how solid is this rotor adapter setup

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.
One side is ok. Slight mis-measurement in wheel spacers? Or perhaps manufacturing tolerance in the wheel. Probably the latter, actually, as a few of the spokes do stick out a bit more than others.

I will think about it more and decide what to do. I actually found the OEM calipers in a box i thought i threw out. As they are 2 piston, there is a ton of room on the inside of them. So with that in mind, i might also just do what IRK did in post #44 above using the same forks ..... IF i can find dished rotors that would work for my hub. I'd rather go with these for a cleaner look, but we'll see :)

I'll keep posting updates
 

sav0r

Member
On various racing cars I've had there's been as little clearance as like 3mm between various parts and the wheel ID. The main downside is that when you get a piece of gravel or another foreign object stuck between whatever the part is and the wheel it tends to machine your wheel in half and cause a rather abrupt deflation that is worse than a normal deflation because your tire only has one effective side wall.

In your case, I have a hard time believing you'll ever see a piece of gravel stuck between the spokes and the caliper. And it would have to be something really stout to actually stop the wheel, those spokes are likely to self clearance first, not saying this is something you want to try out... Also, clearance is rather binary, either you have it or you don't. Unless you expect thermal expansion or the previously mentioned debris to be an issue.

Here's a wheel in my office that I turned into a clock that was sawed in half by a nut on the left rear upright lower going into turn 4 (no chicane) at Mid Ohio while going about 135mph. I surprisingly did not crash but it likely cost me pole position and a race win as I had gotten pole, reset the lap record, and won the race the day before in a convincing manner.

 
On various racing cars I've had there's been as little clearance as like 3mm between various parts and the wheel ID. The main downside is that when you get a piece of gravel or another foreign object stuck between whatever the part is and the wheel it tends to machine your wheel in half and cause a rather abrupt deflation that is worse than a normal deflation because your tire only has one effective side wall.

In your case, I have a hard time believing you'll ever see a piece of gravel stuck between the spokes and the caliper. And it would have to be something really stout to actually stop the wheel, those spokes are likely to self clearance first, not saying this is something you want to try out... Also, clearance is rather binary, either you have it or you don't. Unless you expect thermal expansion or the previously mentioned debris to be an issue.

Here's a wheel in my office that I turned into a clock that was sawed in half by a nut on the left rear upright lower going into turn 4 (no chicane) at Mid Ohio while going about 135mph. I surprisingly did not crash but it likely cost me pole position and a race win as I had gotten pole, reset the lap record, and won the race the day before in a convincing manner.

Valid points, but this bike will never see 130mph or hard braking repeated enough for thermal expansion to be an issue, i don't think. That said, i'm going to do more testing on here for sure, before i commit to this solution.

The rocks are definitely more of an issue on car calipers. Has anyone had this be an issue on a bike? I haven't heard of any cases. The car rims being a large surface area cylinder are just ideal of trapping a rock and wedging it in between the bigger calipers.

I think you'd have to really be one unlucky SOB to run into the rock pebble problem on a bike.
 
Thoughts on running these bolts? I'd like to run stainless, but they do have a significantly lower tensile strenght than some of their other non-stainless offerings (70,000 vs 170,000).
That said, Google shows me shear strength is about 50% of tensile strength ..... so 35,000 psi PER BOLT still seems plenty enough for this application

Where i'm a bit unclear, is that this is such a long bolt, it could experience shear forces on BOTH sides of the hub, potentially slightly different forces as well, since no brake caliper is 100% identical in performance.

The bolts i need are 125mm, so i'm leaning toward 130mm, cut down to 125mm, to ensure i have max thread engagement. The 120mm would leave about 4.5 mm of threads

130mm is just over 5" so it's definitely a long bolt.
bolts.JPG
 

doc_rot

Oh the usual... I bowl, I drive around...
DTT SUPPORTER
DTT BOTM WINNER
more than adequate. these bolts will mostly see shear forces.
 
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.


Hey IRK, how is that SV caliper held on to the bracket? For the SV both sliding pins are on the caliper itself, but i don't see any any nut on the back of the top bolt. Side facing out is not accessible. Side facing in has no nut. What am i missing here?
svcaliper.JPG
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Hey IRK, how is that SV caliper held on to the bracket? For the SV both sliding pins are on the caliper itself, but i don't see any any nut on the back of the top bolt. Side facing out is not accessible. Side facing in has no nut. What am i missing here?View attachment 227016
That bracket itself is threaded. My adapter plates are drilled with two holes and the screws thread into the bracket through the adapter place. I drill two more holes in the adapter bracket for the fork mounts and use two weld nuts on the adapter bracket to thread the fork screws.
 
That bracket itself is threaded. My adapter plates are drilled with two holes and the screws thread into the bracket through the adapter place. I drill two more holes in the adapter bracket for the fork mounts and use two weld nuts on the adapter bracket to thread the fork screws.
Ok thanks! So on the SV both of the sliders are on the caliper. I was looking at some 80s honda ones here and they have one slider on the caliper one on the bracket. Kind of a silly setup.
 
I am considering IRKs approach with the SV calipers and adapter if the GSXR calipers are a fail, but I'm also looking at how much I can shave off the calipers here for a sleek fork-caliper OEM combo.

Turns out the caliper is actually thicker than I thought. I measured it with a dial indicator, several times, each time getting between 4.3 and 4.6 mm. Just in case anyone is curious what these 4 pot gsxr ones are for thickness

20200626_200800.jpg


Using the vernier caliper - that's a lot of meat before you break through. Shaving 2mm is really not going to be an issue here I dont think.

20200626_203443.jpg
 
Last edited:
I'm happy now.

I cant wait to ditch the center stand.... but I still need the thing

Turning radius is going to SUCK. I dont have the skills to do tank dimples that would give the forks clearance, so extended steering stops will have to be the way.

20200626_211918.jpg
 
Last edited:

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
I have shaved calipers for fit on several occasions, and one thing I am watching for is heat transfer. In my case, i currently have an AWD Chevy Astro van which has a 1/2 ton rear end and brakes made for 16" rims. I wanted 15" rims for better offroad tire options, so I shaved a mm or two off the top. So far so good, but something to watch. I imagine boiling brake fluid is going to make your brake really, really soft or non-existent.
 
I have shaved calipers for fit on several occasions, and one thing I am watching for is heat transfer. In my case, i currently have an AWD Chevy Astro van which has a 1/2 ton rear end and brakes made for 16" rims. I wanted 15" rims for better offroad tire options, so I shaved a mm or two off the top. So far so good, but something to watch. I imagine boiling brake fluid is going to make your brake really, really soft or non-existent.
But think of the savings on unsprung weight ;)

Considering that mass is the #1 factor for absorbing heat why do bike rotors continue to be drilled out so much?

In today's post asbestos world, brake pads arent really prone to gas buildup like before. If you look at performance cars, the holes are tiny, and in the really high end cars, the holes are cast into the rotor, not drilled into them to reduce cracking.

So why are the bike rotors still being drilled and drilled so much! Most rotors are all holes. Even my ATV where the rotors arent even visible! Is it for looks?

Sure, the holes increase surface area, but I doubt that the increase in surface area provide a cooling effect that offsets the heat absorption loss from the lower mass after it's been drilled out

Am I out to lunch or is it all looks?
 

sav0r

Member
Bikes don’t generate that much braking force so they don’t generate that much braking heat. What heat they do make they rely on transferring to the hub and wheel, where it is then dissipated.

Cars have way less braking cooling due to their shrouded rotors, they are generally much high mass, and generally brake at much harder rates. All of that means they have way high brake, upright, wheel assembly temperatures after heavy use. To cool them they rely on pumping air through the rotors, or forcing it through via ducts, and in many cases a combination of both.

If you look into this I think you’ll find stuff under ”thermal conductivity” and “thermal transient analysis”, but it’s been a long time since I paid this stuff much attention.
 
Bikes don’t generate that much braking force so they don’t generate that much braking heat. What heat they do make they rely on transferring to the hub and wheel, where it is then dissipated.

Cars have way less braking cooling due to their shrouded rotors, they are generally much high mass, and generally brake at much harder rates. All of that means they have way high brake, upright, wheel assembly temperatures after heavy use. To cool them they rely on pumping air through the rotors, or forcing it through via ducts, and in many cases a combination of both.

If you look into this I think you’ll find stuff under ”thermal conductivity” and “thermal transient analysis”, but it’s been a long time since I paid this stuff much attention.
Yeah, interesting point! The bike rotors are quite a bit more exposed than the concealed car rotors.

The part about transferring the heat to the hub and wheel doesnt sound healthy for the wheel bearings at all. Lol.

It's ok. It was more of a theoretical thought than any concern for me. My bike is not ever going to be ridden as hard as the components on it are built for. I'm not a spirited rider.

(Yes, that means the USD fork is for looks!)
 

DTT Bike Of The Month Gallery

DTT Light or Dark

www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.jadusmotorcycleparts.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom