Topic: The Quest for Brakes and Suspension: GSX-R Treats

[Retro Rocket]

I wish i had got you to throw that bloody axle in Fred, having a hell of a time finding one here...   I'll find one eventually though as i'm not paying stupid shipping for that one...

[sethdhawkins]

Mr Breeze,

After looking at the cost of having machine work done to adapt a harley narrow glide hub to my 2006 gixxer frontend, then more machine work to have a stem made, I went with the easy solution. www.cognitomoto.com
With his hub and stem, a lot of the swap was made easier. You can go to his website and read the parts compatibility...but, I can already tell you that your year gixxer parts won't work with what he's got. He might be willing to work some custom parts, as he's already intimate with the cb750's stock workings. Just a thought

Good luck,

Seth

[mrbreeze]

Well Mick, I can get an estimate but it will probably be outragious as we already know. Maybe if you have anything else being shipped to you or a friend from the States maybe I could send it to someone here to piggyback it to you. After all....it isn't a big piece by any means. So Seth....these parts aren't really worth much unless they were year and model specific to someone?I will remember to check out and read some more about your rear wheel. I just got rid of a K1 part bike that had inside laced rear Harley rim to stock Honda hub but it didn't have anything to do with a rotor....stock early K drum hub. I'm digging the width of your wheel and the clearence Carpy's swinger provides.

[sethdhawkins]

That's the way I would look at it. One would have to put a fair amount of effort and money into making a specific modern frontend work on these bikes...while retaining spoked wheels. When people tell me that the custom hub I picked up was too expensive, I often wonder how much time and money they're willing to expend trying to make something that they thought was cheaper work? I knew from prior experience, that I could get the job done, but I'd be way over budget at the end...just a fact of forging the way.

The rear wheel setup was (relatively) easy. Custom spokes for a deep drop wheel, then laced and trued. I have no idea what the clearance is like on a stock swinger with a 140 sized tire. I've got plenty of room on the Carpy swingarm, but the proportions look odd to me were I to go wider.  The 140 looks HUGE compared to stock.

[calj737]

...but, I can already tell you that your year gixxer parts won't work with what he's got.

Seth - Curious as to why not? If Breeze uses his triple and forks, then Cognito hub is merely an inside/inside laced hub with an awfully large diameter reamed for an axle. Perhaps the wheel bearings would need to be non-standard, but a custom stem or stem swap and this should go...? Maybe theres something completely odd about the '89 gSX1100 that I'm unaware of?

I'd think:
Cognito hub
aftermarket rims
custom spokes
non-standard wheel bearings
stem swap

Am I completely misguided? I know Retro will have good insight on this too. What am I missing Retro?

[Retro Rocket]

Well Mick, I can get an estimate but it will probably be outragious as we already know. Maybe if you have anything else being shipped to you or a friend from the States maybe I could send it to someone here to piggyback it to you. After all....it isn't a big piece by any means. So Seth....these parts aren't really worth much unless they were year and model specific to someone?I will remember to check out and read some more about your rear wheel. I just got rid of a K1 part bike that had inside laced rear Harley rim to stock Honda hub but it didn't have anything to do with a rotor....stock early K drum hub. I'm digging the width of your wheel and the clearence Carpy's swinger provides.

Fred, you may be onto something there mate, I am looking at some later model brake parts near Illinois, i'll let you know...

Cal, the Honda stem presses straight into the GSXR1100K clamps , I've already done it, i'm not using it though because 35mm offset triple clamps add to much trail, i don't mind a 5mm difference but 25mm is an inch and that adds up to trail over 4 inches and a real slow turning front end, I'm using the 43mm forks with custom clamps, i am pretty sure you could make the cognito hub work quite easily, bearings will be no problem , spacers may be needed for the discs or even material taken off the cognito hub if its narrower or wider than the 89 hub. I would not give up on it but i would do some very accurate measuring... 

[sethdhawkins]

I wouldn't know any of the specs on that year frontend. We know for a fact that the fork legs are smaller in diameter, and not USD(?), the hub will probably be a different width requiring either shimming or spacing, and who says that the stem has to be anything like the generation gsxr frontend that I used. I know that many of the earlier bikes used steel stems in alloy trees...My point being, you may as well start with a harley hub from scratch at that point.

[sethdhawkins]

Mick beat me to it.

Seth

[calj737]

Retro - I completely understand your point about the offset, but, Breeze stated:

>>So I have the complete triple tree, clip-ons, & front axle with speedo drive. I can't remember if its 42 or 43mm tube size

If he uses the triple he has (certainly not stock Honda offset) and his forks, but uses the CM hub and perhaps a stem swap, shouldn't his rake/trail remain the same and provided he deals with axle/rotor spacing, be on the road?

I spent some time these last couple of days with Devin (CM). We discussed the different offsets on the triples a while. I wonder, with the larger USD forks, does even pushing them back to a "Stock" offset result in the same handling behavior? Does the "math" truly dominate the handling characteristics if you don't take into account the change in technology and standard/inverted forks?

I suspect the math does play an ENORMOUS part, but I also wonder the net result and whether it is truly 1=1 the same?

[Retro Rocket]

Retro - I completely understand your point about the offset, but, Breeze stated:

>>So I have the complete triple tree, clip-ons, & front axle with speedo drive. I can't remember if its 42 or 43mm tube size

If he uses the triple he has (certainly not stock Honda offset) and his forks, but uses the CM hub and perhaps a stem swap, shouldn't his rake/trail remain the same and provided he deals with axle/rotor spacing, be on the road?

I spent some time these last couple of days with Devin (CM). We discussed the different offsets on the triples a while. I wonder, with the larger USD forks, does even pushing them back to a "Stock" offset result in the same handling behavior? Does the "math" truly dominate the handling characteristics if you don't take into account the change in technology and standard/inverted forks?

I suspect the math does play an ENORMOUS part, but I also wonder the net result and whether it is truly 1=1 the same?

I just replied to Devin's post in his thread mate, I explained it there. You must always take wheel size into the equation when working out rake and trail as a smaller wheel regardless of offset will speed up steering, smaller diameter front wheel= quicker steering, its not quite as simple as using what suits other bikes , its a fine balance of rake, trail, offset and wheel diameter that makes it all work,  using smaller diameter wheels also reduces rake by lowering the front end, these things weren't taken into account when Devin made up his chart, that doesn't mean its not useful, but it isn't the full story, the sweet spot of handling is quite small and a lot more complicated than most think, racers like Mick Doohan and others say they can "feel" 1mm differences in offset   

[sethdhawkins]

Ah yes, modern frontend swaps; the new oil thread

I did some pretty bull#$%* rake and trail calculations on an online site earlier...I think there are too many variables. I'm gonna ride it regardless, and if Devin makes those adjustable trees, I may try those too.
I can say affirmatively, I wouldn't have anything to do with running a 19" wheel on this setup. Period. That's all I know, the rest y'all can speculate over it, or just try it yourself.

Have fun.

Seth

[Retro Rocket]

Ah yes, modern frontend swaps; the new oil thread

I did some pretty bull#$%* rake and trail calculations on an online site earlier...I think there are too many variables. I'm gonna ride it regardless, and if Devin makes those adjustable trees, I may try those too.
I can say affirmatively, I wouldn't have anything to do with running a 19" wheel on this setup. Period. That's all I know, the rest y'all can speculate over it, or just try it yourself.

Have fun.

Seth

Gday Seth, I hope its nothing like an oil thread mate, there are measurements that are irrefutable in suspension geometry so hopefully this is a discussion, not a sh1t fight....

[sethdhawkins]

I'll give everyone my full input when I actually swing a leg over it. Keep in mind, my daily driver is a Dodge Ram 2500 cummins diesel....sooooo

[Retro Rocket]

I'll give everyone my full input when I actually swing a leg over it. Keep in mind, my daily driver is a Dodge Ram 2500 cummins diesel....sooooo

Haha, I drive a 2800 turbo diesel as well, only mine is an Isuzu...

[SOHC4 Cafe Racer Fan]

Assuming an 18" front as many run with a modern fork swap (thereby quickening steering), I wonder how the non-stock offset (slowing down steering) works out.  Is it a wash?  Does pairing it with an 18" help/hurt?

[Retro Rocket]

Lots of racers use 18 fronts, I am going to use 18 fronts on 2 of my bikes, on the F  i am going with 45mm offset clamps {stock is 50mm}and on the K i'm going with 50mm offset {stock is 60mm}. The F frame has slightly different rake to the K model frame...

[SOHC4 Cafe Racer Fan]

Thanks, RR.

[bwaller]

Anyone using longer than stock shocks introduces another variable in the front end geometry.

[sethdhawkins]

Don,

I'm running the 18" wheel in the front, but am limited to the least tall of the 18" tire profiles, due to header interference. I'm sure that changing tires three times on the front wheel was an exercise in humor for someone :-/ When I'm done, I'll go ahead and erase my build thread, so that everyone can screw up in the same manner I did

If anyone might be interested in the stock gixxer triple tree setup and 750 stem I have now, drop me a PM...I'm thinking I want the adjustable one, just because.

Seth

[SOHC4 Cafe Racer Fan]

I wonder if you use a tree with more offset whether you can run a larger selection of front tires.

[burlybear]

subsribed

[Terry in Australia]

I wonder if you use a tree with more offset whether you can run a larger selection of front tires.

You can, and then your top triple won't smash into your gas tank every time you turn your handlebars more than a few degrees. I've got the original FZR1000 triples that the PO tried to use on my gold bike, he took them off and made a set of custom triples with more offset when the bike tried to throw him down the road when the forks "tucked under" in tight corners. 

[timbo750]

Terry you have raised an interesting point, most of the time when are turning the bike it is leaning and we are usually either braking or accelerating which will shorten or lengthen the gorks and change all the geometry.  Then there is the profile of the tire, the weight of the bike, the centre of gravity, and I am sure there are plenty of other factors including the tightness of the sphincter.

Project 1 CB750 - http://forums.sohc4.net/index.php?topic=126864

[sethdhawkins]

I wonder if you use a tree with more offset whether you can run a larger selection of front tires.

You can, and then your top triple won't smash into your gas tank every time you turn your handlebars more than a few degrees. I've got the original FZR1000 triples that the PO tried to use on my gold bike, he took them off and made a set of custom triples with more offset when the bike tried to throw him down the road when the forks "tucked under" in tight corners. 

And would allow one to run a 19" wheel and tire combination, should they wish. I think I measured the fork lengths between the cb750k1 forks I had, and the gixxer forks...I think they were an 7/8" shorter, or something like that. I should probably do that again.

[Retro Rocket]

I wonder if you use a tree with more offset whether you can run a larger selection of front tires.

As long you don't end up with any more than the stock 60mm offset on a K model 750 frame and 50mm on a F model frame you'll be OK, more offset means less trail and less trail on a cb750 would make for an extremely nervous front end and prone to tank slappers, the Honda 750K has 3.7 inches of trail stock which, even by todays standards is not a lot, for example most modern sport bikes have around 4 inches of trail or slightly more. Thats the exact reason i'm going with a little less offset with the 18 inch front rims, to add a bit more trail to compensate for the slightly quicker steering 18 inch rim and half inch drop in front suspension height, this should make for a front end that still turns in but is also stable at speed.