Topic: CB550 Cafe Racer Questions - Suspension!!

[jcorrill]

So i am building a cafe racer out of my CB550.  I want to give it that forward lean that all good cafe racers have.  What is the maxium length rear suspension that will fit onto a 1978 CB550?  Any input or advice would really help..  Thanks!!


Jake

[seanbarney41]

You need to be aware that longer rear shocks  decrease your rake and trail numbers, which could cause unsafe handling characteristics.  I wouldn't increase the length more than 1" over stock.  That should give you quicker turn in, but still be stable enough for 70mph or so.  You really need to experiment safely before deciding if this is really an improvement.  A steering dampener should go along with this change.  Cafe racers are really a quest for improved performance, not mindless changes for better looks.

[Duke McDukiedook]

Stock length unless you know what you are doing with your suspension.
And by the way you ask the answer is still stock length.

[calj737]

That "forward lean" is more a visual than a physical alteration. You can accomplish it by clip-ons, clubmans, a slimmer seat. Than guiding principle should be to try to maintain a parallel to ground tank bottom line. This helps keep your carbs "plumb" and bowls filling properly. Even modern aggressive sport bikes, have a "high pillion" but not a forward leaning structure.

I'd bet that if you spent a great deal of time sifting thru images of CB550 cafe racer on Google, you'd notice that almost all the ones you like have stock length shocks, forks and standard height tires. It's the seat and bars that attract your eye.

I may be off on your tastes, but I've undergone this very exercise myself, and with my 3 boys in an effort to determine a design direction. Time and time again, it proves true.

[jcorrill]

Im not trying to have it be off balance, im simply trying to get rid of the fork in the rear direction.  You guys are acting like i want the rear end 5ft of the ground and the front 5inches off the ground lol

I am simply trying to increase my rear suspension by a half or full inch. 

What is there to know?  If im going to spend money, i mise well get what i want.  What other adjustments need to be made to increase the length of your rear suspension?  How am i going to learn if i don't seek answers? 

This is why progress is never made by some people, they are afraid to mess up, change, or try alternitive options.

Fear is mans only limit. 

[calj737]

I think you misunderstand the tone of the responses. Everyone was aimed at answering your question and imparting experience and knowledge to you.

You are always entitled to do what you wish: it's your bike, your butt, your dime. But try not to recoil when the advice you do receive surpasses that limit of the answer you seek. It's that very "extra bit of insight" that has on far too many occasions saved a new project from repeated mistakes.

If you're convinced of the answer and your decision despite the responses, why pose the question?

[dave500]

"This is why progress is never made by some people, they are afraid to mess up, change, or try alternitive options."

plenty have been messed up don't you worry about that.

[Ewan 500K1]

bit of crack on the subject here:  http://forums.sohc4.net/index.php?topic=126131.25.   Cal's point about carb bowl fuel levels is the first time I've seen it mentioned, but must be worth thinking about.

[bwaller]

If you want to raise the rear a couple inches and still maintain adequate trail I have a set of 30mm offset triple clamps from an NSR125 I'd sell that will do just that. Same fork spacing, same fork diameter, just 15mm less offset.

[jcorrill]

bwaller:  i would definitely be interested in that. Would they work on my 550?  Can you send me a picture of what it would look like with them installed or more details on how they would work.  Im having a little trouble picturing how it would work.

I did not mean to come off as a jerk before, i just felt like people were just shutting down my idea instead of giving me advice.  I know it has been done before because i have read many articles about building cafe racer in which the rear end was raised.  Im sorry everyone. 

Also if i adjust the stock suspension to it "hardest" setting would that raise the rear end as well.  I think that with bwaller offset triple clamps would be perfect.

Thanks & sorry again fellas

[Retro Rocket]

Thats cool mate, suspension is built to a formula and its quite complicated, an inch at the rear makes a noticeable effect on rake and trail at the front, these measurements are critical to the way a motorcycle handles and aren't just guessed, they do what they do for very good reason. I read an article years ago that stated that , { i think it was Mick Doohan}, he could tell the difference in a 1mm change to triple clamp offset. Raising the rear steepens the rake which decreases trail which makes for a less stable bike, the earlier advice, even without explanation was correct....  Brents [bwaller} offer of 30mm offset triple clamps adds back the lost trail aiding in a more stable ride, just remember though that, if you go back to stock length shocks you'll need to go back to your stock triple clamps to keep the geometry correct. I have also see lots of "cafe racers" that are built with absolutely no knowledge of suspension or frame geometry and they all "think" their bikes handle well, most  really haven't got a clue....bwaller is a very competent racer and knows his stuff...

[bwaller]

I don't know about competent but I have learned from some mistakes! J there are a couple things to add about the triples I mentioned. There is no means to clamp handlebars to the upper clamp, it's top is flat. You'll need clip-ons. You'll also need to buy a set of All Balls tapered roller brgs for the steering head.

I'll get a picture for you tomorrow.

[Retro Rocket]

I don't know about competent but I have learned from some mistakes! J there are a couple things to add about the triples I mentioned. There is no means to clamp handlebars to the upper clamp, it's top is flat. You'll need clip-ons. You'll also need to buy a set of All Balls tapered roller brgs for the steering head.

I'll get a picture for you tomorrow.

You can buy handlebar mounts Brent, just drill a couple of holes and mount...

[jcorrill]

Thanks gentlemen - this info is really helpful.  Bwaller a pucture would be awesome.  Also what adjustments need to be made in the rear once this is added? 

Jake

[jcorrill]

How much would you want to sell that for?

[Maurice]

I am running 750 shocks. Mostly because they were in better shape than the 550 ones I have. It turns out the handling is a tad improved IMO, a bit quicker turn in. Still plenty stable. The only thing is that the springs are a tad on the harsh side, but that's not too bad. They're not performance shocks by any means but they are still fairly safe.

Which brings me to one point you should keep in mind: be very careful with suspension changes, you could kill yourself in a beat...

[Ewan 500K1]

I am running 750 shocks. Mostly because they were in better shape than the 550 ones I have. It turns out the handling is a tad improved IMO, a bit quicker turn in. Still plenty stable. The only thing is that the springs are a tad on the harsh side, but that's not too bad. They're not performance shocks by any means but they are still fairly safe.

Which brings me to one point you should keep in mind: be very careful with suspension changes, you could kill yourself in a beat...

what is the eye to eye distane of your 750 shocks Maurice ?

[Maurice]

what is the eye to eye distane of your 750 shocks Maurice ?

I'll measure tonight. I think it's something like 3/4" over 550 shocks.

[Maurice]

what is the eye to eye distane of your 750 shocks Maurice ?

Measure the shocks they are a tad over 13", I'd say 13" and 1/8.

[Ewan 500K1]

what is the eye to eye distane of your 750 shocks Maurice ?

Measure the shocks they are a tad over 13", I'd say 13" and 1/8.

cheers, 13.125inch =328mm = 13mm (1/2 inch) longer than stock 500 shocks I think

[Maurice]

what is the eye to eye distane of your 750 shocks Maurice ?

Measure the shocks they are a tad over 13", I'd say 13" and 1/8.

cheers, 13.125inch =328mm = 13mm (1/2 inch) longer than stock 500 shocks I think

Sounds about right. I'll pull the 550k shocks from wherever I chucked them to measure accurately. This way is better than messing with the front IMO (unless you're going with modern forks...) since you get a bit better ground clearance to boot. It does put the chain a tad closer to the swingarm but no risk of rubbing just have to be a bit more on top of adjustments.

Cheers

[HondaMan]

This is why progress is never made by some people, they are afraid to mess up, change, or try alternitive options.
Fear is mans only limit. 

...or death...pardon my inference, but this DID kill someone on my 'watch' in 1973, which is why I still rebuild swingarms stoutly, and for no profit.

The main issue: the 550 starts with a too-soft front suspension, and little travel as the result. I recommend stronger springs or at least spacers to boost the existing ones, and air fork caps to aid in tuning afterward. Don't reduce the trail, or you will easily end up with a chassis that likes to break into tank-slapping speed wobbles after hitting a high-speed bump. Minimum trail in the end should be not less than 3.54" (90mm) . 

[Retro Rocket]

This is why progress is never made by some people, they are afraid to mess up, change, or try alternitive options.
Fear is mans only limit. 

...or death...pardon my inference, but this DID kill someone on my 'watch' in 1973, which is why I still rebuild swingarms stoutly, and for no profit.

The main issue: the 550 starts with a too-soft front suspension, and little travel as the result. I recommend stronger springs or at least spacers to boost the existing ones, and air fork caps to aid in tuning afterward. Don't reduce the trail, or you will easily end up with a chassis that likes to break into tank-slapping speed wobbles after hitting a high-speed bump. Minimum trail in the end should be not less than 3.54" (90mm) . 

And 3.54 is quite small by todays standards, most hyper sport bikes are around 4 inches of trail....100mm is a better target for the street....

[Ewan 500K1]

Attached is a rake and trail calculator that might come in useful.  Based on the 500K, for every 10mm increase in rear shock length there is a 0.48 degree reduction in rake and a 3mm recuction in trail.
Stock trail on a 500 is 102.5mm, so (according to my calcs) using rear shocks that are longer by 25mm would reduce the trail by 7.5mm, bringing it down to 95mm.  A steering damper could be a useful insurance against any tank slapping tendencies introduced by reducing the trail, the NHK 500 ODM damper fits the CB500K quite well. Or ... as already mentioned by bwaller, a triple T with shorter offset can compensate the effects of longer rear shocks on trail.