Topic: to brat or not to brat

[jvandyke]

I'm not doing a slab seat it will be padded, the bike was uncomfortable as a stocker.  Keeping all the parts and just a few welds away from going back but I don't see it happening.  As for trends I don't give a flying %*^# what its trendy, never have, never will, I like it, I like doing the work.

[calj737]

Always build the bike that stirs your soul regardless of others opinion. But, some input on your statements:

- You find the stock riding position and bars to kill your shoulder blades after quite a few miles.
If you have not ridden a CB with rearsets and clip-ons yet, then you are in for a major disappointment. They will be far less comfortable than your current setup. It will be more fun for about 20 minutes, but after 100 miles, you'll be screaming in agony if the current stock config is hard on you.

Rearsets moved back a bit, and lower, can actually improve not only your comfort, but actually improve your technical handling of the bike. Yours are positioned a bit far back, but only time will tell.

Superbike bars, Euro bars or something more "upright" than clip-ons will improve your comfort. Torso up, feet low and slightly back, is the best posture for long riding. You could use clip-ons with higher risers as a great compromise on styling and handling/comfort.

Here's a picture as an example.

Whether you buy or build a seat, don't skimp on comfort. I'm not encouraging a vintage King/Queen blue vinyl abortion from the '70s, but a nicely crafted and gel-padded slim seat is a great addition. It wants to have a slight "crown" in the middle to fit your body's ergonomics. You might investigate the stock pan with a better molder pan and cover to suit your design and comfort goals.

Something that is "trending" due to meeting all the objectives listed above is "street trackers". These bikes ergonomically address the items listed above. Very often the builder cites: "I wanted to build a bike that was actually comfortable to ride, and not just cool to look at."

That admission says volumes to me. So if this will be a heavily used, long term ownership bike, give some thought to these ideas. Better yet, go ride some new bikes in differing styles and decide what about each you like. The bars are comfy, the seat is nice, the pegs fit me... Then use these fitting measurements to build the bike tailored to you, for you. And that, we will all applaud and get behind!

Hope this helps, and doesn't infer any offense.

[SOHC4 Cafe Racer Fan]

Well said Cal. A lot less #$%*y than my post and more constructive.

[FunJimmy]

Sounds like you've put a fair amount of thought into it. I applaud you for keeping the side covers and airbox.
Will be interesting to see if you can pull off the seat without cutting the frame brace. It's pretty integral to the integrity of the frame but an impediment to the clean slab seat asthetics. If you're fabing up the Brat seat with some padding and comfort (height), could you mix it up a bit and integrate the brace into a small custom made lock box and tail light assembly? It's my opinion that a well crafted seat (of any style) fits the tank correctly too. Just thinking out loud.

[FunJimmy]

It also looks like you're comfortable with aluminum fabrication too.
Cal has a good point about rear-set location in relationship to comfort.
Pop over to my Interceptor build and look at my rear-sets.
You could easily make the brackets attach to the swingarm and engine bolts as I have. This would allow you to move them considerably further forward but back from stock as well. They don't need to be multi adjustable either. Flat plate aluminum is much simpler anyway.

[jvandyke]

I think the frame brace has to go, I have saved cutting it as long as possible trying a few ideas but no way to keep it without getting really ugly, going to try to cut carefully so re-welding in the future is possible.  Maybe a faux oil cooler tank surrounding the bracket?
Hmmm that would be interesting
http://www.tcbroschoppers.com/electronics-tank-fake-oil-tank.html
Yes, no interest in the "empty middle" thing that's too much form over function for me.

mine isn't really a brat, more of a "resto-mod, tribute bike", little brat, little 50's Vincent, little Honda, just whatever elements I like

crappy artists concept

[jvandyke]

I'm planning on adding a front fender on the rear wheel. I mocked it up.  It'll work.  I think. My thoughts on riding position concure with yours.  The seat will be far thicker than a a standard brat.  Bars and rear set position can be tweaked ad nauseum until it's dialed in.  99% of my rides are 80 miles or less.  That's what I'm building for.

[jvandyke]

How important is that rear hump?  I'm thinking not so much given there is a brace running across the frame just in front of the shock mounts.  Maybe running 2 up you'd want it.  I'm convincing myself it's not super critical.

[Retro Rocket]

How important is that rear hump?  I'm thinking not so much given there is a brace running across the frame just in front of the shock mounts.  Maybe running 2 up you'd want it.  I'm convincing myself it's not super critical.

It is a brace and adds stability and stops flex to the rear of the frame from forces produced by the suspension, its well documented on the forum....

[jvandyke]

How important is that rear hump?  I'm thinking not so much given there is a brace running across the frame just in front of the shock mounts.  Maybe running 2 up you'd want it.  I'm convincing myself it's not super critical.

It is a brace and adds stability and stops flex to the rear of the frame from forces produced by the suspension, its well documented on the forum....

Sorry, not being clear.  I know it's recommended to keep but has anyone (and I did try to search) actually tested rigidity with and without it?  Wonder if I could, markers and high speed cameras and lots of bouncing?

[calj737]

If you're referring to the flat metal brace that bows up over the rear tire, it's shaped that way to accommodate the rear inner fender. It's purpose is to tie the two seat rails together, especially as the suspension acts.

You can replace it with something of a different design, but you should not remove it and run without it.

One option is to close the rear hoop (hence all the weld-on hoops out there). This accomplishes the same thing, and still allows a flatter seat pan. Just be aware of the tire conflict against the underside of oyur fender, seat pan, or buttocks with your new design.

[jvandyke]

There's already a lot of metal tying those rails together (on a 500k anyway)

[calj737]

There is, but it's in front of the shocks. The rails are hollow and pretty flexible already. Closing the hoop (tied together) is what is structural required as the movement of the shocks will move the rails independently otherwise.

[FunJimmy]

His plan looks like he's cutting right behind the shock mounts. That's already a triangulated structure. I doubt there's much to worry about. Furthermore, hoops are pretty insignificant in their structural contributions. They are typically flat, thin wall tubing with a long reach. Better for finishing off the frame than they are at structural duty.

[calj737]

His plan looks like he's cutting right behind the shock mounts.
That's already a triangulated structure. I doubt there's much to worry about.

I saw his sketch. We differ on whether there needs to be a brace tied to the rails beyond the shock mounts. He asked, some have answered and explained the reasons for it. His bike, his choice.

[Bootsey]

Shouldn't have to worry about getting cold feet with the current rear set setup

[Feets007]

Do what makes you want  to ride it! If your bike looks like everyone else's is it really yours. I have never met a bike I didn't like, though I have seen things I would change on almost every one I've ever seen.

[jvandyke]

Shouldn't have to worry about getting cold feet with the current rear set setup

No kidding!

Here's a shot with the front fender laying over the back wheel, you can see the frame a little too, so much meat across the gap directly in front of the shock mounts I'm going to see how it seems with out an additional brace first.  I've gotta hunt down another fender for the rear.  I like that look and than I get a fender back there.  Clearance issues may develop I know.  New rear shocks may help......anyway.  thanks again.

[SOHC4 Cafe Racer Fan]

Do what makes you want  to ride it! If your bike looks like everyone else's is it really yours. I have never met a bike I didn't like, though I have seen things I would change on almost every one I've ever seen.

Yeah, NO!  Modifying a bike should not be just about aesthetics, but functionality!  That cross-member (along with the one in front of the shock mounts) keeps the back frame rails from twisting out of square when the rear suspension exerts force on the frame.  Even though the frame is fairly secure, I think it would be a good idea to replace the cross-member with one flush in height to the frame rails toward the rear end.  It does not HAVE to be a hoop. 

Both Jim and Cal are correct.  Can you get away without it?  Sure!  But I think it would be a good idea to replace the support to preserve structural integrity. 

[jvandyke]

As in most things, it's a compromise, middle ground and all that.

[calj737]

I use the description of "hoop" as a general reference to a cross brace for the end. It could be a loop, a hoop, a doo-hickey, or whatcha-ma-jigger. Your choice-

[FunJimmy]

It would be good if one (or two) of the engineering types would chime in here with some engineering calculus. From what I gather jvandyke is building to resemble the bike shown below and his sketch suggests cutting the frame spars just behind the shock mounts. Depending on the seat length this bike may be a monoposto, sans pillion. That being said, is there any likelihood that the frame would suffer torsional stress as a result of the intended frame mods? Crack out those scientific calculators and let's see the results.

[Retro Rocket]

It would be good if one (or two) of the engineering types would chime in here with some engineering calculus. From what I gather jvandyke is building to resemble the bike shown below and his sketch suggests cutting the frame spars just behind the shock mounts. Depending on the seat length this bike may be a monoposto, sans pillion. That being said, is there any likelihood that the frame would suffer torsional stress as a result of the intended frame mods? Crack out those scientific calculators and let's see the results.

You don't need an engineer Jim, Its well known in racing circles that the weak point in the back end is the swingarm/ rear shock section, thats an area that usually gets braced with an "X" shaped brace above the swingarm to try and lessen twisting forces in the back end, and small gussets in the corners of the rear triangle, removing any bracing material in the rear will lessen the rigidity and increase twisting... Look at a well braced frame and you'll see what I mean...   I wouldn't remove that brace on a bike I was looking to ride hard, and I would also add some bracing..

[FunJimmy]

You don't need an engineer Jim

Don't say that Mick. You know what a sensitive lot they are.
You're absolutely right. Racing will exploit the strengths and weaknesses and I'm sure Buddy will be really pissed with his decision when he's turning some hot laps at the local track. He might even rethink the rattley fender on the back.

[Retro Rocket]

You don't need an engineer Jim

Don't say that Mick. You know what a sensitive lot they are.
You're absolutely right. Racing will exploit the strengths and weaknesses and I'm sure Buddy will be really pissed with his decision when he's turning some hot laps at the local track. He might even rethink the rattley fender on the back.

I apologize to any engineers that were offended by the expression of my views.....