GT350 Rotor Measurements

[rocket71]

I am hoping someone might have a spec sheet or measured the GT350 rotors. I am looking for the hat offset.

Thanks!

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[Epiphany]

Face of hat to outside face of rotor?

 

[rocket71]

Here is a link to Wilwood. Just click on the diagram. It is hard to describe but it appears to be the back of the hat face to point where the rotor mounts on the hat.

http://www.wilwood.com/Hats/HatList.aspx

 

[Epiphany]

Your link opens a page full of rotor hats and not anything specific.

You mention the "back of the hat face to point where the rotor mounts on the hat." That isn't relevant when the hat is fixed such as that of the GT350 rotor and the had is affixed by radial pins and the hat does not sit on the rotor face. If you can be more specific I can pull up a factory GT350 rotor and give you the most accurate data you can find. I suppose it starts with what do you need the data for or what are you trying to do? Are you trying to adapt a GT350 rotor/caliper to a non-GT350 application?

 

[nastang87xx]

Your link opens a page full of rotor hats and not anything specific.

You mention the "back of the hat face to point where the rotor mounts on the hat." That isn't relevant when the hat is fixed such as that of the GT350 rotor and the had is affixed by radial pins and the hat does not sit on the rotor face. If you can be more specific I can pull up a factory GT350 rotor and give you the most accurate data you can find. I suppose it starts with what do you need the data for or what are you trying to do? Are you trying to adapt a GT350 rotor/caliper to a non-GT350 application?

Fit 18" wheels, from another thread. What I don't understand is why the rotor offset would affect fitting an 18" wheel. It's the caliper that simply doesn't accommodate an 18" wheel barrel. The GT350 wheel offsets are plenty enough to not worry about lateral brake clearance. :shrug:

 

[JAJ]

...What I don't understand is why the rotor offset would affect fitting an 18" wheel. [...] The GT350 wheel offsets are plenty enough to not worry about lateral brake clearance.

You're right, but most wheel barrels have a slope - they're bigger toward the back - so maybe it's about moving the rotor back to move the caliper back to make more room. Or something like that.

 

[Epiphany]

Fit 18" wheels, from another thread.

Gotcha.

Good luck OP adapting any 18" wheel to the factory GT350 rotor/caliper/knuckle. If you had a custom two-piece rotor made that then necessitated moving the caliper further inboard you'd need a custom caliper or caliper bracket that allowed you to offset the caliper relative to the mounting points on the knuckle.

 

[rocket71]

I posted another thread about fitting 18x12's with 335's. I meant that thread to be more geared toward getting the right brake fitment. People want to keep pointing toward BoardKat's fitting to 18x12 and now 18x13's. Or they want to argue the why? or suggest the Essex kit for $4500.

I have pictures of a GT350 running 18x12's with the FACTORY GT350 caliper. I know it will work. I appreciate the pain and struggle the person went through to figure it out. I have his pictures too. Out of respect for a fellow competitor I don't feel right sharing them without permission. I am just trying to get some group help. Here is what I know....

1. Machine 5/8 of an inch off the GT350 spindle from the mount surface of the caliper. This moves the caliper inward 5/8". This takes 5/8" off the radius or 1 1/4" off the diameter of the size of the total brakes. Now you only need a wheel that that can fit 16".

2. With that modification you will need a smaller rotor. (please, yes I know you don't like that but to get to 18" wheel there are sacrifices.) The Essex kit uses a 14.6" rotor. I am not sure a 15" rotor or 14.5" rotor is needed.

3. Here is where I am currently. I need to measure my GT350 rotor hat offset. Why? Because that is the number I need to ensure a new hat will correctly place the rotor in the middle of caliper. Seems simple enough. I will also need to ensure it at least close in thickness.

Finally, I have bought a spindle for testing. I will get it milled and continue my search for the correct rotor.

 

[rocket71]

And Wilwood just confirmed I am on the right track. Once I get them the data I should be in business. BINGO! So internet wisdom says I am crazy but they say I am on the right track. Whoot! Whoot!

 

[nastang87xx]

Did the owner share what wheel manufacturer he's using?

 

[rocket71]

Did the owner share what wheel manufacturer he's using?

Looks like Forgestar in the picture.

 

[Epiphany]

So you want to mill the knuckle faces where they meet the caliper mount faces by 5/8" thereby moving the caliper 5/8" closer to the hub centroid. You are planning on having a two piece rotor made up that mimics the factory "as mounted" dimensions except it will have a 1-1/4" smaller OD than an OEM factory rotor. I assume this means you will also then be drilling the threaded holes where the caliper bolts go an additional depth and then threading to make up for the 5/8" you milled off.

You'll be maintaining the stock rotor (or ring) thickness as well as the inside hat face to outer rotor face (or inner, or center, if you prefer).

 

[rocket71]

So you want to mill the knuckle faces where they meet the caliper mount faces by 5/8" thereby moving the caliper 5/8" closer to the hub centroid. You are planning on having a two piece rotor made up that mimics the factory "as mounted" dimensions except it will have a 1-1/4" smaller OD than an OEM factory rotor. I assume this means you will also then be drilling the threaded holes where the caliper bolts go an additional depth and then threading to make up for the 5/8" you milled off.

You'll be maintaining the stock rotor (or ring) thickness as well as the inside hat face to outer rotor face (or inner, or center, if you prefer).

You stated it better than me. That is the plan. I am not sure about the caliper bolts for sure just yet. Right now I don't plan to have a rotor made as off the shelf parts were used in the original project.

 

[Epiphany]

I pulled up a factory GT350 knuckle and split one of the sides off so that you could visualize how much bolt depth you'll have to work with. The blue line represents 5/8" of the knuckle body that I'm going to remove.

I'd proceed with caution here and ensure that the caliper fastener you use (whether a bolt or a stud) has at least the minimum amount necessary of embedment. You can see that on one side you don't have a lot of additional room left if you need to drill deeper.

Here are the rotor thickness dimensions as well as face of hat to face of rotor.

In case you need a dimension from the inside face of the hat to "X" here is a cross section of the factory GT350 hat where I measured thickness.

You should be able to work the above dimensions in whatever way necessary to provide the data needed.

 

[Norton961]

No gain in running 18” wheels unless you are concerned with price of the wheels and tires.

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