# Any reason this won't work? Wilwood calipers on stock GLI rotors



## leftside (Sep 25, 2005)

My car is a 2000 1.8T Jetta.
I'm looking at picking up some Wilwood Dynapro calipers in a trade. 

I know I'm going to need brackets and lines. Rather than buy 2 piece Wilwood rotors, I want to use plain one piece 12.3" (GLI) rotors. The Wilwood Dynapro brake kit for the MK4 platform uses 12.19" rotor.

Any reason this won't work?

This is the kit the rotors came from
http://www.summitracing.com/parts/WIL-140-8276-D/

Thanks in advance


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## Chickenman35 (Jul 28, 2006)

leftside said:


> My car is a 2000 1.8T Jetta.
> I'm looking at picking up some Wilwood Dynapro calipers in a trade.
> 
> I know I'm going to need brackets and lines. Rather than buy 2 piece Wilwood rotors, I want to use plain one piece 12.3" (GLI) rotors. The Wilwood Dynapro brake kit for the MK4 platform uses 12.19" rotor.
> ...


The difference in diameter is insignificant. What you do want to check is the offset of the rotors ( distance from the backside of the rotor hat to center-line of the rotor ) is the same or very close. Radial mount calipers are nice because you can space the caliper in a horizontal or vertical distance a *small* amount by using shims or spacers . You will have to go to Wilwood's Technical site and get the dimensions of the rotors.


Also make sure that the rotor thickness is very close. Calipers come in various body widths to fit different thickness rotors . They can support a small variation in rotor thickness, but generally no more than .100" thicker. 

Make sure that the piston diameter is the same as in the kit. Calipers with different piston diameters and the pistons must be the correct size or you will have big problems with the the piston ratio calculation . 

If the calipers are not the same part number as in the kit...I would walk away from the deal. Sometimes buying used parts is not a good idea.


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## leftside (Sep 25, 2005)

*FV-QR*

Thanks for the reply!

Wilwood doesn't list an offset for the rotor, but they do list an offset for the hat, which I assume is what I'm looking for. The hat offset is listed as .41" 
I'm not sure how to find the offset of a stock MK4 12.3" rotor...I've been searching but haven't come up with anything yet.

The other issue is the thickness. The thickness of an OEM 12.3" rotor is .98" and the Wilwood rotors are .81" So a difference of .17"
Sounds like that may be a concern as well....but that still seems pretty close. 

The part number of the calipers he gave me is the same as in the kit. Wilwood only makes a couple 4 piston calipers (to the best of my knowledge) so I'm fairly certain it's right.

Unfortunately the Wilwood hats are expensive or I would just buy the Wilwood hats and rotors. 

Not sure if this is going to work or not....

What do you think?

Again, I really appreciate you help on this. I feel a little clueless on aftermarket braking.

For reference, these are the specs on the Wilwood kit
http://www.wilwood.com/BrakeKits/Br...n&model=Jetta&option=Jetta IV 1.8 Liter Turbo


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## leftside (Sep 25, 2005)

*FV-QR*

Went outside and took some crude measurements of my rotor hat with the wheel on the car. Obviously my measurement is less than accurate...but it looks like it's just under half an inch. Probably somewhere between 3/8 and 1/2 inch.


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## Chickenman35 (Jul 28, 2006)

I'll get back to you this evening with some more info that should help. I've got to go to work now...


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## leftside (Sep 25, 2005)

No problem, just got home from work myself.


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## Chickenman35 (Jul 28, 2006)

Sorry it's taken so long to get back to you. Work got really hectic over the last few days.

Bad news is that I don't hink this will work with the GLI rotors. WilWood actually make many different models of the DynaPro, for different rotor widths and different psiton sizes.

The ones in the kit are #120-7376 for .81" rotors. Piston size is 1.375" and come with piston dust boots. Looks like you need #120-7377 which are made for 1.0" rotors and come with piston dust boots. 

The Dynapro does not have much tolerance for over width rotors.....so I don't think you're going to squeeze a .98" rotor and new pads into the calipers designed for the .81" rotors.

Several choices are available.

1: Sell the 120-7376 DynaPro calipers ( .81" width ) and order the #120-7377 Dynapro Calipers from WiWood or elsewhere.

2: Contact Wilwood and see if they can upgrade their complete kit to use 1.0" rotors and the 1.0" wide caliper. You may be surprised at what they can do. Under $1,000 for a BBK like that is still cheap. Trust me..I've built some myself. 

3: Sell the DynaPro calipers and buy some used Porsche Boxster calipers. The Boxster caliper is superior to the WilWood. The Boxster caliper is a Brembo Mono-Bloc and is much stiffer than the DynaPro. The DynaPro's in the kit are bolt together halves, which are not nearly as stiff as a Mono-Bloc.

The Boxster calipers also have differential sized pistons. This is superior to same size pistons as the differential bore calipers reduce pad taper wear. Personally I would go with used Boxster calipers. I got a near mint set off of E-Bay for $350. 

I would buy the Apikol SS brackets. Well worth the price. Steel brackets are the only way to go IMHO. I do not trust aluminum brackets in this critical area. ( Road Racer for over 30 years )

I've got the Boxster calipers, Apikol brackets and pre-made Russell SS lines on my Audi A4. car stops unbelievably well and pedal is rock solid. I instruct at HPDE Track days and big brakes are a must at our local track.


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