have 7 teeth (8 for V8 transmissions). The axle should have 41-14 (ring-pinion) teeth to get 2.93:1 ratio. The odometer should read correctly when the speedometer cable turns 1000 revs/mile.

Calculations:

• Speedometer ratio: 17 / 7 = 2.428571429
• Drive shaft turns/mile: 2.428571429 x 1000 = 2428.571429
• Tire turns/mile: 2428.571429 / 2.928571429 = 829.2682927
• Required Tire Circumference: 5280' / 829.2682927 = 6.367058824'
• Required Tire Diameter: 6.367058824' / PI = 2.026697769'
• Required Tire Diameter: 2.026697769' x 12 = 24.32"

Similarly, with a 2.76 axle (47-17 teeth)and a 17 tooth pinion, I would need a tire that is 22.96" in diameter. This would require something like a 185/60R14 tire but I would rather not use a smaller diameter tire than the 175/80R13 that is on it now.

Doing a quick search on the internet, I see that 16 teeth pinion gears are still readily available but this would mean I would need a 185/70R14, 205/65R14, 185/65R15, or 195/60R15 tire (~24.39"). With tire sizes getting larger and wider now, these 14" tires do not seem to be very common but the 15" low profile tires might look not look right on this car.

From what I could tell, the Duster should have been equipped with a 29 tooth pinion (13 tooth output shaft) that would have required a 25.00" tire (185/75R14). This would have corresponded to a D78-14 / 6.95-14 tire that would have been OEM on the Duster.

Ideally, going to a 15 tooth pinion (26.02") would give me a bit more flexibility in tire sizes. However, it doesn't look like Torqueflite Patty, Laysons, or Brewers Performance have any.

• Does anyone have photos of a similar car with 195/60R15 tires?
• Does anyone have any 15 tooth pinions for 1962-65 Torqueflites?

I have 2 spares-- but I do not think either are the 15 tooth I'll check -- one is natural & one is light blue--- ,Lawrence

Having just checked my service manual, it looks like the 15 tooth speedo pinion does not exist.

I see that for V8 applications, the FSM recommends using an 18 tooth pinion gear and PN 2464421 ratio adapter (0.8000:1) with 7.35-14 or 7.75-14 tires and 3.55 axle. This results in an effective speedo pinion gear of 22.5 teeth. So this would not be any help to me either.

It looks like I will have to either find a lower ratio axle (like a 3.23:1) to use larger tires or I will have to find a suitable tire/wheel combination (~24.39") with the 16 tooth pinion.

So ... would a 185/65R15 or 195/60R15 tire look out-of-place on a 65 Barracuda?

[quote="FrankRaso" So ... would a 195/60R15 tire look out-of-place on a 65 Barracuda?[/quote]

I'm considering using that or something close on my 65 Dart wagon. No pictures unfortunately.

These colors do not appear in my FSM. My guess is that they are for later model transmissions:

• Light Blue - 28 teeth
• Natural (Beige?) - 27 teeth

1962 - 1965 Speedometer Pinions

• 16 - Brown
• 17 - Orange
• 18 - Dark Purple
• 19 - Dark Blue
• 20 - Green
• 21 - Gray

Have you considered a ratio box?

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Too many people who were born on third base actually believe they've hit a triple.

Not until you just mentioned it. Do you have any recommendations?

I did a search last night on wheel upgrades and found some photos of cars with 15" rims.

DonC1965 posted photos of his 65 Barracuda's SSBC disc brake conversion which included photos of his 15x7 rallye wheels:
http://www.slantsix.org/forum/viewtopic ... 526#163526

Doc posted a photo of his 66 Dacuda that also has 15x7 wheels with 225/50R15 tires:
http://www.slantsix.org/forum/viewtopic ... 158#181158

It looks to me that a 185/65R15 or a 195/60R15 would look fine on my car. Going to 15" wheels will also give me the flexibility to upgrade to 12" (11.75") rotors later on.

No specific reco, because I have never needed one, but they do exist — they find common application in hot rods and other modified vehicles — and it seems a shame to constrain your tire and wheel options just because there are very few pre-'66 speedo pinion choices. I wonder if my favourite speedo repair shop (Deluxe Speedometer in Denver) might have them.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'm more interested in having a variety of tire products rather than a variety of tire sizes to choose from. The 185/65R15 is the standard tire on the 2008 Toyota Corolla while the 195/60R15 is the standard tire on the 2008 Chevy Cobalt so I would expect that there would still be a good selection of tires for these vehicles for many years to come. Obviously, staying with the 175/80R13 or 185/80R13 (-1.22% vs +1.37% compared to ideal diameter) would really constrain my tire choices because these sizes on their way to becoming obsolete.

The 185/65R15 would be more accurate than the 195/60R15 (+0.30% vs -0.75% compared to ideal diameter) and I'm looking forward to the improved handing of these these tires over my old 13" tires. I actually have a near-new set of Toyo 800 Ultras from a 1991 Honda Accord EX-R and 2 sets of 15" wheels (rusty) from a 1978 New Yorker so this might work out OK for me. I believe the 195/60R15 tires need a rim width of 5.5"-7.0" while the 185/65R15 tires require 5.0"-6.5" rim and I expect that mine are all 15x5.5.

For those people still using the SBP 13" tires, I think an upgrade to SBP 15" would also be a worthwhile consideration. In this case, with the standard 17 tooth speedo pinion and 2.93 gears, the 185/60R15 and 195/60R15 would still be good choices (+0.61% vs -0.44%). The 185 wide tire should offer slightly better fuel economy and ride while the 195 wide tire should offer slightly better handling.

Cragar - 344 Series Silver Rally
Wheel Vintiques - 61 SERIES CHRYSLER 5 ON 4" RALLYE (SILVER)
Wheel Vintiques - 48 SERIES CHRYSLER RALLYE 5 ON 4 (CHROME)

Frank, go for a bit wider tire, you won't be disappointed.

and BTW 65 Dartman=DonC, though last I heard that nice little cuda of his is going to his son in the Netherlands. He has the best collection of 65 A bodies of anyone I know. I tried to have him adopt me a few years back, but sadly that never happened

MJ

Frank did you ever decide which count you needed-- I have a 19 tooth in my garage-- I'll check Saturday on the count of the other 1--these came from 1962 -1965 transmissions that I have had/parted over the years, Lawrence

I was trying to go as wide as possible while keeping my odometer accurate. For any given axle ratio, the decreasing the speedometer pinion tooth count increases the tire size and the smallest pinion available has 16 teeth. Since I drive this car mainly on the highway, fuel economy is more important to me than acceleration. Keeping the 2.76 axle makes more sense than hunting around for a 3.23:1 axle.

This pinion gear and axle combination restricts my tire diameter to 24.39" (2.76:1 & 16) which is similar to the the original 24.32" (2.93:1 & 17). The trend in modern tires is to go larger and wider so there is a much smaller selection of 14" tires than the larger 15" & 16" tires. If you check the Goodrich Radial T/As, you can see that they are only offered in even aspect ratios (70 & 60) in the useful sizes. The only wider 14" tires that would work would be the P205/70R14 (off by 3.71%), P215/60R14 (off by -0.97%) and the P225/60R14 (off by +0.97%). The P235/60R14 would be off by +2.90%.

In the 15" sizes, I could also go to a P215/55R15 or a P235/50R15 (-0.342% vs -0.584%), but these tires do not seem to be very common. Since I already have a set of four P195/60R15 Toyos, I thought I might as well use them. With luck, my Chrysler NY 15" rallyes will still be round and they'll clean up OK.

I hear ya, the 15" wider sizes are getting hard to find as well, as you found. heck, you can choose something a nice percentage off and constantly exercise your brain by figuring our your speed +/- 2% I think you'd just be happier with 205-215 range instead of the 185 mentioned, but if you have 195s you might as well run them.

MJ

I expect that the P215/60R14 and the P225/60R14 Radial T/As offered by BF Goodrich should be available for a long time as these seem to be common muscle car tires.

I was able to find a P215/55R15 tire (off by -0.04% on 2.93-17 and -0.34% on 2.76-16) on the Kumho Canada site. Strangely, it doesn't appear on the Kumho USA site. I've hunted around a bit this morning and couldn't find any other manufacturers for this size.

The P225/50R5 used by Doc on his Dacuda seems to be much more common. On a 2.93-17 gear combination, it would be out by -1.9% while it would be out by -2.2% on a 2.76-16 combination. P235/50R15 and P265/45R15 would better choices but these seem to be non-existent.

As for the P185/65R15 tires, I'm not sure if most people would find them to be a poorly handling tire compared to the much wider 14" Radial T/As. After all, they were the standard tire on the Saturn SL2 and I found this car to handle well. The P195/60R15 was the standard tire on my 91 Honda EX-R and I found this car to also handle well. Any of the 14" and 15" tires would be huge improvement over the standard P175/80R13 and a quantum leap over the old 6.50-13 bias plies.

For those people pushing the performance of their early A-Bodies, wide tires would be worthwhile investment. However, many people have these cars as their summer cruisers and they might prefer the slightly better fuel economy of a narrower tire. In any case, adding sway bars would help to take advantage of the improved handing of any of the modern wider, lower profile tires.

As for exercising your brain, this isn't necessary anymore with the GPS navigation systems everyone seems to have nowadays. Speedometers aren't always accurate but it's useful for your odometer to be accurate.