how solid is this rotor adapter setup

Thread engegment is much more critical. Better to use 1.5x for aluminum thread engagement. I wouldn't hesitate to cut the caliper mounts. Its farily easy to do if you supply the whole front end. I did it on my KZ750 to fit a big ol 2 piston Brembos on the stock wheel. I would recommend using a ball end mill to prevent a stress raiser
So i dropped off the fork tubes and calipers at the machinist. He agreed with you and we decided that it would be best to take off 2mm off the caliper and 2mm off the fork leg.
Fingers crossed :)
 

ex119x

Member
If you are at the point where you are questioning material strength and thread engagement, I would reconsider using those calipers and look at the ones Irk suggested. Those 2 piston calipers are plenty strong enough as evidenced by the number of SV650 race bikes. Kawasaki also used the sliding 2 piston calipers and they had a larger mounting bracket that may be easier to just redrill to the appropriate caliper mount spacing for your forks. The sliding 2 piston calipers are cheap and readily available.
 
If you are at the point where you are questioning material strength and thread engagement, I would reconsider using those calipers and look at the ones Irk suggested. Those 2 piston calipers are plenty strong enough as evidenced by the number of SV650 race bikes. Kawasaki also used the sliding 2 piston calipers and they had a larger mounting bracket that may be easier to just redrill to the appropriate caliper mount spacing for your forks. The sliding 2 piston calipers are cheap and readily available.
but i'm not. That was only when considering the removal of all 4mm of material off the caliper.
What we are doing is the slightly more expensive option of removing 2mm from the caliper and 2mm from the fork mount.

2mm is 0.0787" .... it will be fine with that amount gone.

The bracket to be CNC machined for an SV 650 caliper would cost MUCH more. What some might be forgetting is that unlike SV650 forks, i can't just mount a bracket to the outside, then mount the caliper to the inside of the bracket, space it as required, and button down.

The fork leg is designed such that it caliper/adapter must mount on the inside. Mounting on the outside would require further machining and removal of more than 2mm to fit an adapter plate .... alternatively, you could forego the machining, but spend much more $$$ for a more complicated CNC'd adapter that would fit those holes from the outside. (See page 2 for pics of adapter friendly forks on SV650 and my forks)

I've concluded that this is my cheapest, and quickest option. I could be wrong .... stay tuned :)
 

irk miller

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Every custom bike I build gets the SV calipers, including those with GSXR and TL1000r front ends. Most of the time, they require nothing more than $2 of flat stock with 4 holes drilled. In most cases, I weld threaded bungs to the brackets but you could just as easily use flanged nuts. It takes far less effort and money than what you are doing here. I've been watching this thread thinking you are taking your approach to avoid the extra bracket, for a cleaner look or something.


 
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teazer

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I like those set ups. I used SV calipers on the Phat Trakka with stock GT750 wheel and forks and they work better than anything I had tried up to that point.

Or dump the Comstar and use a GSXR/TL front wheel.
 
Every custom bike I build gets the SV calipers, including those with GSXR and TL1000r front ends. Most of the time, they require nothing more than $2 of flat stock with 4 holes drilled. In most cases, I weld threaded bungs to the brackets but you could just as easily use flanged nuts. It takes far less effort and money than what you are doing here. I've been watching this thread thinking you are taking your approach to avoid the extra bracket, for a cleaner look or something.



Yes, that would have worked because the caliper is much much thinner on the inside so positioning isnt a big deal.

With the lockdown in place, I cant cross the border to pick up parts, so I had to do with what I could by buying from Canadian sellers. At the time this was my best option.

In hindsight, the easiest thing would have been to use my 2001 tubes, which would have allowed an adapter plate to mount on the OUTSIDE of the fork and given much more flexibility. The '99 tubes were just a bit better shape and just a bit longer which worked better for me.

Definitely not saying this is the best or easiest way to go. But it certainly will be the first case of running these calipers with these comstar wheels that I have seen .... so at this point I'm just documenting all of it in hopes it helps persuade or dissuade someone from taking the same route lol :)

To machine the calipers and fork tubes 2mm each is going to cost $80 canadian at the local machinist. Honestly, at this point it's cheaper to pay for that than to invest in another set of calipers and wait longer.

Let me be clear if it wasnt for covid 19 and borders I would have done what you did, but a small part of me did think just maybe the 4 pot ones would fit.
 
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irk miller

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To understand, you're saying this is a bird-in-hand decision? The SV style Tokico can be bought for as little as $10 on Ebay in usable condition, often with half their life left pads. There are literally hundreds of listings. The pads that the Tokico uses (like I'm promoting) cross-references with, I swear, like 100 different model calipers, including a bunch of Chinese re-pops, so you can get replacements dirt cheap. I admit, I'm a bit confused on how Covid relates to all this considering you could spend under $50 to get the SV calipers and spend another 10 on brackets, but instead you're going through all the effort sending stuff to be machined during the pandemic. I'm in Georgia, in the US, so I may not have a clue on your Canadian restrictions. Also, the red bike I posted has 2001 TL1000r forks, which are the same as your GSXR forks (also Hayabusa). That front wheel is a 17" GL1000 rear rim laced to a GL1000 front hub, so the hub spacing is identical to your CX Comstar. The rotors are 95-96 FZ600r, which shares the same bolt pattern.
 
I cant order stuff from ebay sellers in the USA. They all want at least $50 usd for cross border shipping on top of the price and on top of that I would probably be hit with taxes/duties so it just isnt worth it to order from USA to Canada.

Prior to covid I used to just order to Blaine, Washington, to a drop ship place, and go pick it up myself. It would take me 15 minutes and be much cheaper.

Prices in canada are quite a bit higher than USA. Those calipers would not be $10. Guarantee you that.

So, yeah, bird in hand basically, since covid19 is preventing me from buying from USA sellers
 
What diameter are those fz600r rotors? 300mm? I was under the impression that only 320mm would work with those forks based on caliper positioning.

I guess if I had known that, that would have been the best option. But I didn't find any rotors that matched the bolt pattern at the time.

Didnt you have to space those rotors out?!? My hub width is only 80mm. I think the gsxr hibs are around 130mm.

Did you somehow space the calipers in that much, or are the rotors dished and I just cant see from the pic angle?
 
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irk miller

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What diameter are those fz600r rotors? 300mm? I was under the impression that only 320mm would work with those forks based on caliper positioning.

I guess if I had known that, that would have been the best option. But I didn't find any rotors that matched the bolt pattern at the time.

Didnt you have to space those rotors out?!? My hub width is only 80mm. I think the gsxr hibs are around 130mm.

Did you somehow space the calipers in that much, or are the rotors dished and I just cant see from the pic angle?
300mm, yeah. I misspoke. They're YZF600r. Sorry to mix that up. I can double check the measurement when I get home. They could be 305mm. IIRC, I spaced them 25mm, but they could be spaced at the caliper too as long as there're clearance from the wheel. On the XS, I spaced them 8mm, which is done just by cutting out the center of a stock rotor.
 
300mm, yeah. I misspoke. They're YZF600r. Sorry to mix that up. I can double check the measurement when I get home. They could be 305mm. IIRC, I spaced them 25mm, but they could be spaced at the caliper too as long as there're clearance from the wheel. On the XS, I spaced them 8mm, which is done just by cutting out the center of a stock rotor.
I wish I had contacted you earlier. Every post on this I've ever read had 320mm (or bigger) rotors and adapters to space them out. No one had mentioned there are rotors with matching bolt pattern. I looked at a few catalogs from EBC and also didnt find any. One guy even had custom dished rotors made to avoid an adapter, at a high price of almost $500!

Do you think the 300mm rotors work with my setup with the calipers in stock position (for 320mm)? Or would the pads be grabbing outside the rotor diameter? Because those rotors would certainly be a cheaper option considering the adapter would be so simple to make.

I can mock this up as well, when I get my forks back. I'll just cut out a 300mm rotor out of cardboard and get an idea.
 
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I just looked it up on ebay .... and those YZF600r rotors should be 6 bolts??

What year are yours? The mid 90s ones are all showing as 6 bolt.

The comstar I'm using is 5 bolt PCD is 78mm I believe with a 58mm bore.

But i love that idea of making a spacer with the stock rotor center cut out. That might come in handy as I have 4 of them laying around here.
 

irk miller

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Look at 99 - 07 Hayabusa/GSX1300r front rotors. I think those are the matches for your 5 bolt Comstar. They are also 320mm.
 
Look at 99 - 07 Hayabusa/GSX1300r front rotors. I think those are the matches for your 5 bolt Comstar. They are also 320mm.
The PCD is not the same. There are some options that have a 6 bolt on 78mm PCD pattern, which could be redrilled to 5 bolt I need (cbr900rr certain years) but they are 310mm. And I dont think that would work for me.

I have to see where the 320mm sit and if the 310 would leave 5mm of pad sticking out beyond the 310mm rotor or not.
 
How close is too close?? How much flex can I expect from caliper, fork mount, or wheel in normal riding conditions?

The wheel is on and spins freely. I ended up doing just 2mm off the caliper mount, and shaving the back down a bit.

There is room to fit a business card on some spokes and a regular piece of paper only on two of the spokes.

20200531_170951.jpg
20200531_171202.jpg
 

doc_rot

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If it were me I'd shoot for at least 1mm. this isn't really an area you want to hedge your bets.
 
If it were me I'd shoot for at least 1mm. this isn't really an area you want to hedge your bets.
Got it. Thank you. 1mm is reasonable. I was hoping people would not chime in with more than that.
(The reason it is tight is because the fork legs were not touched. The machinist said it would take too long for him to set them up in addition to the calipers, so i told him no, i'm not paying.)
 
how much meat did he take off the caliper? Could you chamfer one side with a file for a little more clearance?
I didnt take the pistons out to verify material thickness yet, but I'm at my comfort level right now with how much has already been taken off. I dont want to take anymore off.

This should give you a better idea.

20200601_202259.jpg
 

doc_rot

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sharpen the edge of the comstar into a cutting edge that way if there is any contact it will fly cut the caliper and clearance its self.

haha. no, dont do that. but If i was being a cheap ass Id ride to a rough bit of road at low speed and casually mash the brakes and see if anything happens. if it was gonna be catastrophic later it might leave a witness mark under those circumstances. still would prefer 1mm clear.
 

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