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View Full Version : At 130 MPH my speedo is off 5 MPH



Flashback
10-28-2010, 04:23 PM
And also at 40 MPH. I have driven my 53 seventy five miles, and checked the speedo several
times. I guessed at the speedo driven gear. Can any of you (from experience) tell me if I need
to go down on the # of teeth one or two? Like I said it is 5 MPH slow.

StudeMichael
10-28-2010, 05:47 PM
The Alabama Highway Patrol won't care if you are going 125 or 135. They will just put you in jail. :)

ClaymoreWW
10-28-2010, 06:08 PM
similarly, my Lark is off: if i drive 4 miles on the highway (according to highway markers), the odometer registers 5 miles. Do I need more teeth or fewer (on the speedo drive gear)?

--george

studebaker-R2-4-me
10-28-2010, 06:16 PM
similarly, my Lark is off: if i drive 4 miles on the highway (according to highway markers), the odometer registers 5 miles. Do I need more teeth or fewer (on the speedo drive gear)?

--george

George,

What rear ratio do you have? SI has the speedo pinions that you need according to your rear ratio. My Hawk is off too since I changed my rear ratio. I need to buy one myself.

Allen

Jim B PEI
10-28-2010, 06:18 PM
I guess that is supposed to be THIRTY (30) MPH, not 130. The next sentence about the 40 also just makes more sense then.;);) So, what is the answer?

Flashback
10-28-2010, 06:38 PM
It's 130, just jokin. Have only driven 70MPH so far. My car dosen't have a ratio or tire size original.

(S)
10-28-2010, 07:14 PM
This post reminds me of the Commercial where the NASCAR fan gets pulled over in his GEO and the cop asks if he knows his speed. He says 150? As if to say "how'd I do?"

rockne10
10-28-2010, 07:44 PM
if i drive 4 miles on the highway (according to highway markers), the odometer registers 5 miles. Do I need more teeth or fewer (on the speedo drive gear)?

--george
More. Divide your pinion by four, then multiply by five.
If you drive five but it only registers four, divide by five, multiply by four.
If you know the components in your drive-train and are running correct tires you can find the correct pinion from the chart in the chassis catalog.

PackardV8
10-28-2010, 07:45 PM
Fewer teeth = more MPH, so if you are reading slow, go down one tooth.
More teeth = fewer MPH, if you are reading fast, go up one tooth.

IIRC, most Shop Manuals have charts and lists of speedo driven gears.

jack vines

61Lark
10-29-2010, 08:19 AM
And also at 40 MPH. I have driven my 53 seventy five miles, and checked the speedo several
times. I guessed at the speedo driven gear. Can any of you (from experience) tell me if I need
to go down on the # of teeth one or two? Like I said it is 5 MPH slow.

I checked my 61 Lark on the dyno at school for an assignment a few year ago. With the stock rear gear and close to stock tires, my speedo read 65 at 62 mph. It was dead on at 30 MPH, but it read fast below that. So if it is only off 5 mph at 130 I wouldn't worry about it, I'd worry more about its accuracy at 60 mph.

Nick