Wrong Size Rotors - 2004 S80 T6 Topic is solved

[Yendor72]

I'll try to get some pictures this weekend, I need to do a closer inspection anyway. I need this old girl to last me a bit longer.

[RickHaleParker]

I think I got it shorted out ... again.

The 2004 S80 has three wheel size options 15", 16" & 17". Different rotors and brakes for different size rims.

15" Rim, rotor diameter 286 mm, Volvo part number 31262706.
16" Rim, rotor diameter 305 mm, Volvo part number 31262707.
17" Rim, rotor diameter 320 mm, Volvo part number 9475266.

The three part numbers are from VIDA 2014D, they maybe superseded by newer part numbers.

Check the stickers on the inside of both doors, make sure the right size rims for your build are on the car.

PS: Edited for model year 2004.

[Yendor72]

Does that apply to a 2004?

[RickHaleParker]

Does that apply to a 2004?

No it did not. For some reason I had 2008 in my head . I edited it for the 2004 S80.

[mrbrian200]

286 and 305mm use the same exact pads and calipers. If you have 305mm it might look like the pads are a little undersized. The larger rotor provides more thermal mass: in a given braking situation the rotor will take a little longer to heat up, thus a little longer before brake fade sets in. Also, with more surface area the larger rotor dissipates heat a little better, stays cooler, making fade less of an issue.

So, there are two possible scenarios..

1. The shop guy doesn't understand what he's looking at: you have 305mm rotors and there is more 'unoccupied space' than he might normally expect to see. If that's the case, it's fine.

2. The shop guy does know his sssst and caught smaller wheels paired with a larger rotor. There's potential for wheel damage due to the proximity of the outside circumference of the rotor being too close to the inside of the wheel (heat damage). This might happen if a PO or mechanic ordered the wrong (larger) ones and put them on either not noticing the difference or not understanding the risk.

3. A PO fancied larger wheels, such as those from an R, found a set, and stuck them on a car that originally had smaller wheels.
I saw this recently on an S60 2.5T in the pick and pull. The wheels on it were from an R. The brake discs were 286mm + ATE calipers. Which doesn't really cause a problem. You just don't get the 'extra' braking performance of the larger setup. Which is really just better resistance to brake fade.

The standard/smaller brake configuration should still feel adequate for an 'emergency' braking situation. If it doesn't, you have some other problem such as poor quality aftermarket pads/rotors, old worn out OE pads/rotors, an issue with the brake booster, or a little bit of air in the hydraulics that needs to be bled out.

Another possibility...

You might be comparing apples to oranges: the apparent braking behavior during a quick/hard press of the brake pedal to some other (probably newer) vehicle. Emergency Brake Assist, where computer detects fast brake pedal travel and applies the brakes harder and faster than pedal pressure alone would, wasn't yet standard Volvo equipment in 2007. Only DTSC equipped vehicles have this function. Many/most newer cars past 2010 or so, excepting el-cheapo base models, have that now. One of my sisters' 09 VW has it. I personally am not fond of it. Like learning to feather touch the accelerator pedal on turbo Volvos to keep fuel consumption and 'leadfooty' tendencies in check, you have to learn to feather touch the brake pedal on cars equipped with the emergency brake assist, else you scare both yourself and your passengers on a regular basis. And groceries fly. Cell phones don't stay where you want them. And your covfefe doesn't stay contained and makes a nasty mess everywhere it happens to go.

[SuperHerman]

Post a picture.

For my XC90 and old XC70s both had two possible sizes for rotors.

For either of these cars one could put the wrong sized rotor on, but could NOT put the caliper assembly on if the rotor is too big. Think about it - the caliper bracket is made for a fixed diameter rotor and if that is changed the holes will not line up. The caliper bracket will not bolt up and fall short of the mounting holes.

I suppose if a smaller rotor is used then specified the caliper assembly will fit, but will be hanging over the edge of the rotor. Maybe this is what you have going on??

Again post a picture. Also list what size wheel you have, if they are originals. On the Volvos I mentioned smaller rotors were usually found on the smaller wheel size option. Sometimes a wheel that is too small will not fit if the rotors are too big.

[Yendor72]

The wheels, as far as I know, are stock to the car 17". So it's possible that the rotors are the 320 as listed.

[RickHaleParker]

as far as I know,

Don't guess, look at the sicker on the door jam to determine what the car was built with.

[jimmy57]

I ran the VIN in current live VIDA. Nice car with 4C. The build brakes were 16 inch set. I don't think p2 S80 in US ever got 17 inch brakes.

The 15 and 16 brakes use the same pad and caliper but the bracket for caliper is different. It moves the caliper outward few mm to get pad placement to edge of rotor. If 286 mm 15 inch brake set rotors were installed on the car the pads would off the edge of rotor and some of the braking face of rotor would not be covered by the pads. The 19 mm differnce between the 305 mm and 286 mm rotors would change pad location about 10 mm.

[RickHaleParker]

I don't think p2 S80 in US ever got 17 inch brakes.

Good catch.
I looked in product specifications.
The P2 S80 got 15" & 16".
The P3 S80 got 16", 16.5" and 17.5". (rounds to 16, 17, 18).

If he has 17" wheels on a 2004, most likely a PO was one of them that, did not want to give up their Big Wheel.

The 15" and 16" rotor part numbers listed above are correct for his chassis number.