Suspension tuning tips

[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

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.

 

[GregT]

I think what JohnKat was remembering was the story on the GS1000 that Mick Hone ran with Robbie Phyllis on board...heard of him Andy ?
If I remember right, Hone was quoted as saying that they found no gain from a braced frame or the 1100 aluminium arm but best results were with a braced standard steel arm.
Tyres of course have come a long way since then....someone posted some pics of Phyllis current post classic racebike and yes, it's braced.

 

[speedyandypandy]

Mick Hone ran with Robbie Phyllis on board...heard of him Andy ?

No, the only NZ & OZ riders from back then I can think of is Cooley, Tony Hatton , Michael Cole, Crosby and some Ron dude, I think he rode @ Suzuka with Cooley? The other good ones I know from that period is Mike the bike Hailwood, Ron Haslam, Alex George. The others I know, Sheene, Roberts, etc where 500cc GP riders. But I will oogle them, need more pictures for the formula racer.

Sorry for hi-jackin your thread ashdricky But frame and suspension walk hand in hand
I don't think a non braced oem frame stands a chance.
Even braced frames where not good enough, I see good reasons why Harris, Egli, Baker, etc where selling so many frames to the top factory/privat teams.
Jap bikes didn't have good frames before the RC30 ? Can't think of any other that came before the RC30

 

[GregT]

Phyllis carried on into the WSB era and rode works kawasakis alongside Aaron Slight...and the old b...... is still racing.

 

[gs58]

Read an interview with Phillis (I think) a few years ago where he was talking about production racing in the early eighties. They wanted to stiffen the frame so they bored the engine mount holes in the engine cases to the same size as the holes in the engine mount brackets, then used oversize bolts that were a tight fit for both to tie the whole lot together. That really makes the engine a structural member and reduces a lot of the torsional and side flex.

 

[salty_monk]

I think Works performance say that they will rebuild any brand of shock & can upgrade valving etc as necessary.

They are in Woodland Hills California.

 

[ashdricky]

thank you MonK, Andy, and Cafe, Your knowledge is quite helpful, to answer Cafe's question about the make of shock they are older Ohlins, from a Yamaha I am told. I will have to look into geting them serviced. I was told there is a guy about 2 hours away from me who will rebuild them, but I am yet to hear back.

 

[mawg]

I say,find out what the rules are and cheat from there.Put 86-87 GSXR 1100 forks and wheels on it.Ummm... radials and 4 piston brakes.Maybe they won't notice.

 

[gearheadE30]

I'm not a racer (though I will be trying to get to a track day this summer) but I will say that even with my smaller level of experience in performance riding, the switch from 35mm forks to wider 37mm gs1000 forks made a massive difference in cornering stability.

How much of a difference is a fork brace going to make? I'm considering buying one as I continue to get my handling where I want it, if it will make a big enough difference in the front end. It still feels like it flexes too much, especially if there are any bumps at all.