Tire diameter/circumference tolerance AWD [Archive] - Honda Element Owners Club Forum

: Tire diameter/circumference tolerance AWD


rfsmith48
11-04-2013, 11:30 AM
Folks,

We recently had a flat when a 2" chain link went thru the tread of one of our near new tires.

Discount tire claimed they couldn't repair it, and I needed to buy a pair of new tires to protect the AWD system. The new pair would go on the rear of the car. A local independent shop fixed the tire and it appears to be fine.

Question: What is the tire size tolerance for the Element AWD system? The Owners manual didn't say much, and the Shop Manual said less. Honda usually publishes definitive info on common sense/real world situations like this.

Anybody know?

TIA,

Rog Smith

ramblerdan
11-04-2013, 12:12 PM
Welcome, Rfsmith48.

I don't have a specification for you, but if the tire that was punctured was like new, as your post seems to indicate, then you should be fine running a brand-new tire next to a like-new one. Besides, AFAIK what matters to the Element's 4WD system is the relationship between tires front to rear, not side to side.

There has been talk of tire shops that will shave down the tread of new ties to match older ones, but I don't recall anyone having actually done it.

rfsmith48
11-04-2013, 12:22 PM
Folks,

Does anyone know of another Forum that covers this issue?

Thanks,

Rog

ramblerdan
11-04-2013, 02:28 PM
If you mean within EOC, "Tires Wheels and Suspensions" is the place. Otherwise, Google is your friend.

larryziegler
11-04-2013, 05:32 PM
Replacing in pairs is the prudent decision with a 4WD, as it's critical of same tire diameter on the same drive axle as well as the same tire tread. The Owners Manual also confirms that if you are only replacing 2 tires, that they be on the same axle.

EdwardChen
11-05-2013, 01:06 PM
This link describes the RTAWD system in detail: http://www.skidmore.edu/~pdwyer/e/files/rtawd.pdf

It says that the rear pump is 2.5% larger than the front to "compensate for the difference in rotation between the front and rear wheels which is caused by tight corner braking and worn front tires."

I'm not sure if that exactly answers you question for your issue though.

I'm sure you could play with tire pressures a little, or even measure each tire's rollout to get a better measurement.

Just because I'm curious, a stock 215/70R16 tire has a diameter of 27.85". Assuming the tread depth when new was 11/32", and when worn down to 2/32", a total of 9/32" is lost, with a total diameter decreasing to 27.85" - .5625" = 27.29", a loss of about 2.02%.

That's for an absolute worst case. I think if you kept the tires reasonably well rotated, you'd have no issue at all.

HIP2BSQ
11-05-2013, 03:11 PM
1) Not to sound sarcastic, but Discount Tire is in the business to sell tires, not fix them. That's why you were given the pitch that 2 tires would have to be replaced. These guys are trained hard to sell everyone that walks in the door no matter what the real needs are. I have seen them in action, but have not succumb to their sales pitches.
2) The difference in tire diameter of a new tire and one that is, say, 25% worn is very small. That small difference in rotation speed from one side to the other is actually handled by the differential, not the 4WD unit. Where there might be issues is when you put larger size tires on one end or the other.
3) You stated that the tires were 'near new'. No problem here. If you were riding on 4 'maypops' and only wanted to replace one tire, that would cause issues with the 4WD as the one new tire would be rotating a tick slower than the rest.
4) EdwardChen's math gets the the point across, but in actuality the tire has lost 9/32" on the radius of the tire, not the diameter. So the % of difference is around 3.5% from a new tire to an old tire. And that 3.5% is taken from the tire rpms, somewhere around 745 per mile. 3.5% difference is about 26 rpms per mile.
5) You have handled it as it should have been done. When someone's suggestion to do a repair sounds 'off the wall' get a second opinion.

FWIW, my son has a AWD Subaru and when put into a tight turn (parking lot manuver) on a hard surface I can feel the drivetrain 'bind up', as it actually will bring a slowly rolling car to a stop unless you are on the power.

07lmnt
11-05-2013, 06:47 PM
Another Plus for 2WD!

How we check for tire diameter. All tires set to same pressure.

On a flat surface, mark all tires with a crayon at the point where they are at the lowest point. Move the vehicle in a straight line for about 6 tire revolutions. Line up the crayon mark on one tire to the ground. Check all other tires, to see if the mark is off. If not lined up by 2 inches the tire diameter will cause problems for AWD.

GaryS
11-05-2013, 09:29 PM
:lol:
That's measuring the circumference.

ramblerdan
11-06-2013, 01:18 PM
That's measuring the circumference.
Yes, but apropos of this discussion, it's not the specific diameter (or circumference) of any one tire that matters, but how close the four tires are to each other. To that end, it's an elegant method.

EdwardChen
11-06-2013, 01:40 PM
1) Not to sound sarcastic, but Discount Tire is in the business to sell tires, not fix them. That's why you were given the pitch that 2 tires would have to be replaced. These guys are trained hard to sell everyone that walks in the door no matter what the real needs are. I have seen them in action, but have not succumb to their sales pitches.
2) The difference in tire diameter of a new tire and one that is, say, 25% worn is very small. That small difference in rotation speed from one side to the other is actually handled by the differential, not the 4WD unit. Where there might be issues is when you put larger size tires on one end or the other.
3) You stated that the tires were 'near new'. No problem here. If you were riding on 4 'maypops' and only wanted to replace one tire, that would cause issues with the 4WD as the one new tire would be rotating a tick slower than the rest.
4) EdwardChen's math gets the the point across, but in actuality the tire has lost 9/32" on the radius of the tire, not the diameter. So the % of difference is around 3.5% from a new tire to an old tire. And that 3.5% is taken from the tire rpms, somewhere around 745 per mile. 3.5% difference is about 26 rpms per mile.
5) You have handled it as it should have been done. When someone's suggestion to do a repair sounds 'off the wall' get a second opinion.

FWIW, my son has a AWD Subaru and when put into a tight turn (parking lot manuver) on a hard surface I can feel the drivetrain 'bind up', as it actually will bring a slowly rolling car to a stop unless you are on the power.


Oops, sorry, I didn't show all my work, but I doubled 9/32" to get the change of .5625" that is subtracted from the diameter. Either way, diameter or radius, the 2.02% should still be right.