Quote
hoche
From the other thread:

Quote
danster
My dog needed out for a piss so just picked up a front VW 256mm vented disc from the shed.
It fits perfectly on the rear Polo hub, it centres correctly, it's 4 x 100, even the little brake disc retaining screw is in the right place.

And this also means the front 239mm vented or solid disc will fit.

Erik, if you've got your car up in the air can you check to see if the front discs available here will work? That could save some buckskies.

I dug up a solid mk2 front rotor and tried it out on my Polo setup. The short answer is it won't fit. The top-hat on the mk2 rotor is shallower than the Polo rotor. Because of this, the caliper carrier doesn't fit correctly - you end up with a gap between the carrier and where it bolts to the stub axle.

Here's the mk2 front rotor on the left and the Polo rotor on the right. You can see the offset from the hub is shallower on the mk2 rotor. It's also larger in both thickness and diameter by a few mm.



This shot is from the back after I put the mk2 rotor on the hub. You can see the gap between the caliper carrier and the stub axle due to the shallower mk2 rotor.



It might be possible to get longer bolts and space it with some washers, but I'm not sure I would be comfortable doing that on the brake system. You may also have to do a little bit of grinding on the carrier due to the larger dimensions of the rotor (thickness and diameter). So it could be possible, but it's not a simple bolt-on.

I used some machined spacers to get the caliper out in the right spot. I also machined/used a grinder on the caliper carrier and the caliper to fit around the thicker rotor.
I have been looking at Toyota MR2 Rotors, they are about the same thickness (10mm) as the rears. I would just need to make the spacers to get the caliper in the right spot.

Quote
Erik Christiansen

Quote
hoche
From the other thread:

Quote
danster
My dog needed out for a piss so just picked up a front VW 256mm vented disc from the shed.
It fits perfectly on the rear Polo hub, it centres correctly, it's 4 x 100, even the little brake disc retaining screw is in the right place.

And this also means the front 239mm vented or solid disc will fit.

Erik, if you've got your car up in the air can you check to see if the front discs available here will work? That could save some buckskies.

I dug up a solid mk2 front rotor and tried it out on my Polo setup. The short answer is it won't fit. The top-hat on the mk2 rotor is shallower than the Polo rotor. Because of this, the caliper carrier doesn't fit correctly - you end up with a gap between the carrier and where it bolts to the stub axle.

Here's the mk2 front rotor on the left and the Polo rotor on the right. You can see the offset from the hub is shallower on the mk2 rotor. It's also larger in both thickness and diameter by a few mm.

Hi Eric, regarding the use of front discs on the Polo rear hubs, I mentioned they fit in the context of a brake upgrade that would use larger discs, the disc offset differences could be compensated for in the caliper carrier mounting method.
Standard rear discs are 226mm diameter so fitting larger discs would have to involve adjusting the placement of the standard caliper (which will only fit over solid discs), or installing a completely different caliper setup that suits the larger diameter disc diameter (and width if going vented).

I need to dig some axle and brake stuff out of the shed later so will checkout some dimensions on a few different calipers that may have potential. Not sure a solely hydraulic E brake is legal but recall in another thread that scrutineers may not notice....

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Disappointingly not yet a Jackass



Edited 1 time(s). Last edit at 10/18/2013 06:07AM by danster.

This is a very useful and helpful thread. Thank you guys for writing clear information for others to learn from.

Unlucky for me I always removed one of the front wheels on my Golf, never the rear but I would get right on one of these options if I still owned the car.

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In the long run reality always wins.

Quote
danster
I need to dig some axle and brake stuff out of the shed later so will checkout some dimensions on a few different calipers that may have potential. Not sure a solely hydraulic E brake is legal but recall in another thread that scrutineers may not notice....

What increase in rear brake rotor size over the std 226m solid discs do the knowledgeable gravel types here consider a benefit before the weight gain starts to be a factor and further size increase is purely for show over function?

The following sizes fit on the Polo 4 stud hub but will require alternate calipers or brackets:
Oversize options are 239mm solid, 239mm vented, 256mm solid, 256mm vented, and finally the 280mm vented which is too feckin big imo and I'd imagine won't fit under 14inch rims anyway.

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Disappointingly not yet a Jackass



Edited 1 time(s). Last edit at 10/31/2013 04:58PM by danster.

Quote
danster

Quote
danster
I need to dig some axle and brake stuff out of the shed later so will checkout some dimensions on a few different calipers that may have potential. Not sure a solely hydraulic E brake is legal but recall in another thread that scrutineers may not notice....

What increase in rear brake rotor size over the std 226m solid discs do the knowledgeable gravel types here consider a benefit before the weight gain starts to be a factor and further size increase is purely for show over function?

The following sizes fit on the Polo 4 stud hub but will require alternate calipers or brackets:
Oversize options are 239mm solid, 239mm vented, 256mm solid, 256mm vented, and finally the 280mm vented which is too feckin big imo and I'd imagine won't fit under 14inch rims anyway.

Wull, If we were to just look around a bit we might notice that them wuverry F@ cars were all in 15" wheels on gravel and used discs right around 280mm--and solid mind ya. So since you don't have 15, what's there nearest???
Hmmmmmmmmmmmmmmmm?
Aye, wery good laddy 14" which happily enough is what you have on your car.
So what is neawest to 280 but will fit under a weeeee widdle cute little 14"?
Dere ya go! 256! And if solid was good enough for those weally wad F2 cars, solid out to be OK enough for youse.
But don't believe me, I was just told that I am an idiot and wrong about 9 times out of 10...
I think you should find a weal ex-spurt....and not somebody who is a mere expert in braking and worked directly on it... Somebody who has a Docorate.. In anything, because if they have a doctorate in anything that means they're smrat-er-er than you'se and meece.
I mean you've already seen that there's folks who can speak with uncanny certainty on everything to do wif suspenders, which i thought was complicated, but nope, he's dead certain, so simple brake sizing I think you need wiser guys than me..you need a real wise guy.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham
I think you need wiser guys than me..you need a real wise guy.

Or at least a Wisearse....

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Parfois, on fait pas semblant!

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I am from:

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Nowhere.

Quote
Creech

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john vanlandingham
I think you need wiser guys than me..you need a real wise guy.

Or at least a Wisearse....

Wisetits is where it's at for me. And like brake rotor size once they get too big it's just excess weight to carry around.

I only threw the question out there for discussion as many use the standard size rears and seem to manage fine, therefore a jump from 226 to 280 seems a huge step and of questionable merits when the car ain't going to be driven by the likes of Loeb or Ogier.
Plus if the car is built light and only using a small engine then surely the brakes don't need to be sized for what would be used on a heavier and more powerful car.

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Disappointingly not yet a Jackass

I myself haven't experienced this type of failure but I would like to make sure I never will, so this upgrade is appealing to me.

Seeing as WRC Mexico is a few months away, perhaps we could take advantage of the fact that we would have friends in Mexico that could cart a bunch of brake stubs/hubs/discs/bolts back across the border for a modest fee? Thoughts?

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Runamuck Rally

Quote
danster

I only threw the question out there for discussion as many use the standard size rears and seem to manage fine, therefore a jump from 226 to 280 seems a huge step and of questionable merits when the car ain't going to be driven by the likes of Loeb or Ogier.
Plus if the car is built light and only using a small engine then surely the brakes don't need to be sized for what would be used on a heavier and more powerful car.

The reason I used a larger rotor on my first round of adapters was for easy of use and mounting. The caliper bracket bolts just fit in the backside of the adapters with the MASSIVE 239 front mk2 rotor. The added weight is there, but I have no solid numbers to back it up (edit, now I do). I do agree that lighter is better, and mk2/3 VWs do not really need more rear brakes from a larger diameter rotor.

With using a mk4 caliper and carrier, the mounting bolts are pushed further out so the bolts will easily clear the beam. This opens up the amount of rotors substantially, and the calipers are designed for a slightly thicker rotor.

So I was looking on rockauto today and took notice of all the rotor sizes:

mk2 rear w/ integrated hub: 226mm, 4X100, 8mm thick, 10lbs
mk2 front,solid: 239, 4x100 12mm thick, 7.54 lbs
mk2 front, vented: 239, 4x100, 20mm thick, 8.5lbs
mk3 front, vented: 256mm, 4x100, 20mm thick, 10.63lbs
mk5 rear, solid: 232mm, 5x100, 9mm thick, 6.25lbs

Toyota options:
mid-80's MR2 rear, solid: 240mm, 4x100, 9mm thick, 7.75lbs

1990 Honda CRX rear, solid: 239mm, 4x100, 9mm thick, 8lbs

It looks like the mk5 rear is the lightest, but it's in a 5x100 bolt pattern. Drilling out rotors to fit on the hubs would be very easy. VW uses a set screw and the ID to locate the rotor concentrically on the hub. The holes in the rotor are substantially oversized, so enlarging holes to allow the passage of a stud probably isn't a big deal. A file and hand drill could probably do as far as accuracy goes. 99% of the brake torque is probably transferred through the friction of the mounting faces. If anyone known of some lighter rear rotors, I would be interested in the info. Then again, the solid front rotors that I have been using are the second lightest.

Once again, I will mention it. If you are using the Polo brakes and hubs, you have absolutely zero parts availability in the US. This is the main reason I developed my system that used over the counter parts that are available anywhere in the US.
I hope this is enough info for all those wanting a solution

If lightness is so critical there are solutions:



Example:


The little one to the right is a stock Xratty, to the left is a Cosworth 4x4, and center is JVAB 32mm (1.25" x 283mm

It weighs what the stocker weighs and is just a shade bigger.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

John, what are you using for the discs? Off-the-shelf?

---

Parfois, on fait pas semblant!

I am:
I know:
I am from:

Nobody.
Nothing.
Nowhere.

While I do like the aluminum hat and dirt-track rotor, they are serious overkill for the rear of a vw (the front is another story though!) Also, polar moment of inertia is way higher on the larger rotor (function of r^4), so it may weight less but it'll take more energy to speed up and slow down. We all know that the little golves need all the help they can get.
The little bitty vw golves don't need anymore rear brakes. They only have about 400lb per wheel at static!

Quote
Robert Culbertson
While I do like the aluminum hat and dirt-track rotor, they are serious overkill for the rear of a vw (the front is another story though!) Also, polar moment of inertia is way higher on the larger rotor (function of r^4), so it may weight less but it'll take more energy to speed up and slow down. We all know that the little golves need all the help they can get.
The little bitty vw golves don't need anymore rear brakes. They only have about 400lb per wheel at static!

I was making fun at worries about insignificant amount of weight differences in rotors...in cars that seldom have anything really otimised like GEARING or final drive or wheels that point the right way...
When you really should be buying a pre-built Fiesta. Its 280 x 23 rotor and 54mm caliper is so much better than VW 280 x 22 rotor and 54mm caliper.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

There needs to be a sarcasm button somewhere. This whole communication through typing does leave a few things out.

I was slightly confused why you were suggesting such massive brakes for such light cars