Ram Rebel Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
So I bought the ball sockets and threaded rod and did the air ride linkage mod. I don't have any error message and hardly notice a difference in ride quality in normal mode. I put on 35x12.5x17 Toyo Open Country C/T tires, they are considered a winter tire but many run them all year which is what I intend to do. I did get a wheel alignment done, which was necessary because it was off after doing the mod.


No clearance issues, but I was also hoping to put on 1.5 inch wheel spacers and it doesn't look like there will be enough clearance to do it. This will have to do until I can get the 4" BDS lift done. I do notice at highway speed my rpm doesn't come down under 2K now, wonder if I need to get the shift points reprogrammed. If anyone has any input on this it would be appreciated.




 

·
Registered
Joined
·
12 Posts
i am running 35x12.6x17s w/2inch spacers on my rebel with NO real modification. keep in mind i did have to zip tie part of the inner fender back at the bottom and trim a peice of plastic...though nothing major overall. plus i liked the look of the standard height with the 35s...your truck looks amazing though...i swear the rebels were fca's best call on a re-design.
 

·
Registered
Joined
·
8 Posts
i am running 35x12.6x17s w/2inch spacers on my rebel with NO real modification. keep in mind i did have to zip tie part of the inner fender back at the bottom and trim a peice of plastic...though nothing major overall. plus i liked the look of the standard height with the 35s...your truck looks amazing though...i swear the rebels were fca's best call on a re-design.
Which 2" spacers did you use? I'm thinking of using them with the stock 33's for a wider stance. Do you have a pic so I could see what a difference the 2" makes. It would be greatly appreciated.

Thanks
 

·
Registered
Joined
·
8 Posts
Has anyone tried the Revel Performance 2" leveling links? They look well made and all I'm looking to do is level the front.
 

·
Registered
Joined
·
12 Posts
Which 2" spacers did you use? I'm thinking of using them with the stock 33's for a wider stance. Do you have a pic so I could see what a difference the 2" makes. It would be greatly appreciated.

Thanks
there you go! i had them initially on with my 33s and they did look good. this is them with the 35s
 

Attachments

·
Registered
Joined
·
10 Posts
Discussion Starter · #7 ·
there you go! i had them initially on with my 33s and they did look good. this is them with the 35s
Looks great. Odd, with my 35's on when I turn the wheel all the way right, my front driver's side wheel looks like it would rub on the outer rear part of the fender if I put spacers on. I was convinced they wouldn't work, but you have no rubbing so not sure what to do now lol.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #8 ·
So I bought the ball sockets and threaded rod and did the air ride linkage mod. I don't have any error message and hardly notice a difference in ride quality in normal mode. I put on 35x12.5x17 Toyo Open Country C/T tires, they are considered a winter tire but many run them all year which is what I intend to do. I did get a wheel alignment done, which was necessary because it was off after doing the mod.


No clearance issues, but I was also hoping to put on 1.5 inch wheel spacers and it doesn't look like there will be enough clearance to do it. This will have to do until I can get the 4" BDS lift done. I do notice at highway speed my rpm doesn't come down under 2K now, wonder if I need to get the shift points reprogrammed. If anyone has any input on this it would be appreciated.


Just an update on this. I did end up ordering a Hypertech speedometer recalibrator, part number 752501 Error - Hypertech. I did the reprogram and entered the new tire size, took it out for a quick test and it did help bring my rpm down at 60 mph on highway. It is more like it used to be before putting on the 35 inch tires.
 

·
Registered
Joined
·
48 Posts
Hey T Man, can you let us know how changing to 35's affects your fuel economy? I'm sure you are aware but you can check the recalibration of the speed O using the Navigation GPS Trip Computer if you have NAV installed. Just to make sure it is an accurate recalibration.
 

·
Registered
Joined
·
660 Posts
Just an update on this. I did end up ordering a Hypertech speedometer recalibrator, part number 752501. I did the reprogram and entered the new tire size, took it out for a quick test and it did help bring my rpm down at 60 mph on highway. It is more like it used to be before putting on the 35 inch tires.
Recalibrating the speedometer doesn't change your rpm. It just corrects the speedometer calculation. What was happening is that the computer was calculating your speed based on wheel rpm's. But with larger tires, you're actually covering more ground with each rotation. So when your computer thought you still had 33" tires and you were cruising at a calculated speed of 60mph, you were actually running about 64mph. Now your computer is calculating your speed based on larger tires, so you're driving slower, less rpm, to actually run at 60mph.

Your rpm should actually be lower than before with the new 35's. If your engine was running at 2000 rpm at 60 before, now your engine should be running at 1885rpm. (94% of whatever engine speed you were running before.) Assuming same final gear, of course.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #11 ·
Recalibrating the speedometer doesn't change your rpm. It just corrects the speedometer calculation. What was happening is that the computer was calculating your speed based on wheel rpm's. But with larger tires, you're actually covering more ground with each rotation. So when your computer thought you still had 33" tires and you were cruising at a calculated speed of 60mph, you were actually running about 64mph. Now your computer is calculating your speed based on larger tires, so you're driving slower, less rpm, to actually run at 60mph.

Your rpm should actually be lower than before with the new 35's. If your engine was running at 2000 rpm at 60 before, now your engine should be running at 1885rpm. (94% of whatever engine speed you were running before.) Assuming same final gear, of course.
While I understand what your are saying, I was of the impression the shift points (and therefore RPM) were based on the speed the truck "thinks" it is going. If the speedometer is out then it could effect shift points? Anyway, I did the re-calibration with the Hypertech and my mileage at 60 mph has gone back up from 13 mpg to 17 mpg. That's just about where it was before I did the tire swap.
 

·
Registered
Joined
·
660 Posts
On the mileage - You never actually say whether that's "apparent speed" as read from your speedometer, or actual. So I'm assuming that you're talking about apparent speed, what your dash is telling you.

So, here's what little I know that might answer: Your truck was actually probably doing around 64-65mph with the new larger tires. That should have been at the same engine RPM as with the old tires, because the computer would still think same tires, same speed. But in reality larger tires equals higher speed. You would think also better mileage, by a few mpg. However, you also have bigger, heavier tires with more rolling resistance (and higher speed equals even more rolling resistance), which decreases your mileage. Added to that the higher speed = much greater air resistance. And at that speed, air resistance is very high. Plus, at 64-65mph, you were right at about the area where MDS tends to start cutting off, especially if there is any wind. (because air resistance is much, much higher than rolling resistance at those speeds, and increases geometrically)

I've done some measuring and discovered that I lose 1.5mpg between driving at 60 and 65. And more than 3mpg between 65 and 70, about half of which is due to MDS cutoff in that range. My tested mpgs at 60-65-70 were 20.1-18.6-15.7. (those were cruising tests, no stop/starts, explaining the high numbers) So without tire changes, if the MDS cutoff happens right at 65 due to slight change in incline or wind change, I could easily see a 3+mpg drop.

-----

On the shift points - a longer topic and some of it is way outside my expertise. A bunch of inputs are used by modern computers to determine shift points. Some cars do use vehicle speed as an input for shift point, but it's one of many. There's an interesting short list here on wikipedia: https://en.wikipedia.org/wiki/Transmission_control_unit

No idea which inputs Ram is using, though. Final speed may or may not be part of it. And overdrive might be a factor. I know that I end up in final gear at 50mph on smooth country roads, so I don't think your circumstances depended much on speedometer calcs because you were at higher speed. I could be wrong. Need a Ram engineer to answer that.

I remember the old days when auto trannies calculated shift points by the demand - torque converter did it all. :)

-----

So I know I don't have a full answer to the shift point question. But on the mpg it's not too far from what I would expect to see before recalibration. I normally would expect a little less difference than that but considering MDS impact, it's nothing I can throw out and then say definitively that you were failing to shift to final gear. It's quite possible.
 
1 - 12 of 12 Posts
Top