This is the culprit:
(https://www.dotheton.com/index.php?attachments/5a1d5e12-91e8-46e1-b840-b4b33f00c275-jpeg.236381/)
1975 RD350, 1985 Honda CB700SC rear shocks at the lowest preload, 1982 Honda CB650 front forks with air caps, no air pressure, stock springs, 15W fork oil, 17" wheels front and back.
Here's the issue:
I have about a 1/2" of chicken strips to give you an idea where the bike really feels maxed out (less than what this early pic indicates). I don't know what you can glean from one pic, but it should be clear I am a bit squat in the rear. This was intentional, as I expected the rear end to be stiffer than it turned out to be. I expected to also feel more rear end grab in turns and on take off. I get it on take off, not so sure about the turns. There's more shock angle, which may have softened the rear end a bit, but I also have much more preload to add. I like the spring rate and damping on the rear. The front, however, is clearly too stiff. Is it too long? Is my feeling of unease at all related to the power to weight of the bike? Is this a condition of uneven suspension front to back? I absolutely want to put this bike on the track, but I am going to get killed on entry in turns. It's fine going throttle on exit, but it's a combo of throwing weight to the outside (maybe pushing?) and the rear end not feeling like there's enough bite. So I end up way to cautious entering, and raising hell to recover on the way out.
You haven't really described why you think it is going to kill you on entry. It's too slow to turn in? Too fast? Rear end stability isn't good under braking?
Quote from: sav0r on August 15, 2022, 06:32:11 PM
You haven't really described why you think it is going to kill you on entry. It's too slow to turn in? Too fast? Rear end stability isn't good under braking?
Sorry, left stuff out. Rear end feels unstable. There is a sense it may be pushing, like it's slow to turn. I also wonder if my handlebars are too wide and that's factor there. Regardless, there's absolutely a feeling of instability in the rear. Almost like a tire low on air.
Your swingarm has too much angle. Should be 7-10 degrees from horizontal. If you lift the rear 1" you lose 1 degree of head angle. Doesn't the chain drag on the swingarm?
You say it's OK accelerating out of a corner: When you apply the power, the top run of the chain will be pulled to it's shortest distance between the sprockets, which will make the bike "squat"... and take all that angle out of the swingarm.
And once you lower the rear end, yes those forks are WAY TOO long.
Trying to set up modified suspension by "chicken strips" is not gonna get you anywhere, especially with those tires... what size tires and rims are those? Do the edges even contact the ground when you lean it over?
I would put the RD shocks back on, and lift the forks about 2-3" in the triples and see what that does.
Lots of good information here: https://motochassis.com/articles/
Then once you get stuff back in a place where it will work again, you need to set up your transplanted suspension components... lots of good information here: http://didier.clergue.free.fr/gsxr/livres/Livre_Race_Tech%27s_Motorcycle_Suspension_Bible.pdf
That frame works REALLY well in stock form, with stock tire sizes. Yamaha has won a LOT of races with that frame (the RD frame geometry is the same as the TZ frame, except the TZ has 2 degrees less steering head angle... that's not your issue). I have been racing TZs and RDs for years... on 100 front and 120 rear, which works well for me. (Something I wish I learned a LONG time ago: You want to run the SMALLEST tires that will do the job. Tires EAT horse power and smaller tires eat less HP... and turn in with less effort... and stop better... and are cheaper... and don't wear as fast so they last longer). I decided a long time ago that Yamaha's race department is probably smarter than me... and now I kinda follow THEIR lead.
Quote from: bitzz on August 15, 2022, 07:22:46 PM
Your swingarm has too much angle. Should be 7-10 degrees from horizontal. If you lift the rear 1" you lose 1 degree of head angle. Doesn't the chain drag on the swingarm?
You say it's OK accelerating out of a corner: When you apply the power, the top run of the chain will be pulled to it's shortest distance between the sprockets, which will make the bike "squat"... and take all that angle out of the swingarm.
And once you lower the rear end, yes those forks are WAY TOO long.
Trying to set up modified suspension by "chicken strips" is not gonna get you anywhere, especially with those tires... what size tires and rims are those? Do the edges even contact the ground when you lean it over?
I would put the RD shocks back on, and lift the forks about 2-3" in the triples and see what that does.
Lots of good information here: https://motochassis.com/articles/
Then once you get stuff back in a place where it will work again, you need to set up your transplanted suspension components... lots of good information here: http://didier.clergue.free.fr/gsxr/livres/Livre_Race_Tech%27s_Motorcycle_Suspension_Bible.pdf
That frame works REALLY well in stock form, with stock tire sizes. Yamaha has won a LOT of races with that frame (the RD frame geometry is the same as the TZ frame, except the TZ has 2 degrees less steering head angle... that's not your issue). I have been racing TZs and RDs for years... on 100 front and 120 rear, which works well for me. (Something I wish I learned a LONG time ago: You want to run the SMALLEST tires that will do the job. Tires EAT horse power and smaller tires eat less HP... and turn in with less effort... and stop better... and are cheaper... and don't wear as fast so they last longer). I decided a long time ago that Yamaha's race department is probably smarter than me... and now I kinda follow THEIR lead.
Appreciate the time you spent with the response.
The chicken strips reference was specifically made to give you the idea that I am describing a FEELING and not the actual ability of the bike. I should've been more straight forward. I question my ability to effectively communicate often. LOL. The reason for the thread is that I'm trying to find confidence in the suspension and an understanding why I FEEL what I FEEL, so I can make informed decisions going forward. The bike doesn't handle poorly. It mostly doesn't feel the way I think it should feel. Some of it's traits are confusing me (like the soft rear tire feeling), and I've had less success tuning them out. I had an easier time converting an airhead to monolever than tuning this bike.
To respond to some of the specifics: These are 17" wheels and 2.5" width rims front and back tires match. My chain does not hit the swingarm, especially with rider sag. My rake is 25 degrees. One reason for choosing the CB650 front end is because of the offset triple, so the 27 degree head angle of the stock RD is converted to 25 degrees of rake. The swingarm is 2" longer than and RD, so there's a factor there, but as I should've pointed out, this bike also sees the drag strip. Not for points or money, just fun weekend races. I believe it can be made to be decent enough to hold it's own for both, though.
forks are too long, and TBH, 37 year old shocks are never a good idea. id push the forks thru and inch or 2 and get some new shocks for it. like, new. :twocents:
Quote from: m in sc on August 15, 2022, 08:35:41 PM
forks are too long, and TBH, 37 year old shocks are never a good idea. id push the forks thru and inch or 2 and get some new shocks for it. like, new. :twocents:
Fair enough, LOL. Another canned response. It's pretty clear I'm going about this all wrong. Genuinely appreciate the effort. I'll figure it out.
Probably a dumb question but have you measured sag? Sounds like the bike is diving too much under braking and giving the rear a uneasy/loose feeling and makes me wonder if the front/rear spring rates are way off relative to each other.
While I do believe you have some underlying geometry issues due to fork/shock lengths I wonder if incorrectly matched spring rates are giving the bike a Dr. Jekyll/Mr. Hyde effect when the weight transfers.
it's not a 'canned' response. shock and fork oil don't work well when aged. I just replaced the shocks on my 2014 cb1100 because they had lost performance. my opinion, no point in trying to set sag, damping or rebound tuning with half the suspension using worn components. .02. remember, my hybrid was set up very similarly component wise. my rear arm is 4" longer than stock and it turns in plenty quick.
If you want shocks that work, like you're racing for points, you need a modern custom made shock.
A modern shock has 6 way adjustment (hi speed and low speed compression/rebound, preload and shock length) and you NEED to be in the middle of travel in neutral... ya' don't get that with a shock and spring off some 550lb. OEM application or Amazon. You can start with some OEM shock and adapt to your needs... but that's a lot of work and I'm lazy and the local suspension guy entertains my dumb ideas and gives me a good price on stuff... but if you avoid Ohlins like the plague that it is, a decent shock isn't that costly in the grand scale of things... and a decent shock is rebuild able, 'cuz you'll want to change the fork oil and shock oil a couple of times a year
I'll tell you RDs and steel framed TZs don't need or want big stiff forks. They just pass a bunch of forces to the steering head ... that the frame wasn't designed for and doesn't need. The biggest fork Yamaha used was a 35mm, and a 110 tire.
If you're racin' and you're allowed fork upgrades, just drop in a "cartridge" kit. Costs about the same as a shock.
If you don't get unlimited fork updates: run an emulator. You get the same adjustments as a cartridge, but you have to take the fork apart to do the adjusting. Ed Sorbo, of Lindemann Engineering swears by emulators. Jim Lindemann was making "emulator" forks before there was a Race Tech.
... OP: If you want to go drag racing, you want the rear axle almost level with the out put shaft (so the swingarm is almost horizontal) and the front axle as close to the lower triple as you can get it...for weight transfer... but you'd know that if you read the links I posted.
Quote from: irk_miller on August 15, 2022, 06:35:17 PM
Quote from: sav0r on August 15, 2022, 06:32:11 PM
You haven't really described why you think it is going to kill you on entry. It's too slow to turn in? Too fast? Rear end stability isn't good under braking?
Sorry, left stuff out. Rear end feels unstable. There is a sense it may be pushing, like it's slow to turn. I also wonder if my handlebars are too wide and that's factor there. Regardless, there's absolutely a feeling of instability in the rear. Almost like a tire low on air.
The bike should be measured and setup off the stand and weighted. So there isn't much point in looking at the photo and trying to judge. I use an angle finder on the forks, an iPhone works fine, Android likely too but I'm not as familiar with their apps. Then set sags with preload. From there set ride height via preload to achieve rake. That's a basic setup process.
Years ago I found some decent RD setup notes. No idea where those went. But I run my forks a bit high in the clamps and the rear shocks long by like 15mm. I like the front of my bikes a bit stiff. But I haven't raced a motorcycle since I was in my teens.
i mean, just sitting there its obvious its squatting in the back, that you def can tell. and the distance from the slider to the tree shows how much longer that a stock setup would be. I get countering the longer forks with rake angle adjustments and 17" rims.
My bike is actually raised a bit overall as well, but the geometry works. took a while to get right TBH.
I would think struts might be better for the dragstrip. But im not bike drag guy.
just spitballing. :twocents:
I don't think suspension is ever obvious. It's not loaded in any way. Whatever is holding the bike up probably shifts the weight bias 20%.
line of the bottom of the tank is angled up. its higher in the front than the rear. look at the distance of the stanchions free length from the top of the slider to the lower tree.
add a rider the rear is going to squat even more. pretty obvious to me.
:twocents:
I just have a hard time believing any amount of arm chair engineering is going to help via a single photo. Some measurement needs to happen. There has to be a setup and set down routine.
My opinion is the whole bike has to come down, especially the front. Set the preload to have plenty of sag. Then have someone hold it up on one side and you jounce down on the other side foot peg and watch what happens. Do both wheels travel the same amount and rebound at the same rate? Watch how the forks on Moto GP bikes dive under full braking, the springs can't be too stiff. A stock bike configuration handles really well where it doesn't spook the rider.
agreed^
The most important tool anyone has is their eyes to start with. Its pretty blatant to me. also, 40 year old used parts are going to be worn out unless its nos.
I gave no numbers, measurements, or data. just advice as a solid starting point before trying to get it setup. these issues need to be addressed before starting a legit setup process.
a call to a good shock company to get a set of shocks set up for this is a good start, like when i had works set up the ones for my hybrid with the fzr arm and fz front end. not an off the shelf part. :twocents:
http://worxshocks.com/
A Moro gp frame can handle pretty vertical forks for a reason. There is a lot of setup difference there.
I agree by looks the forks are long. In fact I run a 2" or stick out on my RD. I just don't see the point in guessing around.
Quote from: m in sc on August 16, 2022, 12:04:27 PM
line of the bottom of the tank is angled up. its higher in the front than the rear. look at the distance of the stanchions free length from the top of the slider to the lower tree.
add a rider the rear is going to squat even more. pretty obvious to me.
:twocents:
I agree, it squats which would slow the steering. That would result in poor handling.
Quote from: sav0r on August 16, 2022, 04:05:07 PM
I just have a hard time believing any amount of arm chair engineering is going to help via a single photo. Some measurement needs to happen. There has to be a setup and set down routine.
This is honestly what makes me frustrated by this thread right now. LOL
Not to make excuses, but better shocks are coming. I'm doing this on a teacher's salary and the bike literally started as a box of parts. I focused the bulk of my budget on trying to build a 60+ hp engine and electronics. The shocks are good enough to at least get some good riding in to sort the rest out. They have less than 5k miles on them. They do not leak and they passed compression tests. As anyone knows, good shocks don't happen for less than $500. That takes time for me. There is no reason I can't make this setup work decently or at least get a better sense of where my fail points are.
CB650 forks are the same length as RD350 forks, but with thicker tubes. The difference is, a CB650 has an offset triple, so my fork angle changed from the stock RD 27 degrees head angle to the current 25 degree fork angle. Not sure that's enough difference to cause so much consternation over the length, but it has to contribute some. I dropped the forks through the triples one inch and that does improve things. I have zero doubt I need softer springs in the forks. I have always admitted that. The bike weighs 279 lbs, wet with a full tank of gas. I think that might be a little lighter than a CB650.
I also think having handlebars with a smaller angle, and wider, makes a difference here. I used to race mountain bikes, and I always cut a couple of inches off the ends of my bars to quicken my steering and make me fit better between trees.
The body work is not stock. Using body work angles from a picture may not be totally accurate.
The bike is not as squat as everyone is making it out to be. In photography, there's something called parallax that manipulates visual angles. I had hoped my descriptions would be enough to help people lend clues, so I can get feedback on what causes certain conditions. In hindsight, I completely regret submitting a picture at all. That opened me up to the canned responses and typical forum stuff.
The Radian swingarm is 2" longer. These shocks are 14.5", so I hoped it would balance out. I am maxed on rear end height, though, based on my swingarm angle. The chain does not hit the swingarm, but another inch of rear shock and it probably will.
As I said before, the bike doesn't handle poorly, it just has certain conditions I am not yet comfortable with, so I haven't been totally confident going full lean. That's not saying it can't.
I'm no suspension guy but I would try and check some "trail"'numbers and see where your at. Offset trees aren't exactly changing "rake" angles.
agreed.
^
i understand about the angle of the pic, so maybe i stand corrected here. what is the angle of the lower frame rail when on a level surface? then the swingarm? I mean, theres so much geometry changed it all adds up pretty quick. the trail is a good point, i fought that on mine as well a bit. also a reason i stayed with 18" rims.
I still think until you address the rear shocks its all guesswork. also, you say the front is too stiff. can you remove some preload? from what the original post says..
it squats in the back.
the back end doesn't inspire confidence in corners (shock angle and rate seem to be the issue here)
the front is too stiff.(because the forks are designed for a much heavier bike). my fzr front end, i played with spacers and fork oil
weight a lot, and the spacers inside set the preload/sag where i liked it.
again, our bikes arent -that- far apart on setup approach, but i think th eback needs to come up. however, this may affect the turn in.
I run a scotts damper on my bike. its hard to see, but its under the lower tree. with it off, at high speed it can get a bit too quick on the front end..
.02
(https://www.2strokeworld.net/wp-content/uploads/LC-HYBRID/2018-updates/forks-cleanup/lc-fork-and-damper-18_6_zpsdnw4radi.jpg)
(https://www.2strokeworld.net/wp-content/uploads/LC-HYBRID/2020/20191215_155100-scaled.jpg)
Quote from: irk_miller on August 17, 2022, 06:17:09 AM
Quote from: sav0r on August 16, 2022, 04:05:07 PM
I just have a hard time believing any amount of arm chair engineering is going to help via a single photo. Some measurement needs to happen. There has to be a setup and set down routine.
This is honestly what makes me frustrated by this thread right now. LOL
Not to make excuses, but better shocks are coming. I'm doing this on a teacher's salary and the bike literally started as a box of parts. I focused the bulk of my budget on trying to build a 60+ hp engine and electronics. The shocks are good enough to at least get some good riding in to sort the rest out. They have less than 5k miles on them. They do not leak and they passed compression tests. As anyone knows, good shocks don't happen for less than $500. That takes time for me. There is no reason I can't make this setup work decently or at least get a better sense of where my fail points are.
CB650 forks are the same length as RD350 forks, but with thicker tubes. The difference is, a CB650 has an offset triple, so my fork angle changed from the stock RD 27 degrees head angle to the current 25 degree fork angle. Not sure that's enough difference to cause so much consternation over the length, but it has to contribute some. I dropped the forks through the triples one inch and that does improve things. I have zero doubt I need softer springs in the forks. I have always admitted that. The bike weighs 279 lbs, wet with a full tank of gas. I think that might be a little lighter than a CB650.
I also think having handlebars with a smaller angle, and wider, makes a difference here. I used to race mountain bikes, and I always cut a couple of inches off the ends of my bars to quicken my steering and make me fit better between trees.
The body work is not stock. Using body work angles from a picture may not be totally accurate.
The bike is not as squat as everyone is making it out to be. In photography, there's something called parallax that manipulates visual angles. I had hoped my descriptions would be enough to help people lend clues, so I can get feedback on what causes certain conditions. In hindsight, I completely regret submitting a picture at all. That opened me up to the canned responses and typical forum stuff.
The Radian swingarm is 2" longer. These shocks are 14.5", so I hoped it would balance out. I am maxed on rear end height, though, based on my swingarm angle. The chain does not hit the swingarm, but another inch of rear shock and it probably will.
As I said before, the bike doesn't handle poorly, it just has certain conditions I am not yet comfortable with, so I haven't been totally confident going full lean. That's not saying it can't.
Measure the trail, probably not a bad thing to do. I run 25 degrees rake on my street RD, but have a bit of extra trail due to the FZR forks. I find it more than stable, if not a bit too slow on turn in. No damper needed, and never a head shake or wobble unless I am starting to lift the front wheel. I've only managed a little over 100mph on the bike, so certainly not race worthy. So take that for what it is.
For rear dampers, really you just need enough rebound damping. People make this so complicated. Yes, some adjustment is good, yes high speed and low speed rebound adjustments are snazzy, as are high speed and low speed compression. But once you get into that level you are looking at blowoffs and all sorts of other shock options and talking about $5k (or more) a piece dampers. If the damper can control the spring you more often than not are okay. Especially so at the rear of the bike. What people don't realize is that any type of orifice adjustment dampers are basically garbage, the exception being low speed rebound via the shaft needle. Orifice adjustments are just a cheap way to make more money. Generally, they barely change anything, and orifices are the wrong way to change damping. You need additional deflective disk adjustment if you want to do it right and that gets expensive real fast. Sorry for the rant.
My RD is about the same weight, I run 73lbs rear springs on the rear. I find they are just about right. Squats on throttle but not excessively and is compliant and well balanced throughout.
Anyways, develop a nice setup and set down routine. I like to use scale pads, but that's not necessary, I just have them from the race car stuff so I use them. Once you start making changes do them one at a time, assess the change, then measure the bike after the ride. You can use that set down as the setup routine for the next change. Document everything. It is tedious, but with a nice record of adjustment you will start to decipher how those setup changes will come together. It will take time. There probably won't be a single magic bullet, it will take a combination of things to get you comfortable. And of course on a race bike the devil is in the details.
i agree. my shocks arent adjustable and work fine. but they were also built for that exact setup. can be had for well under 1k.
As long as you can get some good numbers for what you want for sag, just checking it will tell you if spring rates are off or not. It won't tell you what you need for springs but it will tell you if it's off rather than saying it "feels too stiff". Get the spring rates in the correct range and it's tuning from there.
Like trail, this is something else that doesn't cost anything and really is needed info for suspension setup. Without starting to get some sort of actual numbers as a base line it really is just guessing.
Lots of interesting input. I would start with some critical measurements including swingarm droop, rake and trail and then sag at both ends. They won't necessarily give you great insight but will give you a baseline. One test I do on suspension after sag is set is to do the bounce test that someone suggested,. Press down firmly at the rear of the tank or front of the seat and see if both ends drop and rise at more or less the same rate. That will help you to see if one end is sprung or damped differently to the other. that will also reveal if teh spring rates are too soft or too hard. Pre-load changes sag but not spring rate, so you can get sag right and still be off on spring rate. The bounce test helps to identify that.
But back to the symptoms. You said it's unsettled as you get off the brakes and flick it in to initiate the turn. Wide bars will accentuate any movement or flex in the frame or suspension and will make it feel less stable, so your idea about narrower bars is spot on there. That frame will flex, quite a bit compared to any modern bike as you probably realize.
Do you trail brake right up to the apex or do you jump on the brakes and let off fast? Rider input and smoothness undoubtedly influence corner entry feel. The fat front tire may also be an issue if the sidewalls are flexing or if it is not hot enough to generate sufficient grip but they usually manifest themselves in front end washout. In my limited experience racing a TZ, heavy front tires are more of a problem mid corner and exiting as the weight can cause chatter, but your issue seems to be corner entry.
Too much forward pitch (dive) under brakes may also be an issue which is where those measurements come in. Try it as-is and then change one variable at a time and see how it changes feeling. And keep a log of the changes and results.
RD frames and TZ frames don't really handle that well compared to almost anything today and do repay smoothness .
Emulators are a great idea if you don't already have them too.
Tony Foale's books are great but leave me wanting to add in extra frame tubes all over the place and all that will do is to move the forces to a different part of the bike that also isn't designed to handle them.
For the drag strip you want as little chassis movement as possible and the front end as low as possible - all to reduce the tendency to stand up and be noticed coming off the line. You could get a set of RD forks and shorten them and add air caps to basically make them short and solid and get a spare pair of shorter rear shocks with minimal movement and stiff springs. You will feel every grain of sand you ride over on the strip but ET and RPM will improve.
Another random thought is that under heavy braking, the back end comes up and it's possible that it needs a stiffer setting on a steering damper to calm the back end down.
Quote from: oxford on August 17, 2022, 07:07:15 AM
I'm no suspension guy but I would try and check some "trail"'numbers and see where your at. Offset trees aren't exactly changing "rake" angles.
25 degrees is measured rake. I will follow up with trail numbers.
Thanks so much for this feedback, fellas. It's exactly what I hoped you guys would bring when I opened the post.
Teazer: I am absolutely trail braking late in the turns. Early on, I started off slamming both front and back brakes in the straight, because the bike felt like it didn't want to slow down and manage the turn, so I would feel the need to add more brake. As I have gotten used to the bike, I am pulling far less front brake on entry, or I am adding a little front brake initially, then transitioning to back brake. I'm completely off the brake by the apex and going full throttle from there on.
On the drag race tip, I have a retired Fazer drag bike I used to race on dirt. I shortened the forks on that bike and dropped them several inches through the triples. I might've had 2" of suspension travel left, if even. I think I added 8 inches of swingarm on that bike, though. I was thinking of simply dropping the forks through the triples just in times to run the strip with the RD. It's absolutely wanting to lift off the ground. The bike wants to wheelie in four gears. That's an easy solution to swap between street riding and putting on the strip some weekends, I would think.
Savor: Your advice has always been great. We're killing it with our Electrathon cars we build in my high school engineering classes. There's are several decisions on those cars that have come from your feedback.
It's pretty clear I am going to waste a bunch of time if I don't get the emulators and springs sorted in the front end. I am comfortable in my geometry, but with that I am not claiming it's totally right. It just doesn't feel like geometry issues to me.
As per Teazer, you set your ride height to match your rake and your swingarm droop. Two different ways of saying the same thing. The language of setup is nuanced I guess.
In racecar terms the bounce is usually called a "bounce and roll." This is because the inherent stiction in all the moving bits needs a bit of movement to get it to settle to where it naturally should be. Especially so the tires, but the tires don't behave the same on a motorcycle when loaded. Penske did a cool study on how to increase low amplitude high frequency sensitivity of suspension components using a shaker rig, they found using WD40 on all bearings to be the best solution. lol. For a motorcycle I have always found just sitting on it is good enough, it bounces well enough. It's a two person job to do a proper setup or set down. You need the rider, then you need somebody to consistently do the measuring and recording. There's just no way around that in my opinion. You can half ass it by yourself, but it is best done by two people. Ask my wife, she loves it... There are tricks to do it alone, zip ties on shock shafts, etc.. If you can do it consistently I suppose it works.
Anyways, when you start at zero you really have to dig away and be methodical. It's not that much fun to be honest. Check out my race car thread. We took a car that won literal races and have spent years picking away at it just trying to finish a 40 minute race on a street course for no prize at all. We aren't trying all that hard, but it takes time and effort and money.
The things we do for our love of machines...
The trick for me with road race braking it to progressively apply the front brake. It happens fast, but squeeze the lever to load the front end and compress the forks and get the tire to bite and then apply more brake to get it slowed down. My son tried the brake grab trick and the front end locked up and spat him and our TZ350E down the track. Too much too soon as they say.
Smooth is the word. And the same with letting the brake off as side loads increase and the front end lightens. Too much residual brake and it overcomes the available friction and down you go. Let it settle unless you are Ok with a loose set up and the bike moving around.
I rarely use the back brake because it just causes lock ups as I enter a corner and I don't need the help to fall. I can do that on my own. Back brakes do serve a purpose to settle the back end and especially in the wet or when it tries to wheelie, but it's hard to moderate braking action with stiff race boots. At least for me it is.
A long long time ago, a certain Stanley Michael Bailey Hailwood rode a Manx Norton in a vintage race at Winton in northern Victoria. It was a handicap race and he started much later than everyone else. Other riders were riding as hard as they could and it showed. Mike the Bike was clearly just out for an afternoon ride on an old bike. Everything he did on the bike was smooth and seemed effortless as he rode around everyone to win the race. I can't ride Like the late SMBH but I can try to be as smooth as possible.
Oxford, I have been misspeaking on rake. I was calling fork angle "rake", and calling the rake "head angle".
Here are the numbers: rake is 27 degrees, which is standard RD, so nothing changes. Fork angle is 25 degrees because of the -2 degree raked triple. The offset is 1.25.
Here's the kicker. Trail is 5.75", which is straight up Harley territory. Thinking I should be closer to 4"? It's stable as hell cruising down the road, that's for sure. Literature seems to vary at where to max out trail. I am inclined to hold fort on the rake and trail and go with narrower bars, but these forks are about to be an investment with springs and emulators to do it.
I am 25 degrees with 3.75" rake trail, I just found my notes. Still pretty damn stable. You are for sure looking at some awful geometry there.
edit: fix my mixed up words there
Quote from: sav0r on August 17, 2022, 06:09:56 PM
I am 25 degrees with 3.75" rake, I just found my notes. Still pretty damn stable. You are for sure looking at some awful geometry there.
No doubt about it. Looks like I am shopping for a new front end swap.
Much thanks for the feedback. It'll be an investment, since everything up front has to change with it. Fortunately, I have a few options on hand.
Maybe put some time in and see if a different set of trees without the offset will fit your forks. I'm sure there is something common that will work.
Newbie here and love reading all the experience and inputs.
I saw the mention of the scales but maybe I missed something about the bar height. True you need measurements and data to get it dialed in. However, the present bar height is going to situate the rider more upright and place the CG high and aft. Combine that with a stiff fork and a squat rear and it reminds me of (no offense) a en454 I had that felt really unstable.
Read a lot about Eric Buell and mass centralization with regard to turning. Low and centralized gives the bike an axis on which it pivots.
Might help it out a lot rather inexpensively with a set of clubmans. They make a big difference
my .02
Quote from: PistonHoles on August 19, 2022, 09:44:34 PM
Newbie here and love reading all the experience and inputs.
I saw the mention of the scales but maybe I missed something about the bar height. True you need measurements and data to get it dialed in. However, the present bar height is going to situate the rider more upright and place the CG high and aft. Combine that with a stiff fork and a squat rear and it reminds me of (no offense) a en454 I had that felt really unstable.
Read a lot about Eric Buell and mass centralization with regard to turning. Low and centralized gives the bike an axis on which it pivots.
Might help it out a lot rather inexpensively with a set of clubmans. They make a big difference
my .02
I'd go clip ons before Clubmans. I have a few sport bike front ends, if I want to go that direction. I'll be happier with a narrower bar and a steeper rise. I ride an airhead with the very bar I have in mind.
I have a few options for a neutral triple tree that fits 37mm fork tubes and comes within a half inch on spread. Turns out, this triple is CB900, not CB650, which explains the rake.
That's even better than inexpensive if you already have them!
Your bike but if it was me, I would certainly put them on. One reason RDs are so much fun is the small mass vs. the power output. That small mass means that the rider position has a greater effect on handling.
I didnt read everything so heres my armchair, up with the rear, down with the front, lower bars.....
Orrrrrr....... just take it to the track as is, we ran plenty of dudes on Harleys and sport tourers around and they all had fun. The faster guys ran out of bike 1/2 way through the day but they still had fun.
Take the tools to the track that you need to make likely adjustments, if its 3 sessions, you have 40 min every hour to futz with it.
Orrrrr..... just ride the bike as it is and ride around whatever problems it has, I'm thinkin ur gonna be way up on that tank, motard style.
It'll be fun, just go:) Take a spare bike if you think it wont be good for the full day.
Quote from: Clem710 on August 29, 2022, 06:21:42 PM
I didnt read everything so heres my armchair, up with the rear, down with the front, lower bars.....
Orrrrrr....... just take it to the track as is, we ran plenty of dudes on Harleys and sport tourers around and they all had fun. The faster guys ran out of bike 1/2 way through the day but they still had fun.
Take the tools to the track that you need to make likely adjustments, if its 3 sessions, you have 40 min every hour to futz with it.
Orrrrr..... just ride the bike as it is and ride around whatever problems it has, I'm thinkin ur gonna be way up on that tank, motard style.
It'll be fun, just go:) Take a spare bike if you think it wont be good for the full day.
Thanks for the feedback, Clem. On that note, I decided to swap it out for a USD. The difference is considerable, obviously. It's for a TL1000r, so 200lbs heavier, but it doesn't feel off in any way. Much better geometry for a baseline, regardless.
(https://www.dotheton.com/index.php?attachments/dbe70742-4bd8-4af4-93cb-af4f05223234-jpeg.236627/)
On home builds or just stuff that may not be real suitable, rider in position, u need someone to balance you, bouncing some weight on footpegs and having another helper eyeball the eveness of the front and rear of the bike as it goes up and down, speed and displacement.
Adjust with whatever is available to get it balanced, you can also do with only one helper and bouncing while rolling slowly.
If up and down is relatively similar, the bike should be rideable. If one end wont cooperate, the rider will have to adjust. Too soft is probably generally preferred over too hard, wallowing vs skipping.
Well what are the numbers? I love sharing data.
Quote from: sav0r on September 05, 2022, 04:11:45 PM
Well what are the numbers? I love sharing data.
Fork angle: 25.5 degrees
Rake: 27 degrees
Trail: 95mm
Offset: 32mm (from the internet)
Clem: Going through sag measuring and then following up with rides is what makes me think I am not too far away with springs, etc. I like a tighter ride, so having it ride that way feels good to me. I don't lose grip.
sweet. :olaf: