What Size are my Front Rotors?

Post by **ggleavitt** » 28 Apr 2020, 12:47

What size front rotors does my Gen1 XC90 have?

Very common problem for XC90 owners is to determine the size of their front brake rotors.

Volvo built front rotors in 3 sizes for the XC90- 316mm, 328mm, and 336mm. A number of folks have tried over the years to get a solid "rule" about which vehicle gets which size as based on wheel size, engine, and MY. A few visual cues can help.

The 328mm front has double pot caliper, and the pad damper looks like this-

: 328mm caliper damper.jpg (73.81 KiB) Viewed 32674 times

If you have this damper on your front brakes, you have a 328mm rotor. That's it.

The 316 and 336mm fronts have a single pot caliper, and the pad damper looks like this-

: 316 336 mm caliper damper.jpg (86.35 KiB) Viewed 32674 times

If you have this damper on your brakes, then it's a matter of determining the rotor size. See this photo for visual cues-

: 316 rear 336.jpg (112.48 KiB) Viewed 32674 times

316mm front on the left, 308mm rear in center and 336 mm front on the right.

316mm has no visual fins at the base of the center, 336mm has fins at the base of the center with approx. 1 inch between them. Photos are of OE rotors, aftermarket may be different.

Hope this helps.

Post by **RickHaleParker** » 28 Apr 2020, 22:42

I would do something silly like measure them.

Post by **ggleavitt** » 29 Apr 2020, 08:58

You probably would. And I would pick up the phone and call Wayne Lyng over at Lisle and ask him so to each their own.

Many folks don't have the opportunity to easily measure, and it's a question that's been asked repeatedly since I joined this forum in 2006.

If someone sees something inaccurate in this post, please let me know, I'm happy to cover any other variances.

qjohn · Post by **qjohn** » 01 Aug 2021, 18:29

This info was extremely helpful to me. On my 2005 XC90 2.5T is 316mm rotors and I was thinking the rotors on my identically equipped 2006 XC90 2.5T would be the same size, but it turns out they are 336mm.

Post by **ggleavitt** » 02 Aug 2021, 21:24

I'm going to add to this.

First photo is a 328mm rotor on the left, a 336mm rotor on the right.

Second photo is what it looks like when you're tired after a long suspension rebuild weekend on your "new to you" '06 Ocean Race and you don't realize until your forum friends point it out that you have a 328 rotor on a 336 calipered vehicle. It's the express reason I have two sets of rotors in the first photo.

Post by **abscate** » 05 Aug 2021, 01:31

ggleavitt wrote: ↑29 Apr 2020, 08:58 You probably would. And I would pick up the phone and call Wayne Lyng over at Lisle and ask him so to each their own.

Many folks don't have the opportunity to easily measure, and it's a question that's been asked repeatedly since I joined this forum in 2006.

If someone sees something inaccurate in this post, please let me know, I'm happy to cover any other variances.

I would just measure too except my Volvos are now dispersed across 400 square miles of the Northeast.

This is great info and we appreciate it.

ylwgto · Post by **ylwgto** » 19 Aug 2021, 11:30

Great post I could have used a week ago!
I have a '09 3.2 R and was told it had 336mm rotors. Ordered them, began instal only to find out the car has the 328mm, twin piston setup. Argh!

BTW, how does one remove the anti-chatter clip on the twin piston caliper? Didn't try to hard to figure it out, but it was not similar to the single piston clips I know well. Is there a "trick"?

Also, your diagram says 308mm instead of 328mm (simple typo)
Thanks!

Post by **ggleavitt** » 19 Aug 2021, 15:36

Top photo is 316 or 336 for the front, 308 rear. I only have the photo of the 328s as I made a mistake when ordering them (the correct 336 are on the right).

Don't know exactly on the 328 clip but I saw this mention in Swedespeed:
"Insert the screwdriver IN the notch and then twist/pry. It's visually counter-intuitive, but it'll pop out with ease. When I tried to remove it the first time, I fussed with trying to pry off the retainer under the notch, etc. to no avail."

Masscomguru · Post by **Masscomguru** » 19 Aug 2021, 15:38

ggleavitt wrote: ↑19 Aug 2021, 15:36 Top photo is 316 or 336 for the front, 308 rear. I only have the photo of the 328s as I made a mistake when ordering them (the correct 336 are on the right).

Don't know exactly on the 328 clip but I saw this mention in Swedespeed:
"Insert the screwdriver IN the notch and then twist/pry. It's visually counter-intuitive, but it'll pop out with ease. When I tried to remove it the first time, I fussed with trying to pry off the retainer under the notch, etc. to no avail."

This is accurate. I use a flathead screwdriver in from the center of the wheel and pry and twist it out. The clips rock out of the mounting holes. To replace, simply align them up and I use a hammer to tap them back in place.

ylwgto · Post by **ylwgto** » 20 Aug 2021, 09:08

Masscomguru wrote: ↑19 Aug 2021, 15:38
ggleavitt wrote: ↑19 Aug 2021, 15:36 Top photo is 316 or 336 for the front, 308 rear. I only have the photo of the 328s as I made a mistake when ordering them (the correct 336 are on the right).

Don't know exactly on the 328 clip but I saw this mention in Swedespeed:
"Insert the screwdriver IN the notch and then twist/pry. It's visually counter-intuitive, but it'll pop out with ease. When I tried to remove it the first time, I fussed with trying to pry off the retainer under the notch, etc. to no avail."
This is accurate. I use a flathead screwdriver in from the center of the wheel and pry and twist it out. The clips rock out of the mounting holes. To replace, simply align them up and I use a hammer to tap them back in place.

thanks all. i'll try when the correct rotors show up