Jerez Oct 10-13

[bmwbadboy]

Don't forget that's 114.9mm of travel on the 2D sensor for *the position it is on, on my bike* the total travel is 124mm according to what I got from HM Racing/Perry

View attachment 4693

Here is my data suspension data from last day.

Looking at reasonable paced laps, our fork travel is more or less inline with each other.

 

[alex]

I see that I still think I had to use too much preload to get there...

- Alex

 

[bmwbadboy]

I see that I still think I had to use too much preload to get there...

- Alex

Why do you think that ? My preload is 8 turns vs. your 6. I havent changed it since it was set by HM racing guy.

preload	8
comp	16
rebound	13

 

[alex]

No, they put 6 in I'm on at least 11 possibly 12...

See post 18

- Alex

 

[Monners]

Hmmm I am sat here, looking through the data and wondering if the zip tie is selling me a dummy. Or if the 2D is off...
Could the tie be slipping on bumps?
Could the 2D need resetting via a DDC CALIB? (Despite not having DDC)

What's the stanchion size? 43mm? Time to get a better zip tie.
https://store.ktechsuspension.com/catalogsearch/result/?cat=&q=Indicator

Not a lot is making sense, for instance, harking back to when it was more of an issue. I know how it felt, I could feel bumping through the bars on aggressive stops. Can I find data to support that, hell no, was the ziptie always near to or at the bottom, yes.
I need to improve the lab conditions and take out some variables.

I 100% guarantee its the zip tie, its almost always the most simple answer with these things. I have one on my forks which theoretically should be reliable but I always compare it to my actual data and 80% of the time it is completely out. If you consider what it is doing - it is getting punched by the bottom of the fork tube thousands of time a session so even a tight zip tie is going to get some momentum or vibration and move further than it should be.

 

[Monners]

I reckon I could easily get you down to a 1'54'' with a change of springs and almost no extra effort from yourself. To make the most simple point to prove what I'm saying: if the front dives more the bike will turn faster. This means you will finish the corner quicker and be accelerating down the straight earlier.

Here is my data suspension data from last day.

Looking at reasonable paced laps, our fork travel is more or less inline with each other.

 

[bmwbadboy]

I reckon I could easily get you down to a 1'54'' with a change of springs and almost no extra effort from yourself. To make the most simple point to prove what I'm saying: if the front dives more the bike will turn faster. This means you will finish the corner quicker and be accelerating down the straight earlier.

So are you saying, because I don't use full 115mm travel I would benefit from 10/10 springs in front?

Re: previous comment, I'm not disagreeing with anything you say, it's all correct. It's just when I'm on track, I can't say that I'm battling with the bike, hence cant imagine that any improvement in suspension will help at this stage. Altho I probably should just try it.

Could you recommend any video guides on changing springs?

 

[alex]

Check the Dave Moss videos

- Alex

 

[Monners]

So are you saying, because I don't use full 115mm travel I would benefit from 10/10 springs in front?

Re: previous comment, I'm not disagreeing with anything you say, it's all correct. It's just when I'm on track, I can't say that I'm battling with the bike, hence cant imagine that any improvement in suspension will help at this stage. Altho I probably should just try it.

Could you recommend any video guides on changing springs?

Yes exactly that. In general you should be looking for just under 120mm in the heaviest braking zone, if you are not using it then you are wasting turning ability and also not using all the available grip. I usually aim for around 118 - 119 just to give a little leeway. Forks usually have another 5mm but that's bumpstop or top out spring.

When I say battling with the bike I just mean that you have to work harder than you would otherwise to make it do stuff. If you wanted to go faster at the moment you would have to trail brake harder into the corner to get it to turn which might be difficult to do or scary. With a lighter spring it will just do it for you without any extra effort.

 

[bmwbadboy]

Yes exactly that. In general you should be looking for just under 120mm in the heaviest braking zone, if you are not using it then you are wasting turning ability and also not using all the available grip. I usually aim for around 118 - 119 just to give a little leeway. Forks usually have another 5mm but that's bumpstop or top out spring.

When I say battling with the bike I just mean that you have to work harder than you would otherwise to make it do stuff. If you wanted to go faster at the moment you would have to trail brake harder into the corner to get it to turn which might be difficult to do or scary. With a lighter spring it will just do it for you without any extra effort.

Understood.

Would 10/10 springs be enough or worth trying 9.5/10 too?

 

[Monners]

I think 10nm will likely be best; but let the data guide you because it changes depending on how you're riding, the track and weather conditions. I dont know your weight but it's rare to go below 10nm on the BMW and at your laptimes because you always needs to square off the corners so the bike has a fair bit of force going through the forks even on fast flowing tracks. Like you 10.25 is my default starting point and I check data from that and adjust.

Fyi my changes this year:

Donnington - Fast and flowing on the national so needs softer springs. The GP Melbourne Loop needs heavier so its a big compromise. I started on 10.25nm and got into the high 1'39'' and then changed to 10nm and got right down to 1'38'' dead. It surprised me since I'm quite hard on the brakes. Fast guys are often on 10.5.

Mugello - Fast and flowing. Again I started on 10.25 and knocked several seconds off going to 10.

Red Bull Ring - Very fast straights into heavy uphill breaking zones. I started on 10.25 and knocked four seconds off going up to 10.5.

Jerez - This was before I started looking at the data and I was on 10.5 and struggling. I got down to 1'56'' by reducing compression/preload but after the trip I had Ducatis Piro Mupo suspension tech look at the data and the first thing he said was I should go to a softer spring.

Cadwell Park - Heavy gradient changes and tight corners. I tried a 10.5 but 10.25 worked better for my level.

Anglesey - 10 or 10.25.

 

[bmwbadboy]

So how do you change springs at the track? Do you need to take the fork tube off or just unscrew the top but and take it all out?

I don't have a front stand that unloads forks as well...

 

[fast_ryan]

Front Forks

Ideally you need an under yoke type stand and then it’s simply a case of removing the top of the forks and extracting the springs. Once you have changed the springs you just need to check the air gap and replace the fork caps. After that you will need to set preload and then make the necessary adjustments to compression and rebound.

 

[alex]

The alternative is a 1Jac or Abba Superbike stand. (Don't get a Constands/Spider frame lift).

 

[fast_ryan]

Front Stand

I personally prefer to use an under yoke type stand as there is less movement from the front end when you are trying to unscrew the fork caps which makes it much easier. If you still have the OEM ABS front brake lines fitted you will need to unbolt the union below the bottom yoke first before fitting the stand and lifting the front end.

 

[alex]

Agreed - I was just offering another way to unload the forks.

I'd go for the Harris Yoke Stand. https://www.harris-performance.com/product/harris-race-front-yoke-type-paddock-stand/

 

[fast_ryan]

Front Stand

I'd go for the Harris Yoke Stand. https://www.harris-performance.com/product/harris-race-front-yoke-type-paddock-stand/

+1. This is the under yoke stand which I use and would highly recommend it.

 

[baz]

Correct. @baz was doing 1.56-something on OEM Gen4 suspension

1.53's,with no mods to the suspension,although I did have the front fork sensor which allowed me to slow the rebound a bit.

 

[Monners]

Thats an awesome laptime on a stock bike Incidently does the front sensor from the Gen 3 fit the Gen 4 ok?

 

[baz]

Thats an awesome laptime on a stock bike Incidently does the front sensor from the Gen 3 fit the Gen 4 ok?

Bearing in mind that I haven't even checked the preload,I found the suspension worked very well as standard,but was improved considerably once comp/rebound were separated.
Next stage,when the bike gets home,is a visit to Darren at MCT to see what can be improved.
The gen 3 fork sensor will fit,but it needs to be placed in front of the forkleg(at least there are no clearance issues)and a simple bracket off the mudguard mounting.
The top clamp is fractionally smaller than the fork tube so,ideally,requires a longer screw and some electrical tape to avoid marking the fork tube.
I will post some photos when I get the bike back.