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Roadster Disc Brake mod mklotz70


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I've been meaning to post this info for some time now. I was going to put it in the Roadster section, but I thought that some of the info might help someone else figure out how to do a disc mod on something other than a Roadster.


Leigh(shifty on the 311s forum) approached with about this at the last Canby. His brake upgrade was based on a fairly common mod where the stock hub has 5mm machined off the backside to allow clearance for the new rotor. He wasn't happy with the wheel to caliper clearance and was wondering if I could make a spacer to add some of the 5mm back to the hub. After looking at it a bit, what I decided to do was to push the entire hub out just a bit with a custom spindle/bearing spacer. In fact, it turned out to need the exact same spacer that I make for the 411 disc brake kit. I'm not going to go over the Volvo caliper mod. Using Volvo calipers is fairly common for the roadster guys and the info is fairly easy to find on the web.



Let's start with some "before" pics. As you can see, he's got a 3mm wheel spacer on the hub to get the wheel to caliper clearance he needed. The rotor is an Altima rotor and the calipers are Volvo calipers. If you look at the first and second to last pic, you can see the difference in the amount of space behind the lug bolt head. In the first pic, there's very little because of the 5mm that had been removed from the caliper mounting surface. In the second to last pic, there's a lot more. It's very expensive to have the hub machined and their fairly rare...as are all Datsun parts....so this new method eliminates a lot of cost and risk. this mod is reversible.



















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The hub does not require any mods, but the rotor's center hole will need to be opened up. Normally, I'd rather modify the "hard part", but there's no way to machine enough of the hub's diameter away to make the rotor fit. The rotors are fairly cheap and the machine work to them fairly simple....so get a second set at the same time if you're that worried about wearing through these rotors. Seriously, these rotors on a tiny Roadster will last quite some time!







Note the slight radius where the pen is pointing. When the rotors are cut, they need to have a slight clearance chamfer on the hole to clear this.









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Like I said, I'm not going to go into the Volvo caliper mod, but this part I had to do for my needs, so I took some pics anyway. The mounting holes on the calipers need to be drilled out to allow the mounting bolts to fit. These calipers are not very expensive, so it's far better to mod the cheap, readily available caliper than the really hard to find stock mounting bracket. If you do it carefully, you can open them up with a 1/2" drill bit in a hand drill. I used the drill press since it's sitting there anyway :)











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Next up...getting the caliper centered on the rotor. I figured it out to be an 1/8". I measured the space with the caliper pulled up against the rotor and then again with it hanging on the rotor. Looking back at my math, I don't think I measured it right, but I guess I got lucky. 1/8" spacers centers the rotor very nicely.










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You can see that I could not make it a simple rectangular spacer because of clearance needed to the stock mounting bracket. I took some measurements, drew it up in CAD, printed it and then used the 1:1 print as a template to hand fabricate the prototype pieces. I will have these laser cut if this kit goes into production.















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We mounted everything up to Leigh's car. We had to tweak the dust shields back a bit, just like in the previous vid. He had more wheel clearance with this mod than with the previous version(machined hubs). I'll have to check and see if I have any vids of the install and fit. Could be I haven't edited them yet.












We tried a factory 14" rim while we were at it. They're really, really close, but it didn't actually rub. I just found the two vids with the stock wheel info, but I'll have to upload them a bit later. I'll just come back and edit this post to include them.









Maybe Leigh has some pics or vids to add. I will post up page on my bluehandsinc.com site when I figure out the pricing. I haven't been in any rush to produce this since there hasn't been much interest in it. It could just be that there hasn't been much interest because I haven't put any of this info up yet. :)

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Nice work in figuring this out.


The L31/G20 rotor is 280 mm diameter. The stock Roadster disk looks to be the same size and a lot lighter. Could you fit the Girling calipers on the stock rotor?


Are the Girling calipers aluminum? They are only $30 each remanufactured.


The brake pads look to have twice the area

1980 Volvo 242 front



vs 1970 2000 Roadster


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Thanks :) Actually, I simply figured out a better way to do an already existing mod. Sorry, I have no clue about any other roadster mods. I'm sure there are a couple of other versions out there that can run the stock rotor, but I hear they're about $120ea these days.....and they still fade badly when running down a hill quickly. This setup is a nice, affordable compromise to the $1500 options that are out there. Feel free to use these ideas to create something else :) oh....someone said something about a 240sx rear rotor.....maybe they've been using those on the fronts as a lighter option? I'd like to have a roadster, but I don't yet, so I haven't spent any time researching them. Shifty from the 311s forum supplied all the info I needed. Basically, I needed to put the info on that forum, but I'm much more familiar with this one....so I posted it here and put a link up there. :)

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Thanks Mike :)


GG....yep....it's quite a bit heavier because of the full frame. The $1500 wilwood option is way overkill unless your putting it on the track, but roadster guys seem to have more money to do that kind of upgrade. This one is for the Ratsun level of roadster owner :)

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I was dead set on getting one, but it seems the only ones I can afford are ones that need way too much of the kind of work I don't want to do. For now, I'll just work on other people's.....plus I don't have to change the oil, wash it, insure it.....just design parts for it, which is about the only thing I want to do with any car any more! LOL! :)

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  • 2 weeks later...

Got a special order for crossdrilled rotors. Turned out that the sides of the top hat were not machined. I had to machine a surface in order to cut the hole open. I machined more than I needed to on the first one, then only what I needed on the second. They got boxed back up and sent out today. And if you're wondering, the grand total, counting rotor cost, machining, postage, paypal fees...was $220.....just for these cross drilled rotors. He's going to be putting the car on the track, so it's what he wanted. :)























I'm starting to remember to use my white board for stuff like this. I can write it on here big enough that I can see it from the lathe....then I don't have to chase paper around the shope :) The second pic is for those guys that didn't see my thread/post about turning my garage door into a white board. :)






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I've posted some of this info already on teh 311s.org forum in answer to a question. Thought I'd put it up here too. I've got 5 sets of bearing spacers done. One of the sets in the pic goes back in a 411 kit. The caliper spacers are on order and should be here in just under 2 weeks. I'm getting ready to place the order for the hardware, so it should show up prior to the laser cut parts. I'm going with 1.5" flanged grade 8 bolts and loctite to mount the calipers. According to my measurements, this will get the fullest engagement without protruding out the back where it might hit the rotor. A .5ml ampule of 242 loctite will be included in the kit.


One of the 4 kits is already spoken for and the extra set of bearing spacers is on hold. I will have 3 kits with rotors available in 2 weeks for $200 + $20 shipping. Anyway....here's some pics, mainly for reference. :)


































Disregarde the 1-5/8" on the paper....it would be the perfect length with a lock washer, but nobody makes that length. I don't want to have to stack washers to make a 1-3/4" bolt work, hence, the 1-1/2" flanged bolt with no washers. As you can see in the pics of the caliper bracket holes, the threads do not go all the way through the plate. A 1/2"-20 gr8 bolt requires about .230" of thread engagement(round to 1/4") and there's only about 5/16"-3/8 of thread in the plate. Not much leeway for bolt length options.



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I've been posting most of the info on the 311s.org thread....guess I should try to keep this one up to date until I can get my webpage made :)


I got the caliper spacers back from the cutter this morning :) They fit perfectly!!!! I also received the rest of the hardware today. I just need to separate it and box it up and they'll be ready to ship.





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I put these up for sale on my site... www.bluehandsinc.com


I have 3 kits available since one of the 4 already sold.


Here's what I came up with for pricing.


$105 shipped for the basic kit(no rotors)

$220 shipped for the kit plus modified rotors.



yep.....that may seem a bit steep on the rotors, but since I have to buy them locally...I'm expecting low quantities at this point....and machine them in small numbers, I wanted to make sure that I could sell them at the same price every time, even if the price I pay varies. Plus, there's an incentive for guys to get them done locally instead of having me do them.


I got the quote back on having the bearing spacers cnc'd. The kit price will stay the same. I need to see some interest before I place an order for 50 spacers! lol :)

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