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Old 09-06-2014, 09:07 PM   #1 (permalink)
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steep downhill coasting

There's a long downhill that I do periodically, with 4 miles of it approaching 7 percent grade, including two sweeping 180 degree downhill curves. Before any mods I did all of the downhill in 5th gear. This transitioned to 4th gear after grill blocks and wheel covers, which may or may not have included some touching of the brakes.

The last trip with the new bumper cover the car was flying down at high revs in 3rd gear (approaching 55-60), and lightly touching the brakes didn't seem to do any good, which freaked me out a bit. Is it possible the car could rev too high in 3rd gear? What if the car is still going too fast, just ride it out, use the brakes more, or start out in 2nd at the crest?

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Old 09-06-2014, 09:24 PM   #2 (permalink)
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Whats the speed limit there? I had some nice down grades in WV, but the tacoma I drove had a terminal velocity of about 55 mph in neutral.
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Old 09-06-2014, 09:30 PM   #3 (permalink)
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The speed limit is 55, and beyond that gets quite dangerous on the curves.

Actually it might be 45 on the curves.

I've been in the 80's in neutral going down much lesser grades.

Last edited by j12piprius; 09-06-2014 at 09:55 PM..
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Old 09-06-2014, 11:49 PM   #4 (permalink)
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Quote:
Originally Posted by johnlvs2run View Post
There's a long downhill that I do periodically, with 4 miles of it approaching 7 percent grade, including two sweeping 180 degree downhill curves. Before any mods I did all of the downhill in 5th gear. This transitioned to 4th gear after grill blocks and wheel covers, which may or may not have included some touching of the brakes.

The last trip with the new bumper cover the car was flying down at high revs in 3rd gear (approaching 55-60), and lightly touching the brakes didn't seem to do any good, which freaked me out a bit. Is it possible the car could rev too high in 3rd gear? What if the car is still going too fast, just ride it out, use the brakes more, or start out in 2nd at the crest?
Is this an auto trans or manual? Sounds like a manual.
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Old 09-07-2014, 12:00 AM   #5 (permalink)
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Yes, a 5 speed manual.
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Old 09-07-2014, 12:02 AM   #6 (permalink)
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Quote:
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Yes, a 5 speed manual.
I'm new to this so bear with me. Why not coast down the hill in neutral or with the clutch in?
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Old 09-07-2014, 12:06 AM   #7 (permalink)
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The car would go too fast in neutral.

I'm keeping the car in gear to slow down and keep from going too fast.

I can easily coast down the entire 10 miles without using any gas.
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Old 09-07-2014, 12:19 AM   #8 (permalink)
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Quote:
Originally Posted by johnlvs2run View Post
The car would go too fast in neutral.
Isn't that what brakes are for?

Back about 20yrs ago when I still rode motorcycles on the street I used to ride with some guys up to Prescot, AZ. On the way back we would descend Yarnell Hill, nearly a 5000ft drop in 8 miles. We would race down the entire thing engine off and coasting. He who used the brakes the least won (there was drafting too). Good times.

Video of the road:
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Old 09-07-2014, 12:32 AM   #9 (permalink)
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What truck drivers do is say a safe speed is 65. In gear press the brake to slow down to 45 keep it in gear to keep the speed down and you will speed up and repeat
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Old 09-07-2014, 12:39 AM   #10 (permalink)
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The object is to not use the brakes, and to not wear them out.

I've been down AZ89 from Prescott. According to the comments there's a 1355 drop (4400 to 3045 feet) in 8 miles, an average 3 percent drop, which I wouldn't compare to 7 percent around two 180 degree curves, and then a sharp 90 degree curve at the end of the second one. There is no way you'd be going 90 on those, not twice anyway.

Basically I'd like to know if letting the engine rev up in 3rd gear is okay.

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