Static Sag v Rider Sag

Static Sag v Rider Sag

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Discussion

bass gt3

10,186 posts

232 months

Monday 30th March 2015
quotequote all
Mr OCD said:
bass gt3 said:
It's an illusion wink If you wound full preload in, you see your total stroke was longer as the preload is overpowering the neutral spring. So the spring will always sag the same amount for a given weight. Preload just moves the range up a bit. It's why springs come in half newton increments, otherwise if preload was able to cover a broad range of springs, there'd be no need for such fine increments.
But given that we're stuck with the springs we have, we can't actually change true sag. The preload will only adjust ride height so it's ok to take a couple of turns out to lower the front. Now you can add a smidge of compression in the front to slow the forks a bit.
Thanks for the explanation... biggrin

I'm actually considering changing the springs if I need to do so as I plan to keep the bike a couple of years so want it riding well. As always it is a compromise... the standard Fireblade suspension is supposed to be very good and as a road bike for 95% of the time commuting spending thousand of pounds on suspension upgrades just isn't justified.

Don't mind spending a couple hundred quid on springs though...

I will change the preload to 7 turns from soft that puts is back to pretty much how it was! biggrinbiggrin

So we've come round full circle...
We may of come full circle, but hopefully you have a better understanding and can see why a set of numbers off the interweb are meaningless.
Rather than blindly buying springs, find someone who's willing to work with you to get the right springs rather than just selling you X or Y and you then finding out it's not right.
Truth is modern suspension is pretty damn good for its intended use, and as BN says, the only requirement is springs if the standard items are out of range.
As for what's currently fitted, if you find a good company, have them dyno the springs and confirm the measurements. Assuming they are a certain value is a waste of time, you need to know so you can decide on what springs to replace them with. If you were here I'd have your forks on a shock dyno before and after as well as full spring assessment. Bu you're not so tough titty, sucks to be you smile

Mr2Mike

20,143 posts

254 months

Monday 30th March 2015
quotequote all
Mr OCD said:
After reading back through this thread last night one question I did raise is given the preload has no affect on spring rate, i.e. preload changes suspension height not stiffness. Why does increasing preload reduce sag?
Preload effectively subtracts a fixed amount from the load on the spring. There is no suspension movement at all, until the load applied to the spring exceeds the preload.

Imagine a simple system with no linkages and a 1:1 ratio. If you weighed, say 80kg, and there was 20kg of preload, the initial suspension movement (i.e. sag) would be the same as a 60kg person sitting on the bike with no preload.

fergus

6,430 posts

274 months

Monday 30th March 2015
quotequote all
bass gt3 said:
As for what's currently fitted, if you find a good company, have them dyno the springs and confirm the measurements. Assuming they are a certain value is a waste of time, you need to know so you can decide on what springs to replace them with. If you were here I'd have your forks on a shock dyno before and after as well as full spring assessment. Bu you're not so tough titty, sucks to be you smile
Steve, a lot of springs have their Nm spring rate stamped into the top half coil (i.e. the bit where the spring is cut off and flattened to sit against the spring perch). Not sure if OEM stuff has these etchings. Either way you'd need a spring compressor to take the top of the cartridge off to be able to see....

OCD - Don't try this at home without an emergency dental appointment setup (or alternatively a spring compressor), as you are likely to end up eating the top of the cartridge very quickly.... (Don't google spring compressor, as you're likely to see something for use on a less tightly coiled spring). Racetech can seel you one for about £100 or so.

bass gt3

10,186 posts

232 months

Monday 30th March 2015
quotequote all
fergus said:
Steve, a lot of springs have their Nm spring rate stamped into the top half coil (i.e. the bit where the spring is cut off and flattened to sit against the spring perch). Not sure if OEM stuff has these etchings. Either way you'd need a spring compressor to take the top of the cartridge off to be able to see....

OCD - Don't try this at home without an emergency dental appointment setup (or alternatively a spring compressor), as you are likely to end up eating the top of the cartridge very quickly.... (Don't google spring compressor, as you're likely to see something for use on a less tightly coiled spring). Racetech can seel you one for about £100 or so.
Agreed. Ohlins fork Tech springs are easy to read. Not sure on the Jap OEM items as they're all the same. Might have a part number rather than a weight value

Mr OCD

Original Poster:

6,388 posts

210 months

Monday 30th March 2015
quotequote all
fergus said:
check out his site, it's got some really interesting stuff on it : http://feelthetrack.com/free-vidoes/setting-sag-2/

you could do a lot worse than to buy this book: http://www.amazon.co.uk/Suspension-Tuning-Handling... It's very easy to read and explains things in an accessible way.



Edited by fergus on Monday 30th March 14:39
Cheers for info ... Just bought that book ... Genuinely finding suspension very interesting biggrin

bass gt3

10,186 posts

232 months

Monday 30th March 2015
quotequote all
Mr OCD said:
Cheers for info ... Just bought that book ... Genuinely finding suspension very interesting biggrin
Good man!

It does get interesting, especially when clown wander around skinning 40 quid for twiddling a couple of adjusters for no apparent improvement.
Fact is, the basics are too so difficult to fathom, and it's good to know how it all functions.

Mr OCD

Original Poster:

6,388 posts

210 months

Monday 30th March 2015
quotequote all
bass gt3 said:
Good man!

It does get interesting, especially when clown wander around skinning 40 quid for twiddling a couple of adjusters for no apparent improvement.
Fact is, the basics are too so difficult to fathom, and it's good to know how it all functions.
It does ... I like things to be 'right' and suspension is the only thing I've not fully grasped in detail when it comes to bikes.

Just got a reply from Maxton who advise both front springs and rear shock springs are a little soft so want to sell me springs, valving and a new rear shock without actually answering my questions.

Yeah ok ... Not.

bass gt3

10,186 posts

232 months

Monday 30th March 2015
quotequote all
Mr OCD said:
bass gt3 said:
Good man!

It does get interesting, especially when clown wander around skinning 40 quid for twiddling a couple of adjusters for no apparent improvement.
Fact is, the basics are too so difficult to fathom, and it's good to know how it all functions.
It does ... I like things to be 'right' and suspension is the only thing I've not fully grasped in detail when it comes to bikes.

Just got a reply from Maxton who advise both front springs and rear shock springs are a little soft so want to sell me springs, valving and a new rear shock without actually answering my questions.

Yeah ok ... Not.
You seem surprised wink

Mr OCD

Original Poster:

6,388 posts

210 months

Monday 30th March 2015
quotequote all
bass gt3 said:
You seem surprised wink
I know, I know ... I shouldn't be ... I just want to be provided with information and helped to achieve my target.

I accept that possible new springs and service work are required which means spending money and that is fine ... But I want more than just parting with cash... wink

In meantime I want to understand what I've got and how I can make it work to best of my ability and until I've done so I aint spending a penny wink

No fancy ohlins, springs, valve kits are going to mean owt if it's not working how it's designed due to poor setup! biggrin

bass gt3

10,186 posts

232 months

Monday 30th March 2015
quotequote all
Mr OCD said:
bass gt3 said:
You seem surprised wink
I know, I know ... I shouldn't be ... I just want to be provided with information and helped to achieve my target.

I accept that possible new springs and service work are required which means spending money and that is fine ... But I want more than just parting with cash... wink

In meantime I want to understand what I've got and how I can make it work to best of my ability and until I've done so I aint spending a penny wink

No fancy ohlins, springs, valve kits are going to mean owt if it's not working how it's designed! biggrin
Agree 100%

In the meantime, I'd bet you can get the bike to 95% of where it needs to be by optimising what you have. Yes, the springs might be a tad soft but you can offset that with a touch of comp as required. The springs aren't so far out as to pose a threat.
If you were going to take her to the track in a serious fashion, then I'd say upgrades would be worth it. But I reckon a refresh with good quality oil set to a decent oil height you'd be spot on


Yazza54

18,464 posts

180 months

Tuesday 31st March 2015
quotequote all
Steve, just spoke to the fella who's doing my forks. They're fitted with bloody 8.5s. Good guess wink

bass gt3

10,186 posts

232 months

Tuesday 31st March 2015
quotequote all
Yazza54 said:
Steve, just spoke to the fella who's doing my forks. They're fitted with bloody 8.5s. Good guess wink
Where do I send my invoice ?? biggrin

Yazza54

18,464 posts

180 months

Tuesday 31st March 2015
quotequote all
bass gt3 said:
Yazza54 said:
Steve, just spoke to the fella who's doing my forks. They're fitted with bloody 8.5s. Good guess wink
Where do I send my invoice ?? biggrin
tongue out


Mr OCD

Original Poster:

6,388 posts

210 months

Tuesday 31st March 2015
quotequote all
bass gt3 said:
Where do I send my invoice ?? biggrin
roflrofl

biggrin

Mr OCD

Original Poster:

6,388 posts

210 months

Tuesday 31st March 2015
quotequote all
Already started reading... and watching Dave Moss videos.

So far I've learnt ...

Once rebound is set properly you shouldn't need to mess about with it, but it is important the sag / spring rates are correct first before fiddling.

Compression is the one to fiddle with as you'd run a bit more on the track to the street obviously... I'm interested to know why the front compression was pretty much fully out on the blade... for a plush ride I guess... ?

All pretty simple stuff TBH but I've been more interested in having the skill to apply it and know how the bike should respond to adjustments. Even knowing how to 'bounce' the bike properly has made a BIG difference.

I used to use the bit behind the tank cap but on the blade this isn't a great idea as it's a plastic cover which flexes... Dave Moss advises using the seat AND the bar to bounce the bike - something I will be trying tonight.

Bike is off the road for a couple days due to the pissing weather so I'm going to buggering about with the suspension for practical experience and turn into a book nerd biggrin

Mr Moss advises 30-35mm rear, 35-40mm front rider sag for the street.

STREET!? - Been watching too many american videos!!! biggrin

fergus

6,430 posts

274 months

Tuesday 31st March 2015
quotequote all
Mr OCD said:
Once rebound is set properly you shouldn't need to mess about with it, but it is important the sag / spring rates are correct first before fiddling.
All the damping does is control the rate of spring movement. If the spring rate is not correct, the damping will either be doing more work than it needs to, or will be ineffective.

This is the reason why getting the static then dynamic (rider) sag is so important to evaluate whether your starting point is good. If not, then go get some new springs and repeat the process....

Biker's Nemesis

38,534 posts

207 months

Tuesday 31st March 2015
quotequote all
Yazza54 said:
Steve, just spoke to the fella who's doing my forks. They're fitted with bloody 8.5s. Good guess wink
I usually run 9.5's. You must be a right old lightweight Ryan.

Yazza54

18,464 posts

180 months

Tuesday 31st March 2015
quotequote all
Biker's Nemesis said:
Yazza54 said:
Steve, just spoke to the fella who's doing my forks. They're fitted with bloody 8.5s. Good guess wink
I usually run 9.5's. You must be a right old lightweight Ryan.
He's recommending 10s.. It was st on 8.5!

Mr OCD

Original Poster:

6,388 posts

210 months

Tuesday 31st March 2015
quotequote all
fergus said:
All the damping does is control the rate of spring movement. If the spring rate is not correct, the damping will either be doing more work than it needs to, or will be ineffective.

This is the reason why getting the static then dynamic (rider) sag is so important to evaluate whether your starting point is good. If not, then go get some new springs and repeat the process....
Agreed ... Hence will be checking both static and dynamic sag. At present its pretty close with 38mm front, 35mm rear and roughly middle of preload settings so the springs are pretty close ...

If anything slightly stiffer fork springs be a good idea but I want to see how I can get on first with current springs before I start messing ...

Biker's Nemesis

38,534 posts

207 months

Tuesday 31st March 2015
quotequote all
Yazza54 said:
He's recommending 10s.. It was st on 8.5!
Chub.