Smart Car of America Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
I installed P195/60r15 rear and P175/65r15 fronts on my 2009 fortwo and have since had my front ABS kicking in (Front brake grab) ever since. This seems to happen most of the times on left turns. The tire diameters are within .2" of each other. My research seemed to indicate that as long as the diameters where close enough front to rear, there shouldn't be any problems. The front tires are wearing like mad no doubt, no help from the ABS cycling and making the tires scrub. I will admit that I didn't check toe-in after new springs and struts up-front. Has anyone here had this specific issue? Would going to a different size front eliminate the errant ABS activation? Thanks
 

·
Registered
Joined
·
617 Posts
Get an alignment ASAP , any change with new steering parts , especially what you had done , needs an alignment , period .
 

·
Super Moderator
Joined
·
28,698 Posts
It's not the relationship front to rear so much as the relationship to stock tire sizes. Nobody seems to know exactly how far out you can be from the stock circumferences, but when you cross the line it triggers the ESP and the car goes into "limp home mode." If that isn't happening with your car then it's probably an issue with the wheel speed sensors on the front wheels. :)
 

·
Registered
Joined
·
2,846 Posts
175/55R15 and 195/50R15 are the sizes from smart on some optional wheels I had:

175/55R15 65 MPH
195/50R15 65.3 MPH

175/65R15 65 MPH
195/60R15 65.7 MPH

Must be enough difference to trigger the issue, sadly.

If you want to test this inflate the front higher to MAX PSI as shown on the sidewall. Then deflate the rear a few PSI each. I recall the rear recommends 36 PSI, so maybe 30 PSI. See if it goes away....
 

·
Registered
Joined
·
10 Posts
Discussion Starter #5
It's not the relationship front to rear so much as the relationship to stock tire sizes. Nobody seems to know exactly how far out you can be from the stock circumferences, but when you cross the line it triggers the ESP and the car goes into "limp home mode." If that isn't happening with your car then it's probably an issue with the wheel speed sensors on the front wheels. :)
Thanks for the information and suggestions. I don't know that's it gone in limp mode and the "!" light really never comes on when it happens. There's also been no abs/traction control codes thrown.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #6
175/55R15 and 195/50R15 are the sizes from smart on some optional wheels I had:

175/55R15 65 MPH
195/50R15 65.3 MPH

175/65R15 65 MPH
195/60R15 65.7 MPH

Must be enough difference to trigger the issue, sadly.

If you want to test this inflate the front higher to MAX PSI as shown on the sidewall. Then deflate the rear a few PSI each. I recall the rear recommends 36 PSI, so maybe 30 PSI. See if it goes away....
Thanks for your reply. I will definitely try your suggestion. The difference in the diameter between the stock front 155 and the 175 that I installed is about 1 5/8" that makes for a +7.3% increase. As an aside to this, fuel mileage has suffered quite a bit.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #7
Get an alignment ASAP , any change with new steering parts , especially what you had done , needs an alignment , period .
My first order of business when I change tires, as soon as I figure out what may make the issue disappear which will have to be soon from the amount of wear I'm seeing. Funny thing is the car tracks super-straight and is very easy to handle...
 

·
Registered
Joined
·
2,846 Posts
My first order of business when I change tires, as soon as I figure out what may make the issue disappear which will have to be soon from the amount of wear I'm seeing. Funny thing is the car tracks super-straight and is very easy to handle...
Someone, I believe member InjuredAgain, noted there is a lot of toe in specified by the factory alignment specs...

That said I looked at my notes on tire sizes, and the original size on the smart had a similar difference, if front is 65 MPH the back would be 65.75 MPH. This is for 155/60R15 and 175/55R15 rear.

In another thread someone reported scary ABS issue where in turns the car tried to pull the driver off the road. I'm still suspicious of the steering angle sensor possibly failing...

Sent from my moto g(7) power using Tapatalk
 

·
Registered
Joined
·
10 Posts
Discussion Starter #9
Someone, I believe member InjuredAgain, noted there is a lot of toe in specified by the factory alignment specs...

That said I looked at my notes on tire sizes, and the original size on the smart had a similar difference, if front is 65 MPH the back would be 65.75 MPH. This is for 155/60R15 and 175/55R15 rear.

In another thread someone reported scary ABS issue where in turns the car tried to pull the driver off the road. I'm still suspicious of the steering angle sensor possibly failing...

Sent from my moto g(7) power using Tapatalk
I can usually tell from the radius and speed of the turn, or it's in the same area/turn that I've traveled preciously. I would describe it as aggravating as a minimum and scary if you haven't anticipated it happening. The angle sensor makes sense because of the fact that it does it predominately on left hand turns. If I slow enough, I can prevent it from happening but you can actually hear the ABS starting to pulse when it finally engages enough to brake the car into the turn and then stops as the steering wheel is straightened.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #10
Thanks for your reply. I will definitely try your suggestion. The difference in the diameter between the stock front 155 and the 175 that I installed is about 1 5/8" that makes for a +7.3% increase. As an aside to this, fuel mileage has suffered quite a bit.
175/55R15 and 195/50R15 are the sizes from smart on some optional wheels I had:

175/55R15 65 MPH
195/50R15 65.3 MPH

175/65R15 65 MPH
195/60R15 65.7 MPH

Must be enough difference to trigger the issue, sadly.

If you want to test this inflate the front higher to MAX PSI as shown on the sidewall. Then deflate the rear a few PSI each. I recall the rear recommends 36 PSI, so maybe 30 PSI. See if it goes away....
I inflated the fronts to 40psi, reduced rears to about 23. no noticeable improvement. I'm considering going one size (dia.) down for the fronts and see what happens, at least it'll get an alignment! Thanks again
 

·
Registered
Joined
·
10 Posts
Discussion Starter #11
I inflated the fronts to 40psi, reduced rears to about 23. no noticeable improvement. I'm considering going one size (dia.) down for the fronts and see what happens, at least it'll get an alignment! Thanks again
Ordered a set of stock fronts (P155/60r15) to replace. I guess now we'll see if they get along with the P195/60r15's on the rear... 40PSI makes for a pretty horrible ride upfront!
 

·
Registered
Joined
·
2,846 Posts
Ordered a set of stock fronts (P155/60r15) to replace. I guess now we'll see if they get along with the P195/60r15's on the rear... 40PSI makes for a pretty horrible ride upfront!
Uh oh. That's the opposite direction...

Sent from my moto g(7) power using Tapatalk
 

·
Registered
Joined
·
10 Posts
Discussion Starter #13
Uh oh. That's the opposite direction...

Sent from my moto g(7) power using Tapatalk
I'm basing that decision on this: "It's not the relationship front to rear so much as the relationship to stock tire sizes". So at least I'll be back to square one up front. I have a potential use for the new 195 rears should I find that I need to go back to stock sizing there also.
 

·
Registered
Joined
·
2,846 Posts
I'm basing that decision on this: "It's not the relationship front to rear so much as the relationship to stock tire sizes". So at least I'll be back to square one up front. I have a potential use for the new 195 rears should I find that I need to go back to stock sizing there also.
Thank you!

I was feeling bad I didn't catch you before you noted you placed the order....

Sent from my moto g(7) power using Tapatalk
 

·
Registered
Joined
·
10 Posts
Discussion Starter #15
I got a chance to check the toe-in. 3/4" of an inch plus! Had a heck of a time getting the tie-rod adjustment jamb nuts loose. Tried PB Blaster, heat, etc. Had to remove the wheel, outer ball joint, use a deep well impact socket and an extension on my 1/2" racket. I thought I was going to twist the inner tie-rod in two. After getting both sides "adjustable" I got it to about 1/8" total toe-in. I have read a 1/16" but It wasn't specified whether that was total or just one side. It certainly looks better and actually rolls easier. It didn't do anything for the ABS cycling issue. I guess installing the stock front tires is next.
 
1 - 15 of 15 Posts
Top