Front suspension question

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Front suspension question

Post  V17R on Fri 13 Jun 2014, 9:16 pm

First topic message reminder :

Sometimes when cornering on my 1250 the front end feels a bit skittish if thats the word.
Sort of like a slight wobble mainly if hitting even very small bumps, tyre pressures and tread depth are ok.
I've been on the same roads on other bikes and haven't had this happen. This is at normal cornering speeds.
Front pre-load is on 3
What causes this and what can be done to correct the problem
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Re: Front suspension question

Post  #Tag on Sun 29 Jun 2014, 4:40 pm

V17R wrote:I remeasured the sag front and rear
took 3 measurements wheel unloaded off the ground, bike standing by itself and with rider on board

front 36mm difference from wheel off ground to bike by itself 
front 46mm difference from wheel of ground to rider on bike

No, that's not right because I'm a complete knob and you shouldn't listen to me.

From your original 46mm sag you've gone to 48 which is the wrong way. we were aiming to reduce the figure to 43 mm which is the road recommended 1/3 of total travel figure.

On reading back through the post it looks like you listened to what I said (you fool)
I specifically said screw the adjuster one ring down into the fork. That is actually completely arse about face and you needed to go up one ring. 

So when you screw your adjusters back up out of the forks two rings you should get close to the 43mm we're after.

I think I told you the wrong way because the standard front end is so mushy that your always telling people to add preload. You'd be the first person I've ever told you need to reduce preload (which backs up the guess that your bike has had a spring upgrade.)

*Editor's note: The last sentence is actually !Tag flailing about for any excuse to make himself look like he's not a git. Embarassed
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Re: Front suspension question

Post  V17R on Sun 29 Jun 2014, 4:50 pm

ok, just wound to 2 rings its now 44mm
had a assistant measuring failure
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Re: Front suspension question

Post  #Tag on Sun 29 Jun 2014, 5:11 pm

Aargh, I'm crap at this forum thing. I just posted up a reply only to have it disappear into interwebz limbo when I did (or didn't?) hit the submit button - take two :

No, that's wrong because I'm a complete knob and you shouldn't listen to me.

You've gone from the original 46mm to 48mm instead of going to the 43mm we were after.

On reading back through the post I specifically said "screw the adjuster down into the fork one more ring" - and you listened to me (you fool)
That is actually completely arse about face and I should have said "screw the adjuster up out of the fork one ring"

So after you curse me out, go back out to the shed and screw the adjuster two rings the other way it should be pretty close to being in the recommended range of :

"The accepted sag is 1/4 of total suspension travel for track and 1/3 of total travel for road.

In the Bandit that works out as between 32.5 mm and 43mm front"

At least you've learned two things ;
1 How to set sag
2 Don't listen to me.
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Re: Front suspension question

Post  #Tag on Sun 29 Jun 2014, 5:16 pm

Yay, the words I typed are now on the forum!!!
I 'm guessing I may have told you the wrong direction because Bandit oem front ends are so mushy I'm always telling people to add preload.
Your the first guy I've come across who needed to reduce preload which backs up my guess that your bike has a spring upgrade.
(Or that the whole last sentence is me flailing about to make myself look less than an utter git Embarassed )
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Re: Front suspension question

Post  barry_mcki on Sun 29 Jun 2014, 5:36 pm

!Tag wrote:Aargh, I'm crap at this forum thing. I just posted up a reply only to have it disappear into interwebz limbo when I did (or didn't?) hit the submit button - take two :

There is an issue when two people responding to the same message press SEND at the same time.  The forum will only take only one reply and it is always the other guys  Crying or Very sad 

Sometimes you are lucky and it will come back to you with a MODIFY (and something else that I just can't remember what it is at the moment..... EDIT It just happened just then, the other button was SAVE...hows that for timing ?...).  Press the MODIFY and you will end back at the edit screen, then hit the SEND again to resubmit.  And it always worth reading what the person that guzzumped you just wrote, it might save a little embaresment if your message is contradictory or repeatitive.  

PS Another annoying thing is the "Notify me" box will be re-ticked if you had it cleared previously when this happens.

And then there are the times where the message just disappears  Shocked   .  This is usually after you spent a couple of hours editing and sorting photos and chasing down links, and besides throwing the computer to the other side of the room there is no satisfactory result when this happens   Sad   .

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Re: Front suspension question

Post  #Tag on Sun 29 Jun 2014, 5:46 pm

I'm glad, its not just me, then. Barry.
I'll have to get into the habit of copying the post to the clipboard before hitting the send button.
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Re: Front suspension question

Post  barry_mcki on Sun 29 Jun 2014, 6:34 pm

Agreed, once you've had it happen on a big post you get a little paranoid.  I'm sure I've pushed other members out in a reply, but it seems to me I'm always on the loosing end.

Hint for the copying:  Whilst holding down the CTRL key press A, this will highlight everything (a for all)  you've typed including photos, then CTRL and C to copy.  If you then need to paste everything again its CTRL P.   This sequence holds true for most edit functions whether it's a forum message, a photo URL sequence or a Word Processing session.
,

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Re: Front suspension question

Post  V17R on Sun 29 Jun 2014, 7:46 pm

!Tag  PM sent
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Re: Front suspension question

Post  #Tag on Sun 29 Jun 2014, 8:39 pm

V17R wrote:ok, just wound to 2 rings its now 44mm
had a assistant measuring failure
You're going to love this:
My brain exploded from tracking both your PMs about what your adjustment achieved and the previous info in the post and I've come to bits.
I apologise but the post about me cocking up the direction you should be adjusting your preload adjusters was wrong.

Screwing your preload adjustment screws down into the fork reduces your sag and raises the front end.
Someone help me out and confirm this, I've got into one of those mental loops where your not sure if your arse is pointed to the ground or not.

Ok, going from the original measurements

front 36mm difference from wheel off ground to bike by itself 
front 46mm difference from wheel of ground to rider on bike

rear 12mm difference from wheel off ground to bike by itself
rear 34mm difference from wheel off ground to rider on bike

we're getting a better balance now.

You were outside the recommended ranges and we've walked you almost into it, but just to make your brain explode:

We've got the basics sorted (tyre pressures, steering head, suspension setting within range) but now the value judgements start.

Remember we were saying having the bike nose down will increase steering speed but the other side of the coin is instability. That is the bike reacts to ALL inputs more rapidly.

You have the rear at the high end of the range and the front at the low end of the range so your still 12mm nose down.

If you want go as far as you can to rule out this as the cause of your instability I'd suggest maxing the fork preload (screwing your preload adjusters completely into the fork What a Face . (Just go till you feel the end of adjustment, don't force it) This will bring your front end up much closer to your rear end and get the steering speed/instability relationship as close as you can to the stability end of the equation.
Dropping your rear end will do exactly the same thing but it is the more laborious route.

Out of interest I run my sags at the upper end of the range (32 and 34 F&R).

I always run the sags at the same end of their range to keep the bike level because I would rather just push the bars a bit harder to get it turning and then get the benefit of stable tracking through the corner.
Having the bike at the upper range gives me more ground clearance (but the tradeoff is increased chance of topping out the suspension and getting chatter)

Give that a run and see how it goes but there is still more areas to go through to eliminate instability.

And feel free to run screaming from this thread to get away from me.
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Re: Front suspension question

Post  V17R on Sun 29 Jun 2014, 8:54 pm

thanks mate your a legend!
I might try softening the rear 1 click and screwing the front down one more grooved line and remeasure again
never knew much about this before, I know a guy who has been riding an old Kawasaki sport bike for years and he has never touched anything since new
reckons they come setup right from the factory. I tried explaining some of this to him but not interested. Good to get help here.
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Re: Front suspension question

Post  #Tag on Mon 30 Jun 2014, 10:03 am

V17R wrote:thanks mate your a legend!
I know a guy who has been riding an old Kawasaki sport bike for years and he has never touched anything since new
reckons they come setup right from the factory. I tried explaining some of this to him but not interested.
I'm not a legend, suspension techs are, they're deadset black magicians. I'm just regurgitating to you what I've learned from people who know their shit.
And the majority of riders are the same as the guy you know.. Whenever the subject is bling or engine mods or touring accessories everyone is in on the conversation but when it turns to suspension adjustment blank looks are the usual reply.(I give that blank unknowing look and shuffle my feet when the conversation turns to cleaning or bling)
You could ask your mate if they come setup from the factory why do they put adjusters on them.

That can be a good thing though. I've been on bikes with full adjustment suspensions that were positively dangerous because the owners set everything soft because it'll be comfortable or hard because that's race setting and it'll go faster.
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Re: Front suspension question

Post  V17R on Tue 08 Jul 2014, 9:15 pm

finally got to ride the bike with the new setting in place, definite improvement and gives the bike a much better feel/balance and gives me more confidence on tight roads
It also makes the bike feel lighter on windy roads
thanks everyone for the reply's
now to get a gear indicator and fix the inaccurate speedo.
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Re: Front suspension question

Post  kewwig on Wed 09 Jul 2014, 6:28 pm

V17R wrote:finally got to ride the bike with the new setting in place, definite improvement and gives the bike a much better feel/balance and gives me more confidence on tight roads
It also makes the bike feel lighter on windy roads
thanks everyone for the reply's
now to get a gear indicator and fix the inaccurate speedo.
Gi-Pro ATRE and Healtech Speedohealer set to -7.0% and you are good to go
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Re: Front suspension question

Post  #Tag on Thu 10 Jul 2014, 11:28 am

^^^^ What he said.

The Gear Indicator/ATRE is primarily a timing retard eliminator that you can have a play with plus an attached gear indicator.

I had a Speedohealer that never worked properly until I gave it to a friend who knows stuff about elecktrickery. He remade all the solder joints on the pcb and said it has worked fine since. That was unusual - most people find Healtech  products reliable.
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Re: Front suspension question

Post  V17R on Thu 10 Jul 2014, 11:32 am

do they run too much timing at idle for some reason?
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Re: Front suspension question

Post  #Tag on Thu 10 Jul 2014, 1:00 pm

Many litre class and above bikes have timing retard and speed limiters built in to their electronics. The most common reason given is safety/ regulation compliance.
The Bandit retards the ignition timing in gears 1 through 4 giving reduced power output. It switches off at full throttle so you have full engine power available at full throttle in all gears.

Its fairly seamless and its another religious argument as to wether or not its worthwhile turning it off.

The Healtech unit costs not much more than a standalone gear indicator and you can have a play switching the retard on or off. It's just the push of a button in the unit.
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Re: Front suspension question

Post  snitter on Mon 14 Jul 2014, 9:02 am

!Tag, I just wanted to thank you for your time and effort in posting to this thread: it's got me seriously thinking about suspension and how I might improve it. I had felt that my Bandit wanted to plough into the road with heavy braking: I assumed it was me.

So yesterday, having read this thread, I worked up the courage to try setting the front pre-load down to two lines from the original three. I rode around town then out to the Hume Highway before and after the mod. Much, much better: I wouldn't say I ever felt that I didn't have control, but the bike definitely had a few ideas of her own when it came to braking and cornering. Now she definitely knows who is boss!

Next, I'll get two literate mates and a tape measure.
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Re: Front suspension question

Post  Dekenai on Mon 14 Jul 2014, 10:01 am

snitter wrote:!Tag, I just wanted to thank you for your time and effort in posting to this thread: it's got me seriously thinking about suspension and how I might improve it. I had felt that my Bandit wanted to plough into the road with heavy braking: I assumed it was me.

So yesterday, having read this thread, I worked up the courage to try setting the front pre-load down to two lines from the original three. I rode around town then out to the Hume Highway before and after the mod. Much, much better: I wouldn't say I ever felt that I didn't have control, but the bike definitely had a few ideas of her own when it came to braking and cornering. Now she definitely knows who is boss!

Next, I'll get two literate mates and a tape measure.

Unless you weigh < 60 kg, just wind them up to the max, std springs are very soft.
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Re: Front suspension question

Post  #Tag on Mon 14 Jul 2014, 11:16 am

What Dekenai said is bang on if you own a GSF. With the OEM GSF springs 95% of riders would need to set preload to max. Its still not enough but its the best you can do with the OEM setup.

If you own a GSX it will probably be different. I haven't had a chance to have a good sit down with a GSX but it appears they had a spring and damping rate upgrade from the GSF and your front springs may suit your weight. But one literate mate with a tape measure, a pencil and two minutes to spare will answer that question.
If you can get your sag within the 1/3 to 1/4 of total suspension travel (between 32.5 mm and 43mm) within the available range of your preload then your springs are good enough.
The plowing front end though is symptomatic of soft springs/too much sag/chassis geometry set nose down scenario. A bike set up like this will be unstable when braking pre corner, stand up and run wide when trail braking on turn in with the front brake and often want to fall further into the corner when turn in is complete and your mid corner. Therein is another conundrum when a bad setup will give different bad behaviours under different conditions.

Learning basic adjustment and maintenance of your suspension gives you the ability to dial out the bad behaviour that most riders just put up with.
And that's what we're after - not to make the bouncy bits better than they can be but just to get rid of the faults that bad setup causes.
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Re: Front suspension question

Post  snitter on Tue 15 Jul 2014, 10:16 am

Gentlemen, thanks very much for that. It's a GSF, so I'll dial the preload to max and put some thought into replacing the springs. Let you know how it goes.
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Re: Front suspension question

Post  snitter on Wed 08 Oct 2014, 11:33 am

Folks, sorry it took me so long to get back about this. About a month ago I upgraded the front springs (don't ask me what tension/weight, I forgot to ask the mechanic!) and replaced the factory tyres with Pirelli Angels front and back (I commute down the Barton Highway, so daily riding for me is a lot like touring). The factory rubber went from "acceptable" to "racing slick" in 100km, so I decided to replace the front springs at the same time.

With the front pre-load set to max on the new springs and with my lovely new tyres, it's like a whole different Bandit. I'm taking corners more aggressively and she's also behaving much better in hard braking.

Thanks, I would never have thought of any of this without this forum!
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Re: Front suspension question

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