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Discussion Starter · #1 ·
I have a weird problem. Since the 2007 V70 2.5t came with many different front rotor sizes, I decided to take the tire off to better indirect the rotor. I had a hard time measuring it, so I wrote down the numbers stamped into the rotor. The rotor appears to be a genuine Volvo rotor and has the following number on it "31471829".

I can't find this part number online for some reason. I found party number "31471827" ending in "27", which is a 305mm rotor and also found part number "31471830" ending in "30", which is a 286mm rotor. But "31471829" can't be found anywhere online.

Can someone please help me out?

Automotive tire Wheel Tire Rim Motor vehicle
 

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You can also look at the caliper bracket for a number. The 286mm and 305mm rotors have different brackets.

To measure the rotor, measure the diameter of rotor hat, then measure the distance from the hat to the rotor edge and multiply that by 2. Add the two numbers up. It should be pretty obvious at that point.

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Motor vehicle Bumper Automotive exterior Font Automotive wheel system

If you don’t have 305mm brakes, you should certainly upgrade. Just need the rotors and brackets; line, pad and caliper remain the same.
 

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Discussion Starter · #5 ·
Automotive tire Gas Rim Bumper Automotive wheel system

Unfortunately, I didn't think about measuring the rotor the way you described. I also didn't disassemble the caliper, bracket, or rotor. I just wanted to figure out the rotor size and look at the wear on the rotor and the pads.

Thought the numbers I got off the hat were going to yield results, but looks like there are weird stock numbers to throw you for a loop.

Like like worst case, I'll have to disassemble some stuff to get that info but the front brakes were in decent shape.

Here is another picture showing the writing on the caliper, but since it's used on two different rotors, the info is probably useless.
 

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Pic looks like 286s. No external webbing on the exterior face of the rotor.
That’s in line with 305s not being offered on 2.5ts
 

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Don't recall part numbers very well but I would agree your model uses the smaller of two basic options.
I do know the minimum spec on them is 23 MM.
The larger option will be marked 25 MM.

The original way to know is by an aluminum plate riveted to the front support under the front hood/bonnett that has the chassis code embossed. One of the numbers/letters within it contain brake specs and can be decoded with a parts catalog, either printed or in VIDA.
Nowadays just put the VIN into VIDA and you can get a veritable build sheet with much greater detail.
 

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The original way to know is by an aluminum plate riveted to the front support under the front hood/bonnett that has the chassis code embossed. One of the numbers/letters within it contain brake specs and can be decoded with a parts catalog, either printed or in VIDA.
Nowadays just put the VIN into VIDA and you can get a veritable build sheet with much greater detail.
The chassis code info is inside the B pillar on the 2007 models. It's separate from the VIN. There's a decoder out there somewhere.

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Discussion Starter · #10 ·
Thanks folks. I provided my VIN to Volvo and asked them for help but I haven't heard back. I also agree that they're probably the smaller ones given the lack of webbing for the vents at the hub. I didn't realize that 2.5ts didn't get the 305mm rotors, that would have made life much easier. It's still weird that the rotor numbers don't exist on Google.

I'm looking at buying some remanufactured brackets for the 305mm rotors and doing the upgrade when I decide to change them in the near future. The rear rotors look like they're in worse shape and I ordered the rear 286mm rotors and pads for them. I just need to order new caliper bracket bolts, which were out of stock.

Do y'all think this car has a stop limiter? I'm finding that the front caliper carrier bolts also come in different sizes M12 55mm, M12 60mm, M10 30mm, etc... The car has 16 inch wheels.

Nothing dealing with the front brakes appears to be easy with this Volvo 😂.
 

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Should have steering stops. Bolts don’t need to be replaced unless they’re super corroded? M12x55 is the bolt for cars with steering stops.
 

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Discussion Starter · #12 ·
Got a resolution from Volvo regarding the rotor size on my vehicle that doesn't seem to exist.

"Thank you for your patience as we looked into this. Your vehicle has 15 inch brakes and the part number for the front rotors is 31471830."

My rotors are indeed the smaller ones and the 1-to-1 replacement is the 31471830. It's weird that these didn't have any note saying that they supersede or replace the 31471829, when I saw them online.

Thank you everyone for your help.
 
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