Steering geometry - confirmation bias

I changed the 19 inch wheels on my Triton to 18 inch to get decent rubber, then found I had to climb off the side of the bike to stop it from running wide coming out of corners. We commonly ride around our bikes handling characteristics. So what comes first - the bikes handling, or the rider's riding style ? What I found with the Seeley was mainly by accident. I knew the TZ350 yokes would be somewhere near right - I did not expect the line-tightening effect which I now use to advantage. It is not something I would recommend if you have a peaky or savage motor. But it has really changed my mental attitude. In the past I used to pussy-foot gingerly at speed around every corner - now I really get stuck into it with full confidence. - Brake a third of the way into the corner, then straight back on the gas with a good solid squirt - the bike does the rest.

Body posturing really don't do that much but affect air flow/resistance. This is significant at race speeds. Dozens of top racers win with many styles and change styles on same cycle same race, sheeze. I think a lot of knee dragging has to do with fear of unpredictable let go so putting knee out ahead of time to buffer low side and give a chance to push up on tires again. I never put a knee out on Ms Peel but frequently did by fear reflex on my SV650 enough so to observe its effects or lack there of. Again we are not talking lolly gagging about but close to max leans and power hook up. A quick knee out creates sudden drag and low pressure area so bike tends to tip and turn that way w/o body or fork effect, but after that sucked in back tight for more stable control on corner cripple. Watch the world class closer to see at times scary harsh turns being done with knee down or tucked close neck and neck. Seriously none of ya have a concept of what's possible with a tamed isolastic Commando that can put down more G's than a drag racer because the turning G's add to the forward thrust G's, so if not in full locked down tight to cycle ya get thrown off. But not like mere elite corner cripples but from it running right out from under.

Where Corner Cripples are hanging off expanding frontal area & significant wind wobble eddies trying to counter some the outward G forces, Peel pressed my ass deep in seat in direct line to axle/patch so nil sense of turning throw off loads but at breath taking apex climaxes.

Al you've answered your own question by accidental fork geometry on accidental beneficially weakened Seleely. You know its really all about the cycle not the pilot unless cheating like Valintino that wins races. So use your wheel base and cycle CoG as base line to slightly experiment with.

I did not really know if my Gravel antics applied to tarmac, so paid Kieth Code $3000 to let me loose till able to complete dangerous turns on same cycle as his top seasoned tract school leader >>> a full gear higher so can be obnoxious bold no speculation on my life/death serious comments. I learned the hard way about limits of moderns on various tire compounds = to snicker at their incompetence that confuses everyone but me. Eat ya hearts out longing for a really neutral handling compliant dampened power pulse hooking up supermotoard. Its way better than brief sex climaxes.

Steve, if you could post some videos of your talents , could be a useful tool for some of us.

Its the abilities of a tamed isolastic Commando that revealed what's wrong with other cycles especially antique Commandos. No digital video available to public in 2004-5 so only Peel stills in raw woods, creek beds, hay bail pastures and THE Gravel, often laying on side crashed. P!! too low to lean and lost it 1975 as too poor student in Houston, so no cycles to learn turning till '99 accidental Combat find. Combat too bent inside to carry on past 6 mo's to see how bad/expensive/over my ability it was, so got used '00 SV650 which ran circles around Commando and just wanted to be rid of obsolete antique now all apart ugh. Discovered non DOT race tires on SV helped Gravel travel as well as tarmac to explore handling quirks/limits in public then track school. World class advice and parts from many famous racer/builders got no name Combat going summer '04 to sell off but wanted to fit & try Patton's and Tryee's rod links first. Was shocked I could not upset it in the worst places that were a terror on spiffed up SV and could out corner speed/pull than Code's semi race bikes - WTF!!!??? It was next day in car still shocked/amazed that Ms Peel name seemed whispered in my ear. Still confused to keep/sell - till 2-1-megaphone-ITITIS so confused surprised pissed me off as too old to be quick enough to grab on then deep depression too old/weak to hang on, till feathering throttle - to split ear/ear grin - as able to easy dice up with moderns acceleration past 100 mph and so so secure in turns.

Peel was so good I'd yell out to sportbike squadrons Hey I need a hot shot to test my antique against to often have everyone point to one guy or a couple/3 would take off with me, or I'd run up on squadrons hanging off like apes to work my way through them- sitting bolt upright - to pull out the only one brave enough to leave the now angry squad out of sight. Gave SV away this year.

Moral of tale is all other cycles will at some point/combo of conditions lose control - but could not upset Peel no matter what I tired - then right before Bruce Mcgreger Drouin arrived to fit on 750, Peel WOT 11,000+ rpm event hit and so began cascade of life crisis just now getting recovered.

More than anything what upsets cycles is front/rear frame twist and rebound. Frame needs to twist some to take up tire conflicts in direction pointed or front hitting lump as rear hits low spot, or a gust of wind hits front then back. Commandos wiggle like diving boards while moderns ring like big bells. Next phase of life hope to leave jaws dropped on video.

I suggest there is a fundamental problem in racing converted road bikes. Bikes such as the Commando are set up to be safe for the average guy on public roads. When you race, the requirements are different. I have raced unmodified road bikes where I've had to sit up on the back of the petrol tank to get around corners. The trouble is that finding better handling can be expensive, but until you actually change your set-up, you don't know the possibilities and making a change can introduce an element of danger. From what I have read about Peter Williams and the handling of the first Commandos, I believe he probably had it right - for racing ! If you put any kid on a bike which handles like a well-developed race bike, they would have a problem. I am not imaging that my bike tightens it's line as I accelerate out of corners - I've got too much experience for that. I am convinced that the way a bike handles dictates the riders' riding styles. If you road race an unimproved road bike, the handling is usually mediocre and you simply adjust to it and go that bit slower.
That comment about the knee-out causing air drag, is something that Peter Williams was big on. On one of his bikes he even had the swing arm pivot outside the engine plates to get his feet closer together. In any case you should never have to do it, if your bike is right. With my bike, conscious body lean etc. is totally un-necessary - I simply move my head. With the different set-up, the steering is much more direct and the natural angle of lean is less.

Al I can appreciate auto steering security of your Seleely but confused if your quest is merely academic or for more experiments with your 850.

After I found out what it took to control moderns near their limits I found out I'm not cut out to seek any more of their constant fear/faith states. To make my bold claims I had to routinely enter/onset all the antics ya see in Isle of Mann or Irish manics, on V twin and inline 4 quirks and a bit more actually - being tricked by Peel tried to practice her lines on SuVee to end up sliding front a few bike lengths or figthing head shake shit out of me with bluff face or railings spitting distance away.

For extra credit 'forced' step through scooters handling. Surprisingly nimble flickable easy lean control leverage while keeping knees together like a good girl at desk. Has more fork range than street bikes so able to skew tires apart safer/further than cycles. Alas small dia wheels + aero dynamics onset warning twiches/sways about 90 mph. Easier than cycles to kick rear out on and drift a bit on dry pasture traction. Its easier to over brake on the small dia. tires even with both linked together but more secure to panic grip for most folks. On THE Grime it would self steer in and out of counter/direct, without thinking action, at survivable speeds 40's mph.

how hobot finds limits to avoid. After tires balance checked then brake grip ability vs pilot fear level traction tests...
1. find feel fouling limits on both sides at slow speed as needed.
2. find full lock fork angle while just avoiding fouling
3. find throttle opening speed/amount that breaks free yet predicable regrip while doing 1 & 2
4. on open hwy zig zag in one lane sharper and sharper, missing paint lines from 25 mph up - till either wisely scared or tires start leaving surface loosing control to either recover or crash grading.
5. by this point can do tight parking lot circles starting out slow direct steering then add speed staying in direct steer but falling/leaning to counter the hi side sling out a bit faster and faster same full lock radious till - it all comes together with only thing left to master is tire temp and pressure on traction limits.

Can learn most all upsetting thresholds below 46 mph in short time except for hi speed aero dynamics usually not encountering in harsher turns.

My primary concern was about the change I made to the pre-load on the rear shocks. However I have figured out the line-tightening effect only happens as I accelerate coming out of corners. This means the cause is the squat at the rear end, which is increasing the rake as the power comes on. By raising the ride height of the rear end, the rake should decrease and the amount by which the bike tightens it's line should decrease slightly. If the change caused the bike to tighten it's line more - could lead to disaster. I have come to rely on the self-steering effect, it allows me to push the bike a whole lot faster.

Even moving the whole engine & gearbox to say, the left can decrease lap times, as revealed by Peter Williams when he wrote that Norton used to keep just two production race bikes for the Brands Hatch circuit only and with that modification could lap 2 seconds quicker than anybody else- crafty!

acotrel said:

However I have figured out the line-tightening effect only happens as I accelerate coming out of corners. This means the cause is the squat at the rear end, which is increasing the rake as the power comes on.

Click to expand...

If your rear suspension squats while rolling on the throttle coming out of a turn, your rake (as well as your trail) will increase.

acotrel said:

By raising the ride height of the rear end, the rake should decrease

Click to expand...

Unless you eliminate or reverse the squat to anti squat, you will only reduce the amount the rake (and trail) will increase.

acotrel said:

and the amount by which the bike tightens it's line should decrease slightly.

Click to expand...

If your rake and trail are increasing as you roll on the throttle, I would expect the bike to tend towards going wider (or as you say tend less to tighten into the turn). Naturally, a lot has to do with where you are starting from with your front end geometry. It sounded like your initial set up was all garbage and you have now corrected it.

Dances with Shrapnel said:

Unless you eliminate or reverse the squat to anti squat, you will only reduce the amount the rake (and trail) will increase.

Click to expand...

If he raises the rear suspension, both rake and trail will be reduced... If he gasses the bike and it squats, both increase. If he gasses the bike and it "anti-squats" both decrease...

o0norton0o said:

If he raises the rear suspension, both rake and trail will be reduced... If he gasses the bike and it squats, both increase. If he gasses the bike and it "anti-squats" both decrease...

Click to expand...

That is exactly what I said. The assumption is that increasing the preload will decrease the ladened sag; increasing preload with same springs will decrease the ladened sag.

You worded your post oddly, so I just wondered what you meant. Funny that if the rear squats when you gas it, which is the most common effect of getting on the gas, the bike will increase rake and trail then tend will push wide out of the turn, not tighten it's line as alan contends... I'm sure his explanation is good for at least 5 more pages here...

How would you set up a bike to Anti-squat when you gas it??

There's another factor always missed in cycle suspension behavior on rake/trail, *forks always extend on slightest leaning onset, -if not (stupidly) hard on brakes while leaned. Found this out with foot forward pegs mounted on Peel fork brace then double checked on SV650 Vtwin by hand and foot so common to all cycles. So what feels like rear squat only is also partially to mostly the forks extending. Braking with forks turned does all sorts of things form upsetting geometry to lowering front turning authority/traction.

So to a large degree the mystery of surprise get offs has to do with pilot technique and lack of trust/faith to tolerate harsher corner loads. I found that if going slow enough/mild radius to tolerate any trail braking - there was enough traction to power on around w/o any brakes after initial straight up inline braking. There's plenty of video of race pilots crashing while holding forks turned &/or trail braking to cause pilot to lose grip on forks and stily ape hanging position to be dragged along bouncing while cycle self corrects enough they can get back in saddle freaked out but loosing place in race. These factors completely negate almost everything discussed here and ignorance of this sets ya up for more let downs w/o knowing what caused it.

Many ways to observe fork extending, by foot or hand, by rod sticking up past bars, video or electronic data logger.

Mz Peel will let forks full extend 6" entering turns like a chopper then suck nose down to blast out of apexes like a dragster w/o wheelie limiting. One the main characteristics of corner cripples I take full advantage of on any cycle is they have to be going fairly slow to not crash trail braking, so I nail brakes inline/upright for most slowing in shortest time then on hi power accelerating past all the trail braking sluggish parking lot cones to gynkannna around them inside or out, no difference to Peel. I pay nil attention to forks, only the rear steering effect by lean angle and power short of break free loss of acceleration.

I have always found that if start to I run out of brakes when entering a corner and I keep the front brake on while turning, the bike always tends to run wide. You usually reach a stage where you run off the edge of the bitumen and have to let go of the brake and simply steer yourself carefully out of trouble at a very long angle. Another alternative is to stand the bike up and do a crash stop while you are still on the bitumen. A dragging front brake can steer you off the bitumen, because you ride with the front pulled down. The line tightening effect as you gas the bike when cranked over is typical of most bikes, at least to a slight extent. As hobot said 'when in doubt, power out' - it is counter-intuitive. The natural thing to do when in trouble is to brake rather than accelerate. In my case, I use the stronger line tightening effect to get around quicker and I rely on it always being there. If it wasn't there, I would crash on the outside of the track while coming out of the corner. What it means is that I am on the gas much earlier when coming out of corners than most others, so I end up going a bit quicker towards the end of the next straight.
This stuff probably only applies to under-powered bikes. With an old British bike you are always at a disadvantage.

o0norton0o said:

How would you set up a bike to Anti-squat when you gas it??

Click to expand...

Not about to get into the narrative of "how to do it" but here is the edge of the rabbit hole for you. Click through the links.

http://www.suspact.com/Anti_Squat.html

I would consult my Tony Foale references; he may even have a program for determining the squat/anti squat.

My Seeley exhibits anti-squat on the dyno and as I recall, my Commando racer squatted on the dyno.

On racebikes, squat is controlled by moving the swingarm pivot up or down. The higher the pivot in relation to the sprocket centers, the less the squat, but that also makes the suspension work differently.

Danno said:

On racebikes, squat is controlled by moving the swingarm pivot up or down. The higher the pivot in relation to the sprocket centers, the less the squat, but that also makes the suspension work differently.

Click to expand...

Old 'race bikes' don't tend to have adjustable swinging arm pivots, certainly my Rickman and most Seeleys I have seen don't. So you would achieve adjustment potentially in two ways, well maybe 3 if you include bending the frame! Which is perhaps more likely with an open Mk3 type Seeley frame like Alan's

One method, move the gearbox mainshaft height? Quite involved, but possible, my 5 Speed TTi is very slightly higher in the frame compared to the original AMC case simply because the TTi cases are thicker, and there was only so much of it I was prepared to grind away! As you can see this was not a deliberate handling change and was completed at original installation and has not since been changed. I think this minor change is potentially mitigated by the next change? And I am sure someone will tell me if that is wrong.

The other way to move the centres relative to the swinging arm pivot is to raise the rear suspension, in effect relatively raising the swinging arm pivot or lowering the rear wheel axle, whichever way you want to think of it. I have have achieved by fitting two inch longer shocks compared to Rickman ( am not the only one to do this, and I went in this direction on the same frame many years ago.

Raising the rear gets you straight into the rake trail discussion. I also have a slightly longer swinging arm, done to accept a wider tyre, which will affect rake/trail as well but not much since originally this bike had 19" wheels and today it is on 18"s.

The point of the comment is that every change you make will have more than one effect, some intended, some not, even if still (sometimes) beneficial.

So, going back the several years that Alan has been discussing the changed offset on his Seeley, that as far as I know no one else has deemed necessary! We should assume that he has something else set differently to most Seeleys! Even if he is not aware what that is!

If it sorted the handling to Alan's satisfaction, one could say just ride it. However, Alan's choice is to continue to discuss the issue, apropos ofwhat, I am not sure.

Unfortunately I am in a position where I have been denuded of funds by a family violence situation which involves 3 young children. Also , in Australia these days temperatures are too high to go riding bikes on race circuits. I am still looking for a ride day and I will scrape the money up to pay for it. In the meantime all I can do is fuss over the bike and try to fix it's oil leaks. So I'm sorry for taking up your time with my trivial problems. I needed to get a better understanding of what was happening with the handling of my bike. The discussion might have helped other people as well.
In the 60s a friend of mine did very well with a Rickman/Triumph. It always seemed to have very stiff handling characteristics. There is another guy here who has copied that bike and uses it in historic racing. I've always liked that frame, but it was created by a scrambles rider. I saw one for about $400 a while back, but it looks as though it was intended for use with a two-stroke motor, so I did not buy it.

Ho hum, here we go the Rickman is 'stiff', even if no one has yet adequately explained to me what exactly that means....

Created by a Scrambles rider....well, yes, but working with a road racing sponsor of note, Tom Kirby and ridden to it's first win by little Bill Ivy within weeks of creation....and the Norton version developed in conjunction with one Paul Dunstall!

Over engineered, probably, but as a club rider I chose that robustness over 'fragile' Seeleys. Modern Seeley frames are much stronger. And there is no doubt people prefer them, but people also like Rob North frames, and the Triumph triple seemed to get an enormous power boost sometime in the '90s, combine these factors and theeffect is that there are almost no Rickman frames still racing, so I will plod on with mine.

I have been denuded of money by simple passing of time transitioning to retired, and these days temperatures are too low to go riding bikes any bloody where! It is also too wet, I hear Paris is currently sinking!

Al, you could pop off to Phillip Island...see how Corser and Edwards get on with the terrier McWilliams and TT man Hickman, I see the British team at the Island Classic are riding 1300cc Harris F1 bikes....basically developed XR69 chassis using Yamaha FJ1100/1200 based engines....I wish the riders well, they are a decent crew, but classics it ain't....

Apparently last year one of these bikes had Honda on the fairing, with a Yamaha motor in a frame originally designed for a Suzuki!

Let's hope I can pass my French flags test and I can race my mongrel here in France as well as in Belgium this year!