Two questions... Speed + 33's? and Fuel Range/tank..

[sourcemine]

1. How off is my speedo/mileage with 33's and a 2.5" lift kit? I can get max speed 80-85 with the thing pinned, so I'm not too worried about speeding on the freeway, that still very ticketable but I was just curious off how the speedo is?

2. With that in mind, how many miles per tank should I be getting, so far it's been around 185, which seems very low... at 12mpg in a 23gallon tank that should be around 270? Is something royally screwed up? i don't know if I can afford gas for this thing if thats all I'm going to be getting even with my work being 2miles away, I'm having it fully inspected at TLC, W-Th-F, they may also notice some other issues.. but this thing has to get more than 185mi per tank...

IF my speedo is off, wouldnt my mileage be off too?

 

[casey]

Yes, the tire size will affect your speedo and odometer. There are lots of calculators online to see what the corrected speed is at any given MPH. Here's one for example:

http://www.mgb.bc.ca/misc/tirecalc.html

Correct me if I'm wrong but I believe the stock tire size was about 29" ??

 

[60wag]

Yes you need to adjust for the tire size. 33/29=1.14 So theoretically your off about 14%. On my worn out BFGs, my GPS reads about 11-12% off. So when my speedo showes 60mph, I'm actually at 67mph. When calc'ing the milage, I've traveled 12% farther than the odometer showes. As for the miles/tank.... Have you ever run it empty? There may be more gas left in the tank than you think when the gauge is reading empty. I'd calc your actual MPG and then decide if you can live with it. I "can" get 17mpg with my 84FJ60 on 33s, stock gears, 2" lift IF I only use miles driven on the highway at constant speed. Real life numbers, including cold starts and city driving range fron 12 to 14 mpg.

 

[87CRUSR]

Running 31's, stock gears, and I get close to 200 miles on a tank when doing mostly highway miles. Certainly not the best especially on long road trips but you can't beat the dependability of knowing you'll get to wherever you need to get as long as you have gas!

 

[Man Jerk]

Here's how you find out how far your speedo / odometer are off.

Next time you are on the highway, pace yourself using the mile markers. Drive 10 miles. Say your speedo only registers 9 miles. devided 10 by 9 and you get 1.1111111111...

now if your odometer shows 270 mi, multiply by 1.11111111... and you get about 300

If your speedo reads 65 the multiply that by 1.11111111... and you get about 72mph.

Once you get your multiplier then just mulitply everything by that. Easy.

I carry a calculator around with me to figure milage and such...

 

[Doc]

Have you done a COMPLETE tune up yet? Plugs, wires, cap, rotor, PCV, etc..? That will help your MPG a lot I bet.

I'm getting betwwen 11-12, and need to finish my tune up.

 

[Doc]

Oh, and check your tire pressure.

 

[TOY350]

Follow this link: Speedo correction , I did the test and had them make me up an adapter and now my speedometer reads correctly as well as mileage.

 

[sourcemine]

Follow this link: Speedo correction , I did the test and had them make me up an adapter and now my speedometer reads correctly as well as mileage.

Called spoke to Bill, for the record, its

$35 for a test if your local in the Los Angeles/Riverside Area(which I am)
$100 for the correcting box
$25 for installation(ifyou want them to do the work)

now I'm wondering if I should keep these 33's on my truck or not, I'd need to know before I went out and bought a box.

 

[TOY350]

I went out and drove 10 miles and used the mile markers on the freeway and my odometer came up with 9.6 or something. I sent them this info and they sent me an adapter for about $75 with shipping. All I did was unscrew the speedo cable from the transfer case and screwed the adapter into the transfer case then the speedo cable into the adapter, all of about 2 minutes. The adatper is about the size of a big ice cube or a couple of tic tac boxes, it's not in the way by any means.

 

[sourcemine]

I went out and drove 10 miles and used the mile markers on the freeway and my odometer came up with 9.6 or something. I sent them this info and they sent me an adapter for about $75 with shipping. All I did was unscrew the speedo cable from the transfer case and screwed the adapter into the transfer case then the speedo cable into the adapter, all of about 2 minutes. The adatper is about the size of a big ice cube or a couple of tic tac boxes, it's not in the way by any means.

What size tires are you running?

 

[TOY350]

What size tires are you running?

33x10.5x15 BFG A/T's with 4.11s. Soon to be 35x12.5x15 somethings with 4.56s.

 

[sourcemine]

so you're running 33's and stock gears? 4.11's? or what are the stockers..

if you change your tires and wheels you will need a new speedo box according to bill, do they recalibrate yours or do you get a new one?

 

[60wag]

Stock is 3.70 on fj60s, 4.11 on FJ62s.

 

[TOY350]

so you're running 33's and stock gears? 4.11's? or what are the stockers..

if you change your tires and wheels you will need a new speedo box according to bill, do they recalibrate yours or do you get a new one?

60WAG is correct, I am not running stock gears, I'm running 4.11's with far from stock tires and wheels. With the adapter they made me it's on the money. I can go hit the freeway and after 10 miles it's dead on.

I don't know why you would need to correct anything. Go out and run 10 miles and tell them what your odometer read, e.g. 9.6 and they should be able to find the correct ratio for the adapter to add between your tcase and speedo cable. It will stay a constant ratio unless you change gearing or tire size. It doesn't matter how fast or slow you go, after 10 miles the odometer will read the same.

Anyone else have any ideas why Bill seems to be complicating things?

 

[sourcemine]

60WAG is correct, I am not running stock gears, I'm running 4.11's with far from stock tires and wheels. With the adapter they made me it's on the money. I can go hit the freeway and after 10 miles it's dead on.

I don't know why you would need to correct anything. Go out and run 10 miles and tell them what your odometer read, e.g. 9.6 and they should be able to find the correct ratio for the adapter to add between your tcase and speedo cable. It will stay a constant ratio unless you change gearing or tire size. It doesn't matter how fast or slow you go, after 10 miles the odometer will read the same.

Anyone else have any ideas why Bill seems to be complicating things?

no he's not, same stuff your saying, but if your going to 35's like you mentioned you'll have to have your adapter regeared.

 

[TOY350]

no he's not, same stuff your saying, but if your going to 35's like you mentioned you'll have to have your adapter regeared.

Yep, I will have to send it back to him just like I did when I changed to 4.11's. I'm hoping I will get lucky and 35's w/ 4.56's will work with or without the adapter, I know it's a long shot. If I don't get lucky then I have to send the adapter back for recalibration. New tires and gears are still a ways down the road for me though.