Suspension tuning tips

[GregT]

In my experience the single biggest mistake with these things is to overspring the rear. The lightest springs you can get away with and decent damping makes a lot of difference. Too much rear spring and they want to swap ends under brakes because the rear end just tops out immediately.
We haven't gone to emulators on our 1000 yet as the rider uses the front end "pop up" to encourage weight transfer...and he's doing pretty good without them.
Andypandy...the Euro rules allowing brake upgrades beyond the period are by no means common in the rest of the world...and IMO, good thing too.
again IMO it's not a safety issue as what can be Waay better brakes can overstress areas of the original frames - under race conditions.
Again away from Europe most race organisations have a max stanchion diameter which reflects what was available in the period.

[John Kat]

I can't speak to the smaller GS, but I race a GS1000 in WERA and AHRMA. I installed Race Tech springs and emulators when I did my build. The springs were way too firm when I raced them for the first time at Barber in October, but Race Tech had a tent there and their great guys spent a half a day (for free!) dialing me in with lighter springs and adjusting the emulators.

I can highly recommend them based on their customer service and know-how.

I installed Ikon shocks on the rear and am happy with them, but if I had more $ I'd run Werks.

Good luck!

Here's mine at Barber...

Nice lean angle
What's the rating of your front springs?
Is that a V&H exhaust you have?

[speedyandypandy]

In my experience the single biggest mistake with these things is to overspring the rear. The lightest springs you can get away with and decent damping makes a lot of difference. Too much rear spring and they want to swap ends under brakes because the rear end just tops out immediately.
We haven't gone to emulators on our 1000 yet as the rider uses the front end "pop up" to encourage weight transfer...and he's doing pretty good without them.
Andypandy...the Euro rules allowing brake upgrades beyond the period are by no means common in the rest of the world...and IMO, good thing too.
again IMO it's not a safety issue as what can be Waay better brakes can overstress areas of the original frames - under race conditions.
Again away from Europe most race organisations have a max stanchion diameter which reflects what was available in the period.

How is not getting better safety equitment a good thing? Frames can be made stronger, no worries

I might have been a bit unclear, the master cylinder can be upgraded, the calipers must stay original(but there are ways to make them perform better), same with the brake discs, they can't be full floaters, in some of the classes half-floaters are allowed.


Suspension wise your experience with "over springing" the back sounds like a person who doesn't no how to set up a bikes suspension from the start

Bigger stanchions, did I say they could be outside the right era? But even in the 70ies you had bikes with 40mm stanchions, and I know of atleast 1 street bike with 39mm stanchions.

Ash : Watch Twist of the wrist suspension set up and read some of Tony Foale, you can do far worse than listen to them.

All: Oh and a bit of a warning, don't use old cast iron discs on a race bike, they are prone to crack during hard racing.

[TheCafeKid]

How is not getting better safety equitment a good thing? Frames can be made stronger, no worries

I might have been a bit unclear, the master cylinder can be upgraded, the calipers must stay original(but there are ways to make them perform better), same with the brake discs, they can't be full floaters, in some of the classes half-floaters are allowed.


Suspension wise your experience with "over springing" the back sounds like a person who doesn't no how to set up a bikes suspension from the start

Bigger stanchions, did I say they could be outside the right era? But even in the 70ies you had bikes with 40mm stanchions, and I know of atleast 1 street bike with 39mm stanchions.

Ash : Watch Twist of the wrist suspension set up and read some of Tony Foale, you can do far worse than listen to them.

All: Oh and a bit of a warning, don't use old cast iron discs on a race bike, they are prone to crack during hard racing.

Here's the deal with what he was saying with the rear springs.
If its sprung too stiffly in back and the damping is too soft the spring by nature will too out under hard braking causing the rear end to go light because of the force of the spring wanting to rebound to hard/quickly.
The rear damping set up must be compliant as to let the rear end "bounce back" quickly enough to take the next bump cleanly, but not so fast as to upset chassis. When leaned over, the suspension is not nearly as efficient as when upright, and the rebound circuit must be able to control rebound (obviously) or the rear will step out. Some talented racers you will find are both on the brake and throttle at the same time to effectively shorten the front end geometry to turn in and corner more quickly. If in this action the rear is too stiff it can break traction and down you go...

As to the original post, you certainly can make the frame stiffer, but there are trade offs... By making the frame more rigid it cannot act as secondary suspension while in mid corner causing a loss of front end feel. The bike will want to stand up and lay back down repeatedly on an undulating surface. A stiff frame is helpful in many situations, but making it overly stiff can be worse than having flex in it. Ask Burgess and Team Ducati about frames being too stiff to tune. They'll tell ya all you wanna know. Hahaha

[GregT]

Thanks for the clarification Kid.
Andy - I build and maintain these old race bikes for a living...From what i've read and heard of the Euro scene the brake and suspension rules are more liberal than here in New Zealand or Australia but conversely we can use 17 inch wheels in the pre 82 class where as I understand it most of the Euro classes are limited to original sizes or 18 inch.
Both approaches have their points...
What I like about the Southern Hemsphere approach is that the bikes retain the handling quirks which make them difficult to ride at the limit...and fun to watch
I am firmly of the opinion that period brakes only should be used - no problem using the best of the period though. Having to ride to the limits of chassis and brakes is part of the atmosphere of the period and should be continued IMO

[salty_monk]

Wera Racer - I'm also interested to know where you ended up with the springs (and what weight you run at if poss).

I think Racetech recommend a 1.1 kg/mm for race use?

[TheCafeKid]

Nice lean angle
What's the rating of your front springs?
Is that a V&H exhaust you have?

It's pretty colours for sure. Everyone gets all bent when their pipe colours like that...if you know it's not dangerously lean I think it looks cool and means you actually push the darn thing. Or it's made of Ti... Hahaha

[ashdricky]

Thanks Andy your knowledge is quite helpful, Im currently looking for someone to rebuild these shocks. I was told that the valving is fine, It seems to be mostly cosmetic, and obviously the incorrect spring rate. Anyone know of a good shop on the U.S. east coast?

[TheCafeKid]

Thanks Andy your knowledge is quite helpful, Im currently looking for someone to rebuild these shocks. I was told that the valving is fine, It seems to be mostly cosmetic, and obviously the incorrect spring rate. Anyone know of a good shop on the U.S. east coast?

What make?
If you need springs only, you can purchase them from race tech or some other suspension dealer and replace them yourself. You'll need to be able to take a few measurements for them (wire diameter, free length, etc) and you'll also probably want to give them the make/model of the bike or it's listed wet weight as well as your own with full gear on.

It should be mentioned that setting the sag correctly both front and rear are the first and most important step in beginning to dial your suspension in. The sag, with you on the bike, in gear and in rising position (feet on the legs etc...you'll need a helper) should not take up more than 25-30% nor be less than 25-30% of the total suspension travel at either end. If you'd like some tips on how to measure this, shoot me a PM and I'll be happy to explain what I have learned. Once you get your springs and valving set up, you'll need to do this. And if you make any adjustments to geometry (dropping forks through the trees etc) or anything that would change static CG you'll need to re-set your sag.
I have spent the last season and the winter delving into the "black art" of suspension set up. You can glean a lot of info from learning to feel what is right and wrong and things like reading your tire wear patterns etc. getting the suspension set up correctly will open an entirely new world to you and your riding. Youll be smoother, faster, more confident than you ever have. While it really isn't a black art, the end product is definitively magical

[speedyandypandy]

Thanks Andy your knowledge is quite helpful, Im currently looking for someone to rebuild these shocks. I was told that the valving is fine, It seems to be mostly cosmetic, and obviously the incorrect spring rate. Anyone know of a good shop on the U.S. east coast?

Ask the local bike shop if they know and can recommend a suspension company.
http://www.racetech.com/page/id/69 I found this with a 5 second google search.
It's a good thing to service rear suspension, not alot of people service them as often as they should be, oil with a hard life should be changed out often.

[speedyandypandy]

What I like about the Southern Hemsphere approach is that the bikes retain the handling quirks which make them difficult to ride at the limit...and fun to watch
I am firmly of the opinion that period brakes only should be used - no problem using the best of the period though. Having to ride to the limits of chassis and brakes is part of the atmosphere of the period and should be continued IMO

Each to it's own I guess, sounds conservative, in Rome......

Do you get to use 180 rear? The Nordic Series allow 17" down to 1980, not sure if there is a width rule. Having heavy rules on making them better is just silly, faster is better, yes?
1979 and older is 18" as minimum. And the rules are not liberal, everything must be period(ish), but no one looks inside to check it, gentlemen's agreement, except the french, if a non french-man/team wins the bol'dor classic they suddenly check the bike and bring out the special rulebook.

As to the original post, you certainly can make the frame stiffer, but there are trade offs... By making the frame more rigid it cannot act as secondary suspension while in mid corner causing a loss of front end feel.

Ok if you say so. Find a plastic ruler, vertical it's supposed to be a bike frame, now where does it flex? sideways and a bit of torsional flex(hope you understand), but nothing up and down
Old frames are like rubber, the flex all over, bracing a frame so that it's closer to the ruler is good? Yes, I think so to.

[TheCafeKid]

N

Each to it's own I guess, sounds conservative, in Rome......

Do you get to use 180 rear? The Nordic Series allow 17" down to 1980, not sure if there is a width rule. Having heavy rules on making them better is just silly, faster is better, yes?
1979 and older is 18" as minimum. And the rules are not liberal, everything must be period(ish), but no one looks inside to check it, gentlemen's agreement, except the french, if a non french-man/team wins the bol'dor classic they suddenly check the bike and bring out the special rulebook.



Ok if you say so. Find a plastic ruler, vertical it's supposed to be a bike frame, now where does it flex? sideways and a bit of torsional flex(hope you understand), but nothing up and down
Old frames are like rubber, the flex all over, bracing a frame so that it's closer to the ruler is good? Yes, I think so to.

Right, but when layed into a turn, the forks and shocks are not as efficient at sucking up road/trackimperfections as they are when the bike is upright by nature of their design and implementation on the frame. Thus, whatever shock they do not absorb is transferred to the wheels and frame/swingarm. A small amount of flex will help to swallow this shock rather than allow it to cause the contact patch of the tire to break contact with the Tarmac. At racing Gs/speeds/lean angles, a fraction of a second of lost traction can be the difference between being on the podium dousing your bike in bubbly, and being on a stretcher with the bike hanging off a wrecker...

I'm not saying the old stuff isn't made of dried noodles. It is. And I'm not saying bracing the frame for racing isn't a good idea, as it is as well. I'm saying there are trade offs, and limits to bracing that take it from good to bad. Some people think stuffing a gusset into every curve and joint is only gonna make it better...and those guys are usually slow in the corners cause their bike feels like it wants to buck them off...

[speedyandypandy]

Agreed Kid

At racing Gs

Gs=Gforce?

There is a fine'ish line when it comes to making braces, but it's not hard, difficult or rocket science, a good local engineering shop should be able to help out, give them a print out of Tony Foales chapters on frame welding and bracing and away you go.

A small bird told me TFs book can be downloaded somewhere on the internet, I wouldn't know what that means, but it's supposed to be a good book.

[John Kat]

Cafekid, I totally agree with you!
When the bike is leaned over at say 45° and you go over a bump, the frame doesn't get fed forces along the wheel axis.
If the frame is overly stiff, the forces will go right from the front wheel to the back wheel and then the other way round when the back wheel goes over the same bump.
I remember a Honda SP1 I owned that felt unsecure. Later after trading it for an Aprilia RSV 1000 Haga that was 10 times more secure, I read that Honda had come out with an SP2 version.
The main differences were related to changes done to the frame to REDUCE the stiffness.
Coming back to the comments of our Norwegian friend, I also remember that a team in NZ ( or Australia?) tried a conventional frame for some races and noticed no differences in roadholding...
A pity by the way to think that the officials at the Bol d' Or race treat the foreigners differently than the locals.
Bad faith must be part of the caracter of some bikers...

[speedyandypandy]

Coming back to the comments of our Norwegian friend, I also remember that a team in NZ ( or Australia?) tried a conventional frame for some races and noticed no differences in roadholding...

What bike was it? And does the story say anything about what their level of riding was, or if the braced/custom frame they used was done correct?

Not bad faith, rule of thumb, it is what it is. I like France by the way, and Curcuit de Ledenon(2011) is one of my favorites. Marseille(2011) is my favorite city in France. MotoGP at Le mans was a good weekend(2006). You have the same rules for Tabac as we in Norway have for Whine&Spirits, the shops closes early.