TR6 TR6 at speed

[bigbadbluetr6]

Since I am driving my TR6 now and my speedo bounces I was wondering what the speeds were at different RPMs. First here is my set up. 73 TR6 with an A type overdrive. Tires are 205 60 15s everything else is stock. How fast am I going at 55, 60 and 65. They pretty close. I think at 2700 is 70 but not sure. Let me know.

 

[tomshobby]

If you have a gps you can use that to get a very good reading.

 

[danstr6]

Your speedo bouncing is most likely due to a frayed speedo cable. I had the same problem. Easy to check. Remove the cable and pull out the internal wire. If it's frayed, replace the whole unit.

 

[bigbadbluetr6]

I was thinking my tires are 205 65 15. Right now I am more worried about the MPH compared to RPMs. I'm driving home after work and there is always a few cops waiting for speeders. A GPS is a good idea and I've thought about using one just haven't had the time. I was hoping someone would have the speeds right off the top of their head The speeds 55 60 and 65 are the speeds on the highway that I drive home. I've been driving at 2300 RPMs and its saying around 65 so I'm guessing thats close to accurate.

 

[prb51]

Eric,
Use this calculator to figure it out

https://www.teammfactory.com/gearcalculat...amp;trannytype=

 

[TR3driver]

Just curious, do you really think a 35 year old mechanical tach is that accurate ?

With original tires, the book gives 395 rpm per 10 mph. So that's
2172.5 @ 55;
2370 @ 60
2567.5 @ 65

I worked it out once, that translates to 781.6 turns per mile for original tires.

Bridgestone Potenzas in size 205/60-15 are rated for 843 tpm (according to TireRack); so for your car, multiply the above numbers by 843/781.6 (about 8%) to get:
2343 @ 55
2556 @ 60
2769 @ 65

 

[BobbyD]

I know that my car with a 4 speed & stock rear end was looking at about 3200 RPMs at 65 MPH. I just used one of the online engine speed calculators and with your tire size it came out to 65 MPH at 3160 RPMs. If you're saying 2300 RPMs at 65 MPH something isn't working right. Either the tach or the speedo.

 

[bigbadbluetr6]

I know that my car with a 4 speed & stock rear end was looking at about 3200 RPMs at 65 MPH. I just used one of the online engine speed calculators and with your tire size it came out to 65 MPH at 3160 RPMs. If you're saying 2300 RPMs at 65 MPH something isn't working right. Either the tach or the speedo.

Bobby,
I have an A type OD so thats why the RPMs are so low.

 

[BobbyD]

Eric..... my bad.... I missed that in your first post.