How do bigger tires affect VSC, TRAC, ABS

[martini]

I've seem some mixed answers for this question. Will increasing the tire size (or even decreasing) affect VSC, TRAC, and/or ABS?

Bigger tires will have a lower RPM for a given speed, so will you have to slip more before any of these systems kick in with a larger tire? Or would this not matter since your tire spins at different RPMs anyway when going different speeds? In terms of TRAC would you require more wheel spin before traction control tries to regulate wheel spin. I'm not sure how ABS monitors but I thought it had to do with the difference in wheel speed between the front and rear wheels. If your tires are bigger would this not matter because both tires are the same size so ABS would start braking and releasing once the same difference between front and rear tire speed is achieved? Or would it take longer for ABS to realize you're sliding since the wheel RPM are lower than the system expects?

I know the 4Runner manual says not to change the tire size, but that may be for liability reasons.

Any insights would be greatly appreciated.

 

[chaz]

i assume you have 265/65/17, going up to 265/70/17 will make no difference except in mph. 55+ speeds will be about 2-3 mph off, but around town it will read correctly.

 

[martini]

I was thinking between 265/65/17 to 265/70/17 or even much larger. I know the difference might not even be noticeable but if you wanted to go much larger would that have any impact?

 

[MikeRiela]

im running a 275/70/R17 and i dont notice any difference besides the speedometer being off at around 5-6mph at high speeds.

 

[martini]

I thought I saw this before which led to this thread, from the owners manual:

"Install all 4 tires of specified size at appropriate pressure: The anti−lock brake system detects vehicle speeds using the speed sensors for respective wheels’ turning speeds. The use of tires other than specified may fail to detect the accurate turning speed resulting in a longer stopping distance."

Page 336

 

[chaz]

maybe this will help u. http://www.toyota120.com/forum/showthread.php?t=4369&highlight=larger+tires+affect+abs

 

[CJ3Flyr]

The thread Chaz linked is good one. IMHO it doesn't matter much to the ABS, VSC or ATRAC sort of... The difference in wheel RPM doesn't cause big issues provided all 4 tires are the same size. What does matter is the taller tire is a lot harder for the brake to affect. The larger diameter tire requires more brake power. Fortunately the T4R brakes are pretty good and can handle it for the most part. To have no loss of performance with these systems you'd have to upgrade the brakes.

Truth is, with a taller tire, stopping distance will increase somewhat, the effectiveness of ATRAC will be diminished slightly and the effectiveness of VSC may be reduced a bit as the VSC doesn't know to hit the brakes 'extra hard' because tall tires not programmed into the software. The VSC will try to slow a wheel, unsuccessfully and then try again harder. This adds time to the process and could negatively impact the overall success of the VSC intervention. In the end-game all the systems will work just slightly less effectively.
:cheers:

 

[Will_4R]

I wonder how easy it would be for a dealer to reprogram the systems for the taller tires. I am guessing it isn't too simple.

 

[chaz]

even if they the dealer did reprogram, the systems can handle more than what size tire its rated for since tires from different manufacturers, even if stated the same size , will vary. some brands 30s can be almost 31, other brands may be just under 30. i just dont think its needed or worth what it might cost since most guys only go up 1 or 2 sizes. like 265/65 to 265/70, or 275 or even 285, now if you were going up to 35s that might be different, but some of those guys dont see/have any problems. personally though, if i went to 285s id want to at least upgrade the brakes, but the sport brakes should be good enough.