Dan Houle
Active Member
Yes, but it also can affect your transmission. Easy fix, when the dealer mounted my 35’s, I had them calibrate the speedometer. People say here you can do it yourself.
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Largest tires on Stock Rebel suspension and wheels
- Thread starter DieselRebel
- Start date
Yes I’m from Canada, I’m off by ~3km/h at 120 km/hr
RamRamBamBam
Active Member
- Joined
- May 12, 2022
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- 34
Affect the transmission how? Like in a bad way?
Dan Houle
Active Member
Yeah. Someone much smarter than me can explain it better. But basically your truck is calibrated to your stock tires. If you don’t have your speedometer recalibrated with bigger tires, it throw everything out of whack. I don’t think it necessarily hurts anything, but you’re not running it as efficiently as it should be if you don’t have it recalibrated.
From a stock 275/70/18 Duratrac (33.2") to the 285/75/18 Cooper AT3 XLT (34.8") you're changing the tire diameter by about 5%. This will "fool" the truck into thinking it's going 5% slower than it actually is. While the difference is minimal, it could effect some of the "decisions" the truck is making in regards to shift points.
The added weight of the larger tire would also have a likely effect on shifting, RPM range, etc. My Duratracs were 83.2 lbs and my Coopers are 85.9 lbs. That's a difference of roughly 3.25% which is pretty small but still not something to be overlooked.
I don't think either of these factors are any where near dangerous or damaging to the truck. The only thing it's really going to hurt is your gas mileage, and even that shouldn't be by too much.
The added weight of the larger tire would also have a likely effect on shifting, RPM range, etc. My Duratracs were 83.2 lbs and my Coopers are 85.9 lbs. That's a difference of roughly 3.25% which is pretty small but still not something to be overlooked.
I don't think either of these factors are any where near dangerous or damaging to the truck. The only thing it's really going to hurt is your gas mileage, and even that shouldn't be by too much.
Attachments
Any rubbing with the new tire size? I have a 2” level and I’m looking at the 285/75/r18 in the at3 xlt and the duratrac
No rubbing at all. I haven't done (and probably won't ever do) any serious off-roading with them, but I just went down the oil well access this morning to go fishing. Even with all the bumps and uneven terrain I didn't get any rubbing. Seems like a pretty solid choice.
As for the Cooper vs the Goodyear. I loved my Duratrac's, they're great tires and I've had them on several trucks. The AT3 XLT seems pretty much on par with them so far. Not a lot of miles on them obviously, but they're quiet and smooth on the road. I haven't driven with them in the rain or snow yet, and the road miles have been limited.
They handled the dirt and mud (soggy soil a few inches deep, not mud bogging) just fine. It seems the Duratrac felt a little more sure footed in the loose stuff but the Coopers were far from struggling. Overall, first impressions are good. I know the Duratrac is good so you should be happy with those. Based on the few days I've had with the AT3 XLT, I suspect you'll be happy with them too so you should be okay with either choice.
Size wise, I've had no clearance issues at all. My only issue with the swap was that one of my wheel weights was hitting the caliper. That was easily remedied by moving it a few mm inboard. That's not a tire issue, that's just the 18" wheel having very little clearance over the brakes and the tire shop not knowing it. It only took me about 10 minutes to relocate it though.
As for the Cooper vs the Goodyear. I loved my Duratrac's, they're great tires and I've had them on several trucks. The AT3 XLT seems pretty much on par with them so far. Not a lot of miles on them obviously, but they're quiet and smooth on the road. I haven't driven with them in the rain or snow yet, and the road miles have been limited.
They handled the dirt and mud (soggy soil a few inches deep, not mud bogging) just fine. It seems the Duratrac felt a little more sure footed in the loose stuff but the Coopers were far from struggling. Overall, first impressions are good. I know the Duratrac is good so you should be happy with those. Based on the few days I've had with the AT3 XLT, I suspect you'll be happy with them too so you should be okay with either choice.
Size wise, I've had no clearance issues at all. My only issue with the swap was that one of my wheel weights was hitting the caliper. That was easily remedied by moving it a few mm inboard. That's not a tire issue, that's just the 18" wheel having very little clearance over the brakes and the tire shop not knowing it. It only took me about 10 minutes to relocate it though.
Perfect, thanks for the review and the heads up about clearance. I’m excited to see how she looks with bigger shoes on.
ALT_F13
Active Member
My Rebel 2020 re-calibrates the speedometer automatically when I swap the wheels from 33" to 35" tires and back. Checked going 80mph using a very accurate GPS speedometer. AlfaOBD shows wheel diameter setting set to "Auto". I assume it works only if you have navigation, which means truck can get speed reading from built-in GPS.
Dan Houle
Active Member
Download a free GPS app, works great.
Dan Houle
Active Member
Wow, you’re the 1st one I heard say that. Pretty cool.
Night Rebel
Well-Known Member
I am installing fuel block wheels in a few days and was wondering if you have a photo of the weight placement? Thank in advance
No photo of the weights, but I'll try to get one for you.
All 4 have the weights in different locations (obviously) but the one that was hitting the caliper had them installed along the inboard edge. The tech had them slightly angled so they started at the inner edge of the wheel and "drifted" a few mm away from it. The weights that were slightly further from the edge were the ones that were hitting. I just removed them, and applied weights in the same place without angling away from the edge. Problem solved.
I'll grab a photo for you though for clarity.
All 4 have the weights in different locations (obviously) but the one that was hitting the caliper had them installed along the inboard edge. The tech had them slightly angled so they started at the inner edge of the wheel and "drifted" a few mm away from it. The weights that were slightly further from the edge were the ones that were hitting. I just removed them, and applied weights in the same place without angling away from the edge. Problem solved.
I'll grab a photo for you though for clarity.
I took the wheel off and took a photo of the weights. All 3 of the other tires have the weights near the face of the wheel instead of along the inner edge like this one. I'm not sure if the tech messed up or if inside/outside affects balance enough that this was the proper placement. They are balanced well so it may have mattered.
Either way, the red line I drew is the approximate location where the edge of the weights were. As you can see by the weights, they were making slight contact where they overhung the groove. With them moved to a straight line there's no contact at all.
Either way, the red line I drew is the approximate location where the edge of the weights were. As you can see by the weights, they were making slight contact where they overhung the groove. With them moved to a straight line there's no contact at all.
Night Rebel
Well-Known Member
No issues. I told discount tire and they center balanced the wheel! Rides great
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Yeah, that's where 3 of the 4 wheels have them. Not sure why the 1 wheel wasn't. No issues now that they've been straightened out though, so no big deal.
And now that I think about it, all 5 of the Duratrac's have the weights in the center too. I guess I'll have to mention it when they mount my Cooper spare, so they do it that way too.
And now that I think about it, all 5 of the Duratrac's have the weights in the center too. I guess I'll have to mention it when they mount my Cooper spare, so they do it that way too.
DieselRebel
Active Member
Sorry haven't been on here in a few months, my Coopers are still doing well with 30k miles on them. They came with 60k warranty where goodyear didn't so that's a plus
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DieselRebel
Active Member
Yes mine was off 3 mph at 75. I changed my tire size in the BCM with AlfaOBD to fix it though.
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Regarding auto recalibration with nav:
I drove past one of those roadside radar signs finally. The displayed speed was within 1 mph of the speedometer, which seems pretty close. However, it was in a 25 zone so I was only going 28 mph at the time (sign showed 29).
The jury is still out on whether the truck recalibrates automatically when you have nav, because the difference from the tires at such a low speed is minimal. I should be traveling 30.5 when the speedometer shows 28, so either the radar was 1 mph above my speedometer, or 1 -2 below my actual speed. That's about as inconclusive as it gets. Has anyone looked into this yet?
I considered going by the radar faster so the difference is great and more evident, but I don't really want the speeding ticket, or to be the a-hole flying through a 25 mph zone. I guess I'll have to keep looking for one set up in a 45 or 55 zone.
I drove past one of those roadside radar signs finally. The displayed speed was within 1 mph of the speedometer, which seems pretty close. However, it was in a 25 zone so I was only going 28 mph at the time (sign showed 29).
The jury is still out on whether the truck recalibrates automatically when you have nav, because the difference from the tires at such a low speed is minimal. I should be traveling 30.5 when the speedometer shows 28, so either the radar was 1 mph above my speedometer, or 1 -2 below my actual speed. That's about as inconclusive as it gets. Has anyone looked into this yet?
I considered going by the radar faster so the difference is great and more evident, but I don't really want the speeding ticket, or to be the a-hole flying through a 25 mph zone. I guess I'll have to keep looking for one set up in a 45 or 55 zone.
