Wheel weight difference a concern for AWD?
09-07-2017, 09:02 AM
#1
Wheel weight difference a concern for AWD?
This thread is about AWD system and staggered wheel setups, specifically WEIGHT difference, assuming tire rotation speed is identical.
Not that I intend to run a staggered setup on my 09 TL awd, but I recently was told something new and want clarification more or less.
Throughout my forever learning endeavor with cars, I've always thought that as long as the outer tire diameter was the same (or within 1% difference) with similar rotation rates, it is fine for AWD systems. BMWs, Mercedes, and other manufacturers I'm sure, offer square and staggered setups for their AWD cars. For example, the e90 335xi base model came from factory with 17" square setup, but sport pkg got the staggered 18" (225/40-18 front, 255/35-18 rear).
It seems to be understood that if the outer tire diameter is off by too much, it will wear and destroy the center diff on the awd system. This makes sense, since if one tire is rotating faster than another, it would cause strain on everything connected to them, like axles, driveshaft, differentials, etc. Something has to compensate for the difference in rotation, such as tire or drive train slip.
A member on the FB group insists that since staggered setups have wheels of different weight front and back,
this would cause excessive wear on the diff and destroy it over time.
While I do see the possibility of the issue, I cannot find anything that backs this up.
Especially once the wheels are rotating, would it really cause much strain on anything??
Does the difference in WEIGHT of a staggered setup on an AWD drive train affect the smooth running and longevity of it?
Not that I intend to run a staggered setup on my 09 TL awd, but I recently was told something new and want clarification more or less.
Throughout my forever learning endeavor with cars, I've always thought that as long as the outer tire diameter was the same (or within 1% difference) with similar rotation rates, it is fine for AWD systems. BMWs, Mercedes, and other manufacturers I'm sure, offer square and staggered setups for their AWD cars. For example, the e90 335xi base model came from factory with 17" square setup, but sport pkg got the staggered 18" (225/40-18 front, 255/35-18 rear).
It seems to be understood that if the outer tire diameter is off by too much, it will wear and destroy the center diff on the awd system. This makes sense, since if one tire is rotating faster than another, it would cause strain on everything connected to them, like axles, driveshaft, differentials, etc. Something has to compensate for the difference in rotation, such as tire or drive train slip.
A member on the FB group insists that since staggered setups have wheels of different weight front and back,
this would cause excessive wear on the diff and destroy it over time.
While I do see the possibility of the issue, I cannot find anything that backs this up.
Especially once the wheels are rotating, would it really cause much strain on anything??
Does the difference in WEIGHT of a staggered setup on an AWD drive train affect the smooth running and longevity of it?
The following users liked this post:
hoonee46 (09-07-2017)
The following users liked this post:
hoonee46 (09-07-2017)
09-07-2017, 09:55 AM
#4
On the TL's SH-AWD system, I would think it's actually even less of an issue, referencing below.
Rear is always over driven by 1.7%, and there are electromagnetic clutches that control power delivery.
SH-AWD® System Layout
The TL SH-AWD® is a full-time all-wheel-drive system that requires no driver interaction or monitoring. A torque-transfer unit is bolted directly to the front-mounted transaxle. The torque-transfer unit receives torque from a helical gear that is attached to the front differential's ring gear, and a short horizontal shaft and hypoid gear set within the torque-transfer unit's case send power to the rear propeller shaft, which in turn transfers power to the rear drive unit.
The TL SH-AWD® rear drive unit is constantly overdriven by 1.7-percent and the resulting overdrive effect is regulated by left and right electromagnetic clutch packs which independently control the power delivered to each rear wheel.
09-07-2017, 01:39 PM
#5
My car was maintained at dealership all its life.
In fact, carfax shows that alignment was checked when dealer took ownership before sale.
Steering was straight, no obvious signs of poor alignment, but a slight wiggling and vibration felt strongest at my foot at 75+ MPH.
I went on a 600mi trip over labor day weekend, and it sucked.
It felt like a bad alignment, so took it in to my trusty alignment shop, and yes, alignment was off, toe out.
Previous owner must have driven on it for a while, so the tire went bad, which dealership rotated to the back to mask symptoms.
I figured this out because 2 tires were more worn than the other two, on opposite corners instead of paired front and back.
Sneaky bastards. "alignment checked" means steering wheel looks straight and car doesn't pull in their books I guess.
Now I have to deal with this noisy tire until I get a new set. SMDH
09-07-2017, 01:43 PM
#6
Hmmm, that's kind of irrelevant hahah
My car was maintained at dealership all its life.
In fact, carfax shows that alignment was checked when dealer took ownership before sale.
Steering was straight, no obvious signs of poor alignment, but a slight wiggling and vibration felt strongest at my foot at 75+ MPH.
I went on a 600mi trip over labor day weekend, and it sucked.
It felt like a bad alignment, so took it in to my trusty alignment shop, and yes, alignment was off, toe out.
Previous owner must have driven on it for a while, so the tire went bad, which dealership rotated to the back to mask symptoms.
I figured this out because 2 tires were more worn than the other two, on opposite corners instead of paired front and back.
Sneaky bastards. "alignment checked" means steering wheel looks straight and car doesn't pull in their books I guess.
Now I have to deal with this noisy tire until I get a new set. SMDH
My car was maintained at dealership all its life.
In fact, carfax shows that alignment was checked when dealer took ownership before sale.
Steering was straight, no obvious signs of poor alignment, but a slight wiggling and vibration felt strongest at my foot at 75+ MPH.
I went on a 600mi trip over labor day weekend, and it sucked.
It felt like a bad alignment, so took it in to my trusty alignment shop, and yes, alignment was off, toe out.
Previous owner must have driven on it for a while, so the tire went bad, which dealership rotated to the back to mask symptoms.
I figured this out because 2 tires were more worn than the other two, on opposite corners instead of paired front and back.
Sneaky bastards. "alignment checked" means steering wheel looks straight and car doesn't pull in their books I guess.
Now I have to deal with this noisy tire until I get a new set. SMDH
moved my eyes from another screen with lines of scripts, so did not look at it carefully~~~, not about alignment~~~
The following users liked this post:
hoonee46 (09-07-2017)
09-07-2017, 01:47 PM
#7
Some shops claim 'full 4 wheel alignment service' when the mechanic only knows how to adjust toe, looking at the computer screen.
Some shops have @$$hole guys that lean on the car to temporarily get it right on paper.
Took some trial and error to find the shop that knows what they are doing and offer free adjustments for a month - they stand by their work.
