Gearing for 16 inch wheels

Paul63

Paul63

New member
Hi everyone - this is my first post on this forum which has I've found to be a fantastic resource, and I'm very grateful to all who have contributed to this site. Anyway I bought an older restoration 31 coupe - it has a healthy engine and is pretty much stock except for its 16 inch Kelsey wheels. Since the smaller wheels lower the gearing, I'm looking for a way to calm the rpms and raise my cruising speed. The various overdrives are outside of the budget I've set aside so I've looked into final gearing. It seems that the 3.27 gear is too tall for most folks, but with the 16 inchers it should give me an effective gearing of 3.43 (according to: http://www.wallaceracing.com/gearcalc1.php putting in 29.8 for original tire diameter and 28.4 for the 6.00 x 16s I have on now - figures I found on this site ) which would split the difference between 3.54 and 3.27 and allow cruising at healthy rpm levels between 55 and 60 mph(?). I'm thinking I would install a Snyder 5.5 and something like a Stipe IB330 camshaft to make up for the loss of power and low end grunt. However I'm new to all this and would greatly appreciate some opinions before spending money on stuff, in terms of benefits and limitations. My goal is to lower my rpms for touring up to +50 mph, in areas where I might encounter moderate hills.
 
Paul
Look into a 3.54 R&P. The cost is the same as a regular 3.78. They may or may not be available used in the UK but they are more available in the USA. All the parts houses carry new ones.

Vic
 
Hey Paul,
I'd keep the 3.27 as they seem to be the most expensive to obtain. Also, in the coupe that I had, 3.27 whith 20" rims/tires....ran along just great, without any mods, other than a 5.5 cr head ! Wished I'd have kept that gear set. I have 3.54 now in my '30 roadster with 16 inch rims/tires, with hot B engine and seems to pull tooo many rpms to get along at higher mile per hour.
 
Thanks everyone - Vic, my car is in the States though I'm curently overseas so I'd be buying parts in the US. I should have emphasised that the car has the original stock 3.78 gearing and I'm considering 3.27.

Tom- would changing the head alone as a stop gap measure increase cruising speed?

Hardtimes - am i right in assumming that putting in a 3.54 with 16" wheels would be would be similar to 19 inch wheels with 3.78? that's why I'm looking into the 3.27 to gain an improvement in cruising speed.
 
Hi Paul

I put a 3.27 rear end in my 29 CCPU (B motor, Winfield head, cam, 97 carb and Mallory dual point) and am very pleased with it

At the VHRA speed trials on Pendine Sands (once the fastest place on earth) in 2013 it pulled 69.87mph on 21" wheels with 4.50 profile tyres (31" approx diameter). Using the Wallace calculators above I worked out it was turning 2411rpm. This year, thinking I could get a few more revs out of it, I changed to 16" wheels with a 6.70 rear tyre (28.62" diameter). Went 3 mph slower, but windier and course wetter.

If you want to do some more maths, tyre diameters can be found on the Northants Tyres website for most popular sizes

http://www.northhantstyres.com/main-tyre-pages/firestone-vintage-pages/670-16-firestone.html

Cruising speed is a comfortable 50mph. Having drop into second for roundabouts the only downside.

Head alone will make a noticeable difference, but cam and carb as well will really wake it up. Don't forget ignition. And brakes. Sammy at Arizona Model A is a source for the 3.27 gear and modern distributors.

Cheers

Juggs
 
My 29 had 16's on it when I bought it also. I ran it that way for 5 years and was always considering doing a gearing change to make things better. She was wound up pretty tight to run along at 45 and first gear was a stump puller. This past fall, I came across a deal for 5 wire wheels, stock 21", and I made the jump. Powder coated in Tacoma Cream and new Lester tires, the car now runs so much better. The ride is better, the speed is better and the car actually gets much more attention. All good. Just a thought...
 
My stock 28 will probably do 60, but I like to travel no faster than 45. If I wanted speed I'd drive modern. I'd like to install the 3.27 gears to slow the engine speed while doing 45. The higher compression head probably wouldn't add much top end speed, but would add the extra power needed to use a lower ratio gear set.
 
If you are only planning on running 50 mph, you are talking about spending a lot of money for no good reason. What you have will work.
Like Tom said, you'd probably see the most benefit from the high compression head. No change in the cruise RPM, but a little more power everywhere.
As a general rule, you can figure about 100 rpm for every 10 points on the gear.
So, the difference in a 3.54 and a 3.27 is only about 300 rpm (270).
Another thing you could consider is getting some 7.50 X 16 tires for the rear. You will get a slight decrease in your cruise RPM and it will also look better in the wheel well and give you a little rubber rake for that hot rod.:)
Good Luck!
 
Thanks a lot for the responses all, you've each given me a lot to think about. It would be nice to gain some speed in reserve for cruising at greater than 50 in certain situations

I hadn't considered the "poor man's overdrive" idea of putting 7.50s in the rear - something to consider, though I'd like for my spare to match all 4 wheels
 
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I have 3.54 in the tudor, with 21 inch wheels. That is pretty good for around here where there are plenty of hills. With a little more power, I would like 3.27 gears. With your smaller wheels, the 3.27 would seem ideal. I put a mitchel overdrive in Barry's coupe, and found that on the flat, I could start off in overdrive and leave it there until a big hill. I am no good at maths, but I think the overdrive with 3.78 gears about equals 3.00, so 3.27 should be no problem.
 
I would suggest that you spend no money now. Wait till you get home and drive your car and drive other cars with options that you are considering. You may know the feeling of spending a lot of money on something that turns out to be NOT what you expected? Not good! Go slow and careful for a better result. Good luck. Ron W
 
Hi Paul, Bill put the Mitchell overdrive in my 29 coupe and it is great, you would love it. Going 50 the engine sounds like 35 but I realize it's pretty expensive and he also put on a Snyders 5.5 head. In the meantime when you replace tires you could consider 6:50 x 16s as the diameter is larger than 6:00 x 16.
 
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Paul63 said:
Thanks everyone - Vic, my car is in the States though I'm curently overseas so I'd be buying parts in the US. I should have emphasised that the car has the original stock 3.78 gearing and I'm considering 3.27.

Tom- would changing the head alone as a stop gap measure increase cruising speed?

Hardtimes - am i right in assumming that putting in a 3.54 with 16" wheels would be would be similar to 19 inch wheels with 3.78? that's why I'm looking into the 3.27 to gain an improvement in cruising speed.
Click to expand...

Hey Paul,
Bigger rear tires can be put to good use in lowering rpms at higher speed. I'm going to install 7.40 or 7.50 rear tires on my 16" rims, to achieve even lower rpms with 3.54 rear gears. May not work , but I like to experiment :)
 
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