Rear end gearing calculations

[Gunny]

I worked up an Excel spreadsheet that does all the calculations for you. Download it HERE

[JSad]

Gunny - thanks for the spreadsheet, that is great! But now I am thinking 4.30's again after looking at the chart and knowing how I drive!!

[lfalzarano]

There are no other factors needed to calculate the theoretical speed. An actual speed calc would bring in other environmental factors and aerodynamics to name a few. But for selecting gear ratios, klukeic and Paul are right on.


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[Gunny]

Originally Posted by JSad

Gunny - thanks for the spreadsheet, that is great! But now I am thinking 4.30's again after looking at the chart and knowing how I drive!!

Take plenty of time playing with the spreadsheet & try out as many "what ifs" as possible. The spreadsheet is nothing more than a quick comparison tool but there are so many other factors at play, you need to view with "eyes totally open".

That said, the default values are for a stock ZR-1 with 3.45 gears. If you change the tire size from rear tires to front the results will change slightly because the diameter from rear to front are not identical - close but not exact.

As Paul mentioned you need to carefully analyze your driving style & habits - that is so important. Paul has been with me on a number of mountain runs and I understand completely why he's reluctant to change from 3.45 to 4.10. I've tried both and for mountain driving the 3.45's work much better (for me, at least). I've never tried 3.73's but I imagine those would be a nice compromise.

Once I got the tires, brakes, and go fast mods set up to my taste I felt my '90 w/3.45 gears was as good as it gets for running the mountains ... but then I added an '02 ZO6 to the stable - bone stock with Nitto NT5 tires I began to run the mountains better than ever - instant twisty-curvy nirvana. And now I have a '19 w/Z51 package ... I've managed the Dragon twice before the shut down and I believe the 90Z and 02 ZO6 can no longer hang with the 19 Z51 - close, but the Z51 is so nice in the twisties. Photos HERE.

Here's a VIDEO of what it's like behind the wheel of a Z51. If possible, view on a big screen with sound up.

I've been a legal driver for 62-odd years now & have enjoyed every moment - but with the cars available today that offer such great performance at affordable prices, I likely wouldn't refuse any offers to turn the clock back a few years.

I'm anxious to get back to the mountains ASAP and have tentatively planned to take a short trip back to the mountains beginning on June 12, the day that our governor is supposed to allow my age group to venture forth from the safety of our homes. I've been under house arrest since March and it's probably a good thing they didn't put an ankle bracelet on me or I would have already been in the pokey for good ... just sayin'

[We Gone]

Great tool Gunny, Love my 3:73s (for my driving style) better use of 2nd & 3rd my favorite mountain gears.

[PhillipsLT5]

http://gearcal.com/

[Paul Workman]

Originally Posted by Gunny

I'm anxious to get back to the mountains ASAP and have tentatively planned to take a short trip back to the mountains beginning on June 12, the day that our governor is supposed to allow my age group to venture forth from the safety of our homes. I've been under house arrest since March and it's probably a good thing they didn't put an ankle bracelet on me or I would have already been in the pokey for good ... just sayin'

I hear ya, Gunny! Wish you could have joined us on the 2018 Rocky Mtn Run. It was every bit as challenging, the routes we picked weren't as "knotted" as the "Dragon" is, with some exceptions: more stretched out, I mean to say. Different, but SAME.

There were more open vistas and views of snow-capped peaks with ribbons of blacktop winding through meadows (did I mention elk lounging on the roadside in some meadows?). Many high-speed straights that dove into stands of conifer on the slopes containing "Dragon" style twisties (quick brake and "heel-toe" from 5th to 2nd or 3rd and be glad your new tires are warmed up! As a consequence, probably out of old habit from the Appalachian "MRs", I lingered in 2nd too much - the RPM dwelled too long, too often at 5k+ and the combo of thin air and thermostat bypassing [above 5k RPM], it got hot and overheated. My bad! We ain't in Tennessee anymore Toto!)

So, in deference to the topic, 3.45s or maybe 3.73s for some driving would by my choice.