Steering geometry - confirmation bias

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Alan, Brooking 850 is giving you some solid and reasonable advice here.

I would see to it that you get your geometry as close to as what Minnovation recommends for their bikes. My Seeleys do not stand up nor go wide and I occasionally brake extremely hard and trail break. My bike goes where I want it to go.

At this point I don't know if you are lamenting on how foul a set up you once had or if you are having difficulties now. As I said, figure your rake and trail now and attempt to back calculate the trail you had with the previous yokes. There's a story in there somewhere.

To find out what trail I was using with the Ducati yokes, I would have to reassemble the old front end arrangement. I am beyond that. The Seeley is now extremely direct and quick steering and tightens it's line a lot when gassed if cranked over. It is really great to ride, but I always have to anticipate a lot about where the bike will end up as it comes out of corners. I'm putting more preload on the rear shocks and expect the steering will become slower with a bit more tendency to run wide in corners. I know the variable is the trail, but I don't know in which direction I should change it to restore the quickness. I don't want to do anything silly and get bitten.
 
Alan, Are you running a Seeley Mk3 or Mk2 frame?

It is an original 1966 Seeley Mk3 frame.

Having had a bit of a think about this, I probably don't have a problem. I was increasing the pre-load on the rear shocks to get more clearance under the seat. If I only change the back of the bike, it will affect the steering by changing the rake. So I will also have to find a way to raise the front of the bike, to simply raise the overall ride height without changing the rake. I think I might be able to use spacers on top of my fork springs or make extensions for the staunchions. Probably only has to be about 12mm change in height at both ends of the bike. A slight change in rake can have a very big effect.
 
You are correct that most bikes will tend to rise under braking conditions and tend to run wide in corners when it happens.
I never stated this; you may be referring to someone else’s assertion.

Your saying your “going to have to go back to suck it and see” is no excuse for getting a thorough understanding of what is happening. Reading your last few posts indicates to me that you are not there yet and most likely are still confused or unwilling to trust what others have told you numerous times.

All you need from the Ducati yokes is the offset and knowledge of the rake and trail you currently have. With a little trigonometry (or draw and scale it) you can get very close to the relative difference in trail between the two offsets which is very useful information. Getting the exact rake and trail you had may be a challenge if you had since mucked around with tire profiles, preload and ride heights.

I believe your doing this comparative analysis excercise will once and for all convince you which way is up and which way is down on this matter. Alternatively, re-read the Holmeslice post earlier in this thread, he has it correct.

And finally, the fact that you are running an original Mk3 Seeley tells me other factors may be in play. I have no direct experience with the Mk3 frames but have “heard from several knowledgeable others” over the years that the Mk3 frames suffered from some lack of ridgidity in the front end (when compared to a Mk2). Take this with a grain of salt. Also consider that (at least what I am seeing) there are not many Commandos mounted in a Mk3 frame and perhaps that is telling us something. Hopefully the collective wisdom of others who have run the Mk3 and Mk2 will come out here.

Furthermore, unless you are the original owner of that 1966 Mk3 and know, with confidence, the complete history of that frame, I would check out some key measures such as rake angle and front to rear alignment.
 
I was closely associated with the original owner of the MK3 Seeley frame and I know it's history - am certain - it has never been crashed. I've also heard the stories about rigidity of the front end of the MK3 - it never moves whatever you do to load it sideways. However I don't use the original ladder arrangement in the front. I have a gusseted and stressed chrome-moly tube bolted in.

I think I've got my head straight about this. I just got a bit freaky over the mishandling when I had the large offset fork yokes. I think what happened when I drastically reduced the offset was I moved the uncertainty in handling from the braking area to the bit as you accelerate out of corners. The bike now self-steers a lot in the correct direction as you accelerate out, cranked over of corners - instead of trying to stand up, when you are braking cranked over into corners. If the bike becomes more stable when you brake, it means the rake has slightly reduced. So if I raise the height of the rear end by increasing the pre-load, that will also reduce the rake and the bike should either self-steer slower as it comes out of corners or turn less. Either way the exercise is probably safe. I've been a bit concerned about this issue and it's been a bit of a turn-off. I'll try to get some more track time at Winton in the new year.
 
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A frame that can flex to take up tire vector conflicts by "some" twist yet only relax back to neutral w/o rebound beyond in cycles is the Holy Grail of motorcycle design. Acotrel is not stupid and very observant, so I'm guessing this is something all of ya are missing in Al's rake and trail logic. So keep in mind his is an earlier 'weaker' front frame, he has also modified/repaired for some reason a brace or tube that is lighter less robust than original. At least that's my impression so pester him more on this detail please. For sure Al is not confused on which combo he had most fun with, so why is that?

ITs SO SO TABOO to ever mention/consider anything but making parts more rigid in every way, so I think its automatic reflex of Al not to mention/consider his frame mod acidently worked well.

The main bugaboo of trail rake issues to me - occurs when cycle in state it starts to fall over on its own if not resisted by power accelerating, then the front can get snatched into real road following to direct steering which puts a severe whiplash through frame often inducing hi sides by tripping over turned way in front tire or rear gets lifted by frame whiplash to step out snag flip over head.

Might also re-picture front geometry above tire patch- stem & axle, as a dual plane double hinge with a short lever ahead of it and longer one behind. If cycle leaned to L and front turned R outward, this makes rear thrust cause hinge to fold inward/downward literally forcing cycle mass down at stem relieving rear load till low sides, if leaned L and front turned inward L too - rear long lever thrust tends to push stem hinge to fold upward outward toward inducing a hi side with extra load on rear patch, till flung heels over head.

Truth is there is no ideal front geometry being skewed with so many factors splashing through, so only way past front traction limits is to enter sharp turns over powered on lightly held bars so as it is falling down on its own tire can snap to direct steer where pilot can then add more or less direct steer pressure to lever more and more of total mass on rear patch so more power don't break traction just powers ya around sharper faster. At max effect can hook so good allows a side ways wheelie from off peg fouling leans. Insane G's all focused on rear axle/patch. Must exceed counter steering traction by entering too hot for any possible trail breaking which would instantly snatch down.

Alas over rigid frames can not tolerate the loads Al's describes as magic of adding power just turns in harder on its own.
May never find out.
 
There is a major advantage in using the TZ350 Yamaha fork yokes. Because the bike self-steers in the right direction as you gas it when cranked over, you can give it a lot more stick. Commandos don't usually have enough go to hi-side you and modern tyres are excellent. The other thing is that the bike tends to stay more vertical and turn under itself. I'm getting a lot more tyre wear on the sides of the tread because the rear end is spinning the wheel as I accelerate harder when cranked over. It is a much safer ride. My only concern is that when making adjustments, I might accidentally make the bike tighten it's line faster. And that might lead to disaster.
When I was racing my 500cc Triton at Winton, I once reduced the gearing a lot and nobody could get near me around the tight parts of the circuit. The Seeley frame with the TZ350 yokes is a leap ahead of that. The problem is that everything happens so fast when the bike is set up like that, you don't need to get it wrong.
I have thought about what Dances said about back-calculating the trail. When I installed the TZ350 fork yokes, the trail became about 92mm. The Ducati fork yokes have 26mm more offset. Because the line through the steering head and the vertical through the axle intersect, the larger offset reduces the trail by about 26mm to about 66mm. With the change of rake when braking hard when cranked over a bit, the combination becomes dangerous.
 
Steve, the advantage is not in the way the bike turns into corners. When doing that, it is extremely direct and everything happens quickly, - if I counter-steered, I would crash. I only brake about a third of the way into the corner, then it is almost immediately back on the gas, even though the bike might be pointing towards the outside fence. The bike does the rest of the turn itself while accelerating hard and staying more upright. The riding style is extremely aggressive. Most race bikes I have ridden would drop you if you did that. Manx Nortons only do it for you a little bit - enough to give confidence. That is the reason they were so good in the old days. A Manx makes good riders out of bum riders.
 
- if I counter-steered, I would crash-
- style is extremely aggressive. Most race bikes I have ridden would drop you-

Al we are the only two here that seem to know what ya talking about, -nil to no counter steering nor much skill or pilot effort after braking interval- but I think I'm the only one that understands why which goes right over the heads of the seasoned racers on their semi corner cripples not to mention the global elite cycle engineers. Fork geometry only mater if going in mild enough front stays in good traction effect, so you-me only need adequate forks to set up for the extra G's after exceeding front tire steering.

What everyone is missing is its not the frame twist that's an issue, its the springing rebounds when loads relieved. Best pilots ever was all say they essentially often just hanging on praying the wiggle wobble settles down instead of escalating out of control SPLAT!

In too flexy unstabilized frames when the big oscillations match suspension rate tend to "hinge" into weeds, when over rigid frames ringing resonates with tire sonics - out of control event follows. Standard simpleton way to keep a bit more speed through some turns is to relieve loads by keepping rear from hooking much acceleration forward by enough spin/loss of traction to flat track slide as too corner crippled to take the conflicting tire vector-loads required to direct steer around on planted rear with most whole mass on it to accelerate eye lids back. Flat tractors on dirt or pavement all still counter steer which widens path or they'd flip a hi side so risk low side off tract instead.

The fact still is that if they make a component strong enough to resist the loads its both too heavy and too ringy rigid yet when they try to weaken some for compliance it tends to bend/break.

The miss conception in over rigids occurs because there are so so many resonating splashes piling up so fast it feels like needs side ways suspension and fork damper etc while its actually the twisting spring backs that's being felt. What makes racing so exciting is how danergous hard to control so close to crashing as no tolerance to switch handling energy to next phase, like ice melting from parking lot direct steering speeds to liquid counter steering phase to steam blast phase back to direct steering to glowing plasma jet leaving any front traction behind. One reason the 2 wheel drive cycles can't keep up with normal tract racers just helps on slow off road climb outs.

Peel evolved to point of needing down force and active flight control aerodynamics to stay planted to accelerate through turns faster as nothing else upset her to explore more black out G spikes. Will have moveable wings in front and tail feathers at rear. Not ever heard of moderns having to deal with ground effects lifting - dropping lean angles but Peel sure did d/t how fast and low she cornered pressurizing cushion of air, which being isolated totally for all the bothers over rigids could also feel the effect of wind eddies spilling off forks so need to stream line the spoke blasts and sliders as well as removing side covers and oil tanks flow blockers. So this is another factor missed in upsetting over rigids the slight lift/drop of lean angle holding with pilot slightly compensating for with forks till out of cycle phase of the oscillations so next little out of time compensation is enough to stop the fun. Moderns are only streamlined for forward blast not much for low down hot turns.

On my SV650 and Ninja I reflexly stuck a knee out to side while upright, an instant for the wind drag to help start the jerk down but then sucked up tight to tank with leg out straight back for more lean clearance. I learned this on Ninja at corner school to beat snot out of head instructor send to teach me apex lession but left him a full shift ahead to swing back to see him just coming out of apexes, pahsaw. I got some mastery on moderns so the more my disdain for them now. Knee 'dragging' is mainly to help pilot dampen down oscillations between bars and pegs and lean less than if CoG kept more in line with tire patches. Of BIG note on Peel direction changes happen too fast to have time to shift body, which allows instants of load let off to induce the wiggle worms, so barely time to catch next good breath to force hold against G spikes at apex. I've practiced climbing around on Peel at about peg fouling power, and heavy cargo leans to find nil effect so no longer waste effort beyond just staying as tight to her as can and bar grip like ski rope stretching wrists harder in turns than flat out drag, which again remind thee Peel could out leap moderns trying to beat me into a tight turn, to see them lift front and fall behind. Then they are freaking out trying to slow while Peel just stays on power - even through 2 decreasers in a row. Ever in your life heard of cycle cable of that! Me either.

So face it you'all Al has accidentally created a compliant dampened Seleely but not recognized as so against corner crippled rigidity philosphy. Best corner cripples can do is compromise forks to least upset their touchy ringing let downs.

After phase 2 counter steering Peel leaves low slow orbit of cycles stuck on tracks so cycles are not Peel's real completion to find pecking order but 1000 hp awd rally cars and F1 down force cars on tighter tracts they can't develop much down force and kind of sluggish to spin on axis to hook up out of turns. Peel is power-heat limited so not 200 mph capable nor beating drag only cycles in 1/4 mile but should out leap wheelie prone road racers to well over the ton in time for next little leaning turn they all brake to pile up like starting race all over again leaving Peel out ahead no way to catch up again. So make my cycle with any ole front to keep stem off the ground, hard-rigid at the extremities but soft-compliant dampening twisty hinged in the middle. Smooth is for stuck on tracks sissies to a jerk off on Peel.
 
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All antics, 50-65 age, were 2001 to 2016 with Peel only existing about 9 mo's in her prime, summer '04-winter'05 + 6ish more after 11,000++rpm test took scary dragster power down to ordinary Combat like sweet Trixie, so was like Ole Yellar ending by my own hand/heart. Spiffed up '00 SV650 had ~40K miles before getting weird cylinder drop outs, after 30 miles fine with extra spunk from going through everything repeatedly to optimalize so not electric nor carb but valve train wearing out, messing with the CV carb slide to flutter like a leaf. After last crash, on purpose being sedate, just leaning 46ish degrees nil power, 40s mph, after some fast tire heating errand runs, it wasn't fun anymore stressing to make it to pavement on such a cripple, gave it away to make room for other priorities. Corner school was spring 2001 after realizing I could best the local squids w/o much risk on SuVee was still too scared to break free on pavement as had on grass and Gravel, so bargained with Code to allow me to learn over doing it stupidly on a real sport cycle. I'd lost all interest in Commando after my SV650 so only keeping promise to late daddy I never finish anything just wanted no name clunker Combat sold to put into serious fast modern.

Another seeming fork associated fault, never mentioned because so few dare or have crisis tests like I have. Type of engine configuration, mass placement and flywheel gryo effects behave opposite in Vtwin vs inline4. Vtwin easy to tip over and stay there but fight ya through the forks trying to pop back up in time, while inline4 fight ya to tip down so extra fork effort throws a wiggle through frame and wiggles to hold down - innately wanting to hi side if pilot can can't work hard enough to resist and too often can't.

Those little hands off bar oscillations that seem to disappear with speed can/will show up again in next level of higher turning loads > much magnified. None of that crap concerns Peel so nil pilot effort/skill to exceed front tire traction.

For significance of hobot ramble, consider - my first outing on ape position sport bike and track getting handy enough to be 'similar' to seasoned pro's, 'comfy' in knee drag leans on good power, got into 270' sweeper (in public would have yellow 35 mph sign), getting to racers edge of steady state short of crashing, NAILED WOT -- YEEEHAWWDOGGYDOODOO EURKEA pavement was child's play easy. So worked into horrific tire hopping crash state oscillations both tires howling - felt like crossing a plowed field sideways til energy enough to easy trip down for the resultant saving hi side launch to both let the oscillations die down before impact and get most the turn done in air. Any other pilots care to discuss how wonderful a planned crash on corner cripple can be?

BUT corner cripples splish-splash so many cycles of harsh oscillations with wind & ground effects and road texture etc adding static till life risky unpredicable to trigger this each/everytime on fleeting right combo of frame/forks,patch/suspension rebounds. Point being I learned on moderns not vintage so can blow smoke out my ass at them as too crippled for such tiny increments of more fun. Hehe unintended Pun as exactly what Peel did to challengers till point elites states around sought out Kingston Norton Nut.

Just like my P!! invited geeky me into 1%'rs rank, Peel invited visiting fast draws sort of like old west. Lived on Peel day and night in favorite ride area, rear cords showing @ 3-4 weeks no chicken gaps extended mileage. Having 2" taller roadholders gave more lean angle and stayed in effect longer than squatty moderns forks by also extending more before lift off. Of course in Ms Peel's case the forks were being direct steered into decreaser to get frame wound up and held there by fork levering mass on rear and stem hinge angle feeling like a sky hook, till just let go like exactly like a sling shot any way I liked at any point in an arc so beside being no such a thing as perfect forks to a perfectly neutral cycle there is no perfect way through a turn, so Peel can turn em all into multi orgasms of sharpened decreasers in a row. Can out stop stoppie limited ABS moderns too so may also have the safest funnest rubbery clunker. Carry on with crippled wisdoms w/o Peel in sight.

Ms Peel is only really Neutral cycle fielded, takes same slight effort to trip down and pop up and no pilot effort needs once a lean set stays there even hands off like a bicyclers do - unless adding throttle or front tire slides across lip in road, so only a dampening effort not steering effort. Adding power or reducing power does not change her line or lean or turn radius - unless breaking rear free then if don't change fork or lean angle with slight effort, only slides on tangent outward till spin stopped to carry on like nothing happened. Flat trackers are swinging rear out but Peel does not as sliding of both tire equally so neither end tending to pass the other.

So bicker and bitch at me or Al but we know what ya missing out on.
 
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I was only asking if Mrs Peel was up and running, didnt need a lifes history lesson and preamble that would scare a youngster getting into the motorcycle world.
I try to encourage and teach young riders, not scare them !!!
 
I was only asking if Mrs Peel was up and running.
I try to encourage and teach young riders, not scare them !!!
+1 Brooking
Amen to that
Cheers,
Tom
 
I was only asking if Mrs Peel was up and running, didnt need a lifes history lesson and preamble that would scare a youngster getting into the motorcycle world.
I try to encourage and teach young riders, not scare them !!!

Indeed, much like I did to a young Italian on the shores of Lago Maggiore.....after he passed me plodding along in my Land Rover, he turned into a left, applied the brakes, it stood up and ran him into a ditch....as I picked him up I told him in my best Italian, don't brake in the turn, if you are going too quick countersteer then drive it out.....

I have seen Steve's diatribes on cornering and various comments on when to countersteer before, and will only say again, it is the only way to steer a motorcycle in any situation! :)

If you are not countersteering, well, actually you are, you just don't know you are!

Remember Peterhansel, the Dakar bike star turned driver, when asked what is the difference driving the event to riding it, he said, I turn the steering the other way!
 
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I agree with what you say about counter-steering. It happens regardless of whether you do it intentionally or not. But if your bike feels so stiff that you have to consciously counter-steer to get your bike to tip into a corner, there is something wrong with the handling. With my bike, you put your mind where you want it and it is there. I have never consciously counter-steered a motorcycle in my life. If I had to do that, I would not ride it.
 
Ludwig, I doubt that I will ever race again where it really matters. I'm considering either an old farts day at Broadford or a ride day at Winton preferably around May in 2018, when the weather will be cooler. There will be races at the old farts day, but Broadford has blind corners, so needs to be treated with caution.
 
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I have told you guys what this is. If any of you decide to reduce your yoke offset with a frame which has 27 degree rake, please be careful. There is obviously a limit to how much you can safely quicken your steering. Whenever I go to Winton, I always relax and do a few laps before I start pushing. There are a few small things which can alter the handling and if you bike steers extremely quickly, you can have the crash.
 
I'm not expert/competent as yoose traditional counter pointers on discussing details of fork/frame/supsension factoids so can't comment much but generalities of rate, off set trail such as can be recorded on charts. Engineering wise two long telescopes is about weakest wobbly twisty bendy bindy worse logical design so a myrid of others have tried to improve on it and some have in their arena of use but 2 pongo sticks still rule the roost.

What's going on behind the stem greatly affects fork behavior that confuses where attention needed. Swingarm pivot height affects squat hook up which affects trail for instance but do ya compensate at front or rear if not sweet as expected?

My personal revelation was a way around fork faults and directly relates to the ole motto, when in doubt POWER OUT. Counter survival intuitive till realizing it unloads front out of influence for more rear authority - even to point of unicycle wheelie steering w/o a front fork installed! Rear is what steers cycles, front is like rudder to help aim rear, if they conflict authority too much to compensate for >>> Bad JuJu.

Initially daily once twice even 3x's Gravel snatch downs while going as securely as I thought I knew how and still be rolling, on modern or Commando, forced me to figure it out or forced to quit by accumulating damage and injury. Not going fast so only levers, lens paint and Lucas bullets or me hurt. Noticed that forks were direct steering as much as counter then noticed if I restrained this natural cycling to stay in counter steering for seeming more stable control through mild Gravel turn or even straight ahead, every now/then combination of suspension and my fork stablizing would skip counter steering front tire out of traction many inches for a whip lash twist wave through frame to jerk rear out too. If I quick enough direct steered bike jerked up before crashed. Then discovered if I only direct steered on loose stuff, could go a lot faster with better turn 'authority' and the otherwise snatch downs tended to just jerk more upright back in line.

Plenty direct steer examples, mostly all off road where rear is not hooking up constantly. So only time would apply to pavement is when rear is not well planted but still thrusting ahead well so cycle would fall to ground if not resisted. On road if not on rear straining power that unloads front - direct steering leads to Hi Side Hell on impact.

As long as can keep good load strains going everything generally fine but surface and wind can combine to relieve loads long enough to let oscillations spike. One can keep constant frame/suspension/forks hard loaded no matter how far over or accelerating by catching the fall down by a flip into direct steering. If done on purpose HOT DAM if by surprise,SPLAT. Its dangerously difficult to do on pavement at speed and only trusted tri-linked iso Peel. I tired to practice Peel lines on my SV650 but couldn't reach the energy levels needed before getting as nutzo as Irish races show, so fear made me quit before SPLAT.

Slightly modified 750 stem fork Roadholders behaved perfect on Peel and wish others similar lack of concern to seek more.
 
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I have told you guys what this is. If any of you decide to reduce your yoke offset with a frame which has 27 degree rake, please be careful. There is obviously a limit to how much you can safely quicken your steering. Whenever I go to Winton, I always relax and do a few laps before I start pushing. There are a few small things which can alter the handling and if you bike steers extremely quickly, you can have the crash.


WRONG AGAIN,... Reducing your offset gives you more trail, will make the bike more stable, and will make the steering slower and heavier as many people have told you previously.
 
I don't know what Steve Shriver does with his bike, but he seems to tolerate flex. Which is something I avoid. As a kid I rode many bikes which had limited relationship between the handle bars and the rear tyre contact patch, Most were pre-unit Triumph 650s. I moved from there to a 650cc Tribsa - a BSA Gold Flash (A10) frame with 60s Triumph fork yokes. I sold it to buy the 500cc Triton which turned out to be far inferior. A BSA Gold Flash based Tribsa with BSA fork yokes is an accident waiting to happen.. It can mishandle extremely badly.
 
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