fork springs (again)

[budd]

Last year I changed my fork springs from the soft OE items to Yacuga progressive springs, plus matching rear spring and oil, (7.5wt IIRC) I fitted the kit and while there as been a significant improvement could I expect further improved with linear (single rate) fork springs matched more closely to my body weight, I can't help thinking the the progressive springs must be a bit of a compromise, so my question is what springs are other people using and why ?, ohlins, K-tech, etc, are popular choices but should I be looking at / considering other brands to ? also how do I chose the correct rating of the spring for my body weight (14st), I'm thinking of changing the fork springs but staying with the 7.5wt oil (new of course), am I correct in saying I need a 410 spring and spacer length with 145mm air gap? just used the racetech spring calculator and it's suggesting a spring rate of .90kg/mm (std is .585kg/mm !!! ) does this sound right ?

[AMCQ46]

I am in the same position.!

I got Roger to do my forks with weight related linear springs [but I dont know what he fitted] and all his other mods, and it was a big step forwards.......BUT then I had a go on Tony.mon's bike and his forks were much stiffer and the front end of his bike worked better than mine, less dive but still good on the normal bumps.........unfortunatly he didnt know what springs were fitted......
This is what I wanted my front end to work like So I swapped my linear ones for progressive ones, but it has made no difference they are the same even though I am running with the preload adjuster on the last ring. next step would be to find out what spring Roger fitted and go for a stiffer one, but now you have got me wondering if he cut down the spacer which might be why I have got to add back most of the preload adjustment.

Anybody know the length of the stock spacer?

[budd]

just measured the standard spacer (well the one that came out and assuming is OE) and it's 100mm the springs are 310mm, nearly had a disaster though, I had the old springs in a box stored in the garage roof, when I pulled the box out the OE rear spring fell out right onto the windscreen of my TVR fortunately it didn't do any damage just bounced off, phew!! I must admit I panicked a bit when it fell god knows how much a new screen would have been, I'm really going to have to stop storing things in the garage roof!!!

[lloydie]

linear springs is what you want .
i have them in my forks (blade forks )
i use 5w oil and the feel is fantastic .
mct suspension is whom you want to call for them
http://www.mctsuspension.com/home.htm

[tony.mon]

I am in the same position.!

I got Roger to do my forks with weight related linear springs [but I dont know what he fitted] and all his other mods, and it was a big step forwards.......BUT then I had a go on Tony.mon's bike and his forks were much stiffer and the front end of his bike worked better than mine, less dive but still good on the normal bumps.........unfortunatly he didnt know what springs were fitted......

?

WP springs, mate. Just didn't know whether they were linear or progressive.

7.5 weight and 145 mm air gap.
I played for days changing the gap by 5mm at a time; 145 for my weight.

No spacer at all, just the spring.

[gl_s_r]

I went to MCT and he changed all mine over to WP (front and back) and set it all up to suit my weight.

Really good service there and come away really happy with the bike and considered it one of the better things I have done.

Sorry I can't help info wise with the changes he made but just wanted to say that I found MCT really good in what he done and the changes in the bike.

[popkat]

In my last firestorm i had 0.875 linear springs with 10wt oil and a 140mm air gap, it was a massive improvement, my weight at the time was 12.5 stone, but i do like the front to be firm, i reckon this set up with your weight will be about right for road and track day too if you want to do them. the springs were the same length as std iirc,and i may have made a spacer up to get the preload i wanted. If you can't get std length make up a spacer to go on top of the springs so you can get a static sag of 25mm. ideally with the preload adjusters around half way out, this will give you a bit to play with for personal preference...

My set up as well as being good on the road got me race wins and a race speed record at Lydden, which i beleive still stands today

[budd]

Thanks for the input guys, I'd forgotten about White Power springs, but can't imagine there'll be much difference in quality between the various brands although I'm prepared to be corrected on this, currently I'm looking at K-tech .90kg/mm with 7.5wt oil, 410length inc spacers and 140mm air gap, I can tweak the spacers to achieve 25mm stactic sag and air gap as required, I favouring K-Tech springs simply because they appear the best value at £85 inc vat, Ohlins are £117 and I just can't see them been £35+ better than the K-Techs, however I'll ring MCT and indeed Brook suspension who are local to me to get some advice, hopefully it won't be to to contradictory and will help me make an informed decision, any further input, adivce and personal experiences more than welcome

[oldbikeman]

I have put 9.0 K-Tech linears in my forks .They are good quality but 9 is just to stiff even on most tracks.I would go for 8.0 for the road and this will still be firm.I use Silkolene 6.25 wt which I mix using 10 and 5wt and is spot on if the dampers are OK.Thats 3parts 5wt to 1part 10wt.
The linears are my prefered spring but it doesn't mean others won,t be OK
NO altered spaces needed with these just back off the pre load.
If I remember right K-Tech are in Newton meters which are a little stiffer than kg/mm.

[Stephan]

Go with 130 mm airgap (again, info from Roger D). With oem internals, use 10w oil. I have racetech compression valves, tapered rebound needles, racetech springs 0.875, and run Motorex 5w oil

[budd]

I have put 9.0 K-Tech linears in my forks .They are good quality but 9 is just to stiff even on most tracks.I would go for 8.0 for the road and this will still be firm.I use Silkolene 6.25 wt which I mix using 10 and 5wt and is spot on if the dampers are OK.Thats 3parts 5wt to 1part 10wt.
The linears are my prefered spring but it doesn't mean others won,t be OK
NO altered spaces needed with these just back off the pre load.
If I remember right K-Tech are in Newton meters which are a little stiffer than kg/mm.

thanks for the input, if you don't mind me asking how much do you weigh? using the k-tech weight calculator my weight of 90kgs suggests a .90 kg/mm springs (k-tech uses kgs Ohlins use newtons), but maybe this is based on super smooth roads or race tracks not the god awful bits of rutted, pot holed tarmac that we are forced to endure in the UK, so dropping to .80 or .85 kg/mm may well be a wise move, that said on the OE springs (rated at just .585 kg/mm ) the bike would bottom out quite often on the road and constantly on track, the first time I braked into clervaux at croft was quite an eye opener (almost a bowel opener to) the forks simply lock up on full travel causing the wheel to skip and bounce off the slight ripples in the braking area not pleasent and that was with the pre load wound fully in, so uprating from OE spec would need quite a big increase to avoid running out of spring, the diablo corsas I have on generate a lot of grip and really load the forks under braking,

[budd]

Go with 130 mm airgap (again, info from Roger D). With oem internals, use 10w oil. I have racetech compression valves, tapered rebound needles, racetech springs 0.875, and run Motorex 5w oil

currently I have yacugar progressive springs, tapered rebound needles (with relieve hole) OE valving, 7.5wt oil and 140 mm air gap, and while it's a very worthwhile improvement on std I still find the front end a bit vague, it's difficult to discribe why, it's just a feeling that doesn't inspire confidence and I know it's probably all in my head but if I don't have confidence in the front then I struggle, I think it's the transition from the softer spring rate to the stiffer rate which is causing me the problems but that's the nature of the progressive non linear fork spring and why I think for me a linear spring would help, looking at your set up I think that this is where I'm going to end up ( or there abouts), it's surprising how apparently small changers effect the overall feeling of the front end and for me it's the difference between been comfortable and relaxed on the to bike or nervous and well non-relaxed.

[Stephan]

budd:I just add that my weight is 80 kg and 0.875 springs are just between road and race calculated rates and works fine, it is important to set sag correctly for sure.
You can try 130 mm air gap and 10w oil with current springs, or just decrease air gap with current oil if you have any, safe minimum can be somewhere at 120 mm. This could help to that vague feeling. But I have personal experience only with my current setup.

[Jazzscot]

maybe a stupid question but I shall ask it anyway.

How would you know if your springs have already been done or not before you bought the bike??? If you were to look at the springs are the updated ones easy to identify compared to stock??

If you dont know what the stock ones look like how can you tell?????


Hmmmm answers on a postcard plz.

Jazz

[sirch345]

any further input, adivce and personal experiences more than welcome

Before you go replacing the fork springs I suggest you try a couple of other things first, that is if you've not already.

I found setting the rebound damping correctly is not something to be over looked. It needs to be set at the fastest possible return (when you push down on the handlebars and allow the front end to return on it's own), but under control. Somewhere around one full turn out from fully in, give or take a quarter of a turn either way is where you'll probably end up.

Also I found if you have dropped the front end too much that can have a negative result as well. When fitting and setting up my breathed on forks by Roger Ditchfield at RevolutionUK I tired 7.5mm drop which didn't suit me at all, so I then tried 5mm which was so much better for me. It's horses for courses, what will suit one will not necessarily suit another.

What rear shock are you using Tyres make a big difference, what have you got

maybe a stupid question but I shall ask it anyway.

How would you know if your springs have already been done or not before you bought the bike??? If you were to look at the springs are the updated ones easy to identify compared to stock??

If you dont know what the stock ones look like how can you tell?????


Hmmmm answers on a postcard plz.

Jazz

Some aftermarket fork springs are marked but many are not, this is where the problem lies. You could try increasing the pre-load (less rings showing), if this makes the front end really hard then my guess you've not got standard springs. Other than that, you'll have to take one spring at least out, measuring the length (if there are no markings on it) may give you a clue. Do take care when testing out different settings, as if you're unaware adjusting fork settings can change the way the bike handles a lot.

Chris.