Thread: Project "Left Overs"

Tweet

Originally Posted by Itoldyouso

Here is a site I have used in the past and it makes it very simple to figure out your rpms. All you do is plug in your gear ratio (no periods or colons), your tire size and your intended speed, and it gives you the rpms for an automatic, aod, manual, and 5 speed transmission. It is very accurate, my tires on the 27 are about 29 inches tall and it pegged my rpms at 2984 and change. On the road I was turning 3,000 at 60 mph on the gps.

http://www.reiderracing.com/rtech-engine-rpm.php

Try this with your cars info and see how it compares.


I have been considering changing to Hurst brand slicks this time on the rpu, but they are a little short, only 28.75 tall, and the Firestones I had on my 23 were 30. That 1.25 makes a little difference, and also looks better IMO.

Don

Don,
The problem with the Reider Racing calculator is you cannot plug in your actual OD ratio. Their 5speed calculation assumes a 0.80 final drive ratio in 5th which may be right for some, but not for me. My TREMEC is 0.64 in 5th, and TREMEC also has their 6 speed (used in the new Hemi Challenger) that has a final 0.50 to 1 OD ratio. Plugging in a 0.80 OD ratio into the calc I gave you yields the same answer as the Reider calculator, which it should.

That's probably true. I can't afford an overdrive transmission, so it works ok for me.

Don

I'm confused... 5280 x 60 x 12 / pi =121,008.4...

Anyway, I missed the part that says "OD ratio". DUH!! If you take my calculated rpm of 3119 x the .64 overdrive it comes out to 1996. Our figures confirm each other then... Where they got the 336 still eludes me though.

Does anyone else have a new screen appearing at the top of the threads? It shows the members who have posted on that thread and their comments. Is this some new feature, or did I hit some button like I usually do without realizing it?

Don

Originally Posted by Itoldyouso

Does anyone else have a new screen appearing at the top of the threads? It shows the members who have posted on that thread and their comments. Is this some new feature, or did I hit some button like I usually do without realizing it?

Don

Don is the screen showing you logged in as Itoldyouso?
Sometimes my computer doesn't get recognized when I connect to this site, so I have to manually log in, and when this happens I get a different screen.

whoops just saw this new post of yours, never seen that screen!

Originally Posted by J. Robinson

I'm confused... 5280 x 60 x 12 / pi =121,008.4...

Anyway, I missed the part that says "OD ratio". DUH!! If you take my calculated rpm of 3119 x the .64 overdrive it comes out to 1996. Our figures confirm each other then... Where they got the 336 still eludes me though.

Jim,
Not to beat a dead horse, but the string [(5280ft/mi x 1hr/60min x 12in/ft) divided by pi] has a numerator of 5280 divided by 60 times 12 which equals 1056, which divided by pi equals 336.13. In the original formula

RPM = (mph x Differential Gear Ratio x 336 x OD Ratio)/Tire Diameter in Inches

you're entering MPH so the values in the 336 factor get you to a numerator of revolutions and speed in inches per minute with pi being dimensionless. Then when you divide by the denominator tire diameter in inches you're left with RPM.

Originally Posted by rspears

Jim,
Not to beat a dead horse, but the string [(5280ft/mi x 1hr/60min x 12in/ft) divided by pi] has a numerator of 5280 divided by 60 times 12 which equals 1056, which divided by pi equals 336.13. In the original formula you're entering MPH so the values in the 336 factor get you to a numerator of revolutions and speed in inches per minute with pi being dimensionless. Then when you divide by the denominator tire diameter in inches you're left with RPM.

Thanks, Roger. I was using 60 as a multiplier instead of as a divisor. DUH!! Even at my age I can still learn things occasionally and as long as somebody is learning, we're not beating a dead horse (That's the school teacher coming out in me...).

Don, sorry we hijacked the thread for a few postings, but some old fart (me) had to have help seeing through "the haze".

Today was like Xmas, UPS brought me a Speedway box. I got the new wishbones and Ford tie rod ends for them. They are really really nice, and so close to the originals you would be hard pressed to tell the difference......except these have no pitting and all that normal stuff.

Once I laid them up against the car I decided to run the front end suicide, so I called Speedway back and ordered the proper perches that screw into these. I also ordered my tires from Coker. I am going to run my usual 5:60 x 15 whitewalls on the front (just like my 27 has) but on the back I am going to run the 8 inch wide Firestone slicks, also whitewalls. I had the same tires on the back of the 23, except 10 inches wide, and after 3 years and lots of miles they still looked good and had lots of tread depth left.

Finally, I took the back two rims to the powdercoater to have them done in black. I already had them do these same two rims in red a while back, but when I got the black ones from Coker for the front they just looked better to me. Not sure yet if I am going to run the Olds hubcaps I have or not. Once the tires and rims are on the car I can figure that one out.

Here is how the new Speedway wishbones look. So glad I bought them.

Don

Geez, I miss a couple of weeks and you just about build a whole new car!!
It really is looking good! I was wondering about the quality of speedways bars, good to here they are nice.
Ken

Nothing different here on my screen... Not yet, anyway.

Don, with the 3.73s, no overdrive, and 30 in. tall tires you will be turning 2507 rpm at 60 mph. With the 28.75 in. tall tires you will got up to 2616 rpm. Not a huge difference...

Yeah, that isn't a big difference. For some reason my CHR site has changed tonight. When I used to go to a thread it would take me to the last viewed post, now it goes right to the very first opening post on page one of that thread. And a new blue screen has shown up at the top of every thread, listing what members have posted on that thread and the first line of what they have posted. Very weird! It also has a lttle tag above it that says Post Reply.

Don

Here, I took a picture of that screen. It is also showing that there are 5 pages to this thread already, but I can only click onto the first 4. Plus, if I click on page 4 it would normally bypass 1 2 and 3, but it just goes to page 1 now.

Yep Steve, I am logged on as usual, but suddenly that new screen has appeared and no matter what I do the thread always starts at the very first post and I have to scroll through to the last one. No one else is getting that screen?? I see Brent is logged in, hope he sees this and has an answer.

Don

I never log off Don, Why do you log off, I can't see any point ???

Screen as normal for me

I don't log off either, Steve. That screen is stil there this morning.

Don

I just logged off and back on and it went away!!!!!!!!!!!! Very strange.