RPMs at 65mph

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RPMs at 65mph

Postby albaran » Mon Jun 26, 2017 10:24 am

This is a little bit of a rehash of a post I did back in 2102: viewtopic.php?f=1&t=14342&p=136379&hilit=freeway+flyer#p136379
When I had the trans built, I put in a 1.04 4th gear which at the time I thought would give kind of a close ration box.
In hindsight, I wish I would have gone for the overdrive 4th. Cruising on the highway, I am doing approximately 55mph at 3000rpm or 65mph at 3500rpm. It always feels like I wish I had another gear to go into. It probably wouldn't be worth the hassle and expense to go for a "freeway flyer" type of trans but I am wondering what do other Spyder owners turn at 65 mph? On the plus side, the car does accelerate well in 4th.
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Re: RPMs at 65mph

Postby RS-60 mark » Mon Jun 26, 2017 12:12 pm

With 3.44 R&P and .93 4th, my calculator says 23.7 mph per 1000 rpm (or 71 mph at 3000 rpm). 205-65R15 rear tires. That's about the same as it looks on my tach.

Here is a calculator to plug in your own numbers: http://johnmaherracing.com/calculators/ ... alculator/
Last edited by RS-60 mark on Tue Jun 27, 2017 8:56 am, edited 1 time in total.
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Re: RPMs at 65mph

Postby RBP » Tue Jun 27, 2017 5:05 am

I have a 3/44 RP and a .89 4th with 205/55/16's in back. I am pretty sure I'm at 70 mph at 3000 RPM and about 80 mph at 3500 RPM. Now I can keep up with the flow of traffic on the expressway and not be revving the bleep out of the engine!

Initially I had a 3/88 RP with a 3.8 1st, 2.06 2nd, 1.26 3rd and a .82 4th. Was ok but didn't even need 1st and the climb from 3rd to 4th was too steep. In town there was always someone in front of me driving at a speed too fast for comfortable RPM in 3rd and too slow for 4th. I pulled the transaxle and replaced the RP with the 3/44 and changed 4th from the .82 to the .89. This works perfect but I wouldn't complain if I had a taller 1st like a 3.10. Was well worth pulling the trans and doing the change. If you have reasonable HP and torque you should consider this configuration. You need a close relationship between 3rd and 4th as these are the gears you will cruising in for extended periods either in town or on the expressway.

If you pull the trans yourself you could get Rancho to do the changes for about 900.00. If you have someone local you can by the 3/44 RP & new 4th from Weddle https://weddleindustries.com/ and have the local shop do the upgrade.
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Re: RPMs at 65mph

Postby DannyP » Wed Jun 28, 2017 3:08 pm

I have the same as Rudy(RBP) above. However, with the new car, GPS speedo and tires are 205/60R15 rear. At 55 I'm reading around 2300-2350. At 65 it's in the neighborhood of 2700.
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Re: RPMs at 65mph

Postby danstern » Sun Jul 02, 2017 1:14 pm

A little under 3,000 rpm at a true 65 mph. Just under 3,500 at 75 mph. Looks like 22 mph/1,000 rpm.
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Re: RPMs at 65mph

Postby TSchommer » Sun Sep 03, 2017 2:37 pm

I finally remembered to start my GPS phone app before a run on an interstate, I'm at about 3,200 rpm at 65 mph. I often go grab for an imaginary 5th gear whenever I'm merging onto a highway from an on ramp. I would not mind if my gearing was a little more highway friendly, but I'm more annoyed with how short my 1st gear is.
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Re: RPMs at 65mph

Postby danstern » Sun Sep 03, 2017 5:28 pm

You obviously don't live in a super hilly area. The short first is handy for that.
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Re: RPMs at 65mph

Postby RBP » Sun Sep 03, 2017 7:11 pm

Keep in mind that the first gear was designed to get a 2500 lb vehicle with less than 50 HP moving! In a 1200 lb vehicle with 200 HP it is virtually useless! Just my observation and opinion.

Also depending on the climb into 4th it sounds like you are running a 4:12 R/P with a .82 4th or a 3:88 R/P with a .89 4th. If you have the 4:12 then the 1st gear will be of no use, way to short.

The right gearing in these cars makes a big difference in driveability! Best recommendation I can make is to determine what you have. I suspect based on how you describe 1st gear you may have the 4:12 R/P with the .82 4th. if that's the case you need to pull the transaxle and change the R/P to a 3:44 and 4th to a .89. You can figure out what you have with the gear ratio spread sheet then go from there.
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Re: RPMs at 65mph

Postby TSchommer » Mon Sep 04, 2017 1:55 pm

I don't really have an issue with my gearing, when I bought the car on eBay the add said it had a 3:88 freeway flyer gear. I think I'm just used to having an overdrive gear, I think the exhaust volume more than anything contributes to wanting an extra gear. I agree that the 1st gear is almost useless, if I'm pulling away from a stop sign I probably shift after moving about 10-15 ft.
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Re: RPMs at 65mph

Postby RBP » Mon Sep 04, 2017 5:27 pm

Agree, and the only way to get a useful 1st is to pull the trans and do the upgrade. While in there do the 3:44, well worth it. Its your car so do as you see fit, just my opinion.
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