R32 GTS-T 28mm caliper over 32mm disc?

[timbosaurus]

I was going to use my R32 GTS-T calipers with 298x28mm falcon rotors.

Turns our that the 65mm height on the standard falcon rotors does not really suit my application, so I'm contemplating a change to the "falcon premium" rotors which are 325x32mm.

I know I could sell my R32 GTS-T calipers and buy some GTR/R33 ones that suit the thicker discs... but do I actually HAVE to?

What I want to know is, has anyone used the 28mm nissan calipers on 32mm thickness discs?

P.S. I have searched, but it always seems to be the mounting location that drives people to use the larger caliper. I don't have that mounting restriction, so it's just the thickness that concerns me.

P.P.S The 'gap' in the caliper is ~35mm, and I can easily physically fit the disc in with worn pads... just not sure about new pads.

[barned01]

could you have the disc machined down a millimetre or two to get closer to the mark (while still being within the machined limits of the disc)?
could you have new pads machined down a little bit also? although i would have thought that with the pads fully set back on each side of the caliper that there wouldn't be that much of a difference in the 35 mm gap of the actual caliper anyway.

edit: actually looking at this http://www.toymods.net/forums/showthread.php?p=89822
the r33gtst caliper i had (still have somewhere?) also had a 35mm spacing for the rotor.
so if you read that a 32mm rotor was used on an r33gtst caliper and the spacing for the 33gtst is the same as the spacing for the caliper you have, then by logical association both calipers would be compatible with the 32mm rotor.

[timbosaurus]

Yeah, I guess I'll fit it all together as it is. When it comes time to fit new pads, I'll just allow enough time to fix the issue if it comes up.

But it certainly would be nice to have a level of confidence that new pads in R32 GTS-T calipers would still fit over a 32mm rotor

[barned01]

note my edit above...
the pads i got with my calipers were pretty full and they sat flush with the caliper edge from memory, so i don't think you will have too much problems with the pads sitting too proud of the gap i don't think

[timbosaurus]

logical association is good enough for me

[The Real Roadrunner]

32gtst will have a hard time going over a 325mm disc. you would have to diegrind the crap out of the ends to get the pads sitting on the disc correctly, change up to a 32GTR cliper and life will be a shitload easier for you.

check Bigmats rides thread, i put 324x30mm discs on his with minimal fuss.

cheers
linden

[timbosaurus]

cool, thanks Linden.

The 32GTS calipers seem to suit the 298mm disc really well.. I didn't think too much about the extra diameter affecting the anulus

[big_zop]

What Falcon rotors are you talking about as there are 3 types that have been used post BA? All dimensions im am certain about are quoted exact, others are estimates based upon background knowledge.

When the BA was introduced, all Falcons had 298x28mm discs and the FPV models had larger 32xmm (there may have been an option for a larger disc/Brembos as in later models but im not sure)

When BF was introduced, all std I6 Falcons kept the old discs and the V8/I6T now had 323x28mm dics (may have been the same as the old FPV but im not sure. also had slightly different offset of the base discs - 56.6 for 298 vs 59 for 323 measured from hub mounting face, hub is 8.25mm) and also had a larger rear disc that was vented. The new FPV discs were 355x32mm (and with much less offset as the other discs - 42.4mm, hub is 8mm) but have different calipers (4F/1R or 6F/4R) pending what package is used.

There was a change when the BF MkII was released (changed the large rear back to the normal solid for V8/I6T). There are also minor differences between the rears of the sedan and utes (sedans are quoted in all cases).

The FG was exactly the same as the BF MkII as far as i can remember.

I do understand what Linden is saying in regards to the inside profile of the calipers not suiting the larger discs. dori dori had the nightpager upgrade on his MZ20 which uses the said caliper and an adaptor to suit a JZA80 330x30mm disc and said there were no issues with the caliper and the size of the disc (apart form the obvious fact that it didnt use an inner percentage of the disc. pm him or Disturbed1 as he is now the new owner of this package.

I also have a set of worn pads (will need to measure to find out how much exactly) for R33 calipers if they will suit the R32 calipers that i can send you for the cost of postage (or pass onto someone up for the drags from toyota fest) so you can use them while you make your mind up?

[timbosaurus]

Thanks big_zop!

The ones I have are the standard six cylinder brakes. they are 298x28mm and the height is 65mm.

The ones I want to try are the 325x32mm BA premium rotors (DBA42104).

I overlaid a 330mm circle over a 300mm circle, and the difference in the curve does not appear very much (<5mm peak)... It would be interesting to see if the pad still kept full contact. I think so

The reason I like these discs is not their larger diameter or thickness (298x28 is fine for me!), but more because the height/disc offset lines the caliper up better for a mount.

The standard falcon discs mean I will have to do a stepped mounting bracket, which might be OK, but obviously not optimal strength.



Unfortunately the larger discs only come in DBA4000 series and above, which means about $530 a set through supersteep

[WDE_BDY]

Hasn't the R33 rotor got a hat height of 54 ish mm? Diameter 298mm and width of 30mm? That could be enough to get around your caliper mount problem compared to the BA rotor.

Callum

[big_zop]

Looks like the 355mm disc is better in that regard (less offset as quoted earlier - 14-18mm) but i guess you dont want 18s to fit them! Besides, suing the same calipers and pads on a larger disc is always going to give you better braking performance - if the tyres and suspension can handle it, at the disadvantage of increased unsprung weight where each kilo shed is worth 3kg lost in sprung (ie. normal) weight loss.

My guess is that the disc you have found (BA FPV) is different to the one i am certain/interested in (BF high po). What struts are these for and what car? How much less offset would you need to give you 'flush' mounting brackets?

EDIT: And as wde-bdy has metioned the R33 discs have about 10mm less offset than the BA discs (its a MX83 bolt on upgrade with a 10.6mm spacer between the caliper and the strut as opposed to the R33/BA which doesnt require such spacer)

[The Real Roadrunner]

I do understand what Linden is saying in regards to the inside profile of the calipers not suiting the larger discs. dori dori had the nightpager upgrade on his MZ20 which uses the said caliper and an adaptor to suit a JZA80 330x30mm disc and said there were no issues with the caliper and the size of the disc (apart form the obvious fact that it didnt use an inner percentage of the disc. pm him or Disturbed1 as he is now the new owner of this package.

I also have a set of worn pads (will need to measure to find out how much exactly) for R33 calipers if they will suit the R32 calipers that i can send you for the cost of postage (or pass onto someone up for the drags from toyota fest) so you can use them while you make your mind up?

when i did Bigmat's and various other large brake upgrades i try to make sure the top of the pad material sits 1.5 mm down from the top of the disc, this requires you to diegrind an r33 gtst caliper (296 or 8mm disc) to sit over a 324mm disc let alone trying to do it with an r32 gtst caliper which was designed for a 280mm disc.

the main part that causes the problem is where the disc enters and leaves the caliper, it will be touching the disc if you try to get the pad sitting correctly without relieving the ends.

Dori dori thought his sat correctly until i pointed out to him that the setup had the same problem (incorrect mounting of caliper) and had asked me to get it sorted out for him, but then the engine died and he would have probly since forgotten.

Timbo, when i was doing the research side of things i also found a couple of other pads that may suit your application better.

The Sumitomo calipers all take the same pad regardless of what they came off ie no difference between r32gtst and r34gtt, so that wont help you but depending on disc anulus etc you can run Evo pads from Brembo's (cut down to suit application) and a pad meant for an Aston Martin also (modded to suit).

Cheers
Linden

[big_zop]

And thats the difference between what you hear to what you know. Thanks for that Linden, its always great to hear sound technical knowledge and makes me proud to be part of this site.

timbo - have you thought of trying the R33 GT-R calipers (dont use a R34 as the mounting hole is 14mm, not the 12mm on the R33/R32 calipers - nesecitating you to open up your strut holes) along with the BF 322mm disc? i know it might not be as cheap, but at least you will have a complete brake upgrade to sell (in the form of your BA/R32 package) and if you have to use a locating ring with the BA disc, it will be the same for the BF one.

[timbosaurus]

I appreciate all your help guys, I really do!

You've all mentioned some really good point... some things which I might not have realised even once I had finished!

So to add some background info...

I had these 5-stud hubs machined up to fit on the standard RA23/8 spindles. I guess they are comparable to the MS65 hubs, except they were machined to fit a 298x28mm falcon disc (71.5mm hole) in a disc-over-hub arrangement.



This is them fitted to the strut.



When the brake disc is on, the rotor *just* clears the standard caliper bracket, which gives you an idea of the 'offset' of the rotor.



Once the caliper is mounted (very roughly for this pic), you can see why I would have to run a 'stepped' mounting bracket.



However, if I space the disc out ~20mm (to simulate the 20mm lower profile FPV rotor) you can see how it will sit the caliper nicely inline with the standard mounting bracket. You would obviously still need to make up a new bracket to suit the R32 bolt positions... but at least it would just be one flat piece of steel cut to a profile.



This leads me to two options:

1) use this setup and spend some time on a stepped bracket (similar to what it looks like you have done on Bigmats brakes, Linden), or

2) use the 20mm 'thinner' rotors from the FPV which have the same centre hole so would mount perfectly. The only downside is the cost of these new rotors, and (as Linden has suggested) the fact that the pads might not sit on the disc anymore.


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More random pics...

Linden, you were spot-on about the pad location. About 2mm between the edge of the pad, and the edge of the rotor. This is with the caliper casting just touching the rotor. Wouldn't want to push it much further than a 298mm rotor. Don't really wanna grind out that bridge either... if i can avoid it. And I will try to make whatever I do work with unmodified pads. A little bit of inconvenience.now will save a lot over the years to come.



This give you an idea of how the setup will sit.



And this is the clearance either side of a 28mm disc, inside the R32 GTST calipers. It is about the same both sides.



Cheers,
Timbo

[PlacentaJuan]

im sure if you made up a stepped bracket there would be a few people (especially me) that would want to do the same thing and buy the bracket...

if you moved the disc out then wouldnt that fuck aroudn with wheel offseet etc? also need new adaptors for the spacer and stuff.

i have been thinging about this (after dori did it) i dunno how much better braking you would get etc, but it would be cheaper than redoing the whole project again with upsized calipers.