Topic: How to evaluate changes to the stock geometry in terms of performance? (CB550K)

[BradyN]

I should preface this by saying, I'm new to motorcycles - both the riding and the mechanical work involved.

I have a '78 cb550 that I just got. So far it has been great. I see some necessary preventive maintenance  looming ahead and I'm trying to plan the best way to go about it. Most notably, I would like to rebuild the wheels, wheel bearings and replace the tires.

While I'm taking the trouble to do that, I'd like to upgrade the handling as much as I can. I am very confused by tire choices, in general. I see cafe racers that are sitting on balloon-like tires, and I'm not sure what that could possibly do for handling. But in terms of staying stock, well they don't even make the mfg recommended tire sizes any more. My bike has the original size up front, and a metric in the back that is 'close' to the honda recommended 3.75", but has a different profile completely. Modern tire technology has advanced quite a bit since 1978, and it seems there are very few choices that fit well on 1.85" rim. If I were to change the rim, could I run different tires that would improve handling? The hubs will stay stock (with new bearings). What about wheel sizes (I don't know if that can be changed with just different spokes on the stock hub?)

I don't think I will change the suspension geometry at all (in terms of ride height, rake and trail, etc) but I would like to rebuild the forks with either new springs and an air valve or using an emulator, which seems a bit more complicated/expensive. Overall I don't have too much to complain about in the front, but I want to do something about the rear suspension. I'm still not an experienced rider, but I definitely feel at the moment that the rear of this bike is a little... loose. and bouncy.
Is there anything you recommend I read up on so that I can make some informed decisions about the best rim/tire combination on these bikes?

And, to be clear, to me best means that it improves the handling and performance of the bike. Aesthetics aren't a consideration.

[slikwilli420]

Welcome to the world of motorcycling. Your approach is the one everyone should take when tackling a new project. This forum is invaluable as a resource for all of your questions.

Regarding tires, there is no need to change rims other than if you want something that is lighter such as aluminum or snazzier like period mag wheels. Using a tire manufacturers chart, you can choose the right metric size tire for your rim width to ensure proper fitment. I have yet to find a since complaint about Avon AM26 tires for our bikes, so I suggest starting there.

From a handling standpoint, there are a few options. Staying stock on the forks is fine and many here do it but most do at least add new springs from Progressive or a package of springs and emulators from Race Tech. No one has ever complained about Race Tech products here so you are in good hands should you choose that route.

Regarding the rear, new shocks are usually in order. You can go anywhere from $250 Hagons to $1400 remote reservoir items from variety of sources. ALL are better than 40 year old stock items. The best part is that you tell them the weight of you plus the bike and they will build them to that spec, no more one size fits all.

This forum has from mild to wild on just about every aspect of a Honda /4 so feel free to browse the project section to get inspiration for your ride.

Good luck!

[754]

Retro Rocket will be along shortly to tell you what you can do to it..

[BomberMann650]

Definitely interested in learning more about the fork rake.
I see modern bikes with much more vertical fork rakes compared to the 550's.  So what is it with the differences in these two bikes that makes a rear lift & front lower so sketchy or difficult to do with positive result?

[FunJimmy]

Retro Rocket will be along shortly to tell you what you can do to it..

And what you can't. 

[FunJimmy]

Definitely interested in learning more about the fork rake.
I see modern bikes with much more vertical fork rakes compared to the 550's.  So what is it with the differences in these two bikes that makes a rear lift & front lower so sketchy or difficult to do with positive result?

Bomber,

Have a look at this thread on Do The Ton.

http://www.dotheton.com/forum/index.php?topic=57497.0

[Retro Rocket]

Definitely interested in learning more about the fork rake.
I see modern bikes with much more vertical fork rakes compared to the 550's.  So what is it with the differences in these two bikes that makes a rear lift & front lower so sketchy or difficult to do with positive result?

Bomber,

Have a look at this thread on Do The Ton.

http://www.dotheton.com/forum/index.php?topic=57497.0

Thats a good thread Jim, lots of good info, most of it accurate, all in the same place, pity it doesn't happen like that here... I like to have suspension mod discussions Via PM's, I don't think Frank likes that...

[BradyN]

Welcome to the world of motorcycling. Your approach is the one everyone should take when tackling a new project. This forum is invaluable as a resource for all of your questions.

Regarding tires, there is no need to change rims other than if you want something that is lighter such as aluminum or snazzier like period mag wheels. Using a tire manufacturers chart, you can choose the right metric size tire for your rim width to ensure proper fitment. I have yet to find a since complaint about Avon AM26 tires for our bikes, so I suggest starting there.

From a handling standpoint, there are a few options. Staying stock on the forks is fine and many here do it but most do at least add new springs from Progressive or a package of springs and emulators from Race Tech. No one has ever complained about Race Tech products here so you are in good hands should you choose that route.

Regarding the rear, new shocks are usually in order. You can go anywhere from $250 Hagons to $1400 remote reservoir items from variety of sources. ALL are better than 40 year old stock items. The best part is that you tell them the weight of you plus the bike and they will build them to that spec, no more one size fits all.

This forum has from mild to wild on just about every aspect of a Honda /4 so feel free to browse the project section to get inspiration for your ride.

Good luck!

Thanks for the info. I'll definitely be getting springs at the very least, maybe an emulator but we'll see. I haven't done any research on rear suspension yet, but I'll get to that eventually.

As far as rim size goes,  from what I've read if the rim size is too small for the tire cornering performance suffers. And the front and rear wheel, including tire, should be the same diameter? I will check out the Avon tires you mentioned.

Definitely interested in learning more about the fork rake.
I see modern bikes with much more vertical fork rakes compared to the 550's.  So what is it with the differences in these two bikes that makes a rear lift & front lower so sketchy or difficult to do with positive result?

Bomber,

Have a look at this thread on Do The Ton.

http://www.dotheton.com/forum/index.php?topic=57497.0

Thanks for the Do The Ton thread, I'll check it out. I also found your build thread of the CB550 Interceptor, looks like there's a ton of good info in there too! Did putting wider rims and tires improve handling over stock? Of course, you made a lot of other custom modifications as well.

[seanbarney41]

Brady, as a new rider don't be in too much hurry to make a bunch of modifications.  Your cb550 will be capable of more than you will be capable of for quite some time.  If you can make your bike work as good as it did when new you will be doing better than most.  Trying out as many different bikes as you can will help you quickly learn what affects what.  You will find that improving performance often has a tradeoff in another area.  Once you have had a good amount of seat time you be able to more intelligently decide whether modifications are "worth it".  Also, you are never really "done" learning how to ride.

[scottly]

Brady, as a new rider don't be in too much hurry to make a bunch of modifications.  Your cb550 will be capable of more than you will be capable of for quite some time.  If you can make your bike work as good as it did when new you will be doing better than most.

I agree with Sean. Since you posted your question on the High-performance/Racing board, much of the advice you're getting is from a racing point of view, and doesn't necessarily apply to a new rider.

[Retro Rocket]

Brady, as a new rider don't be in too much hurry to make a bunch of modifications.  Your cb550 will be capable of more than you will be capable of for quite some time.  If you can make your bike work as good as it did when new you will be doing better than most.

I agree with Sean. Since you posted your question on the High-performance/Racing board, much of the advice you're getting is from a racing point of view, and doesn't necessarily apply to a new rider.

+1000   

[BradyN]

Brady, as a new rider don't be in too much hurry to make a bunch of modifications.  Your cb550 will be capable of more than you will be capable of for quite some time.  If you can make your bike work as good as it did when new you will be doing better than most.

I agree with Sean. Since you posted your question on the High-performance/Racing board, much of the advice you're getting is from a racing point of view, and doesn't necessarily apply to a new rider.

Ok, that makes a lot of sense. I guess I thought I'd ask because the rear wheel will need to be rebuilt this winter (bent spokes) and I'm unsure if the rim is too corroded to clean up. But there's always paint 

Thanks for the links/information everyone, I'll keep reading.

[flatlander]

you are starting out very sensibly, with tyres, suspension and wheel bearings. for shocks, look at koni. they are close to original in looks but offer more adjustment and are generally good quality. for the forks, rebuild them with new seals and some new progressive springs. especially as a beginner rider i'm not sure if you'd benefit from emulators. you could also add a fork brace but that can also come at a later stage.
what's totally worth doing at the same time is, replacing the headset bearings with conical ones, and also swingarm bushings.
all this will make the bike handle better. the stock geometry of the 550 is pretty good, if i were you i wouldn't tinker with it at this stage.

[simon#42]

you cant buy new koni shocks any more they are now called icon  , they are a very good mid priced shock and well worth a look if you decide to upgrade yours .

[Retro Rocket]

you cant buy new koni shocks any more they are now called icon  , they are a very good mid priced shock and well worth a look if you decide to upgrade yours .

+1 

[BradyN]

you are starting out very sensibly, with tyres, suspension and wheel bearings. for shocks, look at koni. they are close to original in looks but offer more adjustment and are generally good quality. for the forks, rebuild them with new seals and some new progressive springs. especially as a beginner rider i'm not sure if you'd benefit from emulators. you could also add a fork brace but that can also come at a later stage.
what's totally worth doing at the same time is, replacing the headset bearings with conical ones, and also swingarm bushings.
all this will make the bike handle better. the stock geometry of the 550 is pretty good, if i were you i wouldn't tinker with it at this stage.

Thanks for the info. Besides a 3K mile service, I don't plan on doing much to the bike this summer. I just want to ride it!

But eventually I'll get a chance to work over the wheels and suspension. Do you recommend just repacking the original wheel bearings if the bike doesn't have too many miles? or is it worth it to just get new bearings?

And regarding the rims, would bumping up the width change the handling much, or just stay at 1.85"? There seem to be few tires that fit that rim and 1.85" is usually the minimum width that the tire can be run on. But I haven't explored all the options yet.

This is pretty academic at this point because I don't plan on doing any of this work til winter.

Thanks

[FunJimmy]

Thanks for the info. Besides a 3K mile service, I don't plan on doing much to the bike this summer. I just want to ride it!

But eventually I'll get a chance to work over the wheels and suspension. Do you recommend just repacking the original wheel bearings if the bike doesn't have too many miles? or is it worth it to just get new bearings?

And regarding the rims, would bumping up the width change the handling much, or just stay at 1.85"? There seem to be few tires that fit that rim and 1.85" is usually the minimum width that the tire can be run on. But I haven't explored all the options yet.

This is pretty academic at this point because I don't plan on doing any of this work til winter.

Thanks

You can't go wrong with slightly wider rims. I've got 2.5" x 18" front and 3" x 18" rear.
Wider rims will give a greater selection of tires to choose from while also increasing the contact patch.
That alone will provide better and more confident handling. Worth it if you're considering new rims anyway.

[grcamna2]

subscribed

[flatlander]

you cant buy new koni shocks any more they are now called icon  , they are a very good mid priced shock and well worth a look if you decide to upgrade yours .

oops yes, i meant ikon: http://www.ikonsuspension.com/

Thanks for the info. Besides a 3K mile service, I don't plan on doing much to the bike this summer. I just want to ride it!

But eventually I'll get a chance to work over the wheels and suspension. Do you recommend just repacking the original wheel bearings if the bike doesn't have too many miles? or is it worth it to just get new bearings?

i would go for good quality, new bearings everywhere. would expect less resistance, lower tolerances and higher quality materials from new ones, compared to the 40 year old ones. but i don't know what new honda OEM bearings felt like...

slightly wider rims should be fine, as funjimmy says. if you go substantially wider it will affect how your bike turns into corners.

[grcamna2]

you cant buy new koni shocks any more they are now called icon  , they are a very good mid priced shock and well worth a look if you decide to upgrade yours .

oops yes, i meant ikon: http://www.ikonsuspension.com/

Thanks for the info. Besides a 3K mile service, I don't plan on doing much to the bike this summer. I just want to ride it!

But eventually I'll get a chance to work over the wheels and suspension. Do you recommend just repacking the original wheel bearings if the bike doesn't have too many miles? or is it worth it to just get new bearings?

i would go for good quality, new bearings everywhere. would expect less resistance, lower tolerances and higher quality materials from new ones, compared to the 40 year old ones. but i don't know what new honda OEM bearings felt like...

slightly wider rims should be fine, as funjimmy says. if you go substantially wider it will affect how your bike turns into corners.

Yes, new good quality wheel bearings and switch to tapered rolling bearing steering head bearings along with new swingarm bearings.

[simon#42]

factory racing bikes went back to ball race head race bearings in the 90's , less friction under load or so im told

[grcamna2]

factory racing bikes went back to ball race head race bearings in the 90's , less friction under load or so im told

I know the tapered(for my street use) are a bit more time to adjust initially for me;maybe it's the All Balls seals that seem to cause some drag.. What brand tapered have you used so far ?

[simon#42]

i do use tapered roller bearings in my road bikes mainly because they are cheap and easy  it was just an observation that on money no object the factory racing bikes ball bearings are used

[FunJimmy]

i do use tapered roller bearings in my road bikes mainly because they are cheap and easy  it was just an observation that on money no object the factory racing bikes ball bearings are used

My Ducati 999R came from the factory with ball bearings in the head tube.

[SOHC4 Cafe Racer Fan]

factory racing bikes went back to ball race head race bearings in the 90's , less friction under load or so im told

I read a recent story that Yamaha's M1 uses ball bearing races in the steering head.