the bb trackday thread.
Discussion
Steve Bass said:
Yep, this is a geo tear..
There's no way you should have the comp & reb wound right in. And they're fast or slow, not hard or soft
With the rebound wound in, when you brake for a corner the front compresses and doesn't return. This is changing the front geo and causing the front to be overloaded and push around the corner.
and setting preload all the way down doesn't change the spring rate, juust the initial pressure/load required to get it moving.
Whatever chop told you to wind the rebound in needs a decent smack in the gob, it's the quickest way to see your arse.... it's frankly f
king dangerous. Rebound is THE MOST important suspension adjustment and nees to be fairly quick, or "open" to allow the wheel to follow the road effectively.
You don't need to go to MCT if you're not changing out components, you can set the suspension yourself.
And when swapping between different tyres or tyre manufacturers, watch out for any differences in tyre height. just becasue a tyre says 190/55 doesn't mean it's the same height as another make 190/55. This difference will change the bikes rake and turn in feel.
You seem real switched on here and its much appreciated! I have years of mx experience but road is so different! I have been doing track days since Feb this year (Did 2 on my road bike in the summer last year as a taster)There's no way you should have the comp & reb wound right in. And they're fast or slow, not hard or soft
With the rebound wound in, when you brake for a corner the front compresses and doesn't return. This is changing the front geo and causing the front to be overloaded and push around the corner.
and setting preload all the way down doesn't change the spring rate, juust the initial pressure/load required to get it moving.
Whatever chop told you to wind the rebound in needs a decent smack in the gob, it's the quickest way to see your arse.... it's frankly f
king dangerous. Rebound is THE MOST important suspension adjustment and nees to be fairly quick, or "open" to allow the wheel to follow the road effectively.You don't need to go to MCT if you're not changing out components, you can set the suspension yourself.
And when swapping between different tyres or tyre manufacturers, watch out for any differences in tyre height. just becasue a tyre says 190/55 doesn't mean it's the same height as another make 190/55. This difference will change the bikes rake and turn in feel.
I know I need to stiffen the front..ALOT but it seems the settings I was told are well off. Would you say once they get the springs right for my weight and oil viscosity/level to have the rebound more out? As in Open? Think I need a bit of help here tbh
Birky_41 said:
You seem real switched on here and its much appreciated! I have years of mx experience but road is so different! I have been doing track days since Feb this year (Did 2 on my road bike in the summer last year as a taster)
I know I need to stiffen the front..ALOT but it seems the settings I was told are well off. Would you say once they get the springs right for my weight and oil viscosity/level to have the rebound more out? As in Open? Think I need a bit of help here tbh
Springs support your weight (and to an extent your riding style), you then use damping (as a function of the oil viscosity and valving) to *control* the spring movement. Without the correct 'weight' springs fitted, the damping will potentially be trying to solve problems it's not designed to. I know I need to stiffen the front..ALOT but it seems the settings I was told are well off. Would you say once they get the springs right for my weight and oil viscosity/level to have the rebound more out? As in Open? Think I need a bit of help here tbh
Why do you think you need to stiffen the front?
Generally, as a rule of thumb, you can open up the rebound (i.e. make the front rebound faster) so that the bike comes up pretty quickly, but is not allowed to bounce at the top of the stroke.
If you ever get the chance to have a bounce on some superbike forks, they are often very plush.
Edited by fergus on Tuesday 26th July 15:01
Edited by fergus on Tuesday 26th July 15:02
fergus said:
Birky_41 said:
You seem real switched on here and its much appreciated! I have years of mx experience but road is so different! I have been doing track days since Feb this year (Did 2 on my road bike in the summer last year as a taster)
I know I need to stiffen the front..ALOT but it seems the settings I was told are well off. Would you say once they get the springs right for my weight and oil viscosity/level to have the rebound more out? As in Open? Think I need a bit of help here tbh
Springs support your weight (and to an extent your riding style), you then use damping (as a function of the oil viscosity and valving) to *control* the spring movement. Without the correct 'weight' springs fitted, the damping will potentially be trying to solve problems it's not designed to. I know I need to stiffen the front..ALOT but it seems the settings I was told are well off. Would you say once they get the springs right for my weight and oil viscosity/level to have the rebound more out? As in Open? Think I need a bit of help here tbh
Why do you think you need to stiffen the front?
Generally, as a rule of thumb, you can open up the rebound (i.e. make the front rebound faster) so that the bike comes up pretty quickly, but is not allowed to bounce at the top of the stroke.
If you ever get the chance to have a bounce on some superbike forks, they are often very plush.
Edited by fergus on Tuesday 26th July 15:01
Edited by fergus on Tuesday 26th July 15:02
First step is to determine if the fitted spings are right for YOUR weight. Setting the sag correctly will give you an idea of this. And you really want the preload somwhere in the midrage to get the right idea. so no more than 3 or 4 turns either side of centre/halfway. If you need to add/remove preload to get the right numbers, look at changing the springs. if it's a dedicated track bike, you should be running harder springs than the factory usually fits anyway. A good starting point for an average Jap bike and mid sized rider is 9.5nm/mm to 10.5nm/mm to get th erequired numbers.
You can use a lighter sping with a bit more preload or conversely, a heavier spring with less preload to achieve the same thing. But the heavier spring is my preference. But having dfferent springs allows you to fine tune the front nicely. 10 and a 10.5 can be combined to provide an effectve rate of 10.25. Might not sound much but you'd notice it.
Also, as a rule of thumb, slicks like stiffer springs than treaded road/race tyres. Which is a good reason to pick a tyre and stick with it rather than changing all the time, aside from the inherent tyre height differences.
For a bike to handle well you want to keep as much of the suspension as consistent as possible and then only change one thing at a time, tyres included.
Preload.....
Remember that preload doesn't change the rate/power of the spring, just the amount of initial force required to move it. As a side effect, 1 turn of preload raises the front by 1mm so the more preload you add, the higher the front gets and the slower the bike turns. Hence why the corect springs are critical as you can't fudge it and make it up elsewhere. This is the same front & rear
Oil....
Next up is oil weight and height. For weight I tend to prefer 5w(for track) as it has a more linear viscosity from cold to hot. This means you get less drift with the suspension settings once it gets hot by lap 5 or so.
Air Gap.....
Next is air gap. Ths is a spring as well and can have a big effect on the front end. The bigger the airgap, the softer the forks reaction at the end of the stroke. Less air makes it much stiffer much quicker at the end of the stroke because air can compress, oil cannot. And a differnce of 10mm has a massive effect so don't think it's a case of "close enough". Normal aigap range for Ohlins/43mm forks with the spring, preload tube and damper tube removed is around 130mm with the fork fully compressd. Don't go more or less than 20mm from this unless you know exactly why and what to expect.
Important Stuff....
Now to Comp and Rebound.
I know I go on about this ad nauseum but the biggest mistake and therefore misunderstanding people make is thinking in terms of Hard or Soft. he only thing thta's hard or soft is the spring. That's it. Everything else is about rate of change.
The Comp & Reb adjusters are valves and control the flow of the fork oil through the shim stacks. So oil can flow quickly or slowly depending on where they're set (and the shim stack config) but they don't affect the hardness or softness. They either allow the fork to compress or rebound quicker or slower. This is really important because if yo think that more rebound makes the fork "harder", you're completely wrong. It makes it slower. Which can feel hard but it isn't. it still compresses the same amount under the same load but slower
Now the REALLY REALLY important bit....
Rebound is THE single most important suspension adjustment. Period.
Its purpose is to keep the wheel pushed against the road surface following a compression event. (a bump) Without it the wheel is floating and a tyre not in contact is a tyre not gripping.... see the importance
So Reb needs to be set reltively quickly, so the fork can recover after beig compressed by a bump or under braking. The simple gauge is to set it as fast (open) as possible but not so fast that the bike double bounces when the suspension recovers. It should recover smartly but not oscillate at the top i.e, raise, drop & raise again, however small the secondary movements.
Compression is down to personal preference but again, it only affects the speed of the forks compression, faster or slower. So when applying the brakes, compression can affect the speed the forks compress but not the amount they compress (which can feel harder but it ain't)
Next up is to be very careful when you start fitting suspension elements from different MY bikes. Manuacturers always fiddle with the bikes geo through the years and this is performed by chanes in things like shock length, triple clamp offset(affects trail), swingar pivot position, linkage ratios, rake, wheelbase and so on. So fitting different parts from differnt year models can cause real issues as you can create a pig of a handling bike by combining the wrong components without realising, as each component fundamentally changes the overall geometry of the bike. For example, why run a shock of a later 1000 GSRX? Can you be 100% it's the same in terms of valvin set up etc and is copatible with the earlier 750 chassis?
And suspension is suspension, regardless of dirt or road or race. Its job is to keep the tyres on the ground and provide grip & traction. if it's set wrong, it can't do this and as soon as the wheel loses contact with the ground because of poor suspension set up, we lose drive or/and grip.
Next week we'll discuss swing arm angle in terms of rear traction and the fundamentals ofsquat/anti squat properties and why big sprocket sets can be a bad thing...
Edited by Steve Bass on Tuesday 26th July 16:49
Cracking day at Donnington today, and not a single red or yellow flag in my group
Unfortunately, some poor chap had an engine blow into Redgate, which left and engine full of oil along the racing line for around 20meters, so the whole corner was covered in the dust, which made for a bit of tip toeing around the corner all day, but fun day none the less
My new track bike has race shift, which took a few sessions to get my head around, but managed not to blow it up by changing down at 14k
Unfortunately, some poor chap had an engine blow into Redgate, which left and engine full of oil along the racing line for around 20meters, so the whole corner was covered in the dust, which made for a bit of tip toeing around the corner all day, but fun day none the less
My new track bike has race shift, which took a few sessions to get my head around, but managed not to blow it up by changing down at 14k
nervous said:
graeme4130 said:
Cracking day at Donnington today, and not a single red or yellow flag in my group
Unfortunately, some poor chap had an engine blow into Redgate, which left and engine full of oil along the racing line for around 20meters, so the whole corner was covered in the dust, which made for a bit of tip toeing around the corner all day, but fun day none the less
My new track bike has race shift, which took a few sessions to get my head around, but managed not to blow it up by changing down at 14k
I was there too! Grey & White MV Agusta F3 and insane fluro yellow and fluro Orange leathers. Oh, and no talent. That's me. Unfortunately, some poor chap had an engine blow into Redgate, which left and engine full of oil along the racing line for around 20meters, so the whole corner was covered in the dust, which made for a bit of tip toeing around the corner all day, but fun day none the less
My new track bike has race shift, which took a few sessions to get my head around, but managed not to blow it up by changing down at 14k
Edited by graeme4130 on Wednesday 27th July 07:55
Biker's Nemesis said:
moto_traxport said:
Cracking! Was it acceptable Northern type hot & sunny or horrible Southern type far too hot and far too sunny? 
Alright Jon.It was in the low 20's today unlike the mid 30's when you saw me at Silverstone last week.
Evening at Brands for me tomorrow just as a taster and test some knackered discs and seized calipers to see whether they're still fit for purpose and it's rain for me I think.
moto_traxport said:
Mainly on gin now due to advancing years!
Those bloody 02-03 R1 triple clamps I had in it for 2 or 3 years did nothing for me except create the same wear pattern Birky is on about and spit bits of the front tyre up the bellypan. They need using in conjunction with a longer shock apparently, or just put the original fast steering ones back in.
Edit - I've f'kin had it with photos on the internet! Photobucket has finally done me in by trying to get me to download stupid Apps for games with cartoon (feathered) birds and the above is my best effort with thumbsnap.
Yep same issue as me right thereThose bloody 02-03 R1 triple clamps I had in it for 2 or 3 years did nothing for me except create the same wear pattern Birky is on about and spit bits of the front tyre up the bellypan. They need using in conjunction with a longer shock apparently, or just put the original fast steering ones back in.
Edit - I've f'kin had it with photos on the internet! Photobucket has finally done me in by trying to get me to download stupid Apps for games with cartoon (feathered) birds and the above is my best effort with thumbsnap.
Edited by moto_traxport on Monday 25th July 20:25
Been doing family (Has to be done on occasions) so just read through these. Cheers Upsidedownmark Fergus and Steve Bass on all that info
Went with Stef at tyres4bikes and suspension. He just said exactly what you lot said. He looked at my style, videos on youtube and got an idea of what Im looking for and will be sorting it for me. Top bloke!
Said like you lot definitely geo but possibly in the heat right now run a slightly harder front compound so Im going to try a medium rather than soft front
Cadwell on the 10th August if anyone fancies it? Loads of spaces still
Went with Stef at tyres4bikes and suspension. He just said exactly what you lot said. He looked at my style, videos on youtube and got an idea of what Im looking for and will be sorting it for me. Top bloke!
Said like you lot definitely geo but possibly in the heat right now run a slightly harder front compound so Im going to try a medium rather than soft front
Cadwell on the 10th August if anyone fancies it? Loads of spaces still
Birky_41 said:
Been doing family (Has to be done on occasions) so just read through these. Cheers Upsidedownmark Fergus and Steve Bass on all that info
Went with Stef at tyres4bikes and suspension. He just said exactly what you lot said. He looked at my style, videos on youtube and got an idea of what Im looking for and will be sorting it for me. Top bloke!
Said like you lot definitely geo but possibly in the heat right now run a slightly harder front compound so Im going to try a medium rather than soft front
Cadwell on the 10th August if anyone fancies it? Loads of spaces still
I think it's more of a geo issue than a tearing issue (related to tyre compound and temp range)Went with Stef at tyres4bikes and suspension. He just said exactly what you lot said. He looked at my style, videos on youtube and got an idea of what Im looking for and will be sorting it for me. Top bloke!
Said like you lot definitely geo but possibly in the heat right now run a slightly harder front compound so Im going to try a medium rather than soft front
Cadwell on the 10th August if anyone fancies it? Loads of spaces still
moto_traxport said:
Evening at Brands for me tomorrow just as a taster and test some knackered discs and seized calipers to see whether they're still fit for purpose and it's rain for me I think.
Great to catch up last night and thanks for the lesson in overtaking. You were far braver (and quicker) than me A chap in out garage had a lovely new BMW Nine T and although it was his first track day he manged to leave with a few trophy "scrapes", mainly the brake lever, pegs and engine case, and that's without falling off! It's a very capable bike indeed.
Andy XRV said:
moto_traxport said:
Evening at Brands for me tomorrow just as a taster and test some knackered discs and seized calipers to see whether they're still fit for purpose and it's rain for me I think.
Great to catch up last night and thanks for the lesson in overtaking. You were far braver (and quicker) than me A chap in out garage had a lovely new BMW Nine T and although it was his first track day he manged to leave with a few trophy "scrapes", mainly the brake lever, pegs and engine case, and that's without falling off! It's a very capable bike indeed.
An absolutely awesome way to spend an evening.
P.S. Rich, my trackday buddy who you also met has an R9T as his roadie and loves it but we both were questioning the (financial) sense of tracking one. It did make an interesting sight going round though.
P.P.S. I was serious about selling my Tracer btw! PM me if you're interested. Bought new in May and only 1500 miles to find out my strange body finds the adventure riding position more uncomfy than the clip ons and rearsets of the sporty stuff.
Birky_41 said:
Forks back tomorrow hoping the new KTec internals and service sort it out for me
Be aware that with an incorrect (static) geometry, even running WSBK spec forks won't alleviate the problem! Were you running with the forks dropped through the yokes, as this may have exacerbated the problem. Small changes, one at a time, and you'll see which direction each change is taking you in, to allow you to get to a good setup within a few sessions. Good luck!!PS what did you have done internally? Who's doing the work?
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