New Truck, Tire question

[Bunn]

Hello everyone, I'm new to the diesel world and new to the TDR. I just purchased an 03 HO 1 ton SRW. Here is the problem, I have the 4. 10 gears and it seems to be way to close to red line on the freeway for my comfort level. Will I do any damage running at 3 grand for an extended length of time? So this leads me to my next question. It seems that a lot of you are running the 315/70R17 BFG's, obviously a set of these would drop my ratio, but what about the speedometer. Does any company make a product to recalibrate the speedo? Thanks for your help.

 

[Dean Upson]

You are running 3 grand in top gear?



Dean

 

[GSaltzman]

As far as your speedo goes your dealership can recalibrate it. It is done by computor. You will need to know the revolutions per mile on the tire you will be putting on. Three grand does seem high. I'm doing just a tad over 2,000 rpm while cruising at 70. This is the H. O. with 6 speed.

 

[Bill Littlefield]

Tire

You better do some checking before you go with the 315's. I put them on mine and had some rubbing problems. I ended up with a 2 inch lift on the front to fix it. Also, they only come in D rates 8 ply. If your using that 3500 for something heavy, you may find your overloading them.



I recommend not going any larger than a 305. That will fill up the wheel wells and I don't think you'll have any real rub issues. Check with the tire dealer first. Also, when I run the 315's down the road in my older truck with a 410, it does keep my RPMs down.

 

[Dean Upson]

There is a useful calculator that has been posted previously http://www.f-body.org/gears/ . 3000 rpm's puts me at 95 mph.



Dean

 

[nkiewel]

My understanding is that the dealer can not recalibrate the speedometer to accomodate for the 315/70/17s. There was a thread on this a while back, but I can not remember what the largest tire that they can adjust for is.



SuperLift is working on a TruSpeed module (~$200) for the new Rams, but it is not out yet. Last I heard, it was supposed to come out during Q3.

 

[nkiewel]

Originally posted by Dean Upson

3000 rpm's puts me at 95 mph.

Wow! Just checked out that link... 3000 RPMs outs me at 119 with 48RE, 3. 73s, and 315/70/17s! Didn't feel like there was that much left when I got her up to 90 the other day though. I love this truck!

 

[lawdog]

I have 3. 73s and 315's and I love them. I had a concern pulling a trailer, but does not seem too bad so far, however I do not pull very heavy, about 7000 lbs on a triple axle. If I remember correctly, the 4. 10 and 315's puts you near stock tires and 3. 73s, so the dealer may be able to just chaNGE THE COMPUTER TO THE TRUCK HAVING 3. 73 GEARS INSTEAD OF 4. 10'S. . oops, hit the caps lock, sorry... ..... Also check out the link to a tire size calculator, it works good... ...



www.miata.net/garage/tirecalc.html

 

[dan_gilson]

Speedo Re-calibrate

You might want to check with Dan at Rickson Trucks to see if the little black box works in the '03's. It is called TrueSpeed.



If it does, it can recalibrate your speedo to exactly whatever you new wheel/tire size needs. It was not inexpensive. I think mine was less than $200. But you don't have to wait and pay a dealer. It is adjustable so, if you change sizes again you can still use it.



It has a 2 position switch that allows me to go back and forth from stock to larger without having to reset the calibration each the time.



Another note to those who have significantly changed their overall rolling diameter: Your ABS system is setup for what ever overall rolling diameter your truck came with. When you change this it effect your ABS as well as your milage and speedo reading. This unit "corrects" the pulse to the ABS unit and "fixes" all of the issues at the same time:



I could have lived without having an accurate Speedo. Explain to the judge that it was out further than the 5% and I did not know, etc. I can also live with the milage being off. But when I have to stop really fast, I want it working 100%. It may not be just my butt on the line. The Mrs. and kids may be in there too.