Lexus AWD System and Rolling Diameter Differences?
07-02-24, 09:23 AM
#1
3rd Gear
Thread Starter
Lexus AWD System and Rolling Diameter Differences?
Hi everyone, I am new to Club Lexus and this is my first post as I just recently acquired a 2016 Lexus GS350 Base AWD model. I have begun digging into wheel and tire specs and in particular, non-staggered setups but have not been able to find a concrete answer to my concern.
I am considering running a 20x9 +30 wheel setup on all 4 corners and ideally I would like to run 255/35/20 tires for better ride quality and wheel durability (NJ potholes are no joke). Using a Wheel Fitment Calculator and comparing against my OEM setup's specs, this would result in a 2.59% rolling diameter difference:
OEM Setup: 18x8 +45 235/45/18
New Setup: 20x9 +30 255/35/20
My question then is, would this big of a rolling diameter difference cause any damage to the AWD system / differentials or trigger any check engine lights? Reason I ask is that my previous car was also AWD (Infiniti G37 Coupe) and I ran a setup that was a rolling diameter of just over 1% bigger and it caused issues with the AWD system / triggered CEL's for an "overheating differential". Once I swapped to tires that were closer to the OEM rolling diameter the fault code went away.
I'm hoping some members with AWD model GS's can chime in and provide some insight on what kind of wheel / tire setups they are running, the rolling diameter difference between their current setup and the stock setup and finally, if you have encountered any issues / error codes?
I am considering running a 20x9 +30 wheel setup on all 4 corners and ideally I would like to run 255/35/20 tires for better ride quality and wheel durability (NJ potholes are no joke). Using a Wheel Fitment Calculator and comparing against my OEM setup's specs, this would result in a 2.59% rolling diameter difference:
OEM Setup: 18x8 +45 235/45/18
New Setup: 20x9 +30 255/35/20
My question then is, would this big of a rolling diameter difference cause any damage to the AWD system / differentials or trigger any check engine lights? Reason I ask is that my previous car was also AWD (Infiniti G37 Coupe) and I ran a setup that was a rolling diameter of just over 1% bigger and it caused issues with the AWD system / triggered CEL's for an "overheating differential". Once I swapped to tires that were closer to the OEM rolling diameter the fault code went away.
I'm hoping some members with AWD model GS's can chime in and provide some insight on what kind of wheel / tire setups they are running, the rolling diameter difference between their current setup and the stock setup and finally, if you have encountered any issues / error codes?
07-02-24, 10:49 AM
#2
Intermediate
AWD owner here (and rabid wheel and tire researcher.)
My research finds you'll likely be bumping into fender liners with that size. There's a megathread about 4gs aftermarket wheel fitment with pics and specs, I used that to formulate an AWD square setup fitment range. In 20" the most likely solution will be 245/35R20, with a 20x8.5 through 20x9.5 all around. Your 20x9 +30 proposed is on the outer cusp of clearing the fender at stock height, but lowered some it should get closer to flush and line up without resorting to excessive camber changes. However, I doubt it will clear with a 255/35R20. I don't think I've ever seen/read a post yet about square oversized fitments causing AWD/differential errors, but I definitely have read many people complaining about rubbing.
I think a 255/35R19 is possible with a perfectly set offset and width (19x9.5 +38 through +40, or rare but out there 19x9 +32 through +35 all seem plausible) but the fallback tire is 245/40R19 which apparently is less of an issue, and also less of a "performance" size with the sidewall sometimes looking a bit tall, depending on the wheel and fitment with suspension height... But that is all for 19", whereas 20" seems to be 245/35R20 as the go-to for most.
Sidewall height is a major concern for myself as well, and as much as I would like to see 20's on my car, I've somewhat already given up on the topic and I'm leaning toward the 19" options to get that extra .3"+ in sidewall. The wheels I've found (Konig MRK1, Oversteer, Neoform, Motegi MR158, some new TSWs like the Daytona and brand new Canard, and on the higher end Enkei GTC02, Weds SA20R. All save the Oversteer are rotary forged so bending the lip should be more difficult on these, especially in 19". One big advantage of compromising to a wide, quality 19" is the huge weight savings, which WILL feel nice and always has anytime I've done it on countless other cars.
Fender liner rubbing, at very light levels can sometimes be remedied with the heat gun/cold compress trick to deform some of the plastic out of the way, but very big tires are going to probably just rub anyways. 255/35R20 is a maybe on that.
My research finds you'll likely be bumping into fender liners with that size. There's a megathread about 4gs aftermarket wheel fitment with pics and specs, I used that to formulate an AWD square setup fitment range. In 20" the most likely solution will be 245/35R20, with a 20x8.5 through 20x9.5 all around. Your 20x9 +30 proposed is on the outer cusp of clearing the fender at stock height, but lowered some it should get closer to flush and line up without resorting to excessive camber changes. However, I doubt it will clear with a 255/35R20. I don't think I've ever seen/read a post yet about square oversized fitments causing AWD/differential errors, but I definitely have read many people complaining about rubbing.
I think a 255/35R19 is possible with a perfectly set offset and width (19x9.5 +38 through +40, or rare but out there 19x9 +32 through +35 all seem plausible) but the fallback tire is 245/40R19 which apparently is less of an issue, and also less of a "performance" size with the sidewall sometimes looking a bit tall, depending on the wheel and fitment with suspension height... But that is all for 19", whereas 20" seems to be 245/35R20 as the go-to for most.
Sidewall height is a major concern for myself as well, and as much as I would like to see 20's on my car, I've somewhat already given up on the topic and I'm leaning toward the 19" options to get that extra .3"+ in sidewall. The wheels I've found (Konig MRK1, Oversteer, Neoform, Motegi MR158, some new TSWs like the Daytona and brand new Canard, and on the higher end Enkei GTC02, Weds SA20R. All save the Oversteer are rotary forged so bending the lip should be more difficult on these, especially in 19". One big advantage of compromising to a wide, quality 19" is the huge weight savings, which WILL feel nice and always has anytime I've done it on countless other cars.
Fender liner rubbing, at very light levels can sometimes be remedied with the heat gun/cold compress trick to deform some of the plastic out of the way, but very big tires are going to probably just rub anyways. 255/35R20 is a maybe on that.
07-02-24, 02:07 PM
#3
3rd Gear
Thread Starter
AWD owner here (and rabid wheel and tire researcher.)
My research finds you'll likely be bumping into fender liners with that size. There's a megathread about 4gs aftermarket wheel fitment with pics and specs, I used that to formulate an AWD square setup fitment range. In 20" the most likely solution will be 245/35R20, with a 20x8.5 through 20x9.5 all around. Your 20x9 +30 proposed is on the outer cusp of clearing the fender at stock height, but lowered some it should get closer to flush and line up without resorting to excessive camber changes. However, I doubt it will clear with a 255/35R20. I don't think I've ever seen/read a post yet about square oversized fitments causing AWD/differential errors, but I definitely have read many people complaining about rubbing.
I think a 255/35R19 is possible with a perfectly set offset and width (19x9.5 +38 through +40, or rare but out there 19x9 +32 through +35 all seem plausible) but the fallback tire is 245/40R19 which apparently is less of an issue, and also less of a "performance" size with the sidewall sometimes looking a bit tall, depending on the wheel and fitment with suspension height... But that is all for 19", whereas 20" seems to be 245/35R20 as the go-to for most.
Sidewall height is a major concern for myself as well, and as much as I would like to see 20's on my car, I've somewhat already given up on the topic and I'm leaning toward the 19" options to get that extra .3"+ in sidewall. The wheels I've found (Konig MRK1, Oversteer, Neoform, Motegi MR158, some new TSWs like the Daytona and brand new Canard, and on the higher end Enkei GTC02, Weds SA20R. All save the Oversteer are rotary forged so bending the lip should be more difficult on these, especially in 19". One big advantage of compromising to a wide, quality 19" is the huge weight savings, which WILL feel nice and always has anytime I've done it on countless other cars.
Fender liner rubbing, at very light levels can sometimes be remedied with the heat gun/cold compress trick to deform some of the plastic out of the way, but very big tires are going to probably just rub anyways. 255/35R20 is a maybe on that.
My research finds you'll likely be bumping into fender liners with that size. There's a megathread about 4gs aftermarket wheel fitment with pics and specs, I used that to formulate an AWD square setup fitment range. In 20" the most likely solution will be 245/35R20, with a 20x8.5 through 20x9.5 all around. Your 20x9 +30 proposed is on the outer cusp of clearing the fender at stock height, but lowered some it should get closer to flush and line up without resorting to excessive camber changes. However, I doubt it will clear with a 255/35R20. I don't think I've ever seen/read a post yet about square oversized fitments causing AWD/differential errors, but I definitely have read many people complaining about rubbing.
I think a 255/35R19 is possible with a perfectly set offset and width (19x9.5 +38 through +40, or rare but out there 19x9 +32 through +35 all seem plausible) but the fallback tire is 245/40R19 which apparently is less of an issue, and also less of a "performance" size with the sidewall sometimes looking a bit tall, depending on the wheel and fitment with suspension height... But that is all for 19", whereas 20" seems to be 245/35R20 as the go-to for most.
Sidewall height is a major concern for myself as well, and as much as I would like to see 20's on my car, I've somewhat already given up on the topic and I'm leaning toward the 19" options to get that extra .3"+ in sidewall. The wheels I've found (Konig MRK1, Oversteer, Neoform, Motegi MR158, some new TSWs like the Daytona and brand new Canard, and on the higher end Enkei GTC02, Weds SA20R. All save the Oversteer are rotary forged so bending the lip should be more difficult on these, especially in 19". One big advantage of compromising to a wide, quality 19" is the huge weight savings, which WILL feel nice and always has anytime I've done it on countless other cars.
Fender liner rubbing, at very light levels can sometimes be remedied with the heat gun/cold compress trick to deform some of the plastic out of the way, but very big tires are going to probably just rub anyways. 255/35R20 is a maybe on that.
As far as outer fender clearance with the 20x9 +30, this isn’t a huge concern for me for a few reasons:
· This size/spec seems to be right around the limits of what can comfortable be run up front without major fender / fender liner modification. As far as the rear, I have seen members running 19/20x10.5 in the rear so I don’t foresee this wheel spec (20x9 +30) having clearance issues.
· The car will be running RSR Sport-I coilovers which will provide me a few degrees of negative camber once lowered, this should help tuck the wheel/tire a bit.
· I’m not opposed to rolling / pulling / trimming the fenders / fender liner as necessary (I have done this on most of my previous cars and am pretty comfortable with the process).
Like you mentioned, 245/35/20 seems to be the tire size to go with as far as fitting 20’s in the front. I was also considering 19’s but I intend on running 3 piece wheels and in IMO, 19” 3 piece wheels with a lip look a tad too small on the 4th gen GS body but that’s just me. If I were to run 19’s it would likely need to be 1 piece with no lip to achieve the appearance I’m after.
Similarly the sidewall height is also a factor for me for a variety of reasons (aesthetics, contact patch, wheel protection, etc.). A 40 sidewall would look too tall and a 30 is more stretch than I’d like to run so 35 seems to be the sweet spot.
You raised a good point too though as far as running forged vs cast wheels from a wheel weight and durability standpoint. I intend on running forged wheels for those very reasons you mentioned.
Rolling Diameter Specs:
18x8 +45 235/45/18 --- 0% (OEM Wheels)
20x9 +30 245/35/20 --- 1.59% rolling diameter difference
19x9 +30 255/35/19 --- (1.15)% rolling diameter difference
19x9 +30 245/40/19 --- 1.46% rolling diameter difference
07-02-24, 04:36 PM
#4
Intermediate
Solid points all around, agreed all around. I only did 3 piece forged wheels once in my life (on a wildly modified Ford Flex, of all options), awesome looks and relatively light...but man the upkeep was something I'd rather forget. That said, you probably have it mentally dialed in for a certain look so I say go get it!
245/35R20 has some awesome tire options and the prices per tire are more reasonable than 19" equivalents, which is a sign of popularity for the 20" size.
I think you'll be on your way with 20x9 +30 all around. Not sure if you'd readily give up easy rotations but if you wanted to, you could go wider or at least lower offset in the rear. That's what I did with my Flex, with 22x9 +37 front, and 22x10 +37 rear, because it was AWD I kept 265/35R22's on it all around. The upkeep was not great but every 10k I had the tires dismounted and swapped wheels so they were able to wear front to back. The additional lip in the rear was deemed "worth it" to my younger, more baller budget self haha.
Can't wait to see what you come up with, I personally would go step-lip these days to benefit from a smaller, lighter disk and step lips can be more resistant to potholes due to their shape, I've found.
245/35R20 has some awesome tire options and the prices per tire are more reasonable than 19" equivalents, which is a sign of popularity for the 20" size.
I think you'll be on your way with 20x9 +30 all around. Not sure if you'd readily give up easy rotations but if you wanted to, you could go wider or at least lower offset in the rear. That's what I did with my Flex, with 22x9 +37 front, and 22x10 +37 rear, because it was AWD I kept 265/35R22's on it all around. The upkeep was not great but every 10k I had the tires dismounted and swapped wheels so they were able to wear front to back. The additional lip in the rear was deemed "worth it" to my younger, more baller budget self haha.
Can't wait to see what you come up with, I personally would go step-lip these days to benefit from a smaller, lighter disk and step lips can be more resistant to potholes due to their shape, I've found.
07-03-24, 08:46 AM
#5
3rd Gear
Thread Starter
I've always liked the Ford Flex it's definitely one of Ford's better designs IMO but for sure the maintenance on 3 piece wheels is no joke. I'll likely only run the 3 piece wheels in the warmer months and swap back to the OEM wheels once fall/winter rolls around.
That's a great tidbit of information though regarding the pricing on the 245/35/20 versus comparable 19" options, was not something I had thought about but definitely something to consider as I tend to burn through tires pretty quick
That's also a great point about running the same wheel size but lower offset in the rear for more lip, now you have me thinking... haha
I'll be sure to post some pics once I get everything delivered and installed! RSR has a 7-9 week backorder on the Sport-i coilovers so I'm hoping to have everything dialed in by September/October.
That's a great tidbit of information though regarding the pricing on the 245/35/20 versus comparable 19" options, was not something I had thought about but definitely something to consider as I tend to burn through tires pretty quick
That's also a great point about running the same wheel size but lower offset in the rear for more lip, now you have me thinking... haha
I'll be sure to post some pics once I get everything delivered and installed! RSR has a 7-9 week backorder on the Sport-i coilovers so I'm hoping to have everything dialed in by September/October.
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