Hatzies 2005 2500HD

[cst204x4]

Very interesting reading I chenged my tire size from 245 to 265 on my 04 2500 HD and my brake pedal has a somewhat mushy feel to it wondering if this is in relation to tire change or problem with the hydro boost brake system. Truck only has 62,000 miles

[hatzie]

Originally Posted by cst204x4

Very interesting reading I chenged my tire size from 245 to 265 on my 04 2500 HD and my brake pedal has a somewhat mushy feel to it wondering if this is in relation to tire change or problem with the hydro boost brake system. Truck only has 62,000 miles

Not sure what all the ABS computer does to the braking outside of panic stops but anecdotally it seems that it may make more of a difference than I thought several years ago.

The mushy pedal is an interesting observation. Mine felt mushy as well and it seemed to be firmer after I set the tire size in the ABS module. I figured it was my subjective opinion at best... but reading that someone else has the same thoughts on the braking begs some questions.

I'd be very interested to know what your subjective opinion is on the change in braking feel after making the tire size change in the ABS controller.

If you have a tool to change the tire size in the PCM I'd be very interested in hearing how that change affects your drive feel as well.

IMHO It will not hurt a thing to flush the old DOT3 fluid out of the brakes with fresh clean DOT3 or DOT4 and change the power steering fluid. Both are likely the stuff that the GM line workers put in your truck on the assembly line. My brake fluid was blacker than pitch and the power steering fluid was not any better. The brake fluid is already getting dark again so I'll flush it out again when the weather improves... probably the power steering as well since the the Hydroboost brake assist is run off the power steering fluid.

You can't change the ABS module tire settings without a Tech 2 or MDI or equivalent with Tech2Win on a laptop. When you get to the ABS tire size change menu in the Tech 2 you're looking for a tire size that's the same OD and similar width. My 31.6" 265/70R17 tires weren't in the list but 31.64" 265/75R16 were. Same 31.6" OD and same 265mm section width. 0.04" difference in diameter is close enough... 638 tire revolutions per mile.

Use the comparison calculator tab on this page to see what difference a change in tire diameter, width, circumference, revs/mile, etc makes.
https://tiresize.com/calculator/

[LC-4540]

That's a great looking truck.

Finding info on the 99-06 trucks can be quite challenging.

Thanks for the little details on your build, really helps down here in Australia.

Cheers Mark

[hatzie]

Originally Posted by LC-4540

That's a great looking truck.

Finding info on the 99-06 trucks can be quite challenging.

Thanks for the little details on your build, really helps down here in Australia.

Cheers Mark

Originally Posted by Palf70Step

Thanks for the info.

Thanks. Glad to know it's useful.

[Keith Seymore]

Originally Posted by hatzie

Thanks. Glad to know it's useful.

Yep - I’m following along too; its just that I’ve been able to manage everything so far on my truck so no need to comment.

K