Racetech fork springs & learning

[rideontt]

these are 8.5Nmm or 48lbs/inch, free height is 315mm.


OD ; is 34.10-34.45 mm for side A and 36.6 to 36.80 sideB.

>the recommendation is 10mm of preload from Race Tech a good point >>for Mortals !!! thoughts goes like following;

OEM spring is 345mm -315mm= 30mm +10mm preload +10mm for that extra sag(OEM spring had 60mm of total sag in front)

this long spacer tube added unintended outcomes.

 

[rideontt]

unintended outcomes; The front really tall(50mm spacer) and the motorcycle won't turn unless its a bumpy potholed road.
The installation of 50mm spacer was difficult being that 8.5 Nmm springs are really robust and a heck of resistance to compress.

I found this info valuable and true to me and fully agree with Bret i should have taken the 8.0 Nmm springs

the motorcycle is for multiple requirements; tour and Occasional track.

 

[rideontt]

at the time I didn't know what was wrong but the motorcycle was a complete disappointment to ride. it won't turn and it was horrible to manage at 25mph/40kmph and above that speed its like a drag motorcycle just straight-line stability.

after many dialogues\ listening to monologues \ checking online and asked fellow riders below are conlusions;

> lower the fork by 1 inch/ 2"inch; I tried it but the issue still there motorcycle won't turn in.
other
>reducing the preload spacer size; this opinion worked

 

[rideontt]

Preload Spacer reduced to 28mm this improved handling from 50mm used earlier

Usage for daily ride/ commute to test it and figure out\ how\what and is there anything more I can improve.

came another issue;
the motorcycle on the corner/curve goes wide on the exit, this was wearing me out and I didn't know why?(i will come back to this)



I took the motorcycle to a fellow rider who has the same motorcycle that I do; he just checked the motorcycle by bouncing the front said hey the fork raises back fast/instantly and that is an issue for exit being wide
[hydraulic damping the rebound too fast ]


&
all this time I was blaming my self that my body position on the motorcycle was the reason for turn exits being wide and require more brain space or concentration to ride

 

[rideontt]

The front really tall(50mm spacer) and the motorcycle won't turn unless its bumpy potholed road.
The installation was difficult being that 8.5 Nmm springs are really robust and a heck of resistance to compress.

I found this info valuable and true to me and fully agree with Bret

I use the motorcycle for multipurpose Occasional track and tour.

being that I had taken a spring selection too stiff as stated by Bret Tkacs I thought well now how to overcome this

this video of Simon Crafar to the rescue

>>> the part of mix n match of fork springs for different rates being that its mounted on a axel ..... me Yaaaaayyyyyy

 

[rideontt]

Since I have seen the process of fork dismantle and reassemble several times I understood what I shouldn't do....

rider @ 180lbs/80kgs

the thing need to check is the height of the damping rod to be = on both legs;
>installed OEM spring on One leg
>315+28 mm spacer was too long -> used a 22mm spacer this matched OEM spring fork leg height


and bigger value fork OIL @ 30W. this is firmer on compression and the rebound slower. Since the fork oil is large(30W) they tend to become softer on compression after 400-1000kms or 30hrs/45hrs+ of riding

the previous setup of 8.5Nmm springs on both forks and using Motul fork oil;

5W; soft compression >rebound fast
7.5W; soft compression> rebound fast
10 W; soft compression> rebound it is fast again
Fork Oil is not to blame, above are my observation's and opinion

the rebound being fast increased fatigue\ increased arm pump and unnecessarily doubting self.

 

[rideontt]

Mix match fork springs & things I Have noticed;

It's easy to recover from over speed/charge into the turn correct it using brakes enough to complete a turn -> fork has linear dive keeps me stable. The tyre bites the tarmac better and the same is noticeable in rain.
air pressure is crucial, yes being that fork feel has improved air pressure values dictate how the front should feel [soft supple(22-24psi) or firm and easy to turn(26-29psi) this values change based on rider ability and or weight]


Braking has improved significantly front stays in line and I can use a lot more brake pressure and ABS intervention has reduced now almost not intervened and "yes it does lift the rear tyre" in certain situations

Other points;
> OEM damping, not enough so rebound speed I believe is dictated by the stronger 8.5N spring
> to try lighter fork OIL on OEM spring installed leg and check how much more travel can be utilised

 

[rideontt]

Spring Free Height(mm)	Spacer(preload) Used (mm)	Total Sag (mm)	Observation	my openion /suggestion
345	OEM springs no spacer	60	its bad at higher speeds (especially in track day secession) easy to bottom out the forks when ridden hard front end chatter and heavy steer feel	suits moderate speed for riders @ 130lb-155lbs.
315	+50	20	front was tall and not easy to turn or lean 25mph/40kmph above these speeds
315	+28 (reduced from above)	40	turn at speeds good, exits were wide being springs selection was stiff and no damping changes done	8.5+8.5=17.0 /2=8.5Nmm
315 & an OEM spring	+22 for race tech spring (further reduced from above) and no spacer for OEM spring	50	turn at speeds better exit wide reduced.	8.5+6.1=14.6/2=7.3Nmm\ try softer Spring rate (7.0Nm to 7.3Nm both fork legs n see if the rebound is slower!)

 

[FaNaTic]

Hello rideontt,
Sorry for my bad english (I'm french).
I just ordered a shock made by Mike Capon for a track only RC125. I'm almost their neighbor !
I'm looking for fork springs with a rate of 7.5 N/mm.
I found something at K-Tech : ref. K35-340-75 seems OK with a 340 mm length and 7.5 rate (other rates are available).
I've seen on this forum that the OD of the OEM spring is 36 mm. K-Tech is 35 mm. What did you measured on yours ?
Do you think those K-Tech springs are a good solution ? Is the 1 mm difference in diameter a problem ?

 

[rideontt]

Hello rideontt,
Sorry for my bad english (I'm french).
I just ordered a shock made by Mike Capon for a track only RC125. I'm almost their neighbor !
I'm looking for fork springs with a rate of 7.5 N/mm.
I found something at K-Tech : ref. K35-340-75 seems OK with a 340 mm length and 7.5 rate (other rates are available).
I've seen on this forum that the OD of the OEM spring is 36 mm. K-Tech is 35 mm. What did you measured on yours ?
Do you think those K-Tech springs are a good solution ? Is the 1 mm difference in diameter a problem ?

I am not the grammar police, your typing I can understand.
wow your neighbour congratulations lucky you
-1mm of dia, not an issue... but out of curiosity how did you select 7.5?

 

[FaNaTic]

 

[FaNaTic]

My RC125 is completely nacked, and is weight is the same than the 125 Duke i. e. 26 kg less compare to the RC390.
I've used the Racetech calculator with a my weight (72 kg) - 26 kg (difference 125 Duke vs RC390) and the result is 7.5 N/mm.
This value is close to your above mixed spring solution (7.3 N/mm).
FYI, we choose with Mike a 500 lbs (9,0 kg) spring for my M-shock 2 (ordered monday, received today !)

 

[rideontt]

My RC125 is completely nacked, and is weight is the same than the 125 Duke i. e. 26 kg less compare to the RC390.
I've used the Racetech calculator with a my weight (72 kg) - 26 kg (difference 125 Duke vs RC390) and the result is 7.5 N/mm.
This value is close to your above mixed spring solution (7.3 N/mm).
FYI, we choose with Mike a 500 lbs (9,0 kg) spring for my M-shock 2 (ordered monday, received today !)

an RC 125; 100% throttle all the time
ohh like that, that's a good thought on using racetech web also is the usage track-only?
M-shock 2 fantastic.

 

[rideontt]

View attachment 6700

can you show how the front looks?

 

[FaNaTic]

This bike is for training on "go kart tracks" and this way, it's not all the time full throttle.
Another reference for spring choice is what I've seen on this forum : 8.0 or 8.5 N/mm for light pilots with RC390 track bikes.
My RC125 is lighter and I'm not riding as fast on my small tracks. For the same reason we choose with Mike a 500 lbs shock spring while he put 550 lbs for the RC390 in SSP championship.
My front fairing is for a Norton Manx. It's awful on the KTM but I already had it unused

 

[rideontt]

This bike is for training on "go kart tracks" and this way, it's not all the time full throttle.
Another reference for spring choice is what I've seen on this forum : 8.0 or 8.5 N/mm for light pilots with RC390 track bikes.
My RC125 is lighter and I'm not riding as fast on my small tracks. For the same reason we choose with Mike a 500 lbs shock spring while he put 550 lbs for the RC390 in SSP championship.
My front fairing is for a Norton Manx. It's awful on the KTM but I already had it unused

the rear spring rate provided is good for a solo lightweight rider, 500lbs will work. the key part is the damping and on that Mike is effective & or whomsoever at Shock Factory


what is your current stock fork spring total sag and what is your total sag after the 7.5N spring upgrade?

 

[FaNaTic]

I don't have the replacement springs yet. I'm looking for a pair.
With the stock spring, the SAG is huge, 60 mm if I remember correctly (but the value is without interest because it is a progressive spring).

 

[rideontt]

My RC125 is completely nacked, and is weight is the same than the 125 Duke i. e. 26 kg less compare to the RC390.
I've used the Racetech calculator with a my weight (72 kg) - 26 kg (difference 125 Duke vs RC390) and the result is 7.5 N/mm.
This value is close to your above mixed spring solution (7.3 N/mm).
FYI, we choose with Mike a 500 lbs (9,0 kg) spring for my M-shock 2 (ordered monday, received today !)

hey how is the ride? after M2 shock

 

[rideontt]

I don't have the replacement springs yet. I'm looking for a pair.
With the stock spring, the SAG is huge, 60 mm if I remember correctly (but the value is without interest because it is a progressive spring).

have you ordered the fork springs?

 

[FaNaTic]

Hello,
Neither one, nor the other ! I am busy on another bike for now.
I’ll tell you when I get back to the RC.