Complicated question, bear with me

[BNewman]

I have the 2000rpm or 70-74mph vibe going on here on my 04. 5 4x4 QQ sb dsl. I've asked about changing to 4:10 ring gears to change the speed-rpm match up. People said 4:10's would put my 2000rpm vibe at around 60mph, naturally I want to it to go higher like 80-85mph.



Heres where it gets difficult If I go up a couple of tire sizes such as {up from 265 stk bfg"s} to a 285 or 295, would that in essence lower my gear ratio? hoping the vibe will appear at around 80mph or so from 70mph? What would really help me if any of you that have these tire sizes could tell me what your tach reads at 70mph with the bigger tires. ie. 2200rpm's

I don't think thie vibe is going to be resolved any time soon, just hoping I can push it out of my normal driving speeds like 80mph. I live at around 72-73 mph. Thanks a million gang, sorry if this was an unwanted challange. Please do the best you can.

 

[bulabula]

Here's a website that you can do all the comparisons you want:

http://www.dakota-truck.net/TIRECALC/tirecalc.html



You got it right though: if you want to raise the vehicle speed where you encounter that vibration, you either need to put on taller tires, or taller (lower numerically) gears.



Compared to what tires you are running now, and going to a set of 315 BFG's, your cruise speed will increase by about 8% at any given rpm. In other words, if you were running at 70 mph with the old tires, you'd be running little over 75 at the same rpm with the new ones.



I think changing tires is easier than doing gears - especially if you've got a 4x4. But changing to 285's or so for circumference alone wouldn't be worth it in my book (would make very little difference in your cruise speed).

 

[BNewman]

thanks thats very helpful

 

[JCleary]

I've read a lot about the 70mph vibe. I guess my truck had it. The steering wheel used to buzz at about 70 or so. So much so that the plastic surrounding the steering column would buzz.



Of course, when I asked the dealer about it, they told me it was normal.



I tried to ignore it, and later installed a Kore suspension with 35" Toyos. Buzz is completely gone. At any speed.



RPM's dropped to about 1850 at 70mph (not too excited about the theoretical 3. 42ish ratio the truck is now running compared to the stock gearing/tires).



But, the good part is that there's no vibe, even at 2000-2400 rpm, at which point you really have to keep an eye out for the law.



315's and a leveling kit at a minimum is the way to go. I had 285's on before and it made no difference.